Adhesive, adhesive sheet, laminate, and display

Abstract

In the present disclosure, provided are an adhesive agent, an adhesive sheet, a laminate and a display, which contain a specific acrylic copolymer (A), a polyolefin (B) and a curing agent (C), have excellent transparency, and are capable of achieving both heat resistance, wet heat resistance, buckling properties and winding properties.

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 image display devices such as liquid crystal displays and organic electroluminescence (EL) displays usually have a laminated structure, that is, a laminated structure including a liquid crystal layer, an organic EL layer and other image forming layers, and an optical film or a cover plate. Generally speaking, an adhesive is 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 a member such as a supporting glass or a supporting film via an adhesive layer. In addition, the polarizing plate film used in the image device is attached to a liquid crystal module or an organic EL module via an adhesive layer. In this way, the components of the image display device are attached and fixed using an 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 a property that does not cause foaming or peeling in a high temperature environment or a high temperature and high humidity environment, but in recent years, further functionalization is 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 that does not cause foaming, floating or peeling when repeatedly bent (dynamic flexibility).

[0005] In order to solve these problems, Patent Document 1 discloses an adhesive containing a urethane compound as a main component resin. Patent Document 2 discloses an adhesive having a weight average molecular weight of 1,000,000 to 2,500,000 and a glass transition temperature of 0°C or less.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-155695

[0009] Patent Document 2: Japanese Patent Application Publication No. 2021-176969 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 the display, the adhesive used needs to have more stringent durability than before. In particular, in foldable displays, in addition to the property that no bubbling, floating or peeling occurs when repeatedly bent (dynamic flexibility), it is also necessary to have the property that no bubbling, floating or peeling occurs when the bent state is maintained for a long time (static flexibility). In addition, in a rollable display, suitability (winding) corresponding to the winding of the display is required so that it can be used for a rollable display. As for the winding property, it is necessary to have the property that no bubbling, floating or peeling occurs when the rolled state is maintained for a long time.

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

[0013] On the other hand, the current situation is that conventional adhesive sheets cannot satisfy the 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, in terms of flexibility, dynamic flexibility, static flexibility, and rollability are required according to the display structure. However, the current situation is that even if these flexibility requirements can be met individually, it is difficult to meet them simultaneously. In addition, dynamic flexibility, static flexibility, and rollability cannot be met in high temperature environments or high temperature and high humidity environments.

[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 rollability.

[0016] Technical means of solving problems

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

[0018] That is, an embodiment of the present invention is an adhesive, characterized in that it includes an acrylic copolymer (A), a polyolefin (B) and a curing agent (C).

[0019] The acrylic copolymer (A) is a copolymer of a monomer mixture containing all of the following monomers (a-1) to (a-4), and,

[0020] Satisfy all of the following (1) to (3).

[0021] (a-1) Alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms

[0022] (a-2) Alkyl (meth)acrylate monomers having an alkyl group with 6 to 12 carbon atoms

[0023] (a-3) Monomer having a hydroxyl group

[0024] (a-4) Monomer having a carboxyl group

[0025] (1) In 100% by mass of the monomer mixture, the mass % of (a-1) is less than the mass % of (a-2)

[0026] (2) In 100% by mass of the monomer mixture, (a-3) / (a-4), which is obtained by dividing the mass % of (a-3) by the mass % of (a-4), is 0.01<(a-3) / (a-4)<6

[0027] (3) The adhesive strength between a 50 μm thick adhesive layer formed of the adhesive and glass after being left to stand at 23° C. and a relative humidity of 50% for 24 hours is 10 N / 25 mm or more.

[0028] Another embodiment of the present invention is the adhesive, characterized in that the adhesive contains 0.1 to 5 parts by mass of the polyolefin (B) based on 100 parts by mass of the acrylic copolymer (A).

[0029] Another embodiment of the present invention is the adhesive, characterized in that the gel fraction is 60% by mass to 90% by mass.

[0030] In another embodiment of the present invention, the adhesive is characterized in that the hardener (C) is an isocyanate compound.

[0031] Another embodiment of the present invention is an adhesive sheet including an adhesive layer, wherein the adhesive layer is a cured product of the adhesive.

[0032] Another embodiment of the present invention is a laminated body including a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the layer is formed of the adhesive.

[0033] Another embodiment of the present invention is a display including the laminated body and an optical element.

[0034] In one aspect, the present disclosure includes the following embodiments.

[0035] [1] An adhesive comprising an acrylic copolymer (A), a polyolefin (B) and a hardener (C),

[0036] The acrylic copolymer (A) is a copolymer of a monomer mixture containing all of the following monomers (a-1) to (a-4), and,

[0037] Satisfy all of the following (1) to (3).

[0038] (a-1) Alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms

[0039] (a-2) Alkyl (meth)acrylate monomers having an alkyl group with 6 to 12 carbon atoms

[0040] (a-3) Monomer having a hydroxyl group

[0041] (a-4) Monomer having a carboxyl group

[0042] (1) In 100% by mass of the monomer mixture, the mass % of (a-1) is less than the mass % of (a-2)

[0043] (2) In 100% by mass of the monomer mixture, (a-3) / (a-4), which is obtained by dividing the mass % of (a-3) by the mass % of (a-4), is 0.01<(a-3) / (a-4)<6

[0044] (3) The adhesive strength between a 50 μm thick adhesive layer formed of the adhesive and glass after being left to stand at 23° C. and a relative humidity of 50% for 24 hours is 10 N / 25 mm or more.

[0045] [2] The adhesive according to [1], characterized in that the adhesive contains 0.1 to 5 parts by mass of the polyolefin (B) based on 100 parts by mass of the acrylic copolymer (A).

[0046] [3] The adhesive according to [1] or [2], wherein the gel fraction is 60% to 90% by mass.

[0047] [4] The adhesive according to any one of [1] to [3], wherein the hardener (C) is an isocyanate compound.

[0048] [5] An adhesive sheet including an adhesive layer, wherein the adhesive layer is a cured product of the adhesive according to any one of [1] to [4].

[0049] [6] A laminate comprising a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the adhesive layer is a layer formed of the adhesive according to any one of [1] to [4].

[0050] [7] A display comprising the laminate according to [6], and an optical element.

[0051] Effects of the Invention

[0052] The present disclosure provides 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 and moisture-heat resistance, as well as flexibility and windability.

[0053] Furthermore, by using the adhesive sheet and laminate of the present disclosure, a display having excellent visibility and contrast is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] [ Figure 1 ] is a schematic cross-sectional view partially showing the adhesive sheet of the present invention.

[0055] [ 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.

[0056] [ 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

[0057] Hereinafter, structural examples of the adhesive, adhesive sheet, laminate, and display of the present disclosure will be described, but the present invention is not limited thereto.

[0058] The following are definitions of the terms used in this specification. The term (meth)acrylate includes acrylate and methacrylate. The term monomer refers to a monomer containing an ethylenically unsaturated group. The term adherend refers to an object to which the adhesive sheet is to be attached. In this disclosure, sheet, film, and tape are synonymous.

[0059] In the present specification, (a-1) a (meth)acrylic acid alkyl ester monomer having 1 to 4 carbon atoms, (a-2) a (meth)acrylic acid alkyl ester monomer having 6 to 12 carbon atoms, (a-3) a monomer having a hydroxyl group, (a-4) a monomer having a carboxyl group, (a-5) other monomers except (a-1) to (a-4), and an acrylic copolymer (A) may be abbreviated as a monomer (a-1), a monomer (a-2), a monomer (a-3), a monomer (a-4), a monomer (a-5), and a copolymer (A), respectively.

[0060] In addition, unless otherwise specified, various components appearing in the present specification may be used alone or in combination of two or more.

[0061] 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.

[0062] "Adhesive"

[0063] The adhesive disclosed herein comprises an acrylic copolymer (A), a polyolefin (B) and a hardener (C), wherein:

[0064] The acrylic copolymer (A) is a copolymer of a monomer mixture containing all of the following monomers (a-1) to (a-4), and,

[0065] Satisfy all of the following (1) to (3).

[0066] (a-1) C1-4 alkyl (meth)acrylate monomer

[0067] (a-2) C 6-12 alkyl (meth)acrylate monomer

[0068] (a-3) Monomer having a hydroxyl group

[0069] (a-4) Monomer having a carboxyl group

[0070] (1) In 100% by mass of the monomer mixture, the mass % of (a-1) is less than the mass % of (a-2)

[0071] (2) In 100% by mass of the monomer mixture, (a-3) / (a-4), which is obtained by dividing the mass % of (a-3) by the mass % of (a-4), is 0.01<(a-3) / (a-4)<6

[0072] (3) When a 50 μm thick adhesive layer obtained from the adhesive is attached to glass and left to stand at 23° C. and 50% relative humidity (hereinafter referred to as 50% RH) for 24 hours, the adhesive strength is 10 N / 25 mm or more.

[0073] <Acrylic copolymer (A)>

[0074] The acrylic copolymer (A) is a copolymer of a monomer mixture containing at least all of the monomers (a-1) to (a-4), and the monomer mixture may contain a monomer (a-5) as necessary.

[0075] (a-1) Alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms

[0076] (a-2) Alkyl (meth)acrylate monomers having an alkyl group with 6 to 12 carbon atoms

[0077] (a-3) Monomer having a hydroxyl group

[0078] (a-4) Monomer having a carboxyl group

[0079] (a-5) Other monomers except (a-1) to (a-4)

[0080] [Monomer (a-1)]

[0081] The monomer (a-1) is an alkyl (meth)acrylate monomer having an alkyl group having 1 to 4 carbon atoms in the molecule, and specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, and tert-butyl (meth)acrylate.

[0082] By containing the monomer (a-1), the cohesive force of the adhesive is improved, a strong adhesive layer is obtained, and the adhesive force can be improved.

[0083] Among these monomers (a-1), methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate are preferred from the viewpoint of cohesive force and adhesive force.

[0084] The content of monomer (a-1) in 100% by mass of the monomer mixture is preferably 2% to 40% by mass, more preferably 5% to 30% by mass. When the content is 2% by mass or more, sufficient cohesion can be easily obtained. In addition, when the content is 40% by mass or less, it is easy to take into account both cohesion and stress relaxation, so it is preferred.

[0085] [Monomer (a-2)]

[0086] The monomer (a-2) is an alkyl (meth)acrylate monomer having an alkyl group having 6 to 12 carbon atoms in the molecule, and specific examples thereof include 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, and dodecyl (meth)acrylate.

[0087] By containing the monomer (a-2), the stress relaxation property of the adhesive is improved, a soft adhesive layer is obtained, and the adhesion can be improved.

[0088] Among these monomers (a-2), 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and dodecyl (meth)acrylate are preferred from the viewpoint of stress relaxation properties and adhesion.

[0089] These monomers (a-2) 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-2) in combination.

[0090] The content of monomer (a-2) in 100% by mass of the monomer mixture is preferably 50% to 98% by mass, more preferably 60% to 90% by mass. By making the content 50% by mass or more, sufficient stress relaxation is easily obtained. In addition, by making the content 98% by mass or less, it is easy to take into account both cohesive force and stress relaxation, so it is preferred.

[0091] [Monomer (a-3)]

[0092] The monomer (a-3) is a monomer having a hydroxyl group.

[0093] The monomer having a hydroxyl group is not limited as long as it has a hydroxyl group in the molecule, and specific examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, allyl alcohol, and 3-butene-1-ol.

[0094] By containing the monomer (a-3), the cohesive force of the adhesive is improved, a strong adhesive layer is obtained, and the adhesive force can be improved.

[0095] Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of cohesive force and adhesive force.

[0096] The content of monomer (a-3) in 100% by mass of the monomer mixture is preferably 0.01% by mass to 4.0% by mass, and more preferably 0.04% by mass to 2.0% by mass. When the content is 0.01% by mass or more, sufficient cohesion can be easily obtained. In addition, when the content is 4.0% by mass or less, it is easy to take into account both cohesion and stress relaxation, so it is preferred.

[0097] [Monomer (a-4)]

[0098] The monomer (a-4) is a monomer having a carboxyl group.

[0099] The carboxyl group-containing monomer is not limited as long as it has a carboxyl group in the molecule, and specific examples thereof include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethylmaleic acid, itaconic acid, citraconic acid, and fumaric acid.

[0100] By containing the monomer (a-4), the cohesive force of the adhesive is improved, a tough adhesive layer is obtained, and the adhesive force can be improved.

[0101] Among these, (meth)acrylic acid is preferred from the viewpoint of cohesive force and adhesive force.

[0102] The content of monomer (a-4) in 100% by mass of the monomer mixture is preferably 0.1% to 5% by mass, and more preferably 0.2% to 4.0% by mass. When the content is 0.1% by mass or more, sufficient cohesion can be easily obtained. In addition, when the content is 5% by mass or less, it is easy to take into account both cohesion and stress relaxation, so it is preferred.

[0103] [Monomer (a-5)]

[0104] The monomer (a-5) is a monomer other than the monomers (a-1) to (a-4). The acrylic copolymer (A) of the present disclosure may contain the monomer (a-5) in addition to the monomers (a-1) to (a-4).

[0105] Examples of the monomer (a-5) include (meth)acrylate monomers other than the monomers (a-1) to (a-4), (meth)acrylic monomers having an epoxy group, (meth)acrylic monomers having an amino group, monomers having an alkyleneoxy group, N-substituted (meth)acrylamide monomers, and other vinyl monomers.

[0106] Examples of the alkyl (meth)acrylate monomer other than the monomers (a-1) to (a-4) include pentyl (meth)acrylate and undecyl (meth)acrylate.

[0107] 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.

[0108] 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.

[0109] 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).

[0110] [Chemistry 1]

[0111]

[0112] [Chemistry 2]

[0113]

[0114] In the general formula (1) and the general formula (2), R1 and R2 are each independently 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, preferably 1≦n≦13 and 1≦m≦5.

[0115] 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 formula (1), R1 is a hydrogen atom, and n=1), methoxydiethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom, and n=2), methoxytriethylene glycol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom, and n=3), methoxypolyethylene glycol #400 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom, and n=9), methoxypolyethylene glycol #600 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom, and n=13), methoxypolyethylene glycol #1000 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom, and n=13), and methoxypolyethylene glycol #1000 acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (1), R1 is a hydrogen atom. , n=23), methoxydiethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a methyl group, n=2), methoxytriethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a methyl group, n=3), methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a methyl group, n=4), methoxypolyethylene glycol #400 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a hydrogen atom, n=9), methoxypolyethylene glycol #600 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a hydrogen atom, n=13), methoxypolyethylene glycol #1000 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the formula (1), R1 is a hydrogen atom, n=23).

[0116] Commercially available products of the monomer represented by the general formula (2) include methoxy tripropylene glycol acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (2), R1 is a hydrogen atom, and m=3), methoxy tripropylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.: in the formula (2), R1 is a methyl group, and m=3)

[0117] Examples of the N-substituted (meth)acrylamide monomer include (meth)acrylamide compounds such as N-methylacrylamide, N-isopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetone acrylamide, and N-(butoxymethyl)acrylamide;

[0118] Compounds containing heterocyclic rings such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholine.

[0119] Examples of the vinyl monomer include vinyl acetate, vinyl crotonate, styrene, and acrylonitrile.

[0120] The content of the monomer (a-5) in 100% by mass of the monomer mixture is preferably 2% to 30% by mass. When the content is 2% by mass or more, the adhesion is further improved. In addition, when the content is 30% by mass or less, it is easy to achieve both cohesive force and adhesion, so it is preferred.

[0121] Regarding the acrylic copolymer (A), in 100% by mass of the monomer mixture constituting the acrylic copolymer (A), the mass % of (a-1) is less than the mass % of (a-2). When the mass % of (a-1) is less than the mass % of (a-2), the stress relaxation property of the adhesive is improved, thereby improving the adhesion.

[0122] Regarding the acrylic copolymer (A), (a-3) / (a-4), which is obtained by dividing the mass % of (a-3) by the mass % of (a-4) in 100 mass % of the monomer mixture constituting the acrylic copolymer (A), is 0.01<(a-3) / (a-4)<6. By 0.01<(a-3) / (a-4)<6, the cohesive force of the adhesive is improved, thereby improving the adhesion. (a-3) / (a-4) may also be 0.30≦(a-3) / (a-4)<6, and (a-3) / (a-4) is more preferably 0.03≦(a-3) / (a-4)≦5.

[0123] [Production of acrylic copolymer (A)]

[0124] The copolymer (A) can be produced by polymerizing a monomer mixture containing (a-1) to (a-4).

[0125] The polymerization may be a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., preferably solution polymerization. The solvent used in the solution polymerization is preferably acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, etc.

[0126] 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.

[0127] The polymerization initiator used in the polymerization is preferably a free radical polymerization initiator. Free radical polymerization initiators are generally peroxides and azo compounds.

[0128] 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.

[0129] Peroxyesters such as tert-butyl peroxybenzoate, tert-butyl peroxyacetate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide;

[0130] 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)valerate;

[0131] Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and 2,5-dimethylcyclohexane-2,5-dihydroperoxide;

[0132] Diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, and 2,4-dichlorobenzoyl peroxide;

[0133] Peroxydicarbonates such as bis(tert-butylcyclohexyl)peroxydicarbonate and the like.

[0134] Examples of the azo compound include 2,2'-azobisisobutyronitrile (abbreviation: AIBN (2,2'-azobisisobutyronitrile)), 2,2'-azobis(2-methylbutyronitrile), and the like;

[0135] 2,2'-azobisvaleronitrile such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobispropiononitrile such as 2,2'-azobis(2-hydroxymethylpropiononitrile);

[0136] 1,1'-Azobis(cyclohexane-1-carbonitrile) and other 1,1'-azobis-1-alkanenitrile and the like.

[0137] 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.

[0138] [Weight average molecular weight (Mw)]

[0139] The weight average molecular weight of the copolymer (A) is preferably 800,000 to 1.8 million, more preferably 1 million to 1.5 million. If it is in the range of 800,000 to 1.8 million, the cohesive force is further improved, and the moisture and heat resistance and heat resistance are further improved. In addition, the weight average molecular weight is a value of polystyrene conversion measured by gel permeation chromatography (GPC). The details are described in the column of the examples.

[0140] <Polyolefin (B)>

[0141] The adhesive disclosed herein comprises a polyolefin (B). The polyolefin (B) disclosed herein forms a high cohesion domain when forming an adhesive layer, thereby achieving the effect of exhibiting high cohesion and high adhesion. As a result, durability, flexibility, and windability are improved.

[0142] Polyolefin (B) is divided into modified polyolefin and unmodified polyolefin.

[0143] Specific examples of the modified polyolefin include acid-modified polyolefin, chlorinated polyolefin, and acid-modified chlorinated polyolefin.

[0144] Among the modified polyolefins, examples of the acid-modified polyolefin include Hardlen M-100, Hardlen M-300, Hardlen M-312, Hardlen PMA-H1100P, Hardlen PMA-F2 (manufactured by Toyobo Co., Ltd.), Umex 100TS, Umex 1001, Umex 1010, Umex 5200 (manufactured by Sanyo Chemical Industries, Ltd.), Auroren 150S, Auroren 2000, and Umex 10010. 0S, Auroren 350S, Auroren 353S (manufactured by Nippon Paper Industries, Ltd.), Unistole XP01B, Unistole XP11B, Unistole XP03F, Unistole XP04A, Unistole H-100, Unistole H-200 (manufactured by Mitsui Chemicals, Ltd.), Diacarna 30M, Surflen P1000 (manufactured by Mitsubishi Chemical Corporation), etc.

[0145] Examples of the chlorinated polyolefin include Hardlen 13-LP, Hardlen 13-LLP, Hardlen 15-LP, Hardlen F-2P (manufactured by Toyobo Co., Ltd.), Superchlon C, Superchlon L-206, Superchlon 813A, Superchlon 803M, Superchlon 803MW, Superchlon 1026, Superchlon 803L, Superchlon 814HS, and Superchlon 390S (manufactured by Nippon Paper Industries, Ltd.).

[0146] Examples of the acid-modified chlorinated polyolefin include Hardlen CY-9122P, Hardlen CY-9124P, Hardlen M-28P, Hardlen F-2P, Hardlen F-6P (manufactured by Toyobo Co., Ltd.), Superchlon 822, Superchlon 892L, Superchlon 930, Superchlon 842LM, and Superchlon 851L.

[0147] Examples of the unmodified polyolefin include polyethylene, polypropylene, α-olefin-propylene copolymers, ethylene-vinyl acetate copolymers, polybutene, polybutadiene and hydrogenated products thereof, polyisoprene and hydrogenated products thereof, process oils, and lubricating oils such as liquid paraffin.

[0148] Among these polyolefins (B), modified polyolefins are preferred from the viewpoint of compatibility with the acrylic copolymer (A), and chlorinated polyolefins and acid-modified chlorinated polyolefins are more preferred from the viewpoint of durability. Specifically, as the chlorinated polyolefin, Superchlon 390S is particularly preferred, and as the acid-modified chlorinated polyolefin, Hardlen CY-9122P, Hardlen CY-9124P, Hardlen M-28P, and Hardlen F-2P are particularly preferred.

[0149] These polyolefins (B) can be used alone or in combination of two or more.

[0150] The polyolefin (B) is preferably contained in an amount of 0.05 to 5 parts by mass, more preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 4.0 parts by mass, relative to 100 parts by mass of the copolymer (A). If the content is 0.1 parts by mass or more, heat resistance and adhesion are further improved, and if the content is 5 parts by mass or less, transparency can be maintained.

[0151] <Hardener (C)>

[0152] The adhesive disclosed herein contains a hardener (C). The hardener (C) reacts with the hydroxyl group and / or carboxyl group of the copolymer (A), thereby improving the cohesive force of the adhesive layer and improving durability and stain resistance.

[0153] Examples of the curing agent (C) include isocyanate compounds, epoxy compounds, aziridine compounds, carbodiimide compounds, and metal chelate compounds.

[0154] Among these, the use of an isocyanate compound as the curing agent (C) is preferred because adhesion and durability can be improved.

[0155] The isocyanate compound is an isocyanate having two or more isocyanate groups, and isocyanate monomers, biuret forms, urate forms, and adducts such as aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, and alicyclic polyisocyanates are preferred.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] The urate body is a trimer of an isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of toluene diisocyanate.

[0162] 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.

[0163] 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. The isocyanate compound is preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a ureate of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, a ureate of toluene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, and a ureate of isophorone diisocyanate, more preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of toluene diisocyanate, and a trimethylolpropane adduct of isophorone diisocyanate.

[0164] 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.

[0165] 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.

[0166] 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, and 09 are preferably used due to their excellent compatibility with organic solvents.

[0167] 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.

[0168] The curing agent (C) is preferably contained in an amount of 0.02 to 4.0 parts by mass, more preferably 0.04 to 1.0 parts by mass, relative to 100% by mass of the copolymer (A). When the content is 0.02 parts by mass or more, the cohesive force is further improved, and when it is 4.0 parts by mass or less, it is easy to achieve both cohesive force and flexibility, which is preferred.

[0169] <Organosilane compounds>

[0170] The adhesive of the present disclosure may further contain an organic silane compound.

[0171] 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;

[0172] Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane;

[0173] 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; alkoxysilane compounds having a mercapto group such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane;

[0174] 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;

[0175] Tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane;

[0176] 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.

[0177] 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 of the copolymer (A).

[0178] 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.

[0179] <Adhesion>

[0180] The adhesive of the present disclosure has an adhesive strength of 10 N / 25 mm or more when a 50 μm thick adhesive layer obtained from the adhesive is attached to glass and left to stand in a 23° C.-50% RH environment for 24 hours. In the adhesive strength measurement, an adhesive is applied to a first polyethylene terephthalate (PET) film after peeling treatment in such a manner that the thickness after drying becomes 50 μm, and the adhesive layer is formed by drying at 100° C. for 3 minutes to remove the solvent. Subsequently, a second PET film after peeling treatment is attached to the surface of the adhesive layer opposite to the surface in contact with the first PET film after peeling treatment. After standing for 7 days at 40° C., an adhesive sheet having an adhesive layer with a thickness of 50 μm is manufactured (structure: PET film after peeling treatment / adhesive layer / PET film after peeling treatment). The second PET film after peeling treatment is peeled off from the adhesive sheet and attached to a PET film with a thickness of 50 μm that has not been peeled off. Then, the first PET film after peeling treatment is peeled off, and the adhesive layer obtained in this way is used as the measurement surface for measurement. Specifically, in the measurement conducted after attaching the measuring surface of the adhesive layer with a thickness of 50 μm obtained by the adhesive disclosed in the present invention to glass and placing it under 23°C-50% RH environment for 24 hours, the adhesive force is preferably 10N / 25mm or more, and more preferably 13N / 25mm or more. By being 10N / 25mm or more, sufficient durability can be obtained. There is no particular upper limit, but it is usually 50.0N / 25mm or less. The details of the measuring method are described in the column of the embodiment.

[0181] <Gel fraction>

[0182] The gel fraction of the adhesive for flexible display 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 improved to obtain a tough adhesive layer, thereby improving durability. If the gel fraction is 90% by mass or less, the stress relaxation property of the adhesive is improved to obtain a soft adhesive layer, thereby improving adhesion.

[0183] [Gel fraction measurement method]

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

[0185] (Formula 1)

[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 of the present disclosure is an adhesive sheet for forming the adhesive layer in a laminate including a light-transmitting substrate and an adhesive layer, that is, the adhesive sheet of the present disclosure is used for bonding a light-transmitting substrate.

[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, 1 is the adhesive layer 1, and 2 is the release film.

[0193] like Figure 1 As shown, the adhesive sheet of the present disclosure has a structure in which release films are formed on both sides of an adhesive layer, and the adhesive layer formed between the release films is an adhesive layer formed of a mixture of an acrylic copolymer (A), a polyolefin (B), and a curing agent (C).

[0194] <Release film>

[0195] There is no particular limitation on the release film, 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 polymethylmethacrylate (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 transparent plastic substrates mentioned above, 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. is also preferably used. 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 in the form of a single layer or multiple layers. In addition, 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 a mixture of an acrylic copolymer (A), a polyolefin (B), and a hardener (C) (hereinafter, sometimes simply referred to as "adhesive") on the release-treated surface of a release film in such a manner that the thickness after drying becomes a predetermined thickness to form an adhesive layer, and then attaching the release film; or coating an adhesive on the release-treated surfaces of two release films in such a manner that the thickness after drying becomes a predetermined thickness to form two adhesive layers respectively, 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. A thickness of the adhesive layer of 10 μm to 500 μm is preferred because sufficient cohesive force can be easily obtained and heat resistance, moisture and heat resistance, flexibility, and windability can be highly balanced.

[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 a suitable width and wound into a roll to have a form of an adhesive tape wound into a roll.

[0204] "Layered"

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

[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, 3 is a light-transmitting substrate (cover plate), 1 is an adhesive layer 1, and 4 is a polarizing plate.

[0208] exist Figure 2In the laminate shown, the light-transmitting substrate (cover plate) is attached to the polarizing plate via an adhesive layer 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 by 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., can also be preferably used. 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 3 is a light-transmitting substrate (cover plate), 1 is an adhesive layer 1, 4 is a polarizing plate, 5 is an adhesive layer 2, 6 is a barrier layer such as silicon nitride, 7 is an organic EL layer, 8 is a support such as polyimide, and 10 is an organic EL unit. In addition, the structure of the display is not limited to Figure 3 .

[0216] exist Figure 3In the display shown, the light-transmitting substrate (cover plate) is attached to the polarizing plate via an adhesive layer (adhesive layer 1) containing the adhesive of the present disclosure, and further attached to the organic EL unit via an adhesive layer for polarizing plate (adhesive layer 2). In this way, the adhesive sheet of the present disclosure can be used in a form in which the transparent adhesive layer formed by the adhesive is attached to the light-transmitting substrate (cover plate) and the polarizing plate, and further the laminate is attached to the organic EL unit via the adhesive layer for polarizing plate.

[0217] For example, in Figure 3 In the embodiment of the present invention, the adhesive of the present invention can be used for either the adhesive layer 1 or the adhesive layer 2 .

[0218] Generally speaking, when the adhesive layer 1 is compared with the adhesive layer 2, the adhesive layer 1 has higher requirements for the quality required of the adhesive layer, and the adhesive disclosed in the present invention has good adhesion and adhesion to the substrate, so it is preferably used for the adhesive layer 1. At this time, the adhesive used to form the adhesive layer 2 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 to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass", "%" means "mass %", and "RH" means relative humidity. In addition, the amount of preparation in the table is part by mass. In addition, the blank column in the table means that no preparation is made.

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

[0223] <Measurement of Weight Average Molecular Weight of Acrylic Copolymer>

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

[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 copolymer (A-1))

[0232] In a reaction container (hereinafter simply referred to as "reaction container") including a stirrer, a thermometer, a reflux cooling tube, a dripping device, and a nitrogen introduction tube, 30 parts of methyl acrylate (MA) as a monomer (a-1), 68.97 parts of 2-ethylhexyl acrylate (EHA) as a monomer (a-2), 0.03 parts of 2-hydroxyethyl acrylate as a monomer (a-3), 1 part of acrylic acid as a monomer (a-4), and 0.2 parts of 2,2'-azobisisobutyronitrile (hereinafter simply referred to as "AIBN") as an initiator were placed, and the atmosphere in the reaction container was replaced with nitrogen. Then, the reaction was started by heating to 60°C while stirring under a nitrogen atmosphere. 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 (A-1) solution having a non-volatile content of 30% and a viscosity of 8000 mPa·s. The weight average molecular weight of the obtained copolymer (A-1) was 1,200,000.

[0233] (Acrylic copolymers (A-2 to A-12, A'-1 to A'-7))

[0234] Copolymers (A-2 to A-12, A'-1 to A'-7) were produced by the same method as that for producing the acrylic copolymer (A-1), except that the compositions and blending amounts (parts by mass) were changed to those shown in Tables 1 and 2.

[0235] Tables 1 and 2 show the weight average molecular weights (Mw) of the obtained copolymers (A-2 to A-12, A′-1 to A′-7).

[0236] [Table 1]

[0237] Table 1.

[0238]

[0239] [Table 2]

[0240] Table 2.

[0241]

[0242] The abbreviations in the table are as follows.

[0243] (Monomer (a-1))

[0244] MA: methyl acrylate (the carbon number of the alkyl group is 1) EA: ethyl acrylate (the carbon number of the alkyl group is 2) BA: butyl acrylate (the carbon number of the alkyl group is 4) (monomer (a-2))

[0245] EHA: 2-ethylhexyl acrylate (the carbon number of the alkyl group is 8)

[0246] OA: Octyl acrylate (the carbon number of the alkyl group is 8)

[0247] DOA: dodecyl acrylate (the carbon number of the alkyl group is 12)

[0248] (Monomer (a-3))

[0249] HEA: 2-Hydroxyethyl Acrylate

[0250] HBA: 4-Hydroxybutyl Acrylate

[0251] (Monomer (a-4))

[0252] AA: Acrylic acid

[0253] MAA: Methacrylic acid

[0254] (Monomer (a-5))

[0255] MEA: 2-methoxyethyl acrylate (a monomer in which R1 is a hydrogen atom and n=1 in the general formula (1))

[0256] ACMO: Acryloylmorpholine

[0257] (Example 1)

[0258] <Preparation of adhesive>

[0259] To 100 parts of the nonvolatile components of the acrylic copolymer (A-1), 0.5 parts of Hardlen M-100 (B-1) as a polyolefin (B), 0.5 parts of a trimethylolpropane adduct of toluene diisocyanate (C-1) as a curing agent (C), 0.1 parts of 3-glycidyloxypropyltrimethoxysilane (S-1) as an organic silane compound, and ethyl acetate in an amount of 20% of the nonvolatile components were mixed and stirred to obtain an adhesive.

[0260] <Manufacturing of adhesive sheets>

[0261] 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 for one week at 40°C to obtain an adhesive sheet.

[0262] (Examples 2 to 16, Comparative Examples 1 to 9)

[0263] Except having changed the kind and compounding amount (mass parts) of the copolymer and the hardener as shown in Table 3, it carried out similarly to Example 1, and obtained the adhesive sheet.

[0264] [Table 3]

[0265] Table 3.

[0266]

[0267] The abbreviations in the table are as follows.

[0268] <Polyolefin (B)>

[0269] B-1: Hardlen M-100 (acid-modified polyolefin, manufactured by Toyobo Co., Ltd.)

[0270] B-2: Umex 100TS (acid-modified polyolefin, manufactured by Sanyo Chemical Industries, Ltd.) B-3: Superchlon 390S (chlorinated polyolefin, manufactured by Nippon Paper Industries, Ltd.) B-4: Hardlen CY-9122P (acid-modified chlorinated polyolefin, manufactured by Toyobo Co., Ltd.) B-5: Hardlen CY-9124P (acid-modified chlorinated polyolefin, manufactured by Toyobo Co., Ltd.) B-6: Hardlen M-28P (acid-modified chlorinated polyolefin, manufactured by Toyobo Co., Ltd.) B-7: Hardlen F-2P (acid-modified chlorinated polyolefin, manufactured by Toyobo Co., Ltd.) B-8: Floblen QB200 (unmodified polyolefin, manufactured by Sumitomo Seika Co., Ltd.)

[0271] <Hardener (C)>

[0272] C-1: Trimethylolpropane adduct of toluene diisocyanate

[0273] C-2: Trimethylolpropane adduct of hexamethylene diisocyanate

[0274] C-3: Trimethylolpropane adduct of xylylene diisocyanate

[0275] C-4: N,N,N',N'-tetraglycidyl-m-xylylenediamine

[0276] C-5: 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane

[0277] <Organosilane compounds>

[0278] S-1: 3-Glycidyloxypropyltrimethoxysilane

[0279] 《Measurement and evaluation of physical properties of adhesive sheets》

[0280] The obtained adhesive sheet was used to evaluate adhesive strength, gel fraction, and the following transparency, heat resistance, moisture and heat resistance, dynamic flex resistance, static flex resistance, and windability.

[0281] <Preparation of test adhesive sheet>

[0282] 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.) at 23° C. and 50% RH using a laminator to prepare a test adhesive sheet consisting of PET film / adhesive layer / release film.

[0283] <Adhesion>

[0284] The test adhesive sheet was cut into a size of 25 mm in width×100 mm in length to prepare a test adhesive sheet 1 including a PET film / adhesive layer / peeling film.

[0285] The release film of the test adhesive sheet 1 was peeled off and attached to an alkali-free glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) using a laminator at 23°C and 50% RH. After being left for 24 hours, the adhesive strength when the sample was peeled off from the alkali-free glass plate was measured using a tensile testing machine ("Tensilon" manufactured by Orientec) in accordance with Japanese Industrial Standards (JIS) Z0237 at a peeling speed of 300 mm / min and a peeling angle of 180°.

[0286] <Gel fraction>

[0287] 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 pasted on a 200-mesh 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.

[0288] Gel fraction (mass %) = ((XY) / X) × 100

[0289] X = mass of adhesive layer before immersion (g)

[0290] Y = Mass of adhesive layer after immersion (g)

[0291] <Transparency>

[0292] The test adhesive sheet 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 2 consisting of a PET film / adhesive layer / peeling film.

[0293] The release film was peeled off from the test adhesive sheet 2, 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 50% RH using a laminator to measure the haze. The haze was measured using a turbidimeter NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd. The evaluation criteria were as follows.

[0294] [Evaluation criteria]

[0295] ○: Haze is less than 1.0 (good).

[0296] ×: Haze is 1.0 or more (poor).

[0297] <Heat resistance, heat and humidity resistance>

[0298] The peeling film is peeled off from the test adhesive sheet 2 prepared separately, and the exposed adhesive layer is pasted on the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% RH atmosphere using a laminator to obtain a test laminate comprising a PET film / adhesive layer / polarizing plate. Next, as a heat resistance test, after being placed at 105°C for 500 hours and cooled at 25°C and 50% RH atmosphere, the generation of bubbles and the floating or 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% RH atmosphere for 500 hours, and after being cooled at 25°C and 50% RH atmosphere, the generation of bubbles and the floating or peeling of the adhesive sheet are visually evaluated under the following conditions. Regarding heat resistance and moisture and heat resistance, evaluation is based on the following three-stage evaluation criteria.

[0299] [Evaluation criteria]

[0300] ◎: No generation of bubbles or floating / peeling was observed, and there was no practical problem at all.

[0301] ○: The generation of bubbles and floating / peeling were observed at less than 5 locations, but there was no problem in practical use.

[0302] ×: Generation of bubbles, floating, and peeling were observed at 5 or more locations, which is problematic in practical use.

[0303] <Dynamic flexural resistance: flexural resistance [1], flexural resistance [2], flexural resistance [3]>

[0304] The peeling film was peeled off from the separately prepared test adhesive sheet 2, 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% RH using a laminator, thereby obtaining a test laminate comprising 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% RH: flexure resistance [1]; as a heat resistance test at 85°C: flexure resistance [2]; and as a wet heat resistance test at 60°C and 95% RH: flexure resistance [3], so that the inner diameter (diameter) when bent using a bending tester (manufactured by Yuasa System Machinery Co., Ltd.) was 6 mm, and bending and opening at 180° were repeated as one cycle for 300,000 cycles. With regard to dynamic flexure, the appearance after the test was evaluated using the following viewpoints.

[0305] Appearance: The presence or absence of bubbles in the test laminate and the presence or absence of floating or peeling of the adhesive layer were visually evaluated under the following conditions.

[0306] [Evaluation criteria]

[0307] ◎: No generation of bubbles or floating / peeling was observed, and there was no practical problem at all.

[0308] ○: The generation of bubbles and floating / peeling were observed at less than 5 locations, but there was no problem in practical use.

[0309] ×: Generation of bubbles, floating, and peeling were observed at 5 or more locations, which is problematic in practical use.

[0310] <Static flexural resistance: flexural resistance[1], flexural resistance[2], flexural resistance[3]>

[0311] The peeling film is peeled off from the separately prepared test adhesive sheet 2, and the exposed adhesive layer is pasted to the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% RH atmosphere using a laminator to obtain a test laminate comprising PET film / adhesive layer / polarizing plate. Next, for the test laminate, the test was tested for bending resistance [1] at 25°C and 50% RH atmosphere as a normal test, bending resistance [2] at 85°C atmosphere as a heat resistance test, and bending resistance [3] at 60°C and 95% RH atmosphere as a wet heat resistance test. The test piece was kept in a bent state with a bending radius of 3 mm and a bending angle of 180° using a planar body unloaded U-shaped expansion and contraction tester with the surface on the polarizing plate side of the test piece as the inner side, and maintained for 240 hours. Regarding static bending, the appearance after the test was evaluated using the following viewpoints.

[0312] Appearance: The presence of bubbles in the test laminate and the presence of floating or peeling of the adhesive layer were visually evaluated under the following conditions.

[0313] [Evaluation criteria]

[0314] ◎: No generation of bubbles or floating / peeling was observed, and there was no practical problem at all.

[0315] ○: The generation of bubbles and floating / peeling were observed at less than 5 locations, but there was no problem in practical use.

[0316] ×: Generation of bubbles, floating, and peeling were observed at 5 or more locations, which is problematic in practical use.

[0317] <Winding properties>

[0318] The peeling film is peeled off from the test adhesive sheet 2 prepared separately, and the exposed adhesive layer is pasted to the polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) at 25°C and 50% RH atmosphere using a laminator to obtain 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 in the long side direction with the surface of 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 50% RH for 240 hours. Regarding the winding property, the appearance after the test is evaluated using the following viewpoints.

[0319] Appearance: The presence of bubbles in the test laminate and the presence of floating or peeling of the adhesive layer were visually evaluated under the following conditions.

[0320] [Evaluation criteria]

[0321] ◎: No generation of bubbles or floating / peeling was observed, and there was no practical problem at all.

[0322] ○: The generation of bubbles and floating / peeling were observed at less than 5 locations, but there was no problem in practical use.

[0323] ×: Generation of bubbles, floating, and peeling were observed at 5 or more locations, which is problematic in practical use.

[0324] [Table 4]

[0325] Table 4.

[0326]

[0327] The abbreviations in the table are as follows.

[0328] Test adhesive sheet and test laminate layer structure

[0329] [A]: PET film / adhesive layer / glass

[0330] [B]: PET film / adhesive layer / polarizing plate

[0331] Test conditions

[0332] Flexibility[1]: 25°C, 50% relative humidity

[0333] Flexibility[2]: 85°C atmosphere

[0334] Flexibility[3]: 60°C, 95% relative humidity

[0335] According to the results in Table 4, it can be confirmed that the adhesive sheets of Examples 1 to 16 have good transparency, heat resistance, moisture and heat resistance, flexibility and windability. Therefore, 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.

[0336] On the other hand, the adhesive sheets of Comparative Examples 1 to 7 could not satisfy all of the above characteristics.

[0337] Description of Figure Numbers

[0338] 1: Adhesive layer 1

[0339] 2: Peel off film

[0340] 3: Translucent substrate (cover plate)

[0341] 4: Polarizing plate

[0342] 5: Adhesive layer 2

[0343] 6: Barrier layer

[0344] 7: Organic EL layer

[0345] 8: Support body

[0346] 9: Organic EL unit

[0347] The present disclosure includes the following embodiments.

[0348] (Item 1)

[0349] An adhesive, characterized in that it comprises an acrylic copolymer (A), a polyolefin (B) and a hardener (C),

[0350] The acrylic copolymer (A) is a copolymer of a monomer mixture containing all of the following monomers (a-1) to (a-4), and,

[0351] Satisfy all of the following (1) to (6).

[0352] (a-1) Alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms

[0353] (a-2) Alkyl (meth)acrylate monomers having an alkyl group with 6 to 12 carbon atoms

[0354] (a-3) Monomer having a hydroxyl group

[0355] (a-4) Monomer having a carboxyl group

[0356] (1) In 100% by mass of the monomer mixture, the mass % of (a-1) is less than the mass % of (a-2).

[0357] (2) In 100 mass % of the monomer mixture, (a-3) / (a-4) obtained by dividing the mass % of (a-3) by the mass % of (a-4) is 0.30<(a-3) / (a-4)<5.00.

[0358] (3) The adhesive strength between a 50 μm thick adhesive layer formed of the adhesive and glass after being left to stand at 23° C. and a relative humidity of 50% for 24 hours is 10 N / 25 mm or more.

[0359] (4) The content of (a-4) in 100% by mass of the monomer mixture is 0.1% by mass to 5% by mass.

[0360] (5) The polyolefin (B) includes at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, and acid-modified chlorinated polyolefins.

[0361] (6) The polyolefin (B) is contained in an amount of 0.1 to 5 parts by mass based on 100 parts by mass of the acrylic copolymer (A).

[0362] (Item 2)

[0363] The adhesive according to item 1, wherein the gel fraction is 60% by mass to 90% by mass.

[0364] (Item 3)

[0365] The adhesive according to item 1 or 2, wherein the hardener (C) is an isocyanate compound.

[0366] (Item 4)

[0367] An adhesive sheet includes an adhesive layer, wherein the adhesive layer is a cured product of the adhesive according to any one of items 1 to 3.

[0368] (Item 5)

[0369] A laminated body characterized by comprising a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the adhesive layer is a layer formed of the adhesive according to any one of items 1 to 4.

[0370] (Item 6)

[0371] A display comprises the laminate according to item 5, and an optical element.

[0372] The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2022-167583 filed on October 19, 2022, and all the disclosed contents are incorporated herein by reference.

Claims

1. An adhesive, characterized in that: It comprises an acrylic copolymer (A), a polyolefin (B) and a hardener (C), The acrylic copolymer (A) is a copolymer of a monomer mixture containing all of the following monomers (a-1) to (a-4), and, Satisfy all of the following (1) to (5): (a-1) Alkyl (meth)acrylate monomer having an alkyl group with 1 to 4 carbon atoms (a-2) Alkyl (meth)acrylate monomers having an alkyl group with 6 to 12 carbon atoms (a-3) Monomer having a hydroxyl group (a-4) Monomer having a carboxyl group (1) In 100% by mass of the monomer mixture, the mass % of (a-1) is less than the mass % of (a-2) (2) In the monomer mixture of 100% by mass, (a-3) / (a-4), which is obtained by dividing the mass % of (a-3) by the mass % of (a-4), is 0.30≦(a-3) / (a-4)<6 (3) The adhesive strength between the adhesive layer with a thickness of 50 μm formed by the adhesive and the glass after being placed in an environment of 23° C. and a relative humidity of 50% for 24 hours is 10 N / 25 mm or more. (4) The polyolefin (B) comprises at least one selected from the group consisting of acid-modified polyolefin, chlorinated polyolefin and acid-modified chlorinated polyolefin. (5) The polyolefin (B) is contained in an amount of 0.05 to 5 parts by mass based on 100 parts by mass of the acrylic copolymer (A).

2. The adhesive according to claim 1, wherein The content of (a-4) in 100% by mass of the monomer mixture is 0.1% by mass to 5% by mass.

3. The adhesive according to claim 1 or 2, wherein The polyolefin (B) is contained in an amount of 0.1 to 5 parts by mass based on 100 parts by mass of the acrylic polymer (A).

4. The adhesive according to any one of claims 1 to 3, characterized in that The gel fraction is 60% to 90% by mass.

5. The adhesive according to any one of claims 1 to 4, characterized in that The hardener (C) is an isocyanate compound. 6 . An adhesive sheet comprising an adhesive layer, wherein the adhesive layer is a cured product of the adhesive according to claim 1 .

7. A laminated body, characterized in that: The invention comprises a light-transmitting substrate, an adhesive layer, and a polarizing plate, wherein the adhesive layer is a layer formed of the adhesive according to any one of claims 1 to 5.

8. A display comprising the laminated body according to claim 7, and an optical element.

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