TW201814020A - Adhesive for flexible display, adhesive sheet, flexible laminate member and flexible display excellent in bending resistance and capable of withstanding repeated bending when being applied to a flexible display - Google Patents

Abstract

The subject of the present invention is to provide an adhesive for a flexible display, an adhesive sheet, a flexible laminate member and a flexible display excellent in bending resistance and capable of withstanding repeated bending when being applied to a flexible display. To solve the problem, the adhesive for flexible display is used for adhering one flexible member to another flexible member for constituting a flexible display, which is characterized that: the storage elasticity modulus G'(-20) at -20 DEG C is more than 0.05 MPa and less than 1 MPa, and an elasticity modulus change rate derived by the following formula (1) is more than 350% and less than 10000% based on the aforementioned storage elasticity modulus G'(-20) and the storage modulus G'(40) at 40 DEG C, wherein formula (1) is: elasticity modulus change rate (%) = (G'(-20)/G'(40))×100.

Description

   Adhesive for flexible display, adhesive plate, flexible laminated member, and flexible display   

The present invention relates to an adhesive for a flexible display, an adhesive plate, a flexible laminated member, and a flexible display.

In recent years, as a display body (display) of an electronic device, there is a proposal of a flexible display, a so-called flexible display. Flexible displays are expected to be widely used, for example, as fixed-type displays that can be flexibly installed in a columnar column or the like, or as mobile displays that can be folded or rolled.

Examples of the type of the flexible display include an organic electroluminescence (organic EL) display, an electrophoretic display (electronic paper), and a liquid crystal display using a plastic film as a substrate.

In the flexible display as described above, it is generally considered that a flexible member (flexible member) and other flexible members constituting the flexible display are adhered to an adhesive layer of a plate. Sticky. Here, as the adhesive sheet of a conventional inflexible display, for example, the adhesive sheets shown in Patent Documents 1 and 2 are known.

The flexible display is not only formed once on the curved surface, but may be repeatedly flexed (bent) as described in Patent Document 3. When the conventional adhesive sheet is used for a flexible display for such a purpose, the adhesive layer of the repeatedly flexed portion generates a line or turbidity, which reduces the appearance and reduces the visibility of the display.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-174907

[Patent Document 2] Japanese Patent Laid-Open No. 2016-774

[Patent Document 3] Japanese Patent Laid-Open No. 2016-2764

The present invention has been made in view of the above-mentioned circumstances, and provides an adhesive, an adhesive sheet, and flexibility for a flexible display that are resistant to repeated deflection and have excellent flex resistance when used in a flexible display. Laminated members and flexible displays are targeted.

To achieve the above object, first, the present invention is an adhesive for a flexible display, which is an adhesive for a flexible display for bonding a flexible member constituting a flexible display and other flexible members. , Characterized in that the storage elastic modulus G '(-20) at -20 ° C is 0.05 MPa or more and less than 1 MPa, based on the storage elastic modulus G' (-20) and the storage elastic modulus at 40 ° C. G '(40), the elastic modulus change rate derived from the following formula (1) is 350% or more and 10000% or less: elastic modulus change rate (%) = (G' (-20) / G '(40)) × 100 ... (1) (Invention 1).

Regarding the adhesive of the above invention (Invention 1), it has a G '(-20) and an elastic modulus change rate, and becomes a very soft material having a lot of stress relaxation properties. It is used repeatedly in flexible displays. When bent, it can suppress the occurrence of threads or turbidity in the adhesive layer, and it has excellent flex resistance.

In the above invention (Invention 1), the gel fraction is preferably 60% to 100% (Invention 2).

In the above inventions (Inventions 1, 2), the glass transition temperature (Tg) of the main polymer of the adhesive for flexible displays is preferably -80 ° C or higher and -40 ° C or lower (Invention 3).

Secondly, the present invention provides an adhesive sheet, which is an adhesive sheet having an adhesive layer for adhering a flexible member and other flexible members constituting a flexible display, characterized in that: The layer is formed by the above-mentioned adhesive for flexible displays (Inventions 1 to 3) (Invention 4).

In the above invention (Invention 4), the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched by the release sheet so as to contact the release surfaces of the two release sheets (Invent 5) ).

Thirdly, the present invention provides a flexible laminated member including a flexible member and other flexible members constituting a flexible display, and a flexible member and the other flexible members described above. The flexible laminated member of the adhesive layer with the members adhered to each other is characterized in that the adhesive layer is an adhesive layer (invention 6) of the adhesive sheet (inventions 4 and 5).

In the above invention (Invention 6), it is preferable that at least one of the above-mentioned one flexible member and the other flexible member is a flexible display element (Invention 7).

In the above inventions (Inventions 6, 7), the Young's modulus of the one flexible member and the other flexible members are preferably 0.1 to 10 GPa (Invention 8).

In the above inventions (Inventions 6 to 8), the thickness of the one flexible member and the other flexible members is preferably 10 to 3000 μm, respectively (Invention 9).

In the above inventions (Inventions 6 to 9), the interlayer adhesion between the one flexible member and the other flexible members is preferably 1 to 30 N / 25 mm (Invention 10).

Fourthly, the present invention provides a flexible display comprising the above-mentioned flexible laminated member (Inventions 6 to 10) (Invention 11).

The adhesive and sheet for a flexible display of the present invention, as well as the flexible laminated member and the adhesive layer of a flexible display, are excellent in flex resistance during repeated flexing.

1‧‧‧ Adhesive sheet

11‧‧‧ Adhesive layer

12a, 12b ‧‧‧ peeling sheet

2‧‧‧ Flexible laminated member

21‧‧‧The first flexible member

22‧‧‧ 2nd flexible member

FIG. 1 is a cross-sectional view of an adhesive sheet according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of a flexible laminated member according to an embodiment of the present invention.

Embodiments of the present invention will be described below.

[Adhesive for flexible displays]

The adhesive for a flexible display of the present embodiment (hereinafter, sometimes referred to simply as an "adhesive") is used to adhere a flexible member constituting a flexible display to another flexible member. Agent. The flexible display and the flexible member will be described later.

Regarding the adhesive of this embodiment, the storage elastic modulus G '(sometimes referred to as "G' (-20)" in this specification) at -20 ° C is 0.05 MPa or more and less than 1 MPa, based on G '( -20) and storage elastic modulus G '(sometimes referred to as "G' (40)" in this specification) at 40 ° C. The elastic modulus change rate derived from the following formula (1) is 350% or more and 10,000. %the following.

Elastic modulus change rate (%) = (G '(-20) / G' (40)) × 100 ... (1)

G '(-20) and G' (40) are values measured in accordance with the method of JIS K7244-6, and specific measurement methods are shown in the test examples described later.

The adhesive of this embodiment has a G '(-20) and an elastic modulus change rate as described above, and becomes a very soft material having a lot of stress relaxation properties. When used in a flexible display and repeatedly flexed, It can suppress the appearance of thread or cloudiness in the adhesive layer, and has excellent flex resistance. Therefore, when the flexible display using the adhesive layer formed of the adhesive of the present embodiment is repeatedly flexed with a predetermined portion, deterioration of appearance or visibility can be suppressed at the flexed portion.

From the above viewpoint, G '(-20) is preferably 0.9 MPa or less, and particularly preferably 0.8 MPa or less. The lower limit of the G '(-20) is not particularly limited, but is preferably 0.10 MPa or more, and particularly preferably 0.30 MPa or more.

In addition, the aforementioned elastic modulus change rate is preferably 6000% or less, and particularly preferably 3000% or less. The lower limit value of the elastic modulus change rate is preferably 500% or more, and particularly preferably 800% or more, from the viewpoint of ensuring an appropriate interlayer adhesion.

G '(40) is preferably from 0.005 to 0.28 MPa, more preferably from 0.008 to 0.18 MPa, and further preferably from 0.01 to 0.1 MPa from the viewpoint of easily satisfying the above-mentioned elastic modulus change rate.

Regarding the adhesive of this embodiment, the gel fraction is preferably 60% or more, particularly preferably 65% or more, and more preferably 70% or more. In addition, the gel fraction is preferably 100% or less, particularly preferably 95% or less, and further preferably 90% or less. Regarding the adhesive of this embodiment, by making the gel fraction 60% or more, stress relaxation can be maintained and flex resistance can be further improved. The method of measuring the gel fraction is as shown in the test examples described later.

The glass transition temperature (Tg) of the main polymer (the polymer constituting the adhesive and the polymer with the largest mixing ratio) of the adhesive of this embodiment is preferably -40 ° C or lower, and particularly -45 ° C or lower Preferably, it is more preferably -50 ° C or lower. The glass transition temperature (Tg) is preferably -80 ° C or higher, particularly -75 ° C or higher, and further preferably -70 ° C or higher. By setting the glass transition temperature (Tg) of the main polymer of the adhesive of this embodiment to -40 ° C or lower, the elastic modulus of the adhesive is not easily changed in the actual temperature range, and it is easy to satisfy the above. Rate of change in elastic modulus. The method for measuring the glass transition temperature (Tg) is shown in the test example described later.

The type of the adhesive of this embodiment is not particularly limited as long as it satisfies the above-mentioned physical properties. For example, any of an acrylic adhesive, a polyester adhesive, a polyurethane adhesive, a rubber adhesive, and a silicone adhesive. Either can be used. In addition, the adhesive may be any of a latex type, a solvent type, and a solventless type, and may also be a bridged type or a non-bridged type.

Among the above, an acrylic adhesive that satisfies the above-mentioned physical properties and is also excellent in adhesive physical properties and optical characteristics is preferred. The acrylic adhesive may include a main polymer having no bridge, or may include a main polymer bridged by a bridging agent. Considering the ease with which the above-mentioned physical properties are satisfied, it is preferable to include a main polymer bridged by a bridging agent. Here, the main polymer of the acrylic adhesive is usually a (meth) acrylate polymer. In addition, (meth) acrylic acid means both acrylic acid and methacrylic acid in this specification. Other similar terms are the same. In addition, "polymer" also includes the concept of "copolymer".

As for the adhesive agent of this embodiment, the adhesive composition containing the (meth) acrylate polymer (A) and the bridge | crosslinking agent (B) mentioned below as a main polymer is preferable (henceforth, may be called "Adhesive composition P".) Bridged adhesive. The adhesive obtained by bridging the adhesive composition P (hereinafter, sometimes referred to as "adhesive Q") is particularly easy to satisfy the physical properties described above.

(1) Ingredients of the adhesive composition P

(1-1) (meth) acrylate polymer (A)

The (meth) acrylate polymer (A) contains an alkyl (meth) acrylate having 2 to 20 carbon atoms in the alkyl group, and a monomer having a reactive functional group in the molecule (reactive functional group-containing) The monomer) is preferably a monomer unit constituting the polymer.

The (meth) acrylic acid ester polymer (A) can exhibit good adhesion by using an alkyl (meth) acrylic acid ester having 2 to 20 carbon atoms in the alkyl group as a monomer unit constituting the polymer. . As the alkyl (meth) acrylate having 2 to 20 carbon atoms in the alkyl group, the glass transition temperature (Tg) of the homopolymer is -40 ° C or lower (hereinafter, sometimes referred to as "low Tg alkyl acrylate Ester. " By containing the low-Tg alkyl acrylate as a constituent monomer unit, the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment can be easily set to the above range, and the elastic modulus change can be easily satisfied. rate.

Examples of the low Tg alkyl acrylate include, for example, n-butyl acrylate (Tg-55 ° C), n-octyl acrylate (Tg-65 ° C), isooctyl acrylate (Tg-58 ° C), and acrylic acid 2 -Ethylhexyl (Tg-70 ° C), isononyl acrylate (Tg-58 ° C), isodecyl acrylate (Tg-60 ° C), isodecyl methacrylate (Tg-41 ° C), methacrylic acid N-lauryl ester (Tg-65 ° C), tridecyl acrylate (Tg-55 ° C), tridecyl methacrylate (-40 ° C), and the like. Among them, from the viewpoint of more effectively reducing the rate of change of the elastic modulus, as the low Tg alkyl acrylate, it is preferable that the Tg of the homopolymer is -45 ° C or lower, and particularly preferably -50 ° C or lower. Specifically, n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. These may be used alone or in combination of two or more. The term "alkyl (meth) acrylate having 2 to 20 carbon atoms in the alkyl group" refers to a linear, branched, or cyclic alkyl group.

The (meth) acrylate polymer (A) is preferably such that the lower limit of the low Tg alkyl acrylate as a monomer unit constituting the polymer is 60% by mass or more, particularly 80% by mass or more. Preferably, the content is more than 90% by mass. When the low-Tg alkyl acrylate is contained in an amount of 60% by mass or more, the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment can be more easily set in the above range.

In addition, the (meth) acrylate polymer (A) is preferably such that the upper limit of the low-Tg alkyl acrylate as a monomer unit constituting the polymer is 99.9% by mass or less, and particularly 99% It is preferably at most% by mass, and more preferably at most 98% by mass. When the low-Tg alkyl acrylate is contained in an amount of 99.9% by mass or less, an appropriate amount of other monomer components (in particular, a reactive functional group-containing monomer) can be introduced into the (meth) acrylate polymer (A).

On the other hand, the (meth) acrylate polymer (A) is preferably a homopolymer in order to easily set the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment to the above range. The content of the monomer (hereinafter, sometimes referred to as “hard monomer”) having a glass transition temperature (Tg) of more than 0 ° C. is as small as possible. Specifically, as the monomer unit constituting the polymer, the (meth) acrylate polymer (A) preferably has a hard monomer content upper limit of 15% by mass or less, and particularly preferably 10% by mass. The content is preferably as follows, and more preferably 5% by mass or less. The hard monomer also includes a reactive functional group-containing monomer described later.

Examples of the hard monomer include methyl acrylate (Tg10 ° C), methyl methacrylate (Tg105 ° C), ethyl methacrylate (Tg65 ° C), n-butyl methacrylate (Tg20 ° C), methyl Isobutyl acrylate (Tg48 ° C), third butyl methacrylate (Tg107 ° C), n-octadecyl acrylate (Tg30 ° C), n-octadecyl methacrylate (Tg38 ° C), cyclohexyl acrylate (Tg15 ° C ), Cyclohexyl methacrylate (Tg66 ° C), phenoxyethyl acrylate (Tg5 ° C), phenoxyethyl methacrylate (Tg54 ° C), benzyl methacrylate (Tg54 ° C), isopropyl acrylate Ester (Tg94 ° C), isoamyl methacrylate (Tg180 ° C), acrylic morpholine (Tg145 ° C), adamantyl acrylate (Tg115 ° C), adamantyl methacrylate (Tg141 ° C), acrylic acid ( Tg103 ° C), acrylic monomers such as dimethylacrylamide (Tg89 ° C), acrylamide (Tg165 ° C), vinyl acetate (Tg32 ° C), styrene (Tg80 ° C), and the like.

The (meth) acrylate polymer (A) includes a reactive functional group-containing monomer as a monomer unit constituting the polymer, and a reactive functional group derived from the reactive functional group-containing monomer is described later. The bridging agent (B) reacts to form a bridging structure (three-dimensional network structure), and an adhesive having a desired cohesive force can be obtained.

The reactive functional group-containing monomer contained in the (meth) acrylate polymer (A) as a monomer unit constituting the polymer is preferably a monomer having a hydroxyl group in the molecule (hydroxyl-containing monomer) ), A monomer having a carboxyl group in the molecule (carboxyl-containing monomer), a monomer having an amine group in the molecule (amine-containing monomer), and the like. Among these, a hydroxyl-containing monomer is particularly preferred. There are many hydroxyl-containing monomers having a glass transition temperature (Tg) of 0 ° C or lower, and the glass transition temperature (Tg) of the main polymer of the adhesive of the present embodiment can be easily set within the above range.

Examples of the hydroxyl-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-methacrylate Hydroxybutyl (meth) acrylate and the like, such as hydroxybutyl, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. Among them, from the point of glass transition temperature (Tg), the reactivity of the hydroxyl group of the obtained (meth) acrylate polymer (A) with the bridging agent (B), and the copolymerizability with other monomers, Preferably, at least one of 2-hydroxyethyl acrylate or 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among them, acrylic acid is preferred in terms of the reactivity of the carboxyl group of the obtained (meth) acrylate polymer (A) with the bridging agent (B) and the copolymerizability with other monomers. These may be used alone or in combination of two or more.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, n-butylaminoethyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

The (meth) acrylate polymer (A) is preferably such that the lower limit value of the reactive functional group-containing monomer as a monomer unit constituting the polymer is 0.1% by mass or more, particularly 0.5% by mass. The above is more preferable, and the content is more preferably 1% by mass or more. In addition, the (meth) acrylate polymer (A) is a reactive functional group-containing monomer which is a monomer unit constituting the polymer, and the upper limit is preferably 30% by mass or less, and particularly 20% by mass. It is preferably at most%, and more preferably at most 8 mass%. The (meth) acrylate polymer (A) contains a reactive functional group-containing monomer, particularly a hydroxyl group-containing monomer, in the above-mentioned amount. As a monomer unit, the gel fraction of the obtained adhesive can be easily made. Fall into the above range.

The (meth) acrylic acid ester polymer (A) is preferably acrylic acid that does not include a carboxyl group-containing monomer, particularly a hard monomer, as a monomer unit constituting the polymer. Since the carboxyl group is an acid component, by not containing a carboxyl group-containing monomer, it is possible to prevent the adhesion target of the adhesive from being abnormal due to acid. For example, when a tin-doped indium oxide (ITO) transparent conductive film or a metal film is present, , Such abnormalities (corrosion, resistance change, etc.) due to acid.

The (meth) acrylate polymer (A) may contain other monomers as a monomer unit constituting the polymer, if desired. As the other monomer, a reactive functional group-containing monomer is not hindered, and a monomer having no reactive functional group is preferably not used. Examples of the other monomer include, for example, methoxyacrylate (meth) acrylate and alkoxyalkyl (meth) acrylate, such as ethoxyethyl (meth) acrylate. The monomer having a glass transition temperature (Tg) of the polymer exceeding -40 ° C to 0 ° C (hereinafter, sometimes referred to as "medium Tg alkyl acrylate") and the like. Examples of the intermediate Tg alkyl acrylate include, for example, ethyl acrylate (Tg-20 ° C), isobutyl acrylate (Tg-26 ° C), 2-ethylhexyl methacrylate (Tg-10 ° C), N-lauryl acrylate (Tg-23 ° C), isooctadecyl acrylate (Tg-18 ° C) and the like. These may be used alone or in combination of two or more.

The polymerization state of the (meth) acrylate polymer (A) may be a random copolymer or a block copolymer.

The lower limit of the weight average molecular weight of the (meth) acrylate polymer (A) is preferably 200,000 or more, particularly 400,000 or more, and more preferably 600,000 or more. By setting the lower limit of the weight average molecular weight of the (meth) acrylate polymer (A) to the above, it is possible to suppress abnormalities such as bleeding of the adhesive. In addition, the weight average molecular weight in this specification is a standard polystyrene conversion value measured by the gel permeation chromatography (GPC) method.

The upper limit of the weight average molecular weight of the (meth) acrylate polymer (A) is preferably 2 million or less, particularly 1.5 million or less, and more preferably 900,000 or less. By setting the upper limit value of the weight average molecular weight of the (meth) acrylate polymer (A) to be not more than the above, the interlayer adhesion of the obtained adhesive can easily fall into a suitable range described later.

In addition, in the adhesive composition P, (meth) acrylate polymer (A) may be used individually by 1 type, and may be used in combination of 2 or more type.

(1-2) bridging agent (B)

When the adhesive composition P containing the bridging agent (B) is heated, the bridging agent (B) bridges the acrylate polymer (A) to form a three-dimensional network structure. Thereby, the cohesive force of the obtained adhesive can be improved, and at the same time, the gel fraction of the adhesive easily falls into the above range, and the flex resistance is further improved.

The bridging agent (B) may be any compound capable of reacting with a reactive group of the (meth) acrylate polymer (A), and examples thereof include an isocyanate-based bridging agent, an epoxy-based bridging agent, Amine bridging agent, melamine bridging agent, aziridine bridging agent, hydrazine bridging agent, aldehyde bridging agent, The oxazoline bridging agent, metal alkoxy compound bridging agent, metal chelate bridging agent, metal salt bridging agent, ammonium salt bridging agent, etc. Among the above, when the reactive group of the (meth) acrylate polymer (A) is a hydroxyl group, it is preferable to use an isocyanate-based bridging agent having excellent reactivity with the hydroxyl group. The (meth) acrylate polymer ( A) When the reactive group has a carboxyl group, it is preferable to use an epoxy-based bridging agent having excellent reactivity with a carboxyl group. The bridging agent (B) may be used alone or in combination of two or more.

Isocyanate-based bridging agents include those containing at least a polyisocyanate compound. Examples of the polyisocyanate compound include aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; aliphatic polyisocyanates such as hexamethylene isocyanate; isophorone diisocyanate Alicyclic polyisocyanates, such as hydrogenated diphenylmethane diisocyanate, etc., and these bisureton bodies, trimeric isocyanate bodies, and further ethylene glycol, propylene glycol, neopentyl glycol, and trimethylolpropane, Adducts of reactants of compounds containing low-molecular active hydrogen such as castor oil. Among them, from the viewpoint of reactivity with a hydroxyl group, trimethylolpropane-denatured aromatic polyisocyanates are preferred, and especially trimethylolpropane-modified toluene diisocyanate and trimethylolpropane-modified xylene diisocyanate are used as good.

Examples of the epoxy-based bridging agent include 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl-methane -Xylene diamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidyl aniline, diglycidyl amine, and the like. Among these, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane is preferred from the viewpoint of reactivity with a carboxyl group.

The content of the bridging agent (B) in the adhesive composition P is preferably 0.01 parts by mass or more relative to 100 parts by mass of the (meth) acrylate polymer (A), and particularly preferably 0.05 parts by mass or more. More preferably, it is 0.1 mass part or more. The content is preferably 10 parts by mass or less, particularly 8 parts by mass or less, and further preferably 5 parts by mass or less. When the content of the bridging agent (B) is within the above range, the gel fraction of the obtained adhesive can easily fall within the above range.

(1-3) Various additives

To the adhesive composition P, various additives commonly used in acrylic adhesives can be added, if desired, for example, silane coupling agents, ultraviolet absorbers, antistatic agents, adhesion-imparting agents, oxidation inhibitors, light stabilizers, and softening agents. Agent, filler, refractive index adjuster, etc. It should be noted that a polymerization solvent or a diluting solvent described later is not included in the additives constituting the adhesive composition P.

(2) Production of adhesive composition P

The adhesive composition P can be produced by producing a (meth) acrylate polymer (A), mixing the obtained (meth) acrylate polymer (A) with a bridging agent (B), and adding it as desired. Additive.

The (meth) acrylate polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a usual radical polymerization method. The polymerization of the (meth) acrylate polymer (A) is preferably carried out by a solution polymerization method using a polymerization initiator as desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

Examples of the polymerization initiator include an azo compound, an organic peroxide, and the like, and two or more of them may be used in combination. As the azo compound, include, e.g., 2,2 '- azobisisobutyronitrile, 2,2' - azobis (2-methylbutyronitrile), 1,1 '- azobis (cyclo hexane-1-carbonitrile), 2,2 '- azobis (2,4-dimethylvaleronitrile), 2,2' - azobis (2,4-dimethyl-4-methoxy yl valeronitrile), dimethyl 2,2 '- azobis (2-methylpropionate), 4,4' - azobis (4-cyanovaleric acid), 2,2 '- even azobis (2-hydroxymethylpropionitrile), 2,2 '- azobis [2- (2-imidazolin-2-yl) propane] and the like.

Examples of the organic peroxide include, for example, benzamidine peroxide, tert-butyl peroxybenzoate, cumene hydrogen peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, Di (2-ethoxyethyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxytrimethylacetate, 3,5,5-trimethylhexanonium peroxide, Dipropylammonium peroxide, diethylammonium peroxide, etc.

In the above polymerization step, the weight-average molecular weight of the obtained polymer can be adjusted by blending a chain transfer agent such as 2-mercaptoethanol.

A (meth) acrylate polymer (A) is obtained, and a solution of the (meth) acrylate polymer (A) is added, and a bridging agent (B) is added, and additives and a diluting solvent are mixed as required, and the mixture is sufficiently mixed. An adhesive composition P (coating solution) diluted with a solvent was obtained.

In addition, when any one of the above-mentioned components uses a solid substance, or when precipitation occurs when mixing with other components in a state without dilution, the component may be separately dissolved or diluted with a dilution solvent in advance. And mix with other ingredients.

Examples of the diluting solvent include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as dichloromethane and dichloroethane; methanol, ethanol, Alcohols such as propanol, butanol, 1-methoxy-2-propanol, acetone, methyl ethyl ketone, 2-pentanone, isophorone, cyclohexanone and other ketones, ethyl acetate, acetic acid Esters such as butyl esters, and celestial solvents such as ethyl celex and the like.

The concentration and viscosity of the coating solution prepared in this manner are not particularly limited as long as they are within the applicable range, and can be appropriately selected according to the situation. For example, the concentration of the adhesive composition P is diluted to 10 to 60% by mass. When a coating solution is obtained, the addition of a diluent solvent or the like is not necessary, and the diluent solvent may not be added as long as the adhesive composition P has a coatable viscosity. At this time, the adhesive composition P becomes a coating solution in which a polymerization solvent of the (meth) acrylate polymer (A) is directly used as a dilution solvent.

(3) Manufacturing of adhesive Q

A preferable adhesive Q, which is an adhesive according to this embodiment, is formed by bridging the adhesive composition P. The bridging of the adhesive composition P can usually be performed by heat treatment. In addition, this heat treatment may also be used as a drying treatment when the coating film applied to the adhesive composition P applied to a desired object volatilizes a diluent solvent or the like.

The heating temperature of the heat treatment is preferably 50 to 150 ° C, and particularly preferably 70 to 120 ° C. In addition, the heating time is preferably 10 seconds to 10 minutes, and particularly preferably 50 seconds to 2 minutes.

After the heat treatment, a maturation period of about 1 to 2 weeks may be set at normal temperature (for example, 23 ° C., 50% RH) as required. When this aging period is required, after the aging period has elapsed, and when no aging period is required, the heat treatment is completed to form the adhesive Q.

Through the heat treatment (and maturation) described above, the (meth) acrylate polymer (A) is sufficiently bridged through the bridging agent (B) to form a bridging structure to obtain an adhesive Q. The adhesive Q is particularly easy to satisfy the storage elastic modulus and the elastic modulus change rate.

[Adhesive plate]

The adhesive sheet of this embodiment has an adhesive layer for adhering one flexible member and other flexible members constituting a flexible display, and the adhesive layer is formed of the above-mentioned adhesive.

The specific structure of an example of the adhesive sheet of this embodiment is shown in FIG.

As shown in FIG. 1, the adhesive sheet 1 according to one embodiment is composed of two peeling sheets 12 a and 12 b and two peeling faces connected to the peeling surfaces of the two peeling sheets 12 a and 12 b. The release sheet 12a, 12b of the sheet is composed of an adhesive layer 11 sandwiched therebetween. In addition, the peeling surface of the peeling sheet of this specification means the surface which has peelability in a peeling sheet, and includes the surface which performed the peeling process, and the surface which shows peelability even if it does not perform a peeling process.

(1) Components

(1-1) Adhesive layer

The adhesive layer 11 is composed of the adhesive according to the embodiment described above, and is preferably composed of the adhesive Q bridged by the adhesive composition P.

Regarding the thickness of the adhesive layer 11 of the adhesive sheet 1 according to this embodiment (value measured in accordance with JIS K7130), the lower limit value is preferably 5 m or more, particularly 10 m or more, and more preferably 20 m or more. The upper limit of the thickness of the adhesive layer 11 is preferably 300 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less. When the thickness of the adhesive layer 11 is within the above-mentioned range, a desired adhesive force is easily exhibited, and it is more excellent in flex resistance. In addition, the adhesive layer 11 may be formed in a single layer, or may be formed by laminating a plurality of layers.

(1-2) Peeling sheet

The peeling sheets 12a and 12b are used to protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 of this embodiment, one or both of the peeling sheets 12a and 12b are not necessary.

As the release sheet 12a, 12b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, Polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene (Meth) acrylic copolymer film, ethylene (meth) acrylate copolymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. In addition, such a bridging film can be used. Furthermore, such a laminated film may be used.

It is preferable that the peeling surfaces (particularly the surfaces that are in contact with the adhesive layer 11) of the peeling sheet pieces 12a and 12b be subjected to a peeling treatment. Examples of the release agent used for the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents. In addition, among the peeling sheets 12a and 12b, one of the peeling sheets is a heavy peeling peeling sheet having a large peeling force, and the other peeling sheet is a light peeling peeling sheet having a small peeling force. Better.

The thickness of the release sheet 12a, 12b is not particularly limited, but is usually about 20 to 150 μm.

(2) Physical properties (full light transmittance)

Regarding the total light transmittance (value measured in accordance with JIS K7361-1: 1997) of the adhesive layer 11 of the adhesive sheet 1 of this embodiment, it is preferably 80% or more, particularly 90% or more, and further preferably Above 99% is preferred. When the total light transmittance is 80% or more, it has high transparency and is suitable for optical applications (for display bodies). When the adhesive layer 11 is composed of the adhesive Q, it is easy to satisfy the above-mentioned total light transmittance.

(3) Manufacturing of adhesive sheet

A case where the adhesive composition P is used as an example of the production of the adhesive sheet 1 will be described. On the release surface of one release sheet 12a (or 12b), the coating liquid of the adhesive composition P is applied, and heat treatment is performed to thermally bridge the adhesive composition P to form a coating layer. The release surface of the release sheet 12b (or 12a) is laminated with this coating. When the ripening period is required, the ripening period is left, and when the ripening period is not required, the coating layer directly becomes the adhesive layer 11. Thereby, the above-mentioned adhesive sheet 1 can be obtained. The conditions for heat treatment and aging are as described above.

As another manufacturing example of the adhesive sheet 1, the coating liquid of the adhesive composition P is applied to the peeling surface of one release sheet 12a, and heat treatment is performed to bridge the adhesive composition P to form a coating. Layer to obtain a release sheet 12a with a coating layer. In addition, the coating liquid of the adhesive composition P is applied to the release surface of the other release sheet 12b, and the heat treatment is performed to bridge the adhesive composition P to form a coating layer to obtain a coating. Layer of release sheet 12b. Then, the release sheet 12a with the coating layer and the release sheet 12b with the coating layer are adhered so that the two coating layers are in contact with each other. When the ripening period is required, the ripening period is left, and when the ripening period is not required, the coating layer directly becomes the adhesive layer 11. Thereby, the above-mentioned adhesive sheet 1 can be obtained. According to this manufacturing example, even when the adhesive layer 11 is thick, it can be manufactured stably.

As a method of applying the coating liquid of the above-mentioned adhesive composition P, for example, a bar coating method, a blade coating method, a roll coating method, a blade coating method, a die coating method, or a gravure coating method can be used. Wait.

[Flexible laminated member]

As shown in FIG. 2, the flexible laminated member 2 according to this embodiment has a configuration including a first flexible member 21 (a flexible member) and a second flexible member 22 (other flexible members). Flexible member); and an adhesive layer 11, which is located between these, and the first flexible member 21 and the second flexible member 22 are adhered to each other.

The adhesive layer 11 of the flexible laminated member 2 is the adhesive layer 11 of the adhesive sheet 1.

The flexible laminated member 2 is a flexible display itself or a member constituting a part of the flexible display. Here, the so-called flexible display is a flexible display, and is preferably a display that can be flexed repeatedly (including bending), and examples thereof include organic electroluminescence (organic EL) displays and electrophoretic displays. (Electronic paper), a liquid crystal display, a foldable display, etc. using a plastic substrate (film) as a substrate, or a touch panel.

The first flexible member 21 and the second flexible member 22 are flexible members, and are preferably members that can be flexed repeatedly (including bending), and examples thereof include a cover film, a barrier film, and polarized light. Film, polarizer, retardation film, viewing angle compensation film, brightness enhancement film, contrast enhancement film, diffusion film, transflective film, electrode film, transparent conductive film, metal mesh film, film sensor, liquid crystal polymer Thin films, light-emitting polymer films, thin film liquid crystal modules, organic EL modules (organic EL thin films), electronic paper modules (thin film electronic paper), and the like.

Among the above, it is preferable that at least one of the first flexible member 21 and the second flexible member 22 is a flexible display element, and specifically, it is a liquid crystal polymer film, a light emitting polymer film, or a thin film. Liquid crystal module, organic EL module (organic EL film), or electronic paper module (thin film electronic paper).

The Young's modulus of the first flexible member 21 and the second flexible member 22 is preferably 0.1 to 10 GPa, particularly 0.5 to 7 GPa, and more preferably 1.0 to 5 GPa. By setting the Young's modulus of the first flexible member 21 and the second flexible member 22 within this range, each flexible member can be easily flexed repeatedly.

The thickness of the first flexible member 21 and the second flexible member 22 is preferably 10 to 3000 μm, particularly 25 to 1000 μm, and more preferably 50 to 500 μm. When the thicknesses of the first flexible member 21 and the second flexible member 22 are within this range, each of the flexible members can easily be flexed repeatedly.

The lower limit of the interlayer adhesion (adhesive force) between the first flexible member 21 and the second flexible member 22 is preferably 1N / 25mm or more, particularly preferably 2N / 25mm or more. 5N / 25mm or more is preferred. When the adhesion between the layers is 1N / 25mm or more, it is excellent in flex resistance as a flexible display. In addition, the upper layer adhesion is preferably 30N / 25mm or less, more preferably 25N / 25mm or less, and particularly preferably 20N / 25mm or less. When the interlayer adhesion is 20 N / 25 mm or less, excellent reworkability can be achieved. Thereby, even when an error occurs in the adhesion between the flexible members, the two can be easily peeled off, and the flexible member (especially the expensive flexible member) can be reused.

Here, the interlayer adhesion (adhesive force) in this specification is basically the adhesive force measured by the 180 degree pull-peel method in accordance with JIS Z0237: 2009, but the measurement sample is 25mm wide and 100mm long. The laminated body formed by 1 flexible member / adhesive layer / second flexible member is pressed at 0.5 MPa and 50 ° C for 20 minutes, and then left under normal pressure, 23 ° C and 50% RH for 24 hours. After an hour, it was measured at a peeling speed of 300 mm / min.

In manufacturing the above-mentioned flexible laminated member 2, as an example, one of the release sheet 12 a of the adhesive sheet 1 is peeled off, and the exposed adhesive layer 11 and the first flexible member 21 of the adhesive sheet 1 are peeled off. One side is glued.

After that, the other release sheet 12b is peeled from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is adhered to the second flexible member 22 to obtain a flexible laminate. Component 2. In addition, as another example, the bonding order of the first flexible member 21 and the second flexible member 22 may be changed.

[Flexible display]

The flexible display of this embodiment is a thing provided with the said flexible laminated body 2, It may be formed only with the flexible laminated body 2, or it may be equipped with the multiple flexible laminated body 2 and other flexible Sexual components. When a flexible laminated member 2 is laminated with other flexible laminated members 2 or when the flexible laminated member 2 is laminated with other flexible members, the above-mentioned adhesive sheet 1 is used for adhesion. The agent layer 11 is preferably laminated.

With regard to the flexible display of this embodiment, since the flexible member is laminated using the adhesive layer 11 having excellent flexibility resistance, it is possible to suppress the adhesive layer 11 from being bent when the flexible portion is repeatedly bent at a predetermined portion. Part of the appearance is reduced or visibility is reduced.

The embodiments described above are described for easy understanding of the present invention and are not described for limiting the present invention. Therefore, each element disclosed in the said embodiment is the summary including all the design changes or an equivalent thing which belongs to the technical scope of this invention.

For example, one or both of the release sheets 12 a and 12 b of the adhesive sheet 1 may be omitted, and a desired optical member may be laminated instead of the release sheets 12 a and / or 12 b.

[Example]

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

[Example 1]

1. Preparation of (meth) acrylate polymer (A)

47.8 parts by mass of n-butyl acrylate, 47.8 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of acrylic acid, and 0.4 parts by mass of 2-hydroxypropyl acrylate were polymerized to prepare a (meth) acrylate polymer (A). The molecular weight of this (meth) acrylate polymer (A) was measured by the method described later, and the weight average molecular weight (Mw) was 600,000.

2. Preparation of adhesive composition

100 parts by mass (solid content conversion value; the same applies hereinafter) of the (meth) acrylate polymer (A) obtained in the above step 1 and 0.9 parts by mass of trimethylolpropane-denatured toluenediene as a bridging agent (B) Isocyanate (manufactured by TOYO CHEM Corporation, product name "BHS8515") was mixed, sufficiently stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition P.

3. Manufacture of adhesive sheet

The obtained coating solution of the adhesive composition was applied with a doctor blade coater to a heavy-peeling type release sheet having a silicone-based release agent for peeling one side of a polyethylene terephthalate film. (Manufactured by LINTEC, product name "SP-PET752150"). Then, the coating layer was heat-treated at 90 ° C. for 1 minute to form a coating layer.

Next, the coating layer on the obtained heavy release type release sheet was subjected to a release treatment with a silicone-based release agent on one side of the polyethylene terephthalate film. The light release type release sheet (LINTEC Corporation) (Product name: "SP-PET382120"), adhered in such a way that the release-treated surface of the light release-type release sheet is in contact with the coating layer, and matured for 7 days at 23 ° C and 50% RH to produce a thickness of 25 μm The pressure-sensitive adhesive sheet of the adhesive layer is a pressure-sensitive adhesive sheet formed of a structure of a heavy release type release sheet / adhesive layer (thickness: 25 μm) / light release type release sheet. The thickness of the adhesive layer is a value measured in accordance with JIS K7130 using a constant pressure thickness measuring device (manufactured by TECLOCK, product name "PG-02").

Here, when (meth) acrylate polymer (A) is 100 mass parts (solid content conversion value), each formulation (solid content conversion value) of an adhesive composition is shown in Table 1. Details of the abbreviations and the like described in Table 1 are as follows.

[(Meth) acrylate polymer (A)]

BA: n-butyl acrylate

2EHA: 2-ethylhexyl acrylate

AA: Acrylic

2HPA: 2-hydroxypropyl acrylate

4HBA: 4-hydroxybutyl acrylate

MMA: methyl methacrylate

HEA: 2-hydroxyethyl acrylate

ACMO: N-acrylic morpholine

IBXA: isoamyl acrylate

[Cross-linking agent (B)]

TDI: Trimethylolpropane modified toluene diisocyanate (manufactured by TOYO CHEM, product name "BHS-8515")

XDI: Trimethylolpropane denatured xylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")

Epoxy: 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name "TETRAD-C")

[Examples 2 to 3, Comparative Examples 1 to 5]

The type and ratio of each monomer constituting the (meth) acrylate polymer (A), the weight average molecular weight (Mw) of the (meth) acrylate polymer (A), and the type and Except having changed the compounding quantity as shown in Table 1, it carried out similarly to Example 1, and produced the adhesive sheet.

[Test Example 1] (Measurement of glass transition temperature)

Polymerization of (meth) acrylic acid esters produced in Examples and Comparative Examples was measured using a differential scanning calorimeter (manufactured by TA Instruments Japan, product name "DSC Q2000") under conditions of temperature rise and temperature decrease of 20 ° C / min. Glass transition temperature (Tg) of the substance (A). The results are shown in Table 1.

[Test Example 2] (Measurement of storage elastic modulus (G '))

A plurality of layers of the adhesive layer of the adhesive sheet produced in the examples and comparative examples were laminated to form a laminated body having a thickness of 3 mm. From the laminated body of the obtained adhesive layer, a cylindrical body (height 3 mm) with a diameter of 8 mm was punched out, and this was used as a sample.

Regarding the above-mentioned samples, the storage elastic modulus (G ') (MPa) was measured by a shearing method in accordance with JIS K7244-6 using a viscoelasticity measuring device (DYNAMIC ANALAYZER manufactured by REOMETRIC Corporation) under the following conditions. The results are shown in Table 1.

Measurement frequency: 1Hz

Measurement temperature: -20 ℃, 0 ℃, 23 ℃, 40 ℃

When the storage elastic modulus at -20 ° C is G '(-20) and the storage elastic modulus at 40 ° C is G' (40), the elastic modulus derived from the following formula (1) is calculated. Rate of change. The results are shown in Table 1.

Elastic modulus change rate (%) = (G '(-20) / G' (40)) × 100 ... (1)

[Test Example 3] (Measurement of gel fraction)

The adhesive sheets obtained in the examples and comparative examples were cut into a size of 80 mm × 80 mm, and this adhesive layer was packaged in a polyester mesh (mesh size 200). The mass was measured with a precision balance and the above polyester was deducted. The net mass alone is used to calculate the mass of only the adhesive. Let the mass at this time be M1.

Next, the adhesive packaged in the polyester net was immersed in ethyl acetate at room temperature (23 ° C) for 24 hours. After that, the adhesive was taken out and air-dried in an environment at a temperature of 23 ° C and a relative humidity of 50% for 24 hours, and further dried in an oven at 80 ° C for 12 hours. After drying, weigh the mass with a precision balance and subtract the individual mass of the net to calculate the mass of the adhesive only. Let the mass at this time be M2. The gel fraction (%) is expressed as (M2 / M1) × 100. The results are shown in Table 1.

[Test Example 4] (Measurement of total light transmittance)

The adhesive layer of the adhesive sheet obtained by the Example and the comparative example was adhere | attached to glass, and it was set as the measurement sample. After measuring with glass as a background, the above-mentioned measurement sample was measured for total light transmittance (%) using a haze meter (manufactured by Nippon Denshoku Industries, Inc., product name "NDH-2000") in accordance with JIS K7361-1: 1997. . The results are shown in Table 1.

[Test Example 5] (Measurement of adhesion (adhesion between layers))

In an environment of 23 ° C. and 50% RH, the light-peeling type peeling sheet was peeled from the adhesive sheets obtained in the examples and comparative examples, and the exposed adhesive layer was mixed with polyparaphenylene as the first flexible member. One surface of a polyethylene diformate (PET) film (manufactured by Toyobo Corporation, product name "Cosmoshine 4300", thickness: 100 µm) was adhered. Next, the heavy release type peeling sheet is peeled off, and the exposed adhesive layer and polyparaphenylene terephthalate, which is a transparent conductive film made of tin-doped indium oxide (ITO), is provided on one side of the second flexible member. The surface of the transparent conductive film side of the ethylene formate ester film (made by Oike Industries, Ltd., ITO film, thickness: 125 μm) was adhered. Then, in a high-pressure reactor manufactured by Kurihara Seisakusho Co., Ltd., it was pressurized at 0.5 MPa and 50 ° C. for 20 minutes, and then left under conditions of 23 ° C. and 50% RH for 24 hours. The laminated body (flexible laminated member) formed of the PET film / adhesive layer / ITO film thus obtained was cut into a width of 25 mm and a length of 100 mm, and this was used as a sample.

For the above samples, a PET film was pulled and peeled under a condition of a peeling speed of 300 mm / min and a peeling angle of 180 degrees using a universal tensile tester (product name "Tensilon UTM-4-100" manufactured by ORIENTEC) to measure the adhesive force. (N / 25mm) as the interlayer adhesion. Conditions other than those described here are measured in accordance with JIS Z0237: 2009. The results are shown in Table 1.

[Test Example 6] (Measurement of Young's Modulus of Flexible Member)

The first and second flexible members (PET film and ITO film) used in Test Example 5 were cut into 10 mm × 70 mm test pieces. Then, in accordance with JIS K7161: 1994, the Young's modulus at 23 ° C and 50% RH was measured. Specifically, the above test piece was subjected to a tensile test at a speed of 200 mm / min using a universal tensile tester (manufactured by ORIENTEC, product name "Tensilon RTA-T-2M") with a clamp pitch of 20 mm, The Young's modulus (unit: GPa) was measured. As a result, the Young's modulus of the PET film and the ITO film were both 4.2 GPa.

[Test Example 7] (Flexibility test)

In an environment of 23 ° C and 50% RH, the light-peeling type peeling sheet was peeled from the adhesive sheets obtained in Examples and Comparative Examples, and the exposed adhesive layer was mixed with polyethylene terephthalate (PET ) One side of a film (manufactured by Toyobo Corporation, product name "Cosmoshine 4300", thickness: 100 µm) was adhered. Next, the heavy release type peeling sheet was peeled off, and the exposed adhesive layer and another polyethylene terephthalate (PET) film (manufactured by Toyobo Corporation, product name "Cosmoshine 4300", thickness: 100 μm ) On one side. Then, in a high-pressure reactor manufactured by Kurihara Seisakusho Co., Ltd., it was pressurized at 0.5 MPa and 50 ° C. for 20 minutes, and then left under conditions of 23 ° C. and 50% RH for 24 hours. The thus obtained laminated body formed of the PET film / adhesive layer / PET film was cut into a width of 50 mm and a length of 200 mm, and this was used as a sample.

The obtained sample was repeatedly flexed under the following conditions using a durability tester (product name of "Uta-shaped unloaded U-shaped expansion and contraction tester" manufactured by YUASA SYSTEM). Thereafter, the sample was placed on a horizontal table, and one end portion in the longitudinal direction of the sample was fixed to a table top, and the other end of the sample was measured for a vertical distance (deflection amount) from the table top. The results are shown in Table 1.

Minimum deflection diameter: 4mmφ

Deflection times: 30,000 times

Test temperature: 23 ° C

Moreover, regarding the sample after completion | finish of the said test, the external appearance of a bending part was evaluated visually by the following reference | standard. The results are shown in Table 1.

(Double-circle): There is no line of a bending part.

(Circle): Although the line of a bending part exists, it is hardly noticed when viewed from the front.

△: A line with a bent portion is present, and the presence of the line can be confirmed when viewed from the front, but the line is not cloudy.

×: A line of the flexure is present, and the line is cloudy and conspicuous. Or the adhesive peels off from the substrate.

[Table 1]     

As can be seen from Table 1, the adhesive layer of the adhesive sheet of the example has excellent flex resistance and excellent optical characteristics. In addition, the flexible laminated member obtained by using the adhesive sheet of the example has a good interlayer adhesion.

    [Industrial availability]    

The present invention is suitable for bonding a flexible member (such as various films) and other flexible members (such as display elements) constituting a flexible display.

Claims (11)

    An adhesive for flexible displays, which is an adhesive for flexible displays used to adhere a flexible member constituting a flexible display to other flexible members, and is characterized in that it is stored at -20 ° C. The elastic modulus G '(-20) is 0.05 MPa or more and less than 1 MPa. Based on the storage elastic modulus G' (-20) and the storage elastic modulus G '(40) at 40 ° C, the following formula (1) The derived elastic modulus change rate is from 350% to 10000%: the elastic modulus change rate (%) = (G '(-20) / G' (40)) × 100 ... (1).         The adhesive for flexible displays according to item 1 of the scope of patent application, wherein the gel fraction is 60% or more and 100% or less.         The adhesive for a flexible display according to item 1 of the patent application scope, wherein the glass transition temperature (Tg) of the main polymer of the adhesive for the flexible display is -80 ° C or higher and -40 ° C or lower.         An adhesive sheet is an adhesive sheet having an adhesive layer for adhering a flexible member and other flexible members constituting a flexible display, characterized in that the above-mentioned adhesive layer is applied for by a patent The flexible display described in the range 1 is formed with an adhesive.         The adhesive sheet according to item 4 of the scope of patent application, wherein the adhesive sheet includes two release sheets, and the adhesive layer is peeled off so as to be connected to the release surface of the two release sheets. Plate clamping.         A flexible laminated member is provided with a flexible member and other flexible members constituting a flexible display; and an adhesive layer for adhering the flexible member and the other flexible members to each other. The flexible laminated member is characterized in that the above-mentioned adhesive layer is the adhesive layer of the adhesive sheet described in item 4 of the scope of patent application.         The flexible laminated member according to item 6 of the scope of the patent application, wherein at least one of the flexible member and the other flexible member is a flexible display element.         According to the flexible laminated member described in item 6 of the scope of the patent application, the Young's modulus of the one flexible member and the other flexible members is 0.1 to 10 GPa, respectively.         According to the flexible laminated member described in item 6 of the scope of the patent application, the thickness of the one flexible member and the other flexible members is 10 to 3000 μm, respectively.         The flexible laminated member according to item 6 of the scope of the patent application, wherein the interlayer adhesion between the one flexible member and the other flexible members is 1 to 30 N / 25 mm.         A flexible display comprising the flexible laminated member according to any one of claims 6 to 10 of the scope of patent application.