KR20220158458A - Adhesive composition, and adhesive sheet and stacked structure prepared from the same - Google Patents

Abstract

The present invention relates to an adhesive composition, and more specifically, to an adhesive composition including an acrylic copolymer, a curing agent, and an amine-based additive. An adhesive layer or an adhesive sheet formed from the adhesive composition can provide excellent adhesive durability, reliability, and flexibility even under severe conditions such as high temperature and high humidity. In addition, provided is a stack for an image display device including the adhesive layer and having improved folding characteristics and durability.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet and laminate prepared therefrom

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet and a laminate prepared therefrom. More specifically, the present invention relates to a pressure-sensitive adhesive composition containing an acrylic copolymer, a pressure-sensitive adhesive sheet prepared therefrom, and a laminate for an image display device.

For example, an adhesive or a pressure-sensitive adhesive sheet may be used to bond a display panel of an image display device such as a liquid crystal display (LCD) device or an organic light emitting display (OLED) device to various optical structures or circuit structures. The pressure-sensitive adhesive needs to have improved transparency and excellent adhesion so as not to degrade the optical properties of the image display device.

Recently, displays having excellent reliability under harsh conditions of high temperature and high humidity or external physical impact have been actively studied, and accordingly, a structure coupled to the display can also prevent the structure from falling off or peeling despite harsh conditions or external impact. It needs to be formed so that Accordingly, there is a need for a pressure-sensitive adhesive or pressure-sensitive adhesive sheet having excellent wettability and durability and capable of bonding the display structure.

For example, Korean Patent Publication No. 2010-0039274 discloses an adhesive for a polarizing plate applied to an image display device.

Korean Patent Publication No. 2010-0039274

One object of the present invention is to provide an adhesive composition capable of forming an adhesive layer having improved adhesive properties and durability.

One object of the present invention is to provide an adhesive sheet and a laminate having improved adhesive properties and durability.

1. Acrylic copolymer; a curing agent having a crosslinkable functional group; and an amine-based additive having a propylene oxide group and an amine end group.

2. The pressure-sensitive adhesive composition according to 1 above, wherein the amine-based additive has at least three amine end groups.

3. The pressure-sensitive adhesive composition according to 2 above, wherein at least one of the amine end groups is a primary amine group.

4. The pressure-sensitive adhesive composition according to 2 above, wherein the amine-based additive includes a compound represented by Formula 1 below:

[Formula 1]

(In Formula 1, R ₁ is an aliphatic hydrocarbon having 1 to 10 carbon atoms, R ₂ is a single bond or a methylene group, R ₃ and R ₄ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is 1 to an integer of 40).

5. The pressure-sensitive adhesive composition according to 2 above, wherein the amine-based additive includes a compound represented by Formula 2 below:

[Formula 2]

(In Formula 2, R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms,

x, y and z are each independently an integer from 1 to 35;

x+y+z is an integer from 40 to 100).

6. The pressure-sensitive adhesive composition according to 1 above, wherein the amine-based additive has a weight average molecular weight of 1,000 to 10,000 g/mol.

7. The pressure-sensitive adhesive composition according to 1 above, wherein the curing agent comprises a thermosetting agent containing an isocyanate group.

8. The pressure-sensitive adhesive composition according to 1 above, wherein the content of the amine-based additive is 1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer.

9. The pressure-sensitive adhesive composition according to 1 above, wherein the content of the curing agent is 0.1 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer.

10. A pressure-sensitive adhesive sheet comprising an adhesive layer formed from a pressure-sensitive adhesive composition containing an acrylic copolymer and an amine-based additive and satisfying the following Equation 1:

[Equation 1]

50≤A/B≤320

(In Equation 1, A is the storage modulus at 25° C. of the pressure-sensitive adhesive sheet, and B is the elongation at break at a thickness of 1 mm of the pressure-sensitive adhesive sheet).

11. The pressure-sensitive adhesive sheet according to 10 above, wherein the amine-based additive has a propylene oxide group and an amine end group.

12. The pressure-sensitive adhesive sheet according to 11 above, wherein the amine-based additive includes a compound represented by Formula 2 below:

[Formula 2]

(In Formula 2, R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms,

x, y and z are each independently an integer from 1 to 35;

x+y+z is an integer from 40 to 100).

13. The adhesive sheet according to 10 above, comprising a base film laminated on at least one surface of the adhesive layer.

14. First subject; an adhesive layer disposed on an upper surface of the first object and formed of the adhesive composition according to claim 1; and a second object disposed on the upper surface of the adhesive layer, wherein the first object and the second object are each independently a polarizer, a window cover film, a protective film, a touch screen panel, a display panel, or at least one of these. A laminate for an image display device comprising a laminated structure of.

The pressure-sensitive adhesive composition according to embodiments of the present invention may include an acrylic copolymer, a curing agent having a crosslinkable functional group, and an amine additive having a propylene oxide group and an amine terminal group. Accordingly, an adhesive layer having excellent adhesive durability and reliability and improved adhesion even under severe conditions (high temperature and high humidity) can be provided.

In addition, the pressure-sensitive adhesive sheet according to exemplary embodiments may have excellent bending characteristics and durability as the storage modulus and elongation have a predetermined ratio. For example, it is effectively applied to the bonding of various structures of flexible displays, and improved adhesion durability and flexibility can be maintained even in repeated operations such as folding and bending.

1 is a cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.
2 to 4 are cross-sectional views illustrating a laminate for an image display device according to exemplary embodiments.

The pressure-sensitive adhesive composition according to embodiments of the present invention includes an acrylic copolymer, a curing agent having a crosslinkable functional group, and an amine additive containing a propylene oxide group and an amine end group, and exhibits excellent adhesion even under harsh conditions such as high temperature and high humidity. It is possible to form an adhesive sheet having durability, adhesion and improved folding characteristics.

Hereinafter, the present invention will be described in detail.

<Adhesive composition>

Pressure-sensitive adhesive compositions according to embodiments of the present invention include an acrylic copolymer.

The acrylic copolymer may include a polymer polymerized by including a (meth)acrylate monomer. As used herein, the term "(meth)acrylate" is used to encompass either acrylate or methacrylate.

In some embodiments, the (meth)acrylate monomer may be a (meth)acrylate monomer having an alkyl group having 1 to 14 carbon atoms.

For example, as an example of a (meth)acrylate monomer having an alkyl group having 1 to 14 carbon atoms, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth) Acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (metha)acrylate )Acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n- Tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentafluorooctyl acrylate, 6-(1-naphthyloxy)-1-hexyl acrylate, etc. are mentioned. These can be used individually or in combination of 2 or more types.

In some embodiments, the (meth)acrylate monomer may be included in 80 to 99 parts by weight based on 100 parts by weight of the total monomers used in preparing the acrylic copolymer. If the content of the (meth)acrylate monomer is less than 80 parts by weight, adhesive strength and adhesion may be reduced. If the content is more than 99 parts by weight, cohesive force may be lowered and durability may be lowered.

In some embodiments, the acrylic copolymer may be polymerized by further including a crosslinkable monomer copolymerizable with the (meth)acrylate monomer.

For example, the crosslinkable monomer may be a carboxyl group-containing monomer, a phosphoric acid group-containing monomer, a sulfonic acid group-containing monomer, a cyano group-containing monomer, a vinyl ester, an aromatic vinyl compound, an acid anhydride group-containing monomer, a hydroxy group-containing monomer, an amide group-containing monomer, An amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, or an ether group-containing monomer may be included. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, and the like.

Examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate and the like.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acrylamido-2-methylpropanesulfonic acid, ) Acryloyloxynaphthalenesulfonic acid, sodium vinylsulfonate, etc. are mentioned.

Examples of the cyano group-containing monomer include (meth)acrylonitrile and the like.

Examples of the vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate.

Examples of the aromatic vinyl compound include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrene.

Examples of the acid anhydride-containing monomer include maleic anhydride, itaconic anhydride, and acid anhydrides thereof.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. , 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methylacrylate, N- methylol (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like.

Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, (meth)acryloylmorpholine, and the like. can be heard

Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

Examples of the ether group-containing monomer include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate and acrylonitrile. ilmorpholine etc. are mentioned.

The crosslinkable monomer may be included in 0.05 to 10 parts by weight, preferably 1 to 8 parts by weight, based on 100 parts by weight of the total monomers used in the preparation of the acrylic copolymer. In the above range, the adhesive strength and cohesion of the pressure-sensitive adhesive composition may be excellent, and the adhesion durability of the cured product may be improved.

In addition to the above monomers, other polymerizable monomers known in the art may be further included in an amount that does not reduce adhesive strength, for example, 10 parts by weight or less based on 100 parts by weight of the total monomers used in the preparation of the acrylic copolymer.

In some embodiments, a photopolymerization initiator may be used to polymerize the (meth)acrylate monomer and/or the crosslinkable monomer.

For example, the photopolymerization initiator is benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, 1-hydroxycyclohexyl -1-phenylmethanone, hydroxydimethylacetophenone, dimethylaminoacetophenone, dimethoxy-2-phenylacetophenone, 3-methylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2- Diethoxy-2-phenylacetophenone, 4-chlorocetophenone, 4,4-dimethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-hydroxycyclophenylketone , 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, oligo[2-hydroxy-2-methyl-1 -(4-(1-methylvinyl)phenyl)propanone], 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4 ,4-diaminobenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone Quinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, diphenylketonebenzyl Dimethylketal, acetophenonedimethylketal, p-dimethylaminobenzoic acid ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), fluorene, triphenylamine, carbazole, azobisisobutyronitrile (AIBN ) and the like. These can be used individually or in combination of 2 or more types.

For example, the amount of the photopolymerization initiator may be 0.01 to 1 part by weight based on 100 parts by weight of all monomers used in the preparation of the acrylic copolymer.

The method for producing the acrylic copolymer is not particularly limited, and may be prepared using methods such as bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization commonly used in the art, preferably using a solution polymerization method. It can be manufactured by In addition, solvents, polymerization initiators, and chain transfer agents for molecular weight control, which are commonly used during polymerization, may be used.

In some embodiments, the acrylic copolymer may have a weight average molecular weight (in terms of polystyrene, Mw) of 50,000 to 2,000,000 g/mol as measured by gel permeation chromatography (GPC). Preferably, the weight average molecular weight may be 300,000 to 1700,000 g/mol. When the weight average molecular weight of the acrylic copolymer is less than 50,000 g/mol, cohesive strength between the copolymers may be insufficient and adhesion durability may be deteriorated. If it exceeds 2,000,000 g/mol, a large amount of diluting solvent may be required to ensure fairness during coating.

The curing agent contains a crosslinkable functional group that reacts with the acrylic copolymer, thereby improving cohesion and adhesion of the pressure-sensitive adhesive composition, and maintaining the shape of the pressure-sensitive adhesive after curing.

For example, an isocyanate group, an epoxy group, an oxazoline group etc. are mentioned as said crosslinkable functional group. These may be included singly or in combination of two or more. For example, the curing agent may include an isocyanate-based compound, an epoxy-based compound, an oxazoline-based compound, and the like.

In some embodiments, the curing agent may include a thermosetting agent containing an isocyanate group. Accordingly, compatibility with acrylic copolymers and amine-based additives is excellent, and heat resistance, heat and humidity resistance, and reliability of the cured product may be further improved.

Examples of the isocyanate-based compound include tolylene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxyl diisocyanate compounds such as rendiisocyanate and naphthalene diisocyanate; An adduct obtained by reacting 3 equivalents of a diisocyanate compound with 1 equivalent of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate product obtained by self-condensation of 3 equivalents of a diisocyanate compound, and a diisocyanate obtained from 2 equivalents of 3 equivalents of a diisocyanate compound. polyfunctional isocyanate compounds containing three functional groups, such as biuret bodies obtained by condensation of the remaining 1 equivalent of diisocyanate with urea, triphenylmethane triisocyanate, and methylene bistriisocyanate; etc. can be mentioned. These may be used alone or in combination of two or more.

As an example of the epoxy-based compound Ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether , neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycy Dyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether , sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3- bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and the like. These may be used alone or in combination of two or more.

Examples of the oxazoline-based compound include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isoprorenyl-2. -Polymerized copolymers including at least one monomer containing an oxazoline group such as oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2oxazoline, etc. can be heard These may be used alone or in combination of two or more.

In some embodiments, the content of the curing agent may be 0.1 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer. When the content of the curing agent is less than 0.1 parts by weight, cohesive force may be reduced due to an insufficient degree of crosslinking, and thus, adhesion durability and cutting property may be deteriorated. When the content of the curing agent exceeds 5 parts by weight, it may be difficult to relieve residual stress due to an excessive crosslinking reaction. Preferably, the content of the curing agent may be 0.2 to 1 part by weight based on 100 parts by weight of the acrylic copolymer.

The amine-based additive may contain a propylene oxide group and an amine end group in a molecular structure. When the amine-based additive includes a nitrogen atom capable of hydrogen bonding in its molecular structure, a hydrogen bond may be formed with the acrylic copolymer or the curing agent, and in this case, the elongation of the pressure-sensitive adhesive may increase.

For example, as the amine terminal group has a hydrogen atom or an unshared electron pair, it may form a hydrogen bond with a functional group capable of hydrogen bonding (eg, a hydroxyl group or a carboxyl group) of the acrylic copolymer or curing agent. In this case, as the intermolecular attraction increases, the toughness of the cured product may be improved without decreasing the elastic modulus and adhesion.

In some embodiments, the amine-based additive may contain at least three amine end groups. Since the amine-based additive includes three or more amine end groups capable of forming hydrogen bonds, mechanical properties such as folding properties, heat resistance, and heat and humidity resistance may be excellent.

In some embodiments, the amine terminal group may be a primary amine group, a secondary amine group, or a tertiary amine group.

For example, the secondary amine group or tertiary amine group may have an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms, and more preferably 1 to 3 carbon atoms.

For example, the amine-based additive may include a compound represented by Chemical Formula 1 below.

[Formula 1]

In Formula 1, R ₁ may be an aliphatic hydrocarbon having 1 to 10 carbon atoms, R ₂ may be a single bond or a methylene group, R ₃ and R ₄ may each independently be a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, , n may be an integer from 1 to 40.

In some embodiments, the amine-based additive may include at least one primary amine group as an amine terminal group. For example, the amine terminal group of the amine-based additive may be composed of a primary amine group. In this case, the formation of intermolecular hydrogen bonds may be advantageous due to the high reactivity of the primary amine group. Therefore, flexibility and mechanical properties are improved, so that durability and bending properties of the adhesive layer may be excellent.

According to exemplary embodiments, the amine-based additive may include a compound represented by Chemical Formula 2 below.

[Formula 2]

In Chemical Formula 1, x, y, and z may each independently be an integer of 1 to 40. x+y+z may be an integer of 40 to 100, preferably an integer of 50 to 90. R ₅ may be hydrogen or an alkyl group having 1 to 10 carbon atoms.

For example, as the pressure-sensitive adhesive composition includes the amine-based additive, a cured product or pressure-sensitive adhesive sheet satisfying Equation 1 below may be provided.

[Equation 1]

50≤A/B≤320

In Equation 1, A represents the storage modulus at 25° C. of the cured material or pressure-sensitive adhesive sheet, and B represents the elongation at break of the cured material or gradual sheet at 1 mm thickness.

For example, A is a viscoelasticity measuring device (MCR-301, Anton The storage modulus at 25 ° C measured using Paar Co.) can be represented.

For example, B laminates cured materials or adhesive sheets to a thickness of 1 mm, and then uses a Universal Testing Machine (UTM) to break at a tensile speed of 500 mm/min at 23 ° C and 50% RH. Elongation (%) measured by elongation can be expressed.

In some embodiments, the amine-based additive may have a weight average molecular weight (in terms of polystyrene, Mw) of 1,000 to 10,000 g/mol as measured by gel permeation chromatography (GPC). Preferably, the weight average molecular weight may be 2,500 to 6,000 g/mol. Within the above range, durability under high temperature/high humidity conditions may be improved, and at the same time, adhesion and bending properties may be excellent.

In some embodiments, the content of the amine-based additive may be 1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer. When the content of the amine-based additive is less than 1 part by weight, fewer hydrogen bonds are formed, and thus, bending properties and durability of the cured product may be deteriorated. When the content of the amine-based additive exceeds 10 parts by weight, bending properties may be deteriorated and brittleness may increase due to excessive hydrogen bonding. Preferably, the amount of the amine-based additive may be 1 to 8 parts by weight based on 100 parts by weight of the acrylic copolymer.

In some embodiments, the equivalent ratio (a/b) of the crosslinkable functional group (a) of the curing agent and the amine terminal group (b) of the amine-based additive may be 0.5 to 3, preferably 1 to 2.5 days. can

For example, the equivalent weight of the amine end group means the total number of amine end groups of the amine-based additives included in the pressure-sensitive adhesive composition. For example, the equivalent of the crosslinkable functional group means the total number of crosslinkable functional groups (eg, isocyanate groups) of the curing agent included in the pressure-sensitive adhesive composition.

When the amine end group and the crosslinkable functional group have an equivalence ratio within the above range, the elongation rate of the pressure-sensitive adhesive composition may be improved while preventing excessive stress increase. Accordingly, a cured product having excellent heat resistance and moisture-heat resistance and excellent bending durability can be realized.

The pressure-sensitive adhesive composition according to exemplary embodiments may further include conventional additives known in the art. For example, the antistatic agent, ultraviolet absorber, antioxidant, tackifier, and/or plasticizer may be included.

When the pressure-sensitive adhesive composition includes additives such as an antistatic agent and a tackifier, brittleness may increase while mechanical properties of the composition decrease, and bending characteristics and adhesive durability of the cured product may decrease. However, since the pressure-sensitive adhesive composition according to exemplary embodiments includes an amine-based additive capable of hydrogen bonding, the cured product may have excellent elasticity and wettability, and at the same time, toughness and elongation may be improved.

<Adhesive sheet, laminate, image display device>

The pressure-sensitive adhesive sheet according to embodiments of the present invention may satisfy Equation 1 below.

[Equation 1]

50≤A/B≤320

In Equation 1, A represents the storage modulus at 25° C. of the adhesive sheet, and B represents the elongation at break at a thickness of 1 μm of the adhesive sheet.

For example, A measured the pressure-sensitive adhesive sheet in the temperature range of -30 to 100 ° C. under conditions of a frequency of 1.0 Hz, a strain of 2%, and a heating rate of 5 ° C./min using a viscoelasticity measuring device (MCR-301, Anton Paar). The measured storage modulus at 25°C can be expressed.

For example, B is measured by laminating adhesive sheets to a thickness of 1 mm and then elongating them to breakage at a tensile speed of 500 mm/min at 23°C and 50% RH using a universal testing machine (UTM). One elongation (%) can be expressed.

In Equation 1, when A/B is less than 50, the adhesive strength and adhesive durability of the adhesive sheet may decrease. When A/B is greater than 320, folding characteristics may be deteriorated according to the low elongation compared to the storage modulus, and delamination and peeling of the structure may occur. Preferably, A/B in Equation 1 may be 100 to 300. When the above range is satisfied, adhesion, durability, and flexibility may be excellent, and, for example, a display having a flexible property may be implemented using the adhesive sheet.

The adhesive sheet may include an adhesive layer formed of an acrylic copolymer and an amine-based additive. In some embodiments, the pressure-sensitive adhesive sheet may include an adhesive layer formed from a pressure-sensitive adhesive composition according to exemplary embodiments. For example, the pressure-sensitive adhesive layer may be a cured product of a pressure-sensitive adhesive composition including an acrylic copolymer, a curing agent having a crosslinkable functional group, and an amine additive containing a propylene oxide group and an amine end group.

For example, an adhesive sheet satisfying Equation 1 may be implemented by including an adhesive layer formed from an adhesive composition according to exemplary embodiments. Accordingly, it can have excellent bending and adhesive durability even under severe conditions of high temperature/high humidity.

1 is a schematic cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.

Referring to FIG. 1 , the adhesive sheet includes a base film 120 and an adhesive layer 110 formed on one surface of the base film 120 . For example, the adhesive layer 110 may be formed by coating the aforementioned adhesive composition on one surface of the base film 120 .

The base film 120 is not particularly limited, and a release film commonly used for adhesive sheets may be used. For example, the base film 120 may be a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or polybutyrene naphthalate; polyimide resin; acrylic 　resin; styrene-based resins such as polystyrene and acrylonitrile-styrene; polycarbonate 　 resin; polylactic acid 　resin; polyurethane 　 resin; polyolefins and resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; polyamide = resin; sulfone-based resin; polyether-ether ketone-based resins; Allylate type resin; Alternatively, it may be a release film formed of a mixture of the above resins.

The adhesive layer 110 may be formed by applying the adhesive composition of exemplary embodiments on one surface of the base film 120 and performing a drying and/or curing process. For example, the adhesive layer 110 may be formed by applying the adhesive composition on the base film 120 by a coating method such as roll coating, gravure coating, reverse coating, spray coating, air knife coating, or die coater. .

In some embodiments, the base film 120 may be formed on the upper and lower surfaces of the adhesive layer 110 , respectively. For example, the base film 120 formed on the lower surface of the adhesive layer 110 may be removed and the exposed surface of the adhesive layer 110 may be attached to the object. Thereafter, a laminate may be formed by removing the base film 120 formed on the upper surface and attaching another object to the exposed surface of the adhesive layer 110 .

2 to 4 are schematic cross-sectional views for explaining a laminate according to exemplary embodiments. The laminate may be a laminate for an image display device.

2 to 4, the laminate includes a first object 130, an adhesive layer 110 formed on at least one surface of the first object, and a second object 140 disposed on the adhesive layer 110. can include

In some embodiments, the adhesive layer may be provided in the form of an adhesive sheet in which two base films 120 are attached to both sides of the adhesive layer 110 . For example, after peeling off one base film 120 from the adhesive sheet, the adhesive layer 110 may be bonded onto the first object 130 . Thereafter, by peeling the remaining sheet of the base film 120 and bonding it to the second object 140, for example, a laminate for an image display device may be manufactured.

In some embodiments, the adhesive layer 110 may be formed by directly applying and curing the aforementioned adhesive composition on one surface of the first object 130 . Then, by contacting the second object 140 to the adhesive layer 110, for example, a laminate for an image display device may be manufactured.

The first object 130 and the second object 140 may each include an optical structure known in the art, for example, a polarizer, a retardation film, a hard coating film, a protective film, a window film, and a touch screen panel. , a display panel, and the like, and may have a structure in which two or more of them are combined and stacked. The display panel may be a liquid crystal display panel (LCD) or an organic light emitting display panel (OLED).

In some embodiments, the laminate may be provided as an image display device including a polarizing plate.

For example, an image display device may include a display panel, an adhesive layer disposed on the upper surface of the display panel, and a polarizer attached to the upper surface of the adhesive layer.

The polarizing plate may include a polarizer and a protective film bonded to at least one surface of the polarizer. For example, the adhesive layer may be formed by bonding an adhesive sheet to a protective film, or may be directly coated on a protective film.

The polarizer may be a polarizer known in the art, and may be, for example, one manufactured by swelling, dyeing, crosslinking, stretching, washing with water, and drying a polyvinyl alcohol-based film.

The protective film is not particularly limited as long as it has excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Specifically, polyester-based films such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate; cellulosic films such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based film; acrylic films such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrenic films such as polystyrene and acrylonitrile-styrene copolymer; polyolefin-based film; Vinyl chloride-based film; polyamide-based films such as nylon and aromatic polyamide; Imide-based film; sulfone-based film; polyether ketone-based film; Sulfurized polyphenylene-based film; vinyl alcohol-based film; Vinylidene chloride-based film; vinyl butyral-based film; allylate-based films; polyoxymethylene-based film; Urethane-based film; Epoxy-based film; A silicone type film etc. are mentioned.

The image display device may further include other components known in the art in addition to the above configurations. For example, a retardation film, a hard coating film, a protective film, a window film, a touch panel, and the like may be further included. The components may be adhered to each other by the pressure-sensitive adhesive composition according to exemplary embodiments.

As described above, when the pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition satisfies Equation 1, it may have excellent bending durability and folding characteristics. Therefore, adhesion reliability of the laminate or image display device can be maintained for a long period of time even in repeated bending and folding operations, and breakage, peeling, and lifting of each component can be prevented.

Hereinafter, experimental examples including specific examples and comparative examples are presented to aid understanding of the present invention, but these are only illustrative of the present invention and do not limit the scope of the appended claims, and the scope and technology of the present invention It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope of the spirit, and it is natural that these changes and modifications fall within the scope of the appended claims.

manufacturing example

Preparation Example 1: Preparation of acrylic copolymer (A-1)

97 parts by weight of butyl acrylate (BA), 2 parts by weight of methyl acrylate (MA), and 1 part by weight of hydroxyethyl acrylate (HEA) in a 1L reactor equipped with a cooling device so that nitrogen gas is refluxed and temperature control is easy. After adding the monomer mixture, 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Thereafter, in order to remove oxygen in the reactor, nitrogen gas was introduced for 1 hour to replace the reactor, and then the temperature was maintained at 80°C. After uniformly mixing the above mixture, 0.1 part by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight of about 540,000).

Preparation Example 2: Preparation of acrylic copolymer (A-2)

96 parts by weight of butyl acrylate (BA), 2 parts by weight of methyl acrylate (MA), 1 part by weight of hydroxyethyl acrylate (HEA), After adding a monomer mixture consisting of 1 part by weight of acrylic acid (AA), 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Thereafter, nitrogen gas was introduced into the reactor for 1 hour to replace the reactor, and the temperature was maintained at 80°C. After uniformly mixing the mixture, 0.1 part by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight of about 550,000).

Example

(1) Preparation of pressure-sensitive adhesive composition

After mixing with the ingredients and contents shown in Table 1 below, the pressure-sensitive adhesive compositions of Examples and Comparative Examples were prepared by diluting with ethyl acetate at a solid content of 20% by weight. At this time, the content is parts by weight.

(2) Manufacture of adhesive sheet

An adhesive layer was formed by applying the pressure-sensitive adhesive composition according to Examples or Comparative Examples to a thickness of 20 μm on a release film coated with a silicone release agent and drying at 100° C. for 1 minute. An adhesive sheet was prepared by bonding a release film on the formed adhesive layer.

division
(parts by weight) acrylic copolymer curing agent additive A-1 A-2 B-1 C-1 C-2 C-3 C-4 C-5 Example 1 100 0.5 One Example 2 100 0.5 3 Example 3 100 0.5 5 Example 4 100 0.5 10 Example 5 100 0.5 0.5 Example 6 100 0.5 13 Example 7 100 0.5 18 Example 8 100 0.5 3 Example 9 100 0.5 5 Example 10 100 0.5 3 Example 11 100 0.5 5 Example 12 100 0.5 3 Example 13 100 0.5 5 Example 14 100 0.5 10 Example 15 100 0.5 5 5 Example 16 100 0.5 5 5 Comparative Example 1 100 0.5 One Comparative Example 2 100 0.5 5 Comparative Example 3 100 0.5 One Comparative Example 4 100 0.5 5 Comparative Example 5 100 0.5

The specific component names described in Table 1 are as follows.

acrylic copolymer

A-1: Copolymer prepared in Preparation Example 1

A-2: Copolymer prepared in Preparation Example 2

curing agent

B-1: Coronate-L (manufactured by Nippon Urethane)

additive

C-1: Jeffamine T3000 (Huntsman, molecular weight 3,000)

C-2: Jeffamine T5000 (Huntsman, molecular weight 5,000)

C-3: Jeffamine D2000 (Huntsman, molecular weight 2,000)

C-4: ARUFON UP-1010 (Toagosei, molecular weight 3,000)

C-5: ARUFON UP-1110 (Toagosei, molecular weight 1,700)

Experimental Example

(1) Measurement of storage modulus

The storage modulus at 25° C. of the prepared pressure-sensitive adhesive sheet was measured using a viscoelasticity measuring device (MCR-301, Anton Paar). Specifically, the pressure-sensitive adhesive sheet was cut into a length of 30 mm × width of 30 mm, the release film on one side of the cut pressure-sensitive adhesive sheet was peeled off, and bonded to a glass substrate. Then, in the state of being attached to the measuring tip, measurement is performed under the conditions of a frequency of 1.0 Hz, a strain of 2%, and a heating rate of 5 °C/min in a temperature range of -30 to 100 °C, and the measured value at 25 °C is read. By doing so, the storage modulus was measured.

(2) Measurement of elongation

The release film on one side of the prepared pressure-sensitive adhesive sheet was peeled off, and the exposed adhesive surface was sequentially stacked so that a plurality of pressure-sensitive adhesive sheets had a thickness of about 1 mm. The laminated adhesive sheet is cut into a length of 30 mm × width of 30 mm, the release film of the outermost layer is peeled off, and the tensile speed is 500 mm/min at 23° C. and 50% RH using a universal testing machine (UTM). It was elongated until breakage and the elongation (%) was measured.

(3) Evaluation of folding characteristics

The release film on one side of the prepared adhesive sheet was peeled off, bonded to a PET film having a thickness of 50 μm, and then cut to a length of 20 mm × width of 20 mm to prepare a specimen.

The specimen was fixed to a flexural evaluation device (CFT-720C, COVOTECH), set to be folded with a radius of curvature of 2 mm, and then folded 25 times per minute at -30 ° C, and folding was evaluated under the condition of holding 0.2 seconds after folding once. did One cycle was defined as 1 cycle, and the number of first cycles in which stripes or the like were observed in the folded area, or breakage, lifting, or peeling of the adhesive sheet were observed was evaluated. The folding evaluation was conducted up to 50,000 cycles, and when no stripes or the like were observed at the folding site, or no breakage, lifting, or peeling of the adhesive sheet was observed, it was described as 50,000 cycles.

(4) Adhesion evaluation

A specimen was prepared by cutting the prepared pressure-sensitive adhesive sheet into a length of 250 mm × width of 25 mm. Subsequently, the release film was peeled off and the exposed adhesive sheet surface was attached to alkali-free reinforced glass (EAGLE XG, manufactured by Corning Co.) using a 2 kg roller according to JIS Z 0237. After that, it was allowed to stand for 24 hours under conditions of a temperature of 23° C. and 50% RH. Using an auto graph (AG-1S, manufactured by SHIMADZU), the adhesive force was measured while peeling the adhesive sheet 200 mm from the alkali-free tempered glass at a peeling speed of 2.4 m/min and a peeling angle of 180 ^° .

(5) High temperature reliability evaluation

After the release film on one side of the prepared adhesive sheet was peeled off, the adhesive layer was laminated on an iodine-based polarizing plate including a triacetyl cellulose protective film having a thickness of 185 μm through adhesive processing to prepare a polarizing plate with an adhesive. Thereafter, the release film on the other side of the adhesive sheet was peeled off and a 50 μm thick PET film was bonded to prepare a specimen. After the prepared specimen was left for 10 days under conditions of 85° C. and 85% RH, the occurrence of bubbles or peeling was observed. The evaluation criteria are as follows.

<Evaluation Criteria>

ⓞ: No bubbles or peeling.

○: Bubbles or exfoliation < 5

△: 5 ≤ bubbles or peeling < 10

×: 10 ≤ bubbles or peeling

The results are shown together in Table 2 below.

division Modulus of elasticity (A)
(Pa) Elongation (B)
(%) Modulus of elasticity / elongation
(A/B) Folding characteristics
(cycle) adhesion
(N/25mm) high temperature reliability Example 1 45000 141 319 50000 13 ○ Example 2 41000 191 215 50000 15 ⓞ Example 3 35000 224 156 50000 16 ⓞ Example 4 31000 282 110 50000 17 ⓞ Example 5 46000 137 335 47000 12 △ Example 6 21000 298 70 50000 16 ○ Example 7 15000 319 47 45000 15 △ Example 8 42000 187 224 50000 15 ⓞ Example 9 38000 220 172 50000 16 ⓞ Example 10 44000 137 322 48000 12 ○ Example 11 40000 175 234 50000 13 ○ Example 12 44000 185 238 50000 15 ⓞ Example 13 41000 218 188 50000 16 ⓞ Example 14 37000 274 135 50000 17 ○ Example 15 40000 187 214 50000 15 ○ Example 16 39000 165 236 50000 15 ○ Comparative Example 1 40000 109 365 1800 9 × Comparative Example 2 38000 100 380 1000 7 × Comparative Example 3 42000 110 382 2100 7 × Comparative Example 4 40000 98 408 1500 6 × Comparative Example 5 45400 128 355 41000 10 ×

Referring to Table 2, it can be confirmed that the pressure-sensitive adhesive sheet prepared with the pressure-sensitive adhesive composition according to the above exemplary embodiments satisfies Equation 1, and thus has excellent folding characteristics, adhesion, and durability.

However, since the PSA sheet according to the Comparative Examples did not include the amine-based additive according to the exemplary embodiments, bending properties were not substantially implemented, and adhesion and durability were also deteriorated.

110: adhesive layer 120: base film
130: first object 140: second object

Claims (14)

acrylic copolymers;
a curing agent having a crosslinkable functional group; and
A pressure-sensitive adhesive composition comprising an amine-based additive having a propylene oxide group and an amine terminal group.
The pressure-sensitive adhesive composition according to claim 1, wherein the amine-based additive has at least three amine end groups.
The pressure-sensitive adhesive composition of claim 2, wherein at least one of the amine end groups is a primary amine group.
The pressure-sensitive adhesive composition of claim 2, wherein the amine-based additive includes a compound represented by Formula 1 below:
[Formula 1]

(In Formula 1, R ₁ is an aliphatic hydrocarbon having 1 to 10 carbon atoms, R ₂ is a single bond or a methylene group, R ₃ and R ₄ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is 1 to an integer of 40).
The pressure-sensitive adhesive composition of claim 2, wherein the amine-based additive includes a compound represented by Formula 2 below:
[Formula 2]

(In Formula 1, R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms,
x, y and z are each independently an integer from 1 to 35;
x+y+z is an integer from 40 to 100).
The pressure-sensitive adhesive composition of claim 1, wherein the amine-based additive has a weight average molecular weight of 1,000 to 10,000 g/mol.
The pressure-sensitive adhesive composition according to claim 1, wherein the curing agent comprises a thermosetting agent containing an isocyanate group.
The pressure-sensitive adhesive composition of claim 1, wherein the content of the amine-based additive is 1 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer.
The pressure-sensitive adhesive composition of claim 1, wherein the content of the curing agent is 0.1 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer.
It includes an adhesive layer formed from a pressure-sensitive adhesive composition containing an acrylic copolymer and an amine-based additive,
An adhesive sheet that satisfies Equation 1 below:
[Equation 1]
50≤A/B≤320
(In Equation 1, A is the storage modulus at 25° C. of the pressure-sensitive adhesive sheet, and B is the elongation at break at a thickness of 1 mm of the pressure-sensitive adhesive sheet).
The pressure-sensitive adhesive sheet according to claim 10, wherein the amine-based additive has a propylene oxide group and an amine terminal group.
The pressure-sensitive adhesive sheet according to claim 11, wherein the amine-based additive includes a compound represented by Formula 2 below:
[Formula 2]

(In Formula 2, R ₅ is hydrogen or an alkyl group having 1 to 5 carbon atoms,
x, y and z are each independently an integer from 1 to 40;
x+y+z is an integer from 40 to 100).
The pressure-sensitive adhesive sheet according to claim 10, comprising a base film laminated on at least one surface of the pressure-sensitive adhesive layer.
a first subject;
an adhesive layer disposed on an upper surface of the first object and formed of the adhesive composition according to claim 1; and
Including a second object disposed on the upper surface of the adhesive layer,
The first object and the second object each independently include a polarizing plate, a window cover film, a protective film, a touch screen panel, a display panel, or a laminated structure of at least one of them, a laminate for an image display device.

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