KR102069483B1 - Pressure Sensitive Adhesive composition using foldable display - Google Patents

Abstract

The present application relates to a pressure-sensitive adhesive composition for foldable display and its use.
The pressure-sensitive adhesive composition of the present application is excellent in bending reliability as the change rate of the loss modulus is small in a wide temperature range, and is useful for forming a pressure-sensitive adhesive layer for foldable displays.

Description

Pressure Sensitive Adhesive composition using foldable display}

The present application relates to a pressure-sensitive adhesive composition for foldable display and its use.

Recently, with the development of display-related technology, display devices that can be deformed at the use stage, such as folding, rolling in a roll shape, or stretching like a rubber band, have been researched and developed. Since these displays can be modified in various forms, it is possible to satisfy both the demand for larger display in the use stage and the need for smaller display for portable use.

The deformable display device may be not only deformed in a predetermined form, but also may be deformed in various forms in response to a user's request or in accordance with the needs of a situation in which the display device is used. Therefore, it is necessary to recognize the modified form of the display and to control the display device in response to the recognized form.

On the other hand, since the deformable display apparatus has a problem in that each component of the display apparatus is damaged due to the deformation, each component of the display apparatus must satisfy folding reliability and stability.

Republic of Korea Patent Publication 2015-0011230 A

The present application provides a pressure-sensitive adhesive composition for foldable display and its use.

The pressure-sensitive adhesive composition for foldable display of the present application has a small change in loss modulus in a wide temperature range, and is excellent in bending reliability.

The present application relates to a pressure-sensitive adhesive composition for foldable display and its use.

The pressure-sensitive adhesive composition according to the present application has a small change in loss modulus in a wide temperature range, for example, a temperature range of -20 ° C to 90 ° C, and has suitable physical properties for use in a foldable display.

The pressure-sensitive adhesive composition may be cured to form an pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may be included in a foldable display to attach a display panel and a cover glass.

In the present application, the term “foldable display” is designed to be repeated to be folded and folded like a paper, so that the folded portion may mean a flexible display having a radius of curvature within 5 mm.

Unlike conventional adhesives, the pressure-sensitive adhesive applied to the foldable display should satisfy the bending reliability. In order to have excellent bending reliability, it is preferable that the change of the loss modulus is small in a wide temperature range.

Thus, the applicant has to include a crosslinking functional group acrylic polymer and a different two or more kinds of crosslinking agents capable of crosslinking the acrylic polymer containing the composition, of 10 ⁶ Pa or less in a wide temperature range of -20 ℃ to 90 ℃ It has come to invent an adhesive composition capable of forming an adhesive layer suitable for a foldable display having a loss modulus change rate.

That is, the present application is an acrylic polymer comprising a crosslinkable functional group; And at least two different crosslinking agents for crosslinking the acrylic polymer. In addition, the foldable display adhesive composition satisfies the following Equation 1.

[Equation 1]

ΔG '' (G '' (-20 ℃)-G '' (90 ℃)) ≤10 ⁶ Pa

In Equation 1, G '' (-20 ° C) is the loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of -20 ° C, a frequency of 100 rad / s, and a strain rate of 0.1%, and G '' (90 ° C) is The loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 ° C., a frequency of 100 rad / s, and a strain rate of 0.1%.

As can be seen in Equation 1, the pressure-sensitive adhesive composition of the present application is designed so that the difference between the loss modulus measured at -20 ℃ and the loss modulus measured at 90 ℃ to 10 ⁶ Pa or less. The pressure-sensitive adhesive composition satisfying Formula 1 may provide, for example, a pressure-sensitive adhesive composition having a bending reliability suitable for a foldable display.

The loss modulus value may be, for example, a value measured according to a manual using an advanced rheological expansion system (Ta Instruments) at a frequency of 100 rad / s and a strain condition of 0.1%.

Since the loss modulus value after curing of the pressure-sensitive adhesive composition decreases linearly or nonlinearly from -20 ° C to a temperature of 90 ° C, when the pressure-sensitive adhesive composition satisfies Equation 1, a temperature range of -20 ° C to 90 ° C The rate of change of the loss modulus in all sections may be 10 ⁶ Pa or less.

The term " loss modulus change rate " is a difference between loss T modulus measured at a temperature T1 and a temperature T2 higher than the temperature T1 in the temperature range of -20 deg. C to 90 deg. -G '' (T2)).

Within the range of the loss modulus change rate, it is possible to secure the superior bending reliability suitable for the foldable display.

In another example, the difference between the loss modulus (G '' (-20 ° C)) and the loss modulus G '' (90 ° C) at 90 ° C of the pressure-sensitive adhesive composition (ΔG '' (G '' ( -20 ° C)-G '' (90 ° C)) may be 0.9 x 10 ⁶ Pa or less, 0.85 x 10 ⁶ Pa or less or 0.8 x 10 ⁶ Pa or less.

The pressure-sensitive adhesive composition of the present application includes an acrylic polymer. The acrylic polymer includes a crosslinkable functional group.

The acrylic polymer of the present application may have a glass transition temperature (Tg), for example, in the range of -100 ° C to 0 ° C. Within this range of glass transition temperature (Tg) can be achieved a glass transition temperature (Tg) range of the pressure-sensitive adhesive composition to be described later, it can also provide a pressure-sensitive adhesive composition showing a low storage modulus change rate in a wide temperature range. In another example, the glass transition temperature (Tg) of the acrylic polymer may be in the range of -80 ° C to 0 ° C, -70 ° C to 0 ° C, -60 ° C to -10 ° C, or -60 ° C to -20 ° C. have.

The acrylic polymer of the present application may also have a weight average molecular weight in the range of 5,000 to 3,000,000. As used herein, the term weight average molecular weight may mean a conversion value for standard polystyrene measured by gel permeation chromatography (GPC), and unless otherwise specified, the molecular weight of a polymer may mean the weight average molecular weight of the polymer. Can be. In another example, the weight average molecular weight of the acrylic polymer may be in the range of 100,000 to 2,500,000 or 500,000 to 2,200,000.

The acrylic polymer of this application contains a crosslinkable functional group, and satisfy | fills the above-mentioned glass transition temperature (Tg) and weight average molecular weight, For example, (meth) acrylic acid ester monomer and the said (meth) acrylic acid ester monomer, It can copolymerize and the polymer unit of the monomer which has a crosslinkable functional group can be included.

In the present application, the term "polymer contains a polymerization unit of a monomer" means a state in which the monomer is polymerized in a skeleton such as a main chain or a side chain of a polymer formed by polymerizing the monomer. In addition, the term "(meth) acrylic acid" means acrylic acid or methacrylic acid.

The kind of the (meth) acrylic acid ester monomer is not particularly limited, and for example, an appropriate kind may be selected to allow the acrylic polymer to exhibit the above-mentioned glass transition temperature.

In one example, the (meth) acrylic acid ester monomer may be an alkyl (meth) acrylate. In the above, the term "(meth) acrylate" means acrylate or methacrylate.

The alkyl (meth) acrylate may be an alkyl (meth) acrylate having an alkyl group having 1 to 20 carbon atoms, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl (meth). Acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethyl Butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) ) Acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, octadecyl (meth) acrylate or isobornyl (meth) acrylate Etc It may be illustrated, without being limited thereto.

Further, the monomer having a crosslinkable functional group included as a polymerization unit in the acrylic polymer may be selected without particular limitation as long as it can polymerize with the (meth) acrylic acid ester monomer forming an acrylic polymer to provide a crosslinkable functional group to the polymer. Can be.

The crosslinkable functional group may be selected without limitation as long as it can cause a crosslinking reaction with two or more different crosslinking agents described below at a temperature within a range of about 50 ° C to 300 ° C, for example.

In one example, the crosslinkable functional group may be any one or more selected from the group consisting of a hydroxy group, an isocyanate group, a glycidyl group, an epoxy group, an amine group and a carboxyl group.

The monomer having a hydroxy group is, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) Hydroxyalkyl (meth) acrylates such as acrylate or 8-hydroxyoxyl (meth) acrylate; Hydroxypolyalkylene glycol (meth) acrylates such as hydroxy polyethylene glycol (meth) acrylate or hydroxypolypropylene glycol (meth) acrylate; Etc., but is not limited thereto.

The monomer which has a carboxyl group is (meth) acrylic acid, 2- (meth) acryloyloxy acetic acid, 3- (meth) acryloyloxy propyl acid, 4- (meth) acryloyloxy butyl acid, acrylic acid, for example. There may be a duplex, itaconic acid, maleic acid or maleic anhydride, and the like, but is not limited thereto.

The monomer having an amine group is, for example, 2-aminoethyl (meth) acrylate, 3-aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate or N, N-dimethylaminopropyl ( Methacrylate) and the like, but is not limited thereto.

Among the monomers having various crosslinkable functional groups, an appropriate kind may be selected in consideration of the desired glass transition temperature of the acrylic polymer or the reactivity with the crosslinking agent described later.

In a specific example, the crosslinkable functional group may be a carboxy group. When the acrylic polymer includes a monomer having a carboxy group as a polymer unit, the loss modulus change rate of the desired pressure-sensitive adhesive composition can be achieved by sequentially crosslinking reaction by two or more different crosslinking agents described later.

The acrylic polymer may contain polymer units of (meth) acrylic acid ester monomers and crosslinkable functional groups in a predetermined ratio.

In one example, the acrylic polymer may comprise 50 to 99 parts by weight of (meth) acrylic acid ester monomer and 1 to 20 parts by weight of polymerized unit having a crosslinkable functional group.

In another example, the acrylic polymer has 60 to 99 parts by weight of a (meth) acrylic acid ester monomer and 1 to 15 parts by weight of a monomer having a crosslinkable functional group, or 70 to 99 parts by weight of a (meth) acrylic acid ester monomer and a crosslinkable functional group. It may include 1 to 10 parts by weight of the polymer unit of the monomer.

The term "parts by weight" as used herein means a weight ratio between each component unless otherwise defined.

The acrylic polymer of the present application may also further include polymerized units of other functional monomers in order to achieve the above-mentioned glass transition temperature and weight average molecular weight.

The functional monomers are, for example, (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butoxy methyl (meth) acrylamide, N-vinylpi Nitrogen-containing monomers such as rolidone or N-vinyl caprolactam; Alkylene oxide group-containing monomers such as alkoxy alkylene glycol (meth) acrylic acid esters, alkoxy dialkylene glycol (meth) acrylic acid esters or alkoxy polyethylene glycol (meth) acrylic acid esters; Or a styrene monomer such as styrene or methyl styrene, but is not limited thereto.

The polymerized unit of the functional monomer may be included in the acrylic polymer, for example, in a ratio of 0 to 70 parts by weight.

Acrylic polymers of the present application can be prepared in a variety of ways. For example, the polymer may be selected from the monomers described above, and a mixture of monomers in which the selected monomers are blended in a desired ratio may be subjected to solution polymerization, bulk poylmerization, suspension polymerization. It can be prepared by applying to a method such as polymerization) or emulsion polymerization (emulsion polymerization), it can be prepared by solution polymerization suitably. The manner of preparing the polymer through solution polymerization is not particularly limited.

For example, the solution polymerization method may be performed at a polymerization temperature of 50 ° C. to 140 ° C. for about 6 to 15 hours by mixing a radical polymerization initiator and a solvent in a state where the aforementioned monomer components are mixed at an appropriate weight ratio.

Radical polymerization initiators used for producing the acrylic polymer are known, and include, for example, azo polymerization initiators such as azobis isobutyronitrile or azobiscyclohexane carbonitrile; Or oxides such as benzoyl peroxide or acetyl peroxide; Etc. can be used.

The said polymerization initiator may be used individually or in mixture of 2 or more types, It is preferable that the content is about 0.005-1 weight part.

In addition, the solvent used to prepare the acrylic polymer is known, for example, ethyl acetate or toluene may be used, but is not limited thereto.

The pressure-sensitive adhesive composition of the present application also includes two or more different crosslinking agents.

The present application may provide an adhesive composition having physical properties suitable for application to a foldable display, including two or more crosslinking agents having a functional group capable of reacting with a crosslinkable functional group contained in an acrylic polymer. .

The crosslinking agent is, for example, a bifunctional or higher polyfunctional compound including two or more functional groups capable of reacting with the crosslinkable functional group of the acrylic polymer in one molecule, for example, two to six functional groups in one molecule. It may mean a polyfunctional compound comprising. Two or more functional groups included in one molecule may be the same or different functional groups.

Specifically, the two or more different crosslinking agents are each independently alkoxy silane group, carboxyl group, acid anhydride group, vinyl ether group, amine group, carbonyl group, isocyanate group, epoxy group, aziridinyl group, carbodiimide group and oxazoline group It may include any one or more functional groups selected from the group consisting of. The type of the functional group may vary depending on the type of the crosslinkable functional group included in the acrylic polymer or other, the mechanism for implementing the crosslinked structure.

The crosslinking agent containing the carboxyl group is, for example, o-phthalic acid, isophthalic acid, terephthalic acid, 1,4-dimethyl terephthalic acid, 1,3-dimethylisophthalic acid, 5-sulfo-1,3-dimethylisophthalic acid, 4, 4-biphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, norbornenedicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid Or aromatic dicarboxylic acid, such as phenyl indane dicarboxylic acid; Aromatic dicarboxylic anhydrides such as phthalic anhydride, 1,8-naphthalenedicarboxylic anhydride or 2,3-naphthalenedicarboxylic anhydride; Alicyclic dicarboxylic acids such as hexahydrophthalic acid; Alicyclic dicarboxylic acid anhydrides such as hexahydro phthalic anhydride, 3-methyl-hexahydro phthalic anhydride, 4-methyl-hexahydrophthalic anhydride or 1,2-cyclohexanedicarboxylic anhydride; Or oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, suberic acid, maleic acid, chloromaleic acid, fumaric acid, dodecaneic acid, pimelic acid, citraconic acid, glutaric acid or itaconic acid. Aliphatic dicarboxylic acids and the like.

The crosslinking agent containing the said acid anhydride group is pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, oxydiphthalic acid dianhydride, diphenyl sulfontetracarboxylic dianhydride, for example. , Diphenyl sulfide tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, perylenetetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, and the like.

The crosslinking agent containing the said vinyl ether group, for example, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, propylene glycol divinyl Ether, dipropylene glycol divinyl ether, tripropylene glycol divinyl ether, neopentyl glycol divinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, glycerin divinyl ether, trimethylol Propanedivinylether, 1,4-dihydroxycyclohexanedivinylether, 1,4-dihydroxymethylcyclohexanedivinylether, hydroquinonedivinylether, ethylene oxide modified hydroquinonedivinyl ether, ethylene oxide modified Resorcinin divinyl ether, ethylene oxide modified bisphenol A divinyl ether, ethylene oxide modified bisphenol S divinyl Ether, glycerin trivinyl ether, sorbitol tetravinyl ether, trimethylol propane trivinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol hexavinyl ether, dipentaerythritol polyvinyl ether, dipenta Trimethylolpropanetetravinylether or ditrimethylolpropanepolyvinylether and the like.

The crosslinking agent containing the said amine group, For example, Aliphatic diamines, such as ethylenediamine or hexamethylenediamine; Alicyclic diamines such as 4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 4,4'-diamino-3,3'-dimethyldicyclohexyl, diaminocyclohexane or isophoronediamine Ryu; Or aromatic diamines such as xylenediamine.

The crosslinking agent containing the isocyanate group is, for example, 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylenedi isocyanate, 4,4'-diphenylmethane diisocyanate, 2, 4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4, 4'-diphenyl ether diisocyanate, 4,4 ', 4' '-triphenylmethane triisocyanate, ω, ω-diisocyanate-1,3-dimethylbenzene, ω, ω'-diisocyanate-1,4- Dimethylbenzene, ω, ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylene diisocyanate, 1,3-tetramethyl xylene diisocyanate, xylylene diisocyanate or xylylene diisocyanate Aromatic polyisocyanates; Trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate or 2 Aliphatic polyisocyanates such as 4,4-trimethylhexamethylene diisocyanate; Or 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, methyl-2,4- Alicyclic polyisocyanates such as cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate) or 1,4-bis (isocyanate methyl) cyclohexane; And reactants of one or more polyisocyanates with polyols.

The crosslinking agent containing the said epoxy group, for example, ethylene glycol diglycidyl ether, triglycidyl ether, trimethylol propane triglycidyl ether, N, N, N, N'- tetraglycidyl-1,3- Xylenediamine, or glycerin diglycidyl ether, and the like.

In one example, the pressure-sensitive adhesive composition of the present application may include a crosslinking agent of two different from the crosslinking agent, to perform a crosslinking reaction with a crosslinkable functional group contained in the acrylic copolymer.

In a more specific example, the two or more different crosslinking agents may be composed of a first crosslinking agent reacting with the crosslinkable functional group of the acrylic copolymer and a second crosslinking agent reacting with the crosslinkable functional group formed by the reaction of the first crosslinking agent.

That is, the pressure-sensitive adhesive composition of the present application includes two different crosslinking agents together with the acrylic polymer, and the two crosslinking agents are reacted by the reaction of the first crosslinking agent and the first crosslinking agent to react with the crosslinkable functional group of the acrylic copolymer. It may be a second crosslinking agent that reacts with the formed crosslinkable functional group.

According to the implementation mechanism of the crosslinked structure as described above, in the temperature range of -20 ° C to 90 ° C, the loss modulus change rate of the pressure-sensitive adhesive composition of the present application can be adjusted to 10 ⁶ Pa or less.

In one example, the first crosslinking agent may be a crosslinking agent including an epoxy group, and the second crosslinking agent may be a crosslinking agent including an isocyanate group.

As described above, when the two different crosslinking agents of the present application are crosslinking agents each containing an epoxy group and an isocyanate group, the carboxyl groups and the crosslinking agents included in the acrylic polymer may implement a sequential crosslinking reaction.

Specifically, when the crosslinkable functional group contained in the acrylic polymer of the present application is a carboxyl group, the crosslinking agent including the epoxy group as the first crosslinking agent reacts with the carboxyl group, and the crosslinking agent including the isocyanate group as the second crosslinking agent is used as the crosslinking agent of the first crosslinking agent. The crosslinking structure of the acrylic polymer may be realized by reacting with a hydroxyl group formed by the reaction of an epoxy group with a carboxyl group included in the acrylic polymer.

By such a sequential crosslinking reaction, the desired loss modulus change rate of the pressure-sensitive adhesive composition can be achieved.

The two or more different crosslinking agents may be included in the pressure-sensitive adhesive composition within a content range capable of achieving the above object.

In one example, two or more different crosslinkers may be included in the composition in the range of 0.001 to 5 parts by weight relative to 100 parts by weight of the acrylic polymer. In another example, the two or more different crosslinking agents may be included in the composition in the range of 0.001 to 3 parts by weight 0.01 to 2 parts by weight or 0.02 to 2 parts by weight relative to 100 parts by weight of the acrylic polymer. When the content of the crosslinking agent is more than 5 parts by weight or less than 0.001 parts by weight, the desired storage modulus change rate cannot be achieved within the temperature range of -20 ° C to 90 ° C.

In a specific example, when the two or more different crosslinking agents consist of the first crosslinking agent and the second crosslinking agent described above, the first crosslinking agent is in the range of 0.0005 to 3.5 parts by weight relative to 100 parts by weight of the acrylic copolymer, and the second crosslinking agent is acrylic It may be included in the pressure-sensitive adhesive composition in the range of 0.0005 to 1.5 parts by weight relative to 100 parts by weight of the copolymer.

In addition to the acrylic polymer and the crosslinking agent described above, the pressure-sensitive adhesive composition of the present application may be known further components such as antistatic agents, tackifying resins, curing agents, ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers, antifoaming agents, surfactants, or plasticizers. It may further comprise.

As described above, the pressure-sensitive adhesive composition of the present application has a change rate of loss modulus of 10 ⁶ Pa or less within a temperature range of -20 ° C to 90 ° C, thereby forming a pressure-sensitive adhesive layer having a bending reliability suitable for foldable displays. useful.

For example, after the curing, the pressure-sensitive adhesive composition may have a loss modulus measured in a temperature range of −20 ° C. to 90 ° C. in a range of 10 ⁴ Pa to 10 ⁶ Pa.

The pressure-sensitive adhesive composition of the present application also, in order to prevent a radical change in the loss modulus value of the pressure-sensitive adhesive composition in the temperature range (-20 ℃ to 90 ℃) to achieve the desired loss modulus change rate, the glass transition temperature (Tg) of the composition It can be kept lower than the lower limit value (-20 ℃) of the temperature section (-20 ℃ to 90 ℃).

In one example, the pressure-sensitive adhesive composition of the present application may have a glass transition temperature (Tg) of −20 ° C. or less while an acrylic polymer and two or more different crosslinking agents implement a crosslinking structure. Through the above conditions, it is possible to provide a pressure-sensitive adhesive composition having a loss modulus change rate of 10 ⁶ Pa or less and a storage modulus in a range of 10 ⁴ Pa to 10 ⁶ Pa in a temperature range of −20 ° C. to 90 ° C.

In another example, the pressure-sensitive adhesive composition may have a glass transition temperature (Tg) of −25 ° C. or less, −28 ° C. or less or −30 ° C. or less while implementing a crosslinked structure. The lower limit of the glass transition temperature (Tg) of the pressure-sensitive adhesive composition may be, for example, -100 ° C or higher, -90 ° C or higher, or -80 ° C or higher.

The present application also relates to the use of the pressure-sensitive adhesive composition. Since the pressure-sensitive adhesive composition of the present application has a bending reliability suitable for a foldable display, it may be used, for example, for attaching a panel and a cover glass to a foldable display.

In one example, the present application is directed to a foldable display comprising an adhesive layer that is a cured product of the adhesive composition. In addition, the pressure-sensitive adhesive composition, acrylic polymer containing a crosslinkable functional group; And two or more different crosslinking agents for crosslinking the acrylic polymer, and may satisfy Formula 1 below.

[Equation 1]

△ G '' (G '' (-20 ℃)-G '' (90 ℃)) ≤10 ⁶ Pa

In Equation 1, G '' (-20 ° C) is the loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of -20 ° C, a frequency of 100 rad / s, and a strain rate of 0.1%, and G '' (90 ° C) is The loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 ° C., a frequency of 100 rad / s, and a strain rate of 0.1%.

Other specific configurations of the foldable display are known, for example, by Korean Patent Application Publication No. 2015-0138450 and the like, and the present application may include without limitation the configuration of the known foldable display. .

The present application can provide a pressure-sensitive adhesive composition having a bending reliability suitable for application to a foldable display.

Hereinafter, the adhesive composition for a foldable display according to the present application will be described in more detail with reference to Examples and Comparative Examples, but the following examples are only examples according to the present application, and limit the technical spirit of the present application. It is not.

Physical properties of the pressure-sensitive adhesive composition of the present application was evaluated by the following method.

1. Molecular weight measurement

The weight average molecular weight (Mw) was measured under the following conditions using GPC, and the measurement results were converted using standard polystyrene of Agilent system for the production of calibration curves.

< Measurement condition>

Meter: Agilent GPC (Agilent 1200 series, U.S.)

Column: Connect 2 PL Mixed B

Column temperature: 40 ℃

Eluent: THF (Tetrahydrofuran)

Flow rate: 1.0 mL / min

Concentration: ~ 1 mg / mL (100 μL injection)

2. Loss modulus measurement

After coating the pressure-sensitive adhesive composition prepared in Examples and Comparative Examples between the release film and cut to a size of 15 cm × 25 cm, remove the release film on one side, and then laminated several times, the thickness was about 1mm. Subsequently, the laminate was cut into a circle having a diameter of 8 mm, compacted using glass, and left to stand overnight to improve wetting at the interface between the layers. The sample was prepared by removal. Subsequently, the sample was placed on a parallel plate, the gap was adjusted, the zero point of Normal & Torque was set, the stability of the normal force was confirmed, and then the loss modulus was measured.

(1) measuring instruments and measuring conditions

Measuring instrument: ARES-RDA with forced convection oven, TA Instruments Inc.

(2) measurement conditions:

geometry: 8 mm parallel plate

Thickness: about 1 mm

test type: dynamic strain frequency sweep

Strain = 0.1 [%]

Initial temperature: -20 ℃, Final temperature: 90 ℃

Frequency: 100 rad / s

Example  One

Adhesive composition ( C1 Manufacturing

Nitrogen gas was refluxed inside, and 98 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) were added to a 1 L reactor provided with a cooling device for easy temperature control. Subsequently, 150 parts by weight of ethyl acetate (EAc) was added as a solvent, purged with nitrogen gas for 60 minutes to remove oxygen, and azobisisobutyronitrile, which is a reaction initiator, while maintaining the temperature at 60 ° C. AIBN) 0.02 parts by weight was added, and after the reaction was initiated, the reactant reacted for about 1 hour was diluted with ethyl acetate (EAc) to prepare an acrylic polymer (A1) having a molecular weight of about 2 million. 0.03 parts by weight of N, N, N ', N'-tetraglycidyl-m-xylene diamine (BXX-5240, manufactured by Samyoung Ink Co.) as a crosslinking agent based on 100 parts by weight of the acrylic polymer (A1), Pressure-sensitive adhesive composition (C1) was prepared by uniformly mixing 0.005 parts by weight of xylene diisocyanate (BXX-5627, manufactured by Samyoung Ink Co., Ltd.).

Of pressure-sensitive adhesive layer (E1)  formation

SKC's silicone release film (RF12N) was coated with the pressure-sensitive adhesive composition (C1) to a thickness of about 25 μm, dried, and then applied to a light release mold release film (RF02N), and cured at 40 ° C. for 2 days to prepare the pressure-sensitive adhesive layer (E1). Formed.

Example  2

0.06 parts by weight of azobisisobutyronitrile (AIBN), which is a reaction initiator, was prepared to prepare a pressure-sensitive adhesive composition (C2) containing an acrylic polymer (A2) having a molecular weight of about 1 million, using the pressure-sensitive adhesive layer (E2) Except that was formed, the pressure-sensitive adhesive layer (E2) was formed in the same manner as in Example 1.

Example  3

A pressure-sensitive adhesive composition (C3) containing an acrylic polymer (A3) having a molecular weight of about 2 million, prepared by adjusting the ratio of n-butyl acrylate (BA) and acrylic acid (AA) to 94: 6, was prepared using the pressure-sensitive adhesive. The pressure-sensitive adhesive layer E3 was formed in the same manner as in Example 1 except that the layer E3 was formed.

compare Production Example  One

60 parts by weight of ethylhexyl acrylate (EHA), 25 parts by weight of isobornyl acrylate (IBOA) and 15 parts by weight of hydroxyethyl acrylate (HEA) were charged to a 1 L reactor, and the gas was purged for 60 minutes to remove oxygen. Purging) and 0.5 parts by weight of Iragacure 184 as a photoinitiator, and then irradiated with ultraviolet light for 15 minutes to prepare a UV syrup. An acrylic polymer (B1) having a molecular weight of 1,000,000 was prepared by uniformly mixing 0.5 parts by weight of Iragacure 184, 0.1 parts by weight of 1,6-hexanediol diacrylate (HDDA), to the UV syrup. An adhesive composition (D1) including the acrylic polymer (B1) was prepared without a separate crosslinking agent.

Thereafter, the pressure-sensitive adhesive layer (F1) was formed in the same manner as in Example 1 using the pressure-sensitive adhesive composition (D1).

compare Production Example  2

A pressure-sensitive adhesive composition (D2) was prepared by adding 0.5 parts by weight of a platinum catalyst CAT PT 50T to 100 parts by weight of Shin-Etsu KR-3700, a silicone pressure-sensitive adhesive.

Thereafter, the pressure-sensitive adhesive composition (D2) was coated and dried to a thickness of 25 μm on a TACS fluorine-based release film (TS-502S), and a fluorine-based release film (TS-502S) was applied to prepare an adhesive layer (F2). .

Experimental Example  1-Measurement of loss modulus

After curing of the compositions according to the Examples and Comparative Examples, in order to determine the rate of change of the loss modulus with temperature, -20 ° C and 90 according to the measurement method described above using ARES-RDA, TA instruments equipped with a forced convection oven The loss modulus at ℃ was measured and shown in Table 1.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Loss modulus at -20 ℃ (G '' (-20 ℃), Pa) 29 x 10 ⁴ 35 x 10 ⁴ 79 x 10 ⁴ 970 x 10 ⁴ 738 x 10 ⁴ Loss modulus at 90 ℃ (G '' (90 ℃), Pa) 2 x 10 ⁴ 2 x 10 ⁴ 2 x 10 ⁴ 2 x 10 ⁴ 18 x 10 ⁴ △ G '' 27 x 10 ⁴ 33 x 10 ⁴ 77 x 10 ⁴ 968 x 10 ⁴ 720 x 10 ⁴

ΔG '' = G '' (-20 ° C)-G '' (90 ° C)

Experimental Example  2 - dynamic folding test

A PI film laminate was formed by using a PI film (SKC KOLONE PI Co., IF 70) having a thickness of 50 μm as a structure of a PI film / adhesive layer / PI film / adhesive layer / PI film, and prepared in Examples and Comparative Examples. One adhesive layer was laminated with the laminate, and then cut to a size of 140 mm x 80 mm. Then, using a bending test equipment, a radius of curvature 2.5mm, repeated 2500 times per hour to perform a total of 100,000 times the dynamic folding test, and when the lifting occurs at the interface of the PI film laminate and the adhesive, NG, lifting occurs When evaluated as OK, it is shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Dynamic folding test OK OK OK NG NG

Experimental Example  3- static folding test

A PI film laminate was formed by using a PI film (SKC KOLONE PI Co., IF 70) having a thickness of 50 μm as a structure of a PI film / adhesive layer / PI film / adhesive layer / PI film, and prepared in Examples and Comparative Examples. One adhesive layer was laminated with the laminate, and then cut to a size of 140 mm x 80 mm. Thereafter, the interface between the PI film laminate and the pressure-sensitive adhesive layer was observed after 24 hours in a state of being folded at a curvature radius of 2.5 mm. When lifting occurs at the PI film laminate and the adhesive interface, NG, and if lifting does not occur, evaluate the static folding test results for each temperature as shown in Table 3 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Room temperature OK OK OK NG OK -40 ℃ OK OK OK NG OK 60 ℃, 90RH% OK OK OK NG NG 80 ℃ OK OK OK NG NG

Experimental Example  4-glass transition temperature measurement

The pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was thinly applied between the two substrates on which the release film was laminated, and after irradiation with ultraviolet rays, the two substrates were removed. Thereafter, the release film cured by the pressure-sensitive adhesive composition was cut into a width of 0.5 cm and a length of 4 cm, and the glass transition temperature (Tg) was measured by increasing the temperature by 5 ° C./min from −30 ° C. to 150 ° C. using a DMA measuring instrument. 4 is shown.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Tg -34 ℃ -34 ℃ -25 ℃ -1 ℃ 77 ℃

Claims (16)

Acrylic polymers comprising at least one carboxyl group as a crosslinkable functional group; And
At least two different crosslinking agents for crosslinking the acrylic polymer,
The two or more different crosslinking agents include a first crosslinking agent reacting with a carboxyl group of the acrylic polymer and a second crosslinking agent reacting with a crosslinkable functional group formed by the reaction of the first crosslinking agent,
Pressure-sensitive adhesive composition for a foldable display that satisfies the following formula 1:
[Equation 1]
ΔG '' (G '' (-20 ℃)-G '' (90 ℃)) ≤10 ⁶ Pa
In Equation 1, G '' (-20 ° C) is the loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of -20 ° C, a frequency of 100 rad / s, and a strain rate of 0.1%, and G '' (90 ° C) is The loss modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 ° C., a frequency of 100 rad / s, and a strain rate of 0.1%. The method of claim 1,
The acrylic polymer can be copolymerized with the (meth) acrylic acid ester monomer and the said (meth) acrylic acid ester monomer, and the adhesive composition for foldable displays containing the polymerization unit of the monomer which has a crosslinkable functional group. The method of claim 2,
The (meth) acrylic acid ester monomer is an alkyl (meth) acrylate, The adhesive composition for foldable displays. The method of claim 3, wherein
Alkyl (meth) acrylates are methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (Meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth A acrylate, tetradecyl (meth) acrylate, octadecyl (meth) acrylate, and isobonyl (meth) acrylate, any one or more selected from the group consisting of foldable (foldable) pressure-sensitive adhesive composition. The method of claim 1,
The crosslinkable functional group further comprises at least one selected from the group consisting of a hydroxy group, an isocyanate group, a glycidyl group, an epoxy group and an amine group. delete The method of claim 2,
The acrylic polymer is a pressure-sensitive adhesive composition for foldable display comprising 50 to 99 parts by weight of (meth) acrylic acid ester monomer and 1 to 20 parts by weight of polymerized unit having a crosslinkable functional group. The method of claim 1,
Two or more different crosslinking agents are multifunctional compounds containing at least two functional groups capable of reacting with a crosslinkable functional group of an acrylic polymer in one molecule. The method of claim 1,
Two or more different crosslinking agents are each independently selected from the group consisting of alkoxy silane groups, carboxy groups, acid anhydride groups, vinyl ether groups, amine groups, carbonyl groups, isocyanate groups, epoxy groups, aziridinyl groups, carbodiimide groups and oxazoline groups Pressure-sensitive adhesive composition for foldable (foldable) display containing any one or more functional groups. delete The method of claim 1,
1st crosslinking agent is a crosslinking agent containing an epoxy group, and a 2nd crosslinking agent is a crosslinking agent containing an isocyanate group, The adhesive composition for foldable displays. The method of claim 1,
The content of two or more different crosslinking agents is in the range of 0.001 to 5 parts by weight relative to 100 parts by weight of the acrylic polymer. The method of claim 1,
The content of the first crosslinking agent is in the range of 0.0005 to 3.5 parts by weight based on 100 parts by weight of the acrylic polymer, and the content of the second crosslinking agent is in the range of 0.0005 to 1.5 parts by weight relative to 100 parts by weight of the acrylic polymer. . The method of claim 1,
The pressure-sensitive adhesive composition for foldable display having a loss modulus measured in a temperature range of −20 ° C. to 90 ° C. after curing, in a range of 10 ⁴ Pa to 10 ⁶ Pa. The method of claim 1,
A pressure-sensitive adhesive composition for foldable display having a glass transition temperature (Tg) of -20 ° C or less in a state in which an acrylic polymer and two or more different crosslinking agents implement a crosslinking structure. A foldable display comprising a pressure-sensitive adhesive layer which is a cured product of the pressure-sensitive adhesive composition for foldable display of claim 1.