KR20170097856A - Pressure Sensitive Adhesive composition using foldable display - Google Patents

Abstract

The present invention relates to an adhesive composition for foldable displays, and a use thereof. The adhesive composition ensures excellent reliability in regard to bending owing to low variation rate in loss modulus within a wide range of temperatures, and thus can be useful for forming adhesive layers for foldable displays. To this end, the adhesive composition contains: an acrylic polymer containing a cross-linked functional group; and at least two different types of cross-linking agents which cross-link the acrylic polymers.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pressure sensitive adhesive composition for a foldable display,

The present application relates to a pressure-sensitive adhesive composition for foldable displays and uses thereof.

With the recent development of display related technologies, display devices which can be deformed at the use stage such as folding, rolling, or stretching like rubber are being studied and developed. Since these displays can be modified into various forms, it is possible to satisfy both demands for enlargement of the display at the use stage and miniaturization of the display for carrying.

The deformable display device can be transformed into various forms in accordance with the needs of the user as well as the requirements of the situation in which the display device is used, as well as being transformed into a predetermined form. Therefore, it is necessary to recognize the deformed shape of the display and to control the display device in accordance with the recognized shape.

On the other hand, since the deformable display device has a problem that each configuration of the display device is damaged according to the modification, each of the configurations of the display device must satisfy the folding reliability and stability.

Korean Patent Publication No. 2015-0011230 A

The present application provides a pressure-sensitive adhesive composition for foldable displays and uses thereof.

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

The present application relates to a pressure-sensitive adhesive composition for foldable displays and uses thereof.

The pressure-sensitive adhesive composition according to the present application has a property that is suitable for use in a foldable display because the loss modulus changes little over a wide temperature range, for example, a temperature range of -20 ° C to 90 ° C.

Such a pressure-sensitive adhesive composition may be used, for example, to cure to form a 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.

The term " foldable display " in this application is intended to mean a flexible display in which the folded portion is designed to be folded and folded like a paper, with a curvature radius of 5 mm or less.

Unlike conventional pressure sensitive adhesives, the pressure sensitive adhesive applied to the foldable display must satisfy the bending reliability. In order to have excellent bending reliability, it is preferable that the change in the loss elastic 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 ℃ A pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer suitable for a foldable display having a loss elastic modulus change rate has been invented.

That is, the present application relates to an acrylic polymer comprising a crosslinkable functional group; And a pressure-sensitive adhesive composition for a foldable display comprising two or more different crosslinking agents crosslinking the acrylic polymer. The pressure-sensitive adhesive composition for a foldable display satisfies the following formula (1).

[Equation 1]

? G "(G" (-20 ° C.) -G "(90 ° C.)) ≤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% The loss elastic modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 DEG C, a frequency of 100 rad / s and a strain rate of 0.1%.

As can be seen from the above formula (1), the pressure-sensitive adhesive composition of the present application is designed so that the difference between the loss elastic modulus measured at -20 ° C and the loss elastic modulus measured at 90 ° C is 10 ⁶ Pa or less. The pressure-sensitive adhesive composition satisfying the formula (1) can provide a pressure-sensitive adhesive composition having bending reliability suitable for a foldable display, for example.

The loss elastic modulus value may be a value measured according to a manual using a rheometer (Advanced Rheometric Expansion System, Ta Instruments) at a frequency of, for example, 100 rad / s and a strain rate of 0.1%.

Since the loss elastic modulus value after curing of the pressure-sensitive adhesive composition is linearly or nonlinearly decreased from a temperature of -20 ° C to a temperature of 90 ° C, when the pressure-sensitive adhesive composition satisfies the formula 1, The rate of change in loss modulus in the entire section may be 10 ⁶ Pa or less.

The term " loss elastic modulus change rate " is a difference in loss modulus (G '' (T1)) measured at any temperature T1 between -20 DEG C and 90 DEG C and at a temperature T2 higher than the temperature T1, - G " (T2)).

Within the range of the loss elastic modulus change rate, excellent bending reliability suitable for a foldable display can be secured.

In another example, the difference ΔG '' (G "'(G''') between the loss modulus (G '' (-20 ° C.) at -20 ° C. of the pressure-sensitive adhesive composition and the loss modulus 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 comprises an acrylic polymer. The acrylic polymer includes a crosslinkable functional group.

The acrylic polymer of the present application may have, for example, a glass transition temperature (Tg) in the range of -100 ° C to 0 ° C. It is possible to provide a pressure-sensitive adhesive composition which can attain a glass transition temperature (Tg) range of a pressure-sensitive adhesive composition described later within a range of the glass transition temperature (Tg) and exhibits a low storage elastic modulus change rate over a wide temperature range. In another example, the glass transition temperature (Tg) of the acrylic polymer may be in the range of -80 캜 to 0 캜, -70 캜 to 0 캜, -60 캜 to -10 캜, or -60 캜 to -20 캜 have.

The acrylic polymer of the present application may also have a weight average molecular weight ranging from 5,000 to 3,000,000. The term weight average molecular weight in the present application may mean a conversion value relative to standard polystyrene measured by GPC (Gel Permeation Chromatograph), and unless otherwise specified, the molecular weight of any polymer means the weight average molecular weight of the polymer . In another example, the weight average molecular weight of the acrylic polymer may range from 100,000 to 2,500,000 or from 500,000 to 2,200,000.

The acrylic polymer of the present application contains a crosslinkable functional group and satisfies the above-described glass transition temperature (Tg) and weight average molecular weight. For example, the (meth) acrylic acid ester monomer and the (meth) acrylic acid ester monomer And may include polymerized units of a monomer having a crosslinkable functional group.

In the present application, the term " polymer includes a polymerization unit of a monomer " means a state in which the monomer is polymerized in a backbone such as a main chain or a side chain of a polymer formed by polymerization of a 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 type may be selected so that the acrylic polymer can 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, (Meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Acrylates such as butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (Meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, Etc It may be illustrated, without being limited thereto.

The monomer having a crosslinkable functional group contained in the acrylic polymer as a polymerization unit is not particularly limited as long as it can be polymerized with the (meth) acrylic acid ester monomer forming an acrylic polymer to provide a crosslinkable functional group to the polymer .

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 to be described later, for example, at a temperature within a range of about 50 캜 to 300 캜.

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

Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl Hydroxyalkyl (meth) acrylates such as acrylate or 8-hydroxyoxyl (meth) acrylate and the like; Hydroxypolyalkylene glycol (meth) acrylate such as hydroxypolyethylene glycol (meth) acrylate or hydroxypolypropylene glycol (meth) acrylate; But are not limited thereto.

Examples of the monomer having a carboxyl group include monomers such as (meth) acrylic acid, 2- (meth) acryloyloxyacetic acid, 3- (meth) acryloyloxypropyl acid, 4- (meth) acryloyloxybutyric acid, Dimer, itaconic acid, maleic acid, or maleic anhydride, but is not limited thereto.

The monomer having an amine group may be, for example, 2-aminoethyl (meth) acrylate, 3-aminopropyl (meth) acrylate, N, N- dimethylaminoethyl (meth) acrylate or N, (Meth) acrylate, and the like.

Among the monomers having various crosslinkable functional groups, an appropriate type can 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 contains a monomer having a carboxy group as a polymerization unit, the rate of change in loss modulus of the desired pressure-sensitive adhesive composition can be achieved by sequential crosslinking reaction with two or more different crosslinking agents described below.

The acrylic polymer may contain a polymerization unit of a (meth) acrylic acid ester monomer and a crosslinkable functional group at a predetermined ratio.

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

In another example, the acrylic polymer comprises 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 1 to 10 parts by weight of a monomer.

The term " parts by weight " as used above means the weight ratios between the components unless otherwise defined.

The acrylic polymer of the present application may further comprise polymerized units of other functional monomers to achieve the aforementioned glass transition temperature and weight average molecular weight.

The functional monomer may be, for example, (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butoxymethyl Nitrogen-containing monomers such as lauridone or N-vinylcaprolactam; Alkylene oxide group-containing monomers such as alkoxy alkylene glycol (meth) acrylic acid esters, alkoxy dialkylene glycol (meth) acrylic acid esters or alkoxypolyethylene glycol (meth) acrylic acid esters; Or a styrene-based monomer such as styrene or methylstyrene, but is not limited thereto.

The polymerization unit of the functional monomer may be contained in the acrylic polymer in a proportion of, for example, 0 to 70 parts by weight.

The acrylic polymers of the present application can be prepared in various ways. For example, the polymer may be obtained by selecting monomers necessary from among the monomers described above, and subjecting the mixture of monomers having the desired proportions of the selected monomers to solution polymerization, bulk polymerization, suspension polymerization polymerization, or emulsion polymerization, and may be suitably prepared by solution polymerization. The manner of preparing the polymer through solution polymerization is not particularly limited.

The solution polymerization method may be carried out at a polymerization temperature of 50 to 140 캜 for about 6 to 15 hours, for example, by mixing the above-mentioned monomer components in an appropriate weight ratio, mixing the radical polymerization initiator and the solvent.

The radical polymerization initiator used for producing the acrylic polymer is known, and examples thereof include azo-based polymerization initiators such as azobisisobutyronitrile and azobiscyclohexanecarbonitrile; Or oxides such as benzoyl peroxide or acetyl peroxide; And the like.

The polymerization initiator may be used alone or in combination of two or more. The content thereof is preferably about 0.005 to 1 part by weight.

In addition, the solvent used for preparing the acrylic polymer is known, and for example, ethyl acetate or toluene may be used, but the present invention is not limited thereto.

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

The present application can provide a pressure-sensitive adhesive composition comprising two or more crosslinking agents having a functional group capable of reacting with a crosslinkable functional group contained in an acrylic polymer and having properties suitable for application to a foldable display .

The crosslinking agent may be, for example, a bifunctional or higher functional polyfunctional compound having two or more functional groups capable of reacting with the crosslinkable functional group of the acrylic polymer in one molecule, for example, 2 to 6 ≪ / RTI > The two or more functional groups contained in the molecule may be the same or different kinds of functional groups.

Specifically, the two or more different crosslinking agents are each independently selected from the group consisting of an alkoxysilane group, a carboxyl group, an acid anhydride group, a vinyl ether group, an amine group, a carbonyl group, an isocyanate group, an epoxy group, an aziridinyl group, a carbodiimide group and an oxazoline group And at least one functional group selected from the group consisting of The kind of the functional group may vary depending on the kind of the crosslinkable functional group contained in the acrylic polymer and the mechanism of realization of the crosslinked structure.

Examples of the cross-linking agent containing a carboxyl group include o-phthalic acid, isophthalic acid, terephthalic acid, 1,4-dimethylterephthalic acid, 1,3-dimethylisophthalic acid, 5-sulfo-1,3-dimethylisophthalic acid, 4-biphenyldicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, norbornenedicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid Or aromatic dicarboxylic acids such as phenyl dodecarboxylic acid; Aromatic dicarboxylic acid anhydrides such as phthalic anhydride, 1,8-naphthalene dicarboxylic acid anhydride or 2,3-naphthalene dicarboxylic acid anhydride; Alicyclic dicarboxylic acids such as hexahydrophthalic acid; Alicyclic dicarboxylic acid anhydrides such as hexahydrophthalic anhydride, 3-methyl-hexahydrophthalic anhydride, 4-methyl-hexahydrophthalic anhydride or 1,2-cyclohexanedicarboxylic anhydride; Or an organic acid such as oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, suberic acid, maleic acid, chloromaleic acid, fumaric acid, dodecanedioic acid, pimelic acid, citraconic acid, glutaric acid or itaconic acid Aliphatic dicarboxylic acids, and the like.

The cross-linking agent comprising the acid anhydride group may be, for example, anhydride pyromellitic acid, benzophenonetetracarboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, diphenylsulfonetetracarboxylic acid dianhydride , Diphenyl sulfide tetracarboxylic acid dianhydride, butane tetracarboxylic acid dianhydride, perylene tetracarboxylic dianhydride, or naphthalene tetracarboxylic dianhydride.

The cross-linking agent containing the vinyl ether group is, 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 divinyldecenter, trimethylol Propane divinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethylcyclohexane divinyl ether, hydroquinone divinyl ether, ethylene oxide modified hydroquinone divinyl ether, ethylene oxide modified Resorcin divinyl ether, ethylene oxide modified bisphenol A divinyl ether, ethylene oxide modified bisphenol S divinyl But are not limited to, terpolymers such as terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, terpolymers, Trimethylolpropane tetravinyl ether or ditrimethylolpropane polyvinyl ether, and the like.

Examples of the crosslinking agent containing an amine group include aliphatic diamines such as ethylenediamine and 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.

Examples of the crosslinking agent containing an isocyanate group include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylenediisocyanate, 4,4'-diphenylmethane diisocyanate, Tolylene diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4, 6-tolylene diisocyanate, 4'-diphenyl ether diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, ω, ω-diisocyanate-1,3-dimethylbenzene, ω'-diisocyanate- Dimethylbenzene,?,? '- diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylene diisocyanate, xylylene diisocyanate or xylylene diisocyanate Of an aromatic polyisocyanate; Propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2-methylene diisocyanate, , 4,4-trimethylhexamethylene diisocyanate, and other aliphatic polyisocyanates; Or 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, Alicyclic polyisocyanates such as cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate) or 1,4-bis (isocyanate methyl) cyclohexane, A reaction product of at least one polyisocyanate and the polyol, and the like.

Examples of the cross-linking agent containing an epoxy group include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N, N'-tetraglycidyl- Xylene diamine, or glycerin diglycidyl ether.

In one example, the pressure-sensitive adhesive composition of the present application can carry out a crosslinking reaction with the crosslinkable functional group contained in the acrylic copolymer, including two different crosslinking agents among the crosslinking agents.

In a more specific example, the two or more different crosslinking agents may be composed of a first crosslinking agent which reacts with the crosslinkable functional group of the acrylic copolymer and a second crosslinking agent which reacts 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 comprises two kinds of crosslinking agents together with an acrylic polymer, and the two types of crosslinking agents are selected from the group consisting of a first crosslinking agent which reacts with the crosslinkable functional group of the acrylic copolymer and a second crosslinking agent And may be a second crosslinking agent which reacts with the formed crosslinkable functional group.

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

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

As described above, when the two different crosslinking agents of the present application are each a crosslinking agent containing an epoxy group and an isocyanate group, the crosslinking reaction of the carboxyl group contained in the acrylic polymer and the crosslinking agents can be sequentially performed.

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

Such a sequential crosslinking reaction can achieve the desired loss elastic modulus change rate of the pressure-sensitive adhesive composition.

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

In one example, two or more different crosslinking agents 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 a range of 0.001 to 3 parts by weight, or 0.01 to 2 parts by weight or 0.02 to 2 parts by weight, based on 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 part by weight, the desired storage modulus change rate can not be attained within the temperature range of -20 占 폚 to 90 占 폚.

In a specific example, when the two or more different crosslinking agents are composed of the first crosslinking agent and the second crosslinking agent, 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, May be contained in the pressure-sensitive adhesive composition within a range of 0.0005 to 1.5 parts by weight based on 100 parts by weight of the copolymer.

The pressure-sensitive adhesive composition of the present application may contain known additives such as antistatic agents, tackifier resins, curing agents, ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers, defoamers, surfactants or plasticizers in addition to the acrylic polymer and crosslinking agent May be further included.

As described above, the pressure-sensitive adhesive composition of the present application forms a pressure-sensitive adhesive layer having bending reliability suitable for a foldable display because the rate of change of the loss elastic modulus is 10 ⁶ Pa or less within a temperature range of -20 캜 to 90 캜 useful.

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

The pressure-sensitive adhesive composition of the present application may further comprise a glass transition temperature (Tg) of the composition in order to prevent a radical change in the loss elastic modulus value of the pressure-sensitive adhesive composition in a temperature range (-20 ° C to 90 ° C) Can be kept lower than the lower limit value (-20 DEG C) of the temperature range (-20 DEG C to 90 DEG C).

In one example, the pressure-sensitive adhesive composition of the present application may have a glass transition temperature (Tg) of -20 占 폚 or less in a state in which an acrylic polymer and two or more different crosslinking agents realize a crosslinked structure. Under the above conditions, it is possible to provide a pressure-sensitive adhesive composition having a loss elastic modulus change rate of 10 ⁶ Pa or less and a storage elastic modulus within a range of 10 ⁴ Pa to 10 ⁶ Pa at 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 占 폚 or lower, -28 占 폚 or lower, or -30 占 폚 or lower in a state of implementing a crosslinked structure. The lower limit of the glass transition temperature (Tg) of the pressure-sensitive adhesive composition may be, for example, -100 DEG C or higher, -90 DEG C or higher or -80 DEG C or higher.

The present application is also directed to the use of a pressure sensitive adhesive composition. Since the pressure-sensitive adhesive composition of the present application has a bending reliability suitable for a foldable display, it can be used for applications such as attaching a panel and a cover glass to a foldable display and the like.

In one example, the present application is directed to a foldable display comprising a pressure-sensitive adhesive layer which is a cured product of a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition may further comprise an acrylic polymer containing a crosslinkable functional group; And two or more different crosslinking agents for crosslinking the acrylic polymer, and may satisfy the following formula (1).

[Equation 1]

? G "(G" (-20 ° C.) -G "(90 ° C.)) ≤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% The loss elastic modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 DEG 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, from Korean Patent Laid-Open Publication No. 2015-0138450, and the present application can include without limitation the configuration of such a known foldable display .

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

Hereinafter, the pressure-sensitive adhesive composition for a foldable display according to the present application will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are only examples according to the present application, It does not.

The physical properties of the pressure-sensitive adhesive composition of the present application were evaluated by the following method.

1. Molecular weight measurement

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

< Measurement Conditions>

Measuring instrument: Agilent GPC (Agilent 1200 series, U.S.)

Column: Two PL Mixed B connections

Column temperature: 40 ° C

Eluent: THF (Tetrahydrofuran)

Flow rate: 1.0 mL / min

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

2. Loss modulus measurement

The pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was coated between release films and cut to a size of 15 cm x 25 cm. The release films on one side were removed and laminated several times to a thickness of about 1 mm. Subsequently, the laminate was cut into a circular shape having a diameter of 8 mm, compressed using glass, and allowed to stand overnight to improve wetting at the interface between the respective layers, To prepare a sample. Next, the sample was placed on a parallel plate, the gap was adjusted, the zero point of Normal & Torque was set, the normal force was stabilized, and the loss elastic modulus was measured.

(1) Measuring instruments and measuring conditions

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

(2) Measurement conditions:

geometry: 8 mm parallel plate

Thickness: about 1 mm

test type: dynamic strain frequency sweep

Strain = 0.1 [%]

Initial temperature: -20 캜, final temperature: 90 캜

Frequency: 100 rad / s

Example  One

The pressure-sensitive adhesive composition ( C1 )

98 parts by weight of n-butyl acrylate (BA) and 2 parts by weight of acrylic acid (AA) were fed into a 1 L reactor equipped with a cooling device to easily regulate the temperature. Subsequently, 150 parts by weight of ethyl acetate (EAc) was added with a solvent, and nitrogen gas was purged for 60 minutes to remove oxygen. While maintaining the temperature at 60 占 폚, azobisisobutyronitrile AIBN) was added thereto to initiate the reaction. The reaction product was reacted for about 1 hour and diluted with ethyl acetate (EAc) to prepare an acrylic polymer (A1) having a molecular weight of about 2,000,000. 0.03 parts by weight of N, N, N ', N'-tetraglycidyl-m-xylenediamine (BXX-5240, available from Samyoung Co., Ltd.) as a cross-linking agent was added to 100 parts by weight of the acrylic polymer (A1) And 0.005 part by weight of xylene diisocyanate (BXX-5627, available from Samyoung Co., Ltd.) were uniformly mixed to prepare a pressure-sensitive adhesive composition (C1).

The pressure-sensitive adhesive layer (E1)  formation

The pressure-sensitive adhesive composition (C1) was coated on a silicone release film (RF12N) manufactured by SKC Co., Ltd. to a thickness of about 25 탆 and dried. Then, a light release film (RF02N) was applied and cured at 40 캜 for 2 days to form a pressure- .

Example  2

A pressure-sensitive adhesive composition (C2) comprising an acrylic polymer (A2) having a molecular weight of about 1,000,000 prepared by adding 0.06 parts by weight of azobisisobutyronitrile (AIBN) as a reaction initiator was prepared, Sensitive adhesive layer (E2) was formed in the same manner as in Example 1, except that the pressure-sensitive adhesive layer (E2) was formed.

Example  3

A pressure-sensitive adhesive composition (C3) comprising an acrylic polymer (A3) having a molecular weight of about 2,000, prepared by controlling the ratio of n-butyl acrylate (BA) and acrylic acid (AA) to 94: 6, A pressure-sensitive adhesive layer (E3) was formed in the same manner as in Example 1, except that the layer (E3) was formed.

compare Manufacturing example  One

A 1 L reactor was charged with 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), and the gas was purged Purging), 0.5 parts by weight of Iragacure 184 was added as a photoreaction initiator, and UV irradiation was conducted for 15 minutes to prepare a UV syrup. 0.5 part by weight of Iragacure 184 as a photoreaction initiator and 0.1 part by weight of 1,6-hexanediol diacrylate (HDDA) were uniformly mixed in the UV syrup to prepare an acrylic polymer (B1) having a molecular weight of 1,000,000. A pressure-sensitive adhesive composition (D1) comprising the acrylic polymer (B1) was prepared without any additional crosslinking agent.

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

compare Manufacturing example  2

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

Thereafter, the above pressure-sensitive adhesive composition (D2) was coated on a fluorine release film (TS-502S) of TACS Co., Ltd. to a thickness of 25 탆 and dried, and a fluorine-containing release film (TS-502S) .

Experimental Example  1 - Measurement of loss modulus

To determine the rate of change of loss modulus with temperature after curing of the compositions according to the examples and comparative examples, an ARES-RDA, TA instrument equipped with a forced convection oven was used to measure the temperature at -20 캜 and 90 Lt; 0 &gt; C. The results are shown in Table 1.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 (G &quot; '(-20 &lt; 0 &gt; C), Pa) 29 x 10 ⁴ 35 x 10 ⁴ 79 x 10 ⁴ 970 x 10 ⁴ 738 x 10 ⁴ The loss elastic modulus (G '' (90 ° C), Pa) at 90 ° C, 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

G "= G" (-20 ° C) - G "(90 ° C)

Experimental Example  2 - dynamic folding test

A PI film laminate was formed by using a 50 m thick PI film (SKC KOLONE PI Co., IF 70) as the structure of PI film / pressure-sensitive adhesive layer / PI film / pressure-sensitive adhesive layer / PI film, A pressure-sensitive adhesive layer was laminated with the laminate, and cut into a size of 140 mm x 80 mm. Thereafter, bending test equipment was used to perform a dynamic folding test with a radius of curvature of 2.5 mm and an interval of 2500 times per hour to perform a dynamic folding test. The results are 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 50 m thick PI film (SKC KOLONE PI Co., IF 70) as the structure of PI film / pressure-sensitive adhesive layer / PI film / pressure-sensitive adhesive layer / PI film, A pressure-sensitive adhesive layer was laminated with the laminate, and cut into 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 the folded state with a radius of curvature of 2.5 mm. The static folding test results for each temperature were evaluated as NG if lifting occurred at the interface between the PI film laminate and the pressure sensitive adhesive, and OK if no lifting occurred. The results are 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 ° C OK OK OK NG OK 60 DEG C, 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 applied thinly between two substrates laminated with a release film, irradiated with ultraviolet rays, and then the two substrates were removed. Thereafter, the cured release film was cut to a width of 0.5 cm and a length of 4 cm, and the glass transition temperature (Tg) was measured by a DMA measuring machine at a rate of 5 ° C / min from -30 ° C to 150 ° C, Respectively.

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

Claims (16)

An acrylic polymer comprising a crosslinkable functional group; And
A pressure-sensitive adhesive composition for a foldable display comprising two or more different crosslinking agents for crosslinking the acrylic polymer,
[Equation 1]
? G "(G" (-20 ° C.) -G "(90 ° C.)) ≤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% The loss elastic modulus after curing of the pressure-sensitive adhesive composition measured at a temperature of 90 DEG C, a frequency of 100 rad / s and a strain rate of 0.1%. The method according to claim 1,
The acrylic polymer includes (meth) acrylic acid ester monomers and polymerized units of monomers copolymerizable with the (meth) acrylic acid ester monomers and having a crosslinkable functional group. 3. The method of claim 2,
Wherein the (meth) acrylic acid ester monomer is an alkyl (meth) acrylate. The method of claim 3,
The alkyl (meth) acrylate may be at least one selected from the group consisting of methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (Meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (Meth) acrylate, tetradecyl (meth) acrylate, octadecyl (meth) acrylate, and isobonyl (meth) acrylate. The method according to claim 1,
The crosslinkable functional group is at least one selected from the group consisting of a hydroxyl group, an isocyanate group, a glycidyl group, an epoxy group, an amine group and a carboxyl group. The method according to claim 1,
Wherein the crosslinkable functional group is a carboxyl group. 3. The method of claim 2,
Wherein the acrylic polymer comprises 50 to 99 parts by weight of a (meth) acrylic acid ester monomer and 1 to 20 parts by weight of a monomer having a crosslinkable functional group. The method according to claim 1,
Wherein at least two different crosslinking agents are polyfunctional compounds containing two or more functional groups capable of reacting with the crosslinkable functional groups of the acrylic polymer in one molecule. The method according to claim 1,
The two or more different crosslinking agents are each independently selected from the group consisting of alkoxysilane group, carboxyl group, acid anhydride group, vinyl ether group, amine group, carbonyl group, isocyanate group, epoxy group, aziridinyl group, carbodiimide group and oxazoline group Wherein the pressure-sensitive adhesive composition comprises at least one functional group selected from the group consisting of the following. The method according to claim 1,
Wherein the two or more different crosslinking agents comprise a first crosslinking agent which reacts with the crosslinkable functional group of the acrylic polymer and a second crosslinking agent which reacts with the crosslinkable functional group formed by the reaction of the first crosslinking agent. 11. The method of claim 10,
Wherein the first crosslinking agent is a crosslinking agent comprising an epoxy group and the second crosslinking agent is a crosslinking agent comprising an isocyanate group. The method according to claim 1,
Wherein the content of the two or more different crosslinking agents is in the range of 0.001 to 5 parts by weight based on 100 parts by weight of the acrylic polymer. 11. The method of claim 10,
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 according to claim 1,
The pressure-sensitive adhesive composition for a foldable display according to claim 1, wherein the pressure-sensitive adhesive composition has a loss modulus measured in a temperature range of -20 캜 to 90 캜 after curing in a range of 10 ⁴ Pa to 10 ⁶ Pa. The method according to claim 1,
Sensitive adhesive composition for a foldable display having a glass transition temperature (Tg) of -20 占 폚 or less in a state in which an acrylic polymer and two or more different crosslinking agents realize a crosslinked structure. A foldable display comprising a pressure-sensitive adhesive layer which is a cured product of a pressure-sensitive adhesive composition for a foldable display of claim 1.