WO2022124686A1 - Adhesive composition and adhesive sheet using same - Google Patents

Abstract

The present invention provides an adhesive composition comprising: a urethane oligomer having a radical polymerizable functional group on at least one end thereof; a dilution monomer; and a photo-initiator, wherein: the storage modulus (G') of the adhesive layer at -20℃ and 1Hz after curing is controlled to a particular range; the room-temperature adhesive strength of the adhesive layer to a glass substrate after curing is 5 N/25㎜ or more; and the adhesive strength of the adhesive layer to a glass substrate after heat treatment at 60℃ for 30 seconds is decreased compared with the room-temperature adhesive strength. The adhesive composition according to the present invention has excellent foldability while exhibiting high adhesive strength and superb reworkability.

Description

Adhesive composition and adhesive sheet using same

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same, and more particularly, to a pressure-sensitive adhesive composition showing high adhesion and excellent reworkability and excellent foldability, and a pressure-sensitive adhesive sheet using the same.

Among adhesives, an optically clear adhesive (OCA) having high transparency is used for interlayer adhesion for stacking components in an image display device. These optically transparent pressure-sensitive adhesives require high transmittance and low haze, and must satisfy physical properties such as adhesion to various substrates, heat resistance, and heat-and-moisture resistance.

Recently, a flexible display device or foldable device that can maintain display performance even when bent like paper by using a flexible material such as plastic or UTG (ultra thin glass) instead of a conventional inflexible glass substrate As the display device rapidly rises as a next-generation display device, the development of an optically transparent adhesive having excellent adhesion and excellent bending resistance is required to be suitable for application to these display devices. In addition, in order to secure the quality of products in various environments, development of an optically transparent adhesive having excellent foldability even in extreme environments such as low temperatures is required.

In addition, it is necessary to develop an optically transparent adhesive having excellent reworkability so that it can be removed and re-attached if necessary in the process of laminating parts.

Korean Patent Laid-Open No. 10-2013-0106368 discloses a (meth)acrylic acid ester-based monomer having a hydrocarbon group having 1 to 12 carbon atoms, a (meth)acrylic acid ester-based monomer containing a hydroxyl group, a monomer containing an amide group, and a vinyl ester-based monomer. An acrylic polymer compound obtained by copolymerizing the monomer component containing A pressure-sensitive adhesive composition comprising a crosslinking agent is disclosed.

However, the pressure-sensitive adhesive composition has a problem in that it is difficult to secure reworkability.

One object of the present invention is to provide an adhesive composition excellent in foldability while exhibiting high adhesion and excellent reworkability.

Another object of the present invention is to provide a pressure-sensitive adhesive sheet formed by using the pressure-sensitive adhesive composition.

On the other hand, the present invention is a pressure-sensitive adhesive composition comprising a urethane oligomer having a radically polymerizable functional group at at least one terminal, a diluting monomer and a photoinitiator,

After curing, the storage modulus (G') of the pressure-sensitive adhesive layer at -20 ° C and 1 Hz is 3 to 30 kPa,

Room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is 5 N/25 mm or more, and the adhesion to the glass substrate after heat-treating the pressure-sensitive adhesive layer at 60° C. for 30 seconds is reduced compared to the room temperature adhesion. .

In one embodiment of the present invention, the urethane oligomer may have one or more skeletons selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyester and polyether. .

In one embodiment of the present invention, the dilution monomer may include a (meth)acrylate having a C ₆ -C ₃₀ alkyl group and a (meth)acrylic monomer having a polar functional group.

In one embodiment of the present invention, the (meth)acrylic monomer having the polar functional group may be included in an amount of 3 to 30% by weight based on 100% by weight of the total dilution monomer.

In one embodiment of the present invention, the mixing ratio of the urethane oligomer and the diluting monomer may be 1:9 to 5:5 by weight.

In one embodiment of the present invention, the photoinitiator may be contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the total amount of the urethane oligomer and the diluting monomer.

On the other hand, the present invention provides a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention may be for a foldable display.

The pressure-sensitive adhesive composition according to the present invention exhibits excellent adhesion at room temperature with room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate of 5 N/25 mm or more after curing, and heat treatment of the pressure-sensitive adhesive layer at 60° C. for 30 seconds to the glass substrate The adhesion is reduced compared to the adhesion at room temperature, and thus the reworkability is excellent. In addition, the pressure-sensitive adhesive composition according to the present invention has excellent foldability at low temperature as the storage modulus (G') of the pressure-sensitive adhesive layer at -20°C and 1 Hz after curing is as low as 3 to 30 kPa.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention is a pressure-sensitive adhesive composition comprising a urethane oligomer having a radically polymerizable functional group at at least one terminal, a diluent monomer, and a photoinitiator,

After curing, the storage modulus (G') of the pressure-sensitive adhesive layer at -20 ° C and 1 Hz is 3 to 30 kPa,

Room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is 5 N/25 mm or more, and the adhesion to the glass substrate after heat treatment of the pressure-sensitive adhesive layer at 60 ° C. .

The storage modulus (G') means energy stored without loss due to elasticity, and the storage modulus (G') at -20 °C and 1 Hz is the storage modulus (G') measured at -20 °C and 1 Hz. indicates.

The storage modulus (G ') at -20 °C and 1 Hz is, for example, after curing, for a sample having a pressure-sensitive adhesive layer having a thickness of 25 μm, using a viscoelasticity measuring device (MCR-301, Anton Paar) at a frequency of 1 Hz - It is a value measured at 20 °C.

After curing, the storage modulus (G') of the pressure-sensitive adhesive layer at -20°C and 1Hz may be 3 to 30 kPa, preferably 3 to 20 kPa, as described above. After curing, if the storage modulus (G') is less than 3 kPa at -20°C and 1 Hz, it may be difficult to secure durability, and if it exceeds 30 kPa, it may be difficult to secure low-temperature foldability.

In addition, the pressure-sensitive adhesive composition according to the present invention has a room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is 5 N/25 mm or more, and the adhesion to the glass substrate after heat treatment of the pressure-sensitive adhesive layer at 60° C. for 30 seconds is the room temperature. Reworkability is excellent by lowering compared to adhesion.

The room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is a value measured at room temperature, for example, 23° C., according to the method described in Experimental Examples to be described later with respect to the sample on which the pressure-sensitive adhesive layer having a thickness of 25 μm is formed after curing. For example, the room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is determined by peeling the release film on one side of the pressure-sensitive adhesive sheet, bonding it with a PET film having a thickness of 38 μm, and cutting the specimen to have a width of 25 mm and a length of 200 mm. After manufacturing, the release film on the other side of the specimen was peeled off and attached to a glass substrate using a roller of 2 kg according to JIS Z 0237, stored at room temperature for 1 hour, and then peeled at 300 mm/min. It can be measured by peeling at a rate and peeling angle of 180 degrees.

If the adhesion of the pressure-sensitive adhesive layer to the glass substrate at room temperature after curing is less than 5 N/25 mm, it may be difficult to secure durability.

Adhesion to the glass substrate after the pressure-sensitive adhesive layer is heat-treated at 60° C. for 30 seconds is a value measured according to the method described in Experimental Examples to be described later with respect to a sample having a pressure-sensitive adhesive layer having a thickness of 25 μm after curing. For example, the adhesion to the glass substrate after the pressure-sensitive adhesive layer is heat-treated at 60° C. for 30 seconds is measured in the same manner as when measuring the adhesion at room temperature, and then the release film on the other side of the specimen is peeled off According to the regulations of JIS Z 0237, it can be measured by attaching it to a glass substrate using a roller of 2 kg, heat-treating it at 60° C. for 30 seconds, and then peeling it at a peeling rate of 300 mm/min and a peeling angle of 180 degrees.

After the pressure-sensitive adhesive layer is heat-treated at 60° C. for 30 seconds, the adhesion to the glass substrate is lowered compared to the adhesion at room temperature as described above. That is, the adhesive force to the glass substrate after heat treatment of the pressure-sensitive adhesive layer at 60 ℃ for 30 seconds is less than 5 N/25 mm, for example, 1 to 4 N/25 mm. When the adhesive layer is heat-treated at 60° C. for 30 seconds and the adhesion to the glass substrate is equal to or increased compared to the room temperature adhesion, the reworkability may be reduced.

In one embodiment of the present invention, the urethane oligomer may have a urethane bond in a molecule and a radical polymerizable functional group at at least one terminal.

The urethane oligomer may have an aliphatic skeleton. Specifically, the urethane oligomer may have one or more skeletons selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyester, and polyether.

The radical polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group, in particular a (meth)acryloyloxy group.

For example, the urethane oligomer may have a structure of Formula 1 below.

[Formula 1]

In the above formula,

A is polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyester or polyether,

L is a linking group containing a urethane bond,

B ¹ is an acryloyloxy group, a methacryloyloxy group, or a C ₁ -C ₁₀ alkoxy group,

B ² is an acryloyloxy group or a methacryloyloxy group.

As used herein, C ₁ -C ₁₀ Alkoxy group refers to a straight-chain or branched alkoxy group having 1 to 10 carbon atoms, and includes methoxy, ethoxy, n-propanoxy, butoxy, etc., but is limited thereto not.

Preferably, the urethane oligomer may have a structure of Formula 2 below.

[Formula 2]

In the above formula,

A is polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyester or polyether,

R ¹ is absent or is a C ₁ -C ₁₀ alkylene group,

R ² is a C ₁ -C ₁₀ alkylene group, a C ₃ -C ₁₀ cycloalkylene group or an arylene group,

R ³ is a C ₁ -C ₁₀ alkylene group or a C ₃ -C ₁₀ cycloalkylene group,

B ¹ is an acryloyloxy group, a methacryloyloxy group, or a C ₁ -C ₁₀ alkoxy group,

B ² is an acryloyloxy group or a methacryloyloxy group.

As used herein, a C ₁ -C ₁₀ alkylene group means a straight-chain or branched hydrocarbon consisting of 1 to 10 carbon atoms, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene, etc. included, but not limited thereto.

As used herein, a C ₃ -C ₁₀ cycloalkylene group refers to a simple or fused cyclic hydrocarbon consisting of 3 to 10 carbon atoms, for example, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, etc. included, but not limited thereto.

As used herein, the arylene group includes both an aromatic group, a heteroaromatic group, and partially reduced derivatives thereof. The aromatic group is a 5-membered to 15-membered simple or fused cyclic group, and the heteroaromatic group refers to an aromatic group containing at least one oxygen, sulfur or nitrogen. Representative examples of the arylene group include, but are not limited to, tolylene, phenylene, naphthylene, and the like.

In the C ₃ -C ₁₀ cycloalkylene group and the arylene group, one or more hydrogens may be substituted with a C ₁ -C ₆ alkyl group, a C ₁ -C ₆ alkoxy group, a halogen, or the like.

The urethane oligomer may be prepared by a method known in the art.

For example, the urethane oligomer may be prepared by reacting a polyol, a diisocyanate, and a radically polymerizable compound having a hydroxyl group. In addition to the radically polymerizable compound having a hydroxyl group, a C ₁ -C ₁₀ alcohol compound may be further used.

The polyol may be obtained commercially or may be prepared and used by a method known in the art. For example, the polyol may be a polyolefin, polyester polyol or polyether polyol having hydroxyl groups at both ends.

The polyolefin having hydroxyl groups at both ends may be prepared by reacting the polyolefin with an epoxy compound. As the epoxy compound, ethylene oxide, propylene oxide, or the like may be used. Examples of commercially available polyolefins having hydroxyl groups at both terminals include GI-1000, GI-2000, and GI-3000 manufactured by Nippon Soda Corporation.

The polyester polyol may be preferably a compound represented by the following formula (3).

[Formula 3]

In the above formula,

R is a divalent organic residue,

n is an integer from 1 to 100,

m is an integer from 0 to 100.

In one embodiment of the present invention, R may be a C ₁ -C ₂₀ alkylene group.

As used herein, a C ₁ -C ₂₀ alkylene group refers to a linear or branched divalent hydrocarbon having 1 to 20 carbon atoms, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene. , heptylene, octylene, nonylene, etc. are included, but are not limited thereto.

In one embodiment of the present invention, R may be, for example, an ethylene group or a butylene group.

When the polyester polyol represented by Formula 3 is used, it is preferable in terms of foldability, particularly foldability at low temperature, and adhesion to various substrates.

The number average molecular weight of the polyester polyol may be 200 to 100,000. If the number average molecular weight of the polyester polyol is less than 200, it may be difficult to secure low-temperature foldability due to an increase in low-temperature elastic modulus, and if it exceeds 100,000, it may be difficult to synthesize a urethane oligomer in the process because the viscosity is too high.

The polyether polyol is a product obtained by addition polymerization of alkylene oxide to a compound having two or more active hydrogens, polytetramethylene glycol obtained by ring-opening polymerization of tetrahydrofuran, and a modified copolymer of tetrahydrofuran and alkyl-substituted tetrahydrofuran. It may be polytetramethylene glycol, modified polytetramethylene glycol obtained by copolymerizing neopentyl glycol and tetrahydrofuran.

Ethylene oxide, propylene oxide, butylene oxide, etc. may be used as the alkylene oxide, and may be used alone or in combination of two or more.

Examples of the compound having two or more active hydrogens include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 2-methyl-1, 3-propanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-propanediol, 3-methyl- Molecular weight of 1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, hydroquinone, resorcinol, bisphenol A, bisphenol F, 4,4'-bisphenol, etc. 400 or less dihydroxy compounds; 1,2-cyclobutanediol, 1,3-cyclopentanediol, 1,4-cyclohexanediol, cycloheptanediol, cyclooctanediol, 1,4-cyclohexanedimethanol, hydroxypropylcyclohexanol, tricyclo[ 5.2.1.0 ^2,6 ]decane-dimethanol, bicyclo[4.3.0]-nonanediol, dicyclohexanediol, tricyclo[5.3.1.1]dodecanediol, bicyclo[4.3.0]nonanedimethanol, tricyclo[5.3.1.1]dodecane-diethanol, hydroxypropyltricyclo[5.3.1.1]dodecanol, spiro[3.4]octanediol, butylcyclohexanediol, 1,1'-bicyclohexylidenediol, alicyclic polyols such as cyclohexanetriol, hydrogenated bisphenol A, and 1,3-adamantanediol; polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; Polyester polyols, such as polyhexamethylene adipate, polyhexamethylene succinate, and polycaprolactone, etc. can be used.

The number average molecular weight of the polyether polyol may be 200 to 100,000.

As the diisocyanate compound, an aliphatic diisocyanate compound and/or an aromatic diisocyanate compound may be used.

Examples of the aliphatic diisocyanate compound include methyl diisocyanate, 1,2-ethanediyl diisocyanate, 1,3-propanediyl diisocyanate, 1,4-butanediyl diisocyanate, 1,6-hexanediyl diisocyanate, 3-methyl -octane-1,8-diyl diisocyanate, 1,2-cyclopropanediyl diisocyanate, 1,3-cyclobutanediyl diisocyanate, 1,3-cyclopentanediyl diisocyanate, 1,4-cyclohexanediyl diisocyanate , 1,3-cyclohexanediyl diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, isophorone diisocyanate, cyclohexene 1,4-diisocyanate, 4-methyl-cyclohexane-1,3-diyl di isocyanate and the like.

Examples of the aromatic diisocyanate compound include 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 3-chloro-1,2-benzene diisocyanate, and 4-chloro- 1,2-benzene diisocyanate, 5-chloro-1,2-benzene diisocyanate, 2-chloro-1,3-benzene diisocyanate, 4-chloro-1,3-benzene diisocyanate, 5-chloro-1, 3-Benzene diisocyanate, 2-chloro-1,4-benzene diisocyanate, 3-chloro-1,4-benzene diisocyanate, 3-methyl-1,2-benzene diisocyanate, 4-methyl-1,2- Benzene diisocyanate, 5-methyl-1,2-benzene diisocyanate, 2-methyl-1,3-benzene diisocyanate, 4-methyl-1,3-benzene diisocyanate, 5-methyl-1,3-benzene diisocyanate Isocyanate, 2-methyl-1,4-benzene diisocyanate, 3-methyl-1,4-benzene diisocyanate, 3-methoxy-1,2-benzene diisocyanate, 4-methoxy-1,2-benzene diisocyanate Isocyanate, 5-methoxy-1,2-benzene diisocyanate, 2-methoxy-1,3-benzene diisocyanate, 4-methoxy-1,3-benzene diisocyanate, 5-methoxy-1,3- Benzene diisocyanate, 2-methoxy-1,4-benzene diisocyanate, 3-methoxy-1,4-benzene diisocyanate, 3,4-dimethyl-1,2-benzene diisocyanate, 4,5-dimethyl- 1,3-Benzene diisocyanate, 2,3-dimethyl-1,4-benzene diisocyanate, 3-chloro-4-methyl-1,2-benzene diisocyanate, 3-methyl-4-chloro-1,2- Benzene diisocyanate, 3-methyl-5-chloro-1,2-benzene diisocyanate, 2-chloro-4-methyl-1,3-benzene diisocyanate, 4-chloro-5-methoxy-1,3-benzene Diisocyanate, 5-chloro-2-fluoro-1,3-benzene diisocyanate, 2-chloro-3-bromo-1,4-benzene diisocyanate, 3-chloro-5-isopropoxy-1,4 -Benzene diisocyanate, 4,4'-methylenebis(phenyl isocyanate), 2,2-diphenylpropane-4,4'-diisocyanate, 4,4'-diphenyl diisocyanate, azobenzene -4,4'-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, m - or p-tetramethylxylene diisocyanate, 2,3-diisocyanate pyridine, 2,4-diisocyanate pyridine, 2,5-diisocyanate pyridine, 2,6-diisocyanate pyridine, 2,5-diisocyanate-3 -methylpyridine, 2,5-diisocyanate-4-methylpyridine, 2,5-diisocyanate-6-methylpyridine, etc. are mentioned.

As the radically polymerizable compound having a hydroxyl group, a hydroxyl group-containing (meth)acrylate compound can be used. Examples of the hydroxyl group-containing (meth)acrylate compound include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-n-propyl (meth)acrylate, and 2-hydroxy- n-propyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 2-hydroxy-n-butyl (meth)acrylate, 3-hydroxy-n-butyl (meth)acrylate, 5 -Hydroxy-n-pentyl (meth)acrylate, 2-hydroxy-n-pentyl (meth)acrylate, 3-hydroxy-n-pentyl (meth)acrylate, 4-hydroxy-n-pentyl ( and meth)acrylate, 2-hydroxycyclopropyl (meth)acrylate, 3-hydroxycyclopentyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, and the like.

Examples of the C ₁ -C ₁₀ alcohol compound include methanol, ethanol, n-propanol, and butanol.

The urethane oligomer may have a weight average molecular weight (in terms of polystyrene) of 1,000 to 200,000, preferably 10,000 to 100,000, measured by gel permeation chromatography (GPC). When the weight average molecular weight of the urethane oligomer is out of the above range, it may be difficult to secure fairness or reliability may be reduced.

In one embodiment of the present invention, the diluent monomer is a component that can act as a dispersion medium for the urethane oligomer and can be polymerized by the action of a photoinitiator. In addition, the diluent monomer can be easily coated by diluting the pressure-sensitive adhesive composition to adjust the viscosity.

The dilution monomer may include a (meth)acrylic monomer.

Here, (meth)acryl means acryl and/or methacryl.

Preferably, the dilution monomer may include a (meth)acrylate having a C ₆ -C ₃₀ alkyl group and a (meth)acrylic monomer having a polar functional group.

The (meth)acrylate having a C ₆ -C ₃₀ alkyl group has a low glass transition temperature (Tg) and can lower the storage modulus after curing of the pressure-sensitive adhesive composition, thereby improving foldability.

Examples of the (meth)acrylate having an alkyl group of C ₆ -C ₃₀ include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, Nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, cetyl (meth) Acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate and the like can be used, and among these, 2-ethylhexyl (meth) acrylate and the like are preferable. These can be used individually or in combination of 2 or more types.

The (meth)acrylic monomer having the polar functional group can form a hydrogen bond or an ionic bond with the polar group of the lower substrate, thereby improving the adhesion of the pressure-sensitive adhesive composition.

The (meth)acryl monomer having a polar functional group may be at least one of (meth)acrylate having a hydroxyl group and (meth)acrylamide having a nitrogen atom.

Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl ( Meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, hydroxy having 2-4 carbon atoms in the alkylene group and hydroxyalkylene glycol (meth)acrylate, and among these, 4-hydroxybutyl acrylate and 2-hydroxyethyl (meth)acrylate are preferable.

Examples of the (meth)acrylamide having a nitrogen atom include (meth)acrylamide, dimethyl (meth)acrylamide, acryloylmorpholine, dimethylaminopropyl (meth)acrylamide, isopropyl (meth)acrylamide, diethyl (meth)acrylamide, hydroxyethyl (meth)acrylamide, diacetone (meth)acrylamide, etc. are mentioned.

The (meth)acrylic monomer having the polar functional group may be included in an amount of 3 to 30% by weight based on 100% by weight of the total dilution monomer. When the content of the (meth)acrylic monomer having the polar functional group is less than 3% by weight, the adhesion may be lowered, and if it exceeds 30% by weight, the low-temperature elastic modulus may be increased.

In one embodiment of the present invention, the mixing ratio of the urethane oligomer and the diluting monomer may be 1:9 to 5:5, preferably 2:8 to 6:4 by weight. If the amount of the urethane oligomer in the mixing ratio of the urethane oligomer and the dilution monomer is less than the above range, the thickness deviation may increase in the sheet manufacturing process, and if it is more than the above range, the adhesion may be lowered, thereby reducing reliability.

The diluent monomer may further include other polymerizable monomers in addition to the monomers.

Specific examples of the other polymerizable monomer include n-butyl (meth) acrylate, 2-butyl (meth) acrylate, t-butyl (meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate , n-propyl (meth) acrylate, isopropyl (meth) acrylate, pentyl (meth) acrylate, isobornyl (meth) acrylate, etc., among these, isobornyl (meth) acrylate is preferable. . These can be used individually or in mixture of 2 or more types.

The other polymerizable monomer may be included in an amount of 10% by weight or less based on 100% by weight of the total dilution monomer. When the content of the other polymerizable monomer is more than 10% by weight, the low-temperature elastic modulus may increase.

In one embodiment of the present invention, the photoinitiator means an initiator that absorbs an active energy ray to generate a radical.

The photoinitiators include, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2 ,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl Ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2- Propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone (EAB-F), dichlorobenzophenone, 2-methyl anthraquinone, 2-ethyl anthraquinone, 2- t-Butyl anthraquinone, 2-amino anthraquinone, 2-methyl thioxanthone, 2-ethyl thioxanthone, 2-chloro thioxanthone, 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone Tone (DETX), 4-isopropylthioxanthone (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamino benzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-) Methylvinyl)phenyl]propane], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-(3,4-methylenedioxyphenyl)-4,6-bis(trichloromethyl)-1, 3,5-triazine, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole (HABI-101), 2,2'-bis(2- Methoxyphenyl)-4,4',5,5'-tetraphenylbiimidazole (HABI-107), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxy phenyl)-4',5'-diphenylbiimidazole (TCDM), etc. are mentioned. These can be used individually or in mixture of 2 or more types.

The photoinitiator may be contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the total amount of the urethane oligomer and the diluent monomer. When the amount is less than 0.01 parts by weight, photocuring does not proceed sufficiently, making it difficult to implement mechanical properties or adhesion of the finally obtained pressure-sensitive adhesive sheet.

In addition to the above components, the pressure-sensitive adhesive compositions according to an embodiment of the present invention include a plasticizer, a silane coupling agent, and adhesiveness in order to control the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, antistatic property, etc. required according to the use. Additives such as imparting resins, antioxidants, corrosion inhibitors, leveling agents, surface lubricants, dyes, pigments, defoamers, fillers, light stabilizers, and antistatic agents may be further included.

One embodiment of the present invention relates to a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive sheet may be one in which the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition according to the present invention on the base film, or the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention is interposed between two base films.

The base film may include a polyolefin-based film, a polyester-based film, an acrylic film, a styrene-based film, an amide-based film, a polyvinyl chloride film, a polyvinylidene chloride film, a polycarbonate film, and the like, and these are silicone-based, fluorine-based, silica It may be a mold release treatment suitably made with powder or the like.

The thickness of the base film is preferably 30 to 80㎛. When the thickness is less than 30 μm, the base film is vulnerable to engraving defects, and when it exceeds 80 μm, handling properties may be deteriorated.

An adhesive layer can be formed by the method of coating an adhesive composition on one base film. The coating method is not particularly limited as long as it is a method known in the art, and for example, a method such as a bar coater, air knife, gravure, reverse roll, kiss roll, spray, blade, die coater, casting, spin coating, etc. can be used. . Specifically, it can be formed by coating the pressure-sensitive adhesive composition on one base film, irradiating it with an ultraviolet irradiation amount of about 100 to 2000 mJ/cm 2 , preferably 200 to 1500 mJ/cm 2 , and photocuring it.

The pressure-sensitive adhesive layer may have a thickness of 10 to 2,000 μm, preferably 25 to 1,500 μm. If the thickness of the pressure-sensitive adhesive layer is less than 10㎛, it may be difficult to buffer an impact generated from the outside, and if it exceeds 2,000㎛, transmission may be lowered and optical performance may be deteriorated.

The adhesive sheet according to an embodiment of the present invention may improve adhesion by surface-treating the adhesive layer before bonding.

The surface treatment method is not particularly limited, and for example, the surface of the pressure-sensitive adhesive layer may be activated by a method such as corona discharge treatment, plasma treatment, ultraviolet irradiation, electron beam irradiation, or applying an anchoring agent.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention is applicable to not only a general flat panel display and a flexible display but also a foldable display. In particular, the pressure-sensitive adhesive sheet according to an embodiment of the present invention has excellent foldability because the storage modulus at low temperature is controlled to be in the range of 3 to 30 kPa, so it can be effectively applied to interlayer adhesion for laminating components in a foldable display device. Specifically, the adhesive sheet may be applied to bonding various display materials such as an antenna, a display panel, a polarizer, a touch sensor, a cover window, a bezel, a polymer film, and an FPCB.

Hereinafter, the present invention will be described in more detail by way of Examples, Comparative Examples and Experimental Examples. These Examples, Comparative Examples, and Experimental Examples are only for illustrating the present invention, and it is apparent to those skilled in the art that the scope of the present invention is not limited thereto.

Preparation Example 1: Preparation of urethane oligomer

81 parts by weight of polycaprolactone diol having a number average molecular weight of 1230 [manufactured by Daicel Chemical Industry Co., Ltd., trade name: Placcel212] 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80 ° C. A urethane oligomer having a weight average molecular weight of 70,000 was prepared by reacting 5 parts by weight of 2-hydroxyethyl acrylate with the isocyanate polymer obtained by the reaction.

Preparation Example 2: Preparation of urethane oligomer

81 parts by weight of polycaprolactone diol having a number average molecular weight of 2000 [manufactured by Daicel Chemical Industry Co., Ltd., trade name: Placcel220] 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80 ° C. A urethane oligomer having a weight average molecular weight of 85,000 was prepared by reacting 8 parts by weight of 2-hydroxyethyl acrylate with the isocyanate polymer obtained by the reaction.

Preparation Example 3: Preparation of acrylic copolymer

In a 1L reactor in which nitrogen gas is refluxed and a cooling device is installed for easy temperature control, 80 parts by weight of 2-ethylhexyl acrylate (2-EHA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA) After the monomer mixture was added, 300 parts by weight of ethyl acetate (EAc) as a solvent was added. Then, nitrogen gas was purged for 1 hour to remove oxygen, and then maintained at 80°C. After uniformly mixing the mixture, 0.1 parts 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: 1.56 million, PDI 4.1)

Preparation Example 4: Preparation of acrylic syrup

In a mixture containing 90.5 parts by weight of 2-ethylhexyl acrylate, 9 parts by weight of 2-hydroxyethyl acrylate (2-HEA) and 0.5 parts by weight of 1,6-hexanediol diacrylate, 1-hydroxy- After mixing 0.5 parts by weight of cyclohexyl-phenyl-ketone (1-hydroxy-cyclohexyl-phenyl-ketone), while measuring the viscosity of the mixture using a viscosity measuring device, the viscosity of the mixture is about 20 Pa·s Ultraviolet rays were irradiated using an ultraviolet irradiation device until the The viscosity measurement WHEREIN: The rotor rotation speed of the apparatus was 20 rpm, and the measurement temperature was 30 degreeC. Thereby, a prepolymer composition in which a part of the monomer component in the mixture was polymerized was obtained as a prepolymer composition, that is, an acrylic syrup.

Examples 1 to 4 and Comparative Examples 1 to 2: Preparation of pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

A pressure-sensitive adhesive composition was prepared by mixing with the composition shown in Table 1 below (parts by weight).

		Example				comparative example
		One	2	3	4	One	2
polymer	Preparation Example 1	20		20	20
	Preparation Example 2		20
	Preparation 3					100
	Preparation 4						100
dilution monomer	2-EHA	60	60	75	75
	4-HBA	20	20
	2-HEA			5	4
	DMAA				One
additive	DHEH	One	One	One			One
thermosetting agent	Coronate-L					0.5
photoinitiator	I-184	0.5	0.5	0.5	0.5		0.5

2-EHA: 2-ethylhexyl acrylate

4-HBA: 4-hydroxybutyl acrylate

2-HEA: 2-hydroxyethyl acrylate

DMAA: Dimethylacrylamide

DHEH: bis(2-ethylhexyl)cyclonucleic acid-1,2-dicarboxylate (plasticizer)

Coronate-L: Japanese Urethane (TDI+TMP adduct)

I-184: Igacure 184 (BASF)

The pressure-sensitive adhesive compositions of Examples 1 to 4 and Comparative Examples 1 to 2 prepared above were coated on a release-treated polyethylene terephthalate film (thickness: 75 μm) using a bar coater. Thereafter, the pressure-sensitive adhesive compositions of Examples 1 to 4 and Comparative Example 2 were cured by irradiating ultraviolet rays with a light amount of 2J/cm 2 for 8 minutes using a UV lamp, and the pressure-sensitive adhesive composition of Comparative Example 1 was cured at 100° C. for 5 minutes. By drying and curing, a pressure-sensitive adhesive sheet was prepared so that the pressure-sensitive adhesive composition had a thickness of 25 μm after curing.

Experimental Example 1:

The physical properties of the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 2 below.

(1) Room temperature adhesion

After peeling the release film from one side of the pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples, corona-treating the pressure-sensitive adhesive side, bonding it with a PET film of 38 μm, and cutting it to a width of 25 mm and a length of 100 mm to prepare a specimen prepared. Then, the release film on the other side was peeled off, and the pressure-sensitive adhesive sheet was attached to the alkali glass using a roller of 2 kg according to JIS Z 0237. Alkali glass with adhesive sheet is pressed in an autoclave (50°C, 5 atm) for about 20 minutes, stored for 1 hour in constant temperature and humidity conditions (23°C, 50% relative humidity), and then TA equipment (Texture Analyzer (manufactured by Stable Microsystems, UK), the pressure-sensitive adhesive sheet was peeled from alkali glass at a peeling rate of 300 mm/min and a peeling angle of 180 degrees to measure room temperature adhesion.

(2) 60℃ adhesion

After peeling the release film from one side of the pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples, corona-treating the pressure-sensitive adhesive side, bonding it with a PET film of 38 μm, and cutting it to a width of 25 mm and a length of 100 mm to prepare a specimen prepared. Then, the release film on the other side was peeled off, and the pressure-sensitive adhesive sheet was attached to the alkali glass using a roller of 2 kg according to JIS Z 0237. Alkali glass with adhesive sheet is pressed in an autoclave (50℃, 5 atm) for about 20 minutes, placed on a hot plate at 60℃, left for 30 seconds, and then TA equipment (Texture Analyzer, UK) within 15 seconds Table Microsystems Co., Ltd.), the adhesive sheet was peeled from the alkali glass at a peeling rate of 300 mm/min and a peeling angle of 180 degrees to measure adhesion at 60°C.

(3) Storage modulus (G')

For the adhesive sheets prepared in Examples and Comparative Examples, the storage modulus at -20°C was measured using a viscoelasticity measuring device (MCR-301, Anton Paar). More specifically, the size of the pressure-sensitive adhesive sheet was cut to 30 mm in length × 30 mm in width, and after removing the release film attached to one side of the cut adhesive sheet, it was bonded to a glass substrate, and then the measuring tip and In the adhered state, measurements were made under the conditions of a frequency of 1.0 Hz, a strain of 2%, and a temperature increase rate of 5°C/min in a temperature range of -30 to 100°C, and the measured value at -20°C was read at this time.

(4) foldability

The adhesive sheets prepared in Examples and Comparative Examples were bonded to a 50 μm PET film, cut into 20 mm×100 mm, and used as a specimen. Fix the specimen to a flexibility evaluation device (COVOTECH, CFT-720C) for evaluation of foldability, make it fold with a radius of curvature of 2mm, fold 25 times per minute, and hold 0.2 seconds after folding -20 Foldability was evaluated under the condition of °C. When foldability evaluation is applied, one folding is referred to as 1 cycle, and the number of first cycles in which streaks or other stripes occur in the folding area or breakage, lifting, peeling, etc. of the adhesive sheet are evaluated. , when lifting, peeling, etc. occurred, it was judged as NG, and if not, it was judged as OK.

(5) high temperature reliability

After placing the adhesive sheets prepared in Examples and Comparative Examples between the polarizing plate and the PET film, plywood, and storing them for 10 days at high temperature and high humidity (85°C, 85% relative humidity), visually observe whether bubbles or peeling occur. Confirmed.

<Evaluation criteria>

OK: no air bubbles and peeling

NG: with bubbles and/or peeling

division		Example				comparative example
		One	2	3	4	One	2
adhesion [N/25mm]	room temperature	12.5	13.2	11.2	13.8	12.0	11.3
	60℃, 30sec	6.2	6.3	5.2	7.6	13.4	7.2
Storage modulus (Pa)	-20℃	13000	12000	13000	17000	13000	33000
-20℃ foldability (times)		50,000 OK	50,000 OK	50,000 OK	50,000 OK	50,000 OK	1,000 NGs
high temperature reliability		OK	OK	OK	OK	OK	OK

As can be seen in Table 2, the pressure-sensitive adhesive composition of Examples 1 to 4 comprising a urethane oligomer having a radically polymerizable functional group at at least one end according to the present invention, a diluting monomer and a photoinitiator according to the present invention is a glass substrate of the pressure-sensitive adhesive layer after curing The adhesion to the glass substrate is 5 N/25 mm or more, indicating excellent adhesion at room temperature, and the adhesion to the glass substrate after heat-treating the pressure-sensitive adhesive layer at 60° C. for 30 seconds is lowered compared to the room temperature adhesion. . In addition, it can be seen that the pressure-sensitive adhesive compositions of Examples 1 to 4 have excellent foldability at low temperatures as the storage modulus (G') of the pressure-sensitive adhesive layer at -20°C and 1 Hz after curing is as low as 3 to 30 kPa.

On the other hand, in the thermosetting type pressure-sensitive adhesive composition of Comparative Example 1 using an acrylic copolymer instead of a urethane oligomer having a radically polymerizable functional group at at least one end, the adhesive composition to the glass substrate after heat treatment at 60° C. for 30 seconds was higher than the room temperature adhesion. The pressure-sensitive adhesive composition of Comparative Example 2 of the UV curing type using acrylic syrup instead of the urethane oligomer having a radically polymerizable functional group at at least one end showed that the reworkability was poor, and the pressure-sensitive adhesive composition of Comparative Example 2 was cured at -20°C and The storage modulus (G') at 1 Hz exceeded 30 kPa, indicating that the foldability at low temperature was poor.

As the specific part of the present invention has been described in detail above, for those of ordinary skill in the art to which the present invention pertains, it is clear that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereto. do. Those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (8)

1. A pressure-sensitive adhesive composition comprising a urethane oligomer having a radically polymerizable functional group at at least one terminal, a diluting monomer, and a photoinitiator,

   After curing, the storage modulus (G') of the pressure-sensitive adhesive layer at -20 ° C and 1 Hz is 3 to 30 kPa,

   Room temperature adhesion of the pressure-sensitive adhesive layer to the glass substrate after curing is 5 N/25 mm or more, and the adhesion to the glass substrate after heat treatment of the pressure-sensitive adhesive layer at 60° C. for 30 seconds is lowered compared to the room temperature adhesive composition.
2. The pressure-sensitive adhesive composition according to claim 1, wherein the urethane oligomer has at least one skeleton selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, hydrogenated polyisoprene, polyester and polyether.
3. The pressure-sensitive adhesive composition according to claim 1, wherein the diluting monomer includes a (meth)acrylate having a C ₆ -C ₃₀ alkyl group and a (meth)acrylic monomer having a polar functional group.
4. The pressure-sensitive adhesive composition according to claim 3, wherein the (meth)acrylic monomer having a polar functional group is included in an amount of 3 to 30% by weight based on 100% by weight of the total dilution monomer.
5. The pressure-sensitive adhesive composition of claim 1, wherein a mixing ratio of the urethane oligomer and the diluting monomer is 1:9 to 5:5 by weight.
6. The pressure-sensitive adhesive composition according to claim 1, wherein the photoinitiator is contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the total amount of the urethane oligomer and the diluting monomer.
7. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 6.
8. The pressure-sensitive adhesive sheet according to claim 7, which is for a foldable display.