WO2022124685A1 - Adhesive composition and adhesive sheet using same - Google Patents

Abstract

The present invention provides an adhesive composition comprising: a urethane oligomer having a polyester backbone and having a radical polymerizable functional group at at least one end thereof; a diluent monomer; and a photoinitiator. The adhesive composition according to the present invention exhibits a high adhesiveness on various substrates, and has a low storage modulus (G') at -20°C and 1 Hz of an adhesive layer after curing, and thus provides excellent foldability.

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 that exhibits high adhesion to various substrates and has 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.

Korean Patent Registration No. 10-2084113 discloses a monomer mixture comprising an alkyl group-containing acrylate and a hydroxyl group-containing acrylate; And a pressure-sensitive adhesive composition comprising an initiator is disclosed.

However, the pressure-sensitive adhesive composition has a problem in that it is difficult to secure excellent foldability, particularly, foldability at low temperature when applied to a foldable display device.

One object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits high adhesion to various substrates and has excellent foldability.

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

The pressure-sensitive adhesive composition according to an embodiment of the present invention may have a storage modulus (G') of 3 to 30 kPa at -20°C and 1 Hz after curing.

In one embodiment of the present invention, the radically polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group.

In one embodiment of the present invention, the urethane oligomer may be a reactant of a polyester polyol, a polyisocyanate, and a radically polymerizable compound having a hydroxyl group.

In one embodiment of the present invention, the polyester polyol may be 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, the radically polymerizable compound having a hydroxyl group may include (meth)acrylate having a hydroxyl group.

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 has a polyester backbone, and exhibits high adhesion to various substrates, including a urethane oligomer having a radically polymerizable functional group at at least one end, and storage at -20°C and 1Hz of the pressure-sensitive adhesive layer after curing The elastic modulus (G') is low at a level of 3 to 30 kPa, and the foldability at low temperature is excellent.

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

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

The pressure-sensitive adhesive composition according to an embodiment of the present invention has a polyester backbone and includes a urethane oligomer having a radically polymerizable functional group at at least one end, thereby having a low storage modulus at low temperature and excellent foldability, and adhesion to various substrates This is excellent.

The pressure-sensitive adhesive composition according to an embodiment of the present invention may have a storage modulus (G') of 3 to 30 kPa, preferably 3 to 20 kPa, at -20°C and 1 Hz after curing. 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.

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.

In one embodiment of the present invention, the urethane oligomer has a urethane bond in the molecule, has a polyester skeleton, and has a radically polymerizable functional group at at least one terminal.

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 polyester,

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 polyester,

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, 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 polyester polyol, 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 polyester polyol may be obtained commercially or may be prepared and used by a method known in the art.

Examples of the polyester polyol include a polycaprolactone polyol obtained by ring-opening polymerization of a low molecular weight polyol and ε-caprolactone.

The polyester polyol may be 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.

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.

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 60,000 was prepared by reacting 9 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 80,000 was prepared by reacting 9 parts by weight of 2-hydroxyethyl acrylate with the isocyanate polymer obtained by the reaction.

Preparation Example 3: 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 dibutyltindilaurate catalyst (DBTDL) and 1,6-hexamethylene diisocyanate 10 parts by weight A urethane oligomer having a weight average molecular weight of 70,000 was prepared by reacting 9 parts by weight of 2-hydroxyethyl acrylate with an isocyanate polymer obtained by reacting the parts at 80°C.

Preparation Example 4: Preparation of urethane oligomer

To an isocyanate polymer obtained by reacting 81 parts by weight of polypropylene glycol having a number average molecular weight of 1000 (Hannon-Hwaseong, PPG1000) with 10 parts by weight of isophorone diisocyanate with 500 ppm of dibutyltin dilaurate catalyst (DBTDL) at 80° C. A urethane oligomer having a weight average molecular weight of 60,000 was prepared by reacting 9 parts by weight of hydroxyethyl acrylate.

Examples 1 to 5 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 the composition shown in Table 1 below (parts by weight).

		Example					comparative example
		One	2	3	4	5	One	2
urethane oligomer	Preparation Example 1	40				40
	Preparation Example 2		40		20
	Preparation 3			40
	Preparation 4						40	20
dilution monomer	2-EHA	50	50	50	60	53	50	60
	4-HBA	10	10	10		5	10
	2-HEA				20			20
	ACMO					2
photoinitiator	I-184	One	One	One	One	One	One	One

2-EHA: 2-ethylhexyl acrylate

4-HBA: 4-hydroxybutyl acrylate

2-HEA: 2-hydroxyethyl acrylate

ACMO: acryloyl morpholine

I-184: Igacure 184 (BASF)

The pressure-sensitive adhesive compositions of Examples 1 to 5 and Comparative Examples 1 and 2 prepared above were coated on a release-treated polyethylene terephthalate film (thickness: 75 μm) using a bar coater. Thereafter, an adhesive sheet was prepared so that the thickness after curing of the pressure-sensitive adhesive composition was 50 μm by irradiating ultraviolet rays with a light amount of 2.0 J/cm 2 for 10 minutes using a UV lamp to cure the pressure-sensitive adhesive composition.

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) Adhesion

Adhesion to various substrates of the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples was measured.

After peeling the release film from one side of the pressure-sensitive adhesive sheet, corona-treating the pressure-sensitive adhesive side, bonding it with a PET film of 38 μm, and cutting it to have a width of 25 mm and a length of 100 mm to prepare a specimen. 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 an 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 the alkali glass at a peeling rate of 300 mm/min and a peeling angle of 180 degrees to measure room temperature adhesion.

In addition, PET (polyethylene terephthalate) adhesion was measured in the same manner except for using a PET film attached with a double-sided tape on alkali glass as an adherend.

(2) 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 adhesive sheet was cut to 30 mm in length × 30 mm in width, and the release film attached to one side of the cut adhesive sheet was removed, and then 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.

(3) 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.

(4) 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 in a high temperature and high humidity (85℃, 85% relative humidity) condition, 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	5	One	2
Adhesion (N/25㎜)	alkali glass	12	13	12	15	11	4	6
	PET	9	8	7	11	9	3	5
Storage modulus (Pa)	-20℃	13000	8000	15000	12000	16000	36000	34000
-20℃ foldability (times)		50,000 OK	50,000 OK	50,000 OK	50,000 OK	50,000 OK	1,000 NGs	1,000 NGs
high temperature reliability		OK	OK	OK	OK	OK	OK	OK

As can be seen in Table 2, the pressure-sensitive adhesive composition of Examples 1 to 5 comprising a urethane oligomer, a diluent monomer and a photoinitiator having a polyester backbone and a radically polymerizable functional group at at least one terminal according to the present invention. It can be seen that the adhesion to the substrate is excellent, and the storage modulus (G') of the pressure-sensitive adhesive layer at -20°C and 1 Hz after curing is low at a level of 3 to 30 kPa, indicating excellent foldability.

On the other hand, the pressure-sensitive adhesive composition of Comparative Examples 1 and 2 using a urethane oligomer having a polyester backbone and a polyether backbone instead of a urethane oligomer having a radically polymerizable functional group at at least one terminal is cured at -20°C and 1Hz of the pressure-sensitive adhesive layer The storage modulus (G ') in , it was found that the foldability was poor in excess of 30 kPa.

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 (12)

1. A pressure-sensitive adhesive composition comprising a urethane oligomer having a polyester backbone and a radically polymerizable functional group at at least one terminal, a diluent monomer, and a photoinitiator.
2. The pressure-sensitive adhesive composition according to claim 1, wherein the storage modulus (G') is 3 to 30 kPa at -20°C and 1 Hz after curing.
3. The pressure-sensitive adhesive composition according to claim 1, wherein the radical polymerizable functional group is a (meth)acryloyloxy group or a vinyl group.
4. The pressure-sensitive adhesive composition according to claim 1, wherein the urethane oligomer is a reaction product of a polyester polyol, a polyisocyanate, and a radically polymerizable compound having a hydroxyl group.
5. The pressure-sensitive adhesive composition according to claim 4, wherein the polyester polyol is a compound represented by the following formula (3):

   [Formula 3]

   

   In the above formula,

   R is a divalent organic moiety,

   n is an integer from 1 to 100,

   m is an integer from 0 to 100.
6. The pressure-sensitive adhesive composition according to claim 4, wherein the radical polymerizable compound having a hydroxyl group includes (meth)acrylate having a hydroxyl group.
7. 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.
8. The pressure-sensitive adhesive composition according to claim 7, 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.
9. 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.
10. 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.
11. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 10.
12. The pressure-sensitive adhesive sheet according to claim 11, which is for a foldable display.