JP2023552536A - Adhesive composition and adhesive sheet using the same - Google Patents

Abstract

The present invention provides an adhesive composition containing a urethane oligomer having a polyester skeleton and a radically polymerizable functional group at at least one end, a diluent monomer, and a photoinitiator. The adhesive composition according to the present invention exhibits high adhesion to various substrates, and has a low storage modulus (G') at -20°C and 1 Hz of the adhesive layer after curing, and has good foldability. Excellent.

Description

The present invention relates to an adhesive composition and an adhesive sheet using the same, and more particularly, an adhesive composition that exhibits high adhesion to various base materials and has excellent foldability, and an adhesive sheet using the same. Regarding the seat.

Among adhesives, optically clear adhesive (OCA), which has high transparency, is used for interlayer adhesion for laminating parts in image display devices. Such optical transparent adhesives are required to have high transmittance and low haze, and must satisfy physical properties such as adhesion to various base materials and heat resistance and moist heat resistance durability.

In recent years, flexible materials such as plastic and UTG (ultra thin glass) have been used instead of conventional inflexible glass substrates, which can maintain display performance even when bent like paper. As display devices or foldable display devices are rapidly emerging as next-generation display devices, we would like to discuss optical transparent adhesives with excellent adhesion and bending resistance that are suitable for application to these display devices. development is required. Furthermore, in order to ensure the quality of products in a variety of environments, there is a need to develop transparent adhesives for optical applications that have excellent foldability even in extreme environments such as low temperatures.

Korean Patent No. 10-2084113 discloses an adhesive composition containing a monomer mixture containing an alkyl group-containing acrylate and a hydroxyl group-containing acrylate; and an initiator.

However, when the adhesive composition is applied to a foldable display device, it is difficult to ensure excellent foldability, especially at low temperatures.

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 using the pressure-sensitive adhesive composition.

On the other hand, the present invention provides an adhesive composition containing a urethane oligomer having a polyester skeleton and a radically polymerizable functional group at at least one end, a diluent monomer, and a photoinitiator.

The 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 reaction product of a polyester polyol, a polyisocyanate, and a radically polymerizable compound having a hydroxy group.

In one embodiment of the present invention, the polyester polyol may be a compound represented by Formula 3 below.

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 hydroxy group may include a (meth)acrylate having a hydroxy group.

In one embodiment of the invention, the diluent 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 a 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 diluent monomer may be 1:9 to 5:5 on a weight basis.

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 urethane oligomer and diluent monomer.

On the other hand, the present invention provides a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.
The adhesive sheet according to one embodiment of the present invention may be used for foldable displays.

The pressure-sensitive adhesive composition according to the present invention has a polyester skeleton and contains a urethane oligomer having a radically polymerizable functional group at at least one end, so that it exhibits high adhesion to various substrates, and also exhibits high adhesion after curing. The adhesive layer has a low storage modulus (G') of about 3 to 30 kPa at -20°C and 1 Hz, so it has excellent foldability at low temperatures.

The present invention will be explained in more detail below.

One embodiment of the present invention relates to an adhesive composition containing a urethane oligomer having a polyester skeleton and having a radically polymerizable functional group at at least one end, a diluent monomer, and a photoinitiator.

The adhesive composition according to one embodiment of the present invention has a polyester skeleton and contains a urethane oligomer having a radically polymerizable functional group at at least one end, so that the adhesive composition has a low storage modulus at low temperatures and is foldable. It has excellent adhesion to various base materials.

The 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. If the storage modulus (G') at -20°C and 1 Hz after curing is less than 3 kPa, it may be difficult to ensure durability, and if it exceeds 30 kPa, it may be difficult to ensure low-temperature foldability. .

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

The storage modulus (G') at -20°C and 1 Hz is measured, for example, using a viscoelasticity measuring device (MCR-301, manufactured by Anton Paar) for a sample on which an adhesive layer with a thickness of 25 μm has been formed after curing. ) at -20°C at a frequency of 1Hz.

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

The radically polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group, particularly a (meth)acryloyloxy group.

For example, the urethane oligomer may have a structure represented by Chemical Formula 1 below.

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.

The C ₁ -C ₁₀ alkoxy group used herein means a linear or branched alkoxy group having 1 to 10 carbon atoms, and includes methoxy, ethoxy, n-propanoxy, butoxy, etc. However, it is not limited to these.

Preferably, the urethane oligomer may have a structure represented by Chemical Formula 2 below.

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.

The C ₁ -C ₁₀ alkylene group used herein means a linear or branched hydrocarbon having 1 to 10 carbon atoms, such as methylene, ethylene, propylene, butylene, pentylene, hexylene. These include, but are not limited to.

The C ₃ -C ₁₀ cycloalkylene group used herein means a monocyclic or condensed cyclic hydrocarbon having 3 to 10 carbon atoms, such as cyclopropylene, cyclobutylene, cyclopentylene. , cyclohexylene, etc., but are not limited to these.

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

In the C ₃ -C ₁₀ cycloalkylene group and 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 manufactured by a method known in the art.

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

The polyester polyol may be obtained commercially or may be produced by a method known in the art.

Examples of the polyester polyol include 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 Chemical Formula 3 below.

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 invention, R may be a C ₁ -C ₂₀ alkylene group.

The C ₁ -C ₂₀ alkylene group used herein means a linear or branched divalent hydrocarbon having 1 to 20 carbon atoms, such as methylene, ethylene, propylene, butylene, Examples include, but are not limited to, pentylene, hexylene, heptylene, octylene, nonylene, and the like.

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

The number average molecular weight of the polyester polyol may be from 200 to 100,000. If the number average molecular weight of the polyester polyol is less than 200, the low-temperature elastic modulus may increase and it may be difficult to ensure low-temperature foldability, and if it exceeds 100,000, the viscosity is too high, making it difficult to synthesize urethane oligomers during the process. can be difficult.

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

Examples of the aliphatic diisocyanate compounds include methyl diisocyanate, 1,2-ethanediyl diisocyanate, 1,3-propanediyl diisocyanate, 1,4-butanediyl diisocyanate, 1,6-hexanediyl diisocyanate, and 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 Examples include 4,4'-diisocyanate, isophorone diisocyanate, cyclohexene 1,4-diisocyanate, and 4-methyl-cyclohexane-1,3-diyl diisocyanate.

The aromatic diisocyanate compounds include 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 3-chloro-1,2-benzenediisocyanate, 4-chloro-1,2-benzenediisocyanate. , 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, 2-methyl-1,4-benzene diisocyanate, 3-methyl-1, 4-benzene diisocyanate, 3-methoxy-1,2-benzene diisocyanate, 4-methoxy-1,2-benzene diisocyanate, 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(phenylisocyanate), 2,2-diphenylpropane-4,4'-diisocyanate, 4,4'-diphenyl diisocyanate, azobenzene-4,4'-diisocyanate, 2,4-tri 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 -Diisocyanatepyridine, 2,5-diisocyanatepyridine, 2,6-diisocyanatepyridine, 2,5-diisocyanate-3-methylpyridine, 2,5-diisocyanate-4-methylpyridine, 2,5-diisocyanate-6-methylpyridine Examples include.

As the radical polymerizable compound having a hydroxy group, a hydroxy group-containing (meth)acrylate compound may be used. Examples of the hydroxy group-containing (meth)acrylate compounds include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-n-propyl (meth)acrylate, and 2-hydroxy-n-propyl (meth)acrylate. 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 (meth)acrylate, 2-hydroxycyclopropyl (meth)acrylate, 3-hydroxycyclopentyl (meth)acrylate Examples include acrylate, 4-hydroxycyclohexyl (meth)acrylate, and the like.

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

The urethane oligomer may have a weight average molecular weight (polystyrene equivalent) of 1000 to 200,000, preferably 10,000 to 100,000, as measured by gel permeation chromatography (GPC). When the weight average molecular weight of the urethane oligomer is outside the above range, it may be difficult to ensure processability or reliability may be reduced.

In one embodiment of the invention, the diluent monomer is a component that acts as a dispersion medium for the urethane oligomer and can be polymerized under the action of a photoinitiator. Moreover, the diluent monomer can dilute the adhesive composition to adjust the viscosity, thereby making it easier to apply the adhesive composition.

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

Here, (meth)acrylic means acrylic and/or methacrylic.

Preferably, the diluent 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), can lower the storage modulus of the adhesive composition after curing, and can improve foldability. can.

Examples of the (meth)acrylate having a C ₆ -C ₃₀ alkyl group include hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, and nonyl (meth)acrylate. 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 Among these, 2-ethylhexyl (meth)acrylate is preferred. These may be used alone or in combination of two or more.

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

The (meth)acrylic monomer having a polar functional group may be one or more of (meth)acrylate having a hydroxy group and (meth)acrylamide having a nitrogen atom.

Examples of the (meth)acrylates having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxybutyl (meth)acrylate. Hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, hydroxyalkylene glycol (meth)acrylate in which the alkylene group has 2 to 4 carbon atoms, etc. Among these, 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth)acrylate and the like are preferred.

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, and hydroxyethyl (meth)acrylamide. ) acrylamide, diacetone (meth)acrylamide, etc.

The (meth)acrylic monomer having a 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. If the content of the (meth)acrylic monomer having a polar functional group is less than 3% by weight, the adhesion may decrease, and if it exceeds 30% by weight, the low-temperature elastic modulus may increase.

In one embodiment of the present invention, the mixing ratio of the urethane oligomer and diluent monomer may be 1:9 to 5:5, preferably 2:8 to 6:4 on a weight basis. In the mixing ratio of the urethane oligomer and diluent monomer, if the amount of urethane oligomer is less than the above range, thickness deviation may become large in the sheet manufacturing process, and if it is more than the above range, the adhesion strength will decrease and reliability may deteriorate. Sexuality may decrease.

The diluent monomer may further contain other polymerizable monomers in addition to the monomers described above.

Specific examples of the other polymerizable monomers include n-butyl (meth)acrylate, 2-butyl (meth)acrylate, t-butyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, Examples include n-propyl (meth)acrylate, isopropyl (meth)acrylate, pentyl (meth)acrylate, isobornyl (meth)acrylate, and among these, isobornyl (meth)acrylate is preferred. These may be used alone or in combination of two or more.

The other polymerizable monomer may be contained 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 exceeds 10% by weight, the low-temperature elastic modulus may increase.

In one embodiment of the present invention, the photoinitiator refers to an initiator that absorbs active energy rays and generates radicals.

Examples of the photoinitiator include 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-hydroxycyclohexylphenyl 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-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone , 2,4-diethylthioxanthone (DETX), 4-isopropylthioxanthone (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic 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'-tetraphenylbiimizazole (HABI-101), 2,2'-bis(2-methoxyphenyl) -4,4',5,5'-tetraphenylbiimidazole (HABI-107), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5 '-diphenylbiimidazole (TCDM) and the like. These may be used alone or in combination of two or more.

The photoinitiator may be contained in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of the urethane oligomer and diluent monomer. If it is less than 0.01 parts by weight, photocuring will not be sufficient and it will be difficult to achieve the mechanical properties and adhesion of the final pressure-sensitive adhesive sheet, and if it exceeds 3 parts by weight, the residual The initiator may cause discoloration and reduce durability.

In addition to the above-mentioned components, the adhesive composition according to an embodiment of the present invention adjusts the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, antistatic property, etc. required depending on the application. For plasticizers, silane coupling agents, tackifying resins, antioxidants, corrosion inhibitors, leveling agents, surface lubricants, dyes, pigments, antifoaming agents, fillers, light stabilizers, antistatic agents, etc. It may further contain additives.

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 has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention on a base film, or a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention between two base films. A pressure-sensitive adhesive layer may be interposed therebetween.

Examples of the base film include polyolefin films, polyester films, acrylic films, styrene films, amide films, polyvinyl chloride films, polyvinylidene chloride films, and polycarbonate films, which include silicone films, It may be one that has been appropriately subjected to mold release treatment using fluorine-based powder, silica powder, or the like.

The thickness of the base film is preferably 30 to 80 μm. If it is less than 30 μm, the base film is susceptible to puncture defects, and if it exceeds 80 μm, it may be difficult to handle.

The adhesive layer may be formed by applying an adhesive composition onto a single base film. The coating method is not particularly limited as long as it is a method known in the art, and for example, bar coater, air knife, gravure, reverse roll, kiss roll, spray, blade, die coater, casting, spin coating, etc. are used. good. Specifically, the pressure-sensitive adhesive composition is applied onto a single base film, and is photocured by irradiation with an ultraviolet irradiation amount of approximately 100 to 2000 mJ/cm ² , preferably 200 to 1500 mJ/cm ² . It's fine.

The thickness of the adhesive layer may be 10 to 2,000 μm, preferably 25 to 1,500 μm. If the thickness of the adhesive layer is less than 10 μm, it may be difficult to buffer shocks generated from the outside, and if it exceeds 2,000 μm, transmission may decrease and optical performance may deteriorate.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the pressure-sensitive adhesive layer can be surface-treated to improve adhesion before lamination.

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

The adhesive sheet according to an embodiment of the present invention is applicable not only to ordinary flat panel displays and flexible displays, but also to foldable displays. In particular, the adhesive sheet according to an embodiment of the present invention has a storage elastic modulus at low temperatures controlled in the range of 3 to 30 kPa and has excellent foldability, so it is suitable for interlayer adhesion when laminating components in a foldable display device. can be applied effectively. Specifically, the adhesive sheet can be applied to bond various display materials such as antennas, display panels, polarizers, touch sensors, cover windows, bezels, polymer films, and FPCBs.

Hereinafter, the present invention will be explained more specifically using Examples, Comparative Examples, and Experimental Examples. Note that these Examples, Comparative Examples, and Experimental Examples are merely for illustrating the present invention, and it is obvious for those skilled in the art that the scope of the present invention is not limited thereto.

Production Example 1: Production of urethane oligomer To 81 parts by weight of polycaprolactone diol having a number average molecular weight of 1230 [manufactured by Daicel Chemical Industries, Ltd., trade name: Placcel 212], 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate were added. The isocyanate polymer obtained by the reaction at 80° C. was reacted with 9 parts by weight of 2-hydroxyethyl acrylate to produce a urethane oligomer having a weight average molecular weight of 60,000.

Production Example 2: Production of Urethane Oligomer 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate were added to 81 parts by weight of polycaprolactone diol having a number average molecular weight of 2000 [manufactured by Daicel Chemical Industries, Ltd., trade name: Placcel 220]. The isocyanate polymer obtained by the reaction at 80° C. was reacted with 9 parts by weight of 2-hydroxyethyl acrylate to produce a urethane oligomer having a weight average molecular weight of 80,000.

Production Example 3: Production of Urethane Oligomer 81 parts by weight of polycaprolactone diol having a number average molecular weight of 1230 [manufactured by Daicel Chemical Industries, Ltd., trade name: Placel 212], 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 1,6-hexamethylene An isocyanate polymer obtained by reacting 10 parts by weight of diisocyanate at 80°C was reacted with 9 parts by weight of 2-hydroxyethyl acrylate to produce a urethane oligomer having a weight average molecular weight of 70,000.

Production Example 4: Production of urethane oligomer A urethane oligomer was obtained by reacting 81 parts by weight of polypropylene glycol (manufactured by Hannong Chemicals Inc., PPG1000) with a number average molecular weight of 1000 with 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C. The resulting isocyanate polymer was reacted with 9 parts by weight of 2-hydroxyethyl acrylate to produce a urethane oligomer having a weight average molecular weight of 60,000.

Examples 1 to 5 and Comparative Examples 1 to 2: Production of adhesive compositions and adhesive sheets Adhesive compositions were prepared by mixing the compositions shown in Table 1 below (parts by weight).

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

Experimental example 1:
The physical properties of the pressure-sensitive adhesive sheets manufactured in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 2 below.

(1) Adhesion Strength The adhesive strength of the pressure-sensitive adhesive sheets manufactured in Examples and Comparative Examples to various base materials was measured.

After peeling off the release film on one side of the adhesive sheet and applying corona treatment to the adhesive side, it was laminated with a 38 μm PET film, and then cut into pieces with a width of 25 mm and a length of 100 mm. was manufactured. Next, the remaining release film on the other side was peeled off, and the adhesive sheet was attached to the alkali glass using a 2 kg roller according to the regulations of JIS Z 0237. The alkali glass with the adhesive sheet pasted was pressure-bonded in an autoclave (50°C, 5 atm) for about 20 minutes, stored at constant temperature and humidity conditions (23°C, 50% relative humidity) for 1 hour, and then tested using a texture analyzer ( The pressure-sensitive adhesive sheet was peeled from the alkali glass using a Texture Analyzer (manufactured by Stable Microsystems, UK) at a peeling speed of 300 mm/min and a peeling angle of 180 degrees to measure the adhesion at room temperature.

In addition, the adhesion force of PET (polyethylene terephthalate) was measured using the same method except that the PET film was attached to the alkali glass as the adherend using double-sided tape. .

(2) Storage modulus (G')
The storage modulus of the adhesive sheets produced in Examples and Comparative Examples at -20°C was measured using a viscoelasticity measuring device (MCR-301, manufactured by Anton Paar). More specifically, an adhesive sheet is cut into a size of 30 mm in length x 30 mm in width, the release film pasted on one side of the cut out adhesive sheet is removed, and then the adhesive sheet is pasted on a glass substrate. , Measurement was carried out in the temperature range of -30 to 100°C with a frequency of 1.0Hz, strain of 2%, and temperature increase rate of 5°C/min with the measurement tip attached, and at this time, -20°C The measured value was read.

(3) Foldability The pressure-sensitive adhesive sheets produced in Examples and Comparative Examples were laminated onto a 50 μm PET film, and then cut into a size of 20 mm×100 mm and used as a test piece. The specimen was fixed to a bendability evaluation device (manufactured by COVOTECH, CFT-720C) for evaluation of foldability, and folded to a radius of curvature of 2 mm, and folded 25 times per minute. Foldability was evaluated under the condition of -20°C, with the condition maintained for 0.2 seconds after one folding. When applying the evaluation of foldability, one folding is regarded as one cycle, and the first number of cycles in which striped patterns occur at the folding site, or the adhesive sheet breaks, lifts, or peels off is evaluated, and the folding site is It was judged as NG if a striped pattern appeared or the pressure-sensitive adhesive sheet broke, lifted, or peeled off, and it was judged as OK if it did not.

(4) High temperature reliability After bonding the polarizing plate and the PET film with the adhesive sheets manufactured in Examples and Comparative Examples interposed between them, a high temperature and high humidity (85°C, 85% relative humidity) condition was applied. After being stored for 10 days, it was visually observed to check for the occurrence of bubbles and peeling.

<Evaluation criteria>
OK: No bubbles and peeling NG: Bubbles and/or peeling

As can be seen from Table 2, the adhesives of Examples 1 to 5 contain a urethane oligomer having a polyester skeleton according to the present invention and having a radically polymerizable functional group at at least one end, a diluent monomer, and a photoinitiator. The composition has excellent adhesion to various substrates, and the adhesive layer after curing has a low storage modulus (G') of 3 to 30 kPa at -20°C and 1 Hz, and has excellent foldability. I can confirm that there is.

On the other hand, the pressure-sensitive adhesive compositions of Comparative Examples 1 and 2 in which a urethane oligomer having a polyester skeleton and having a radically polymerizable functional group at at least one end was used instead of a urethane oligomer having a polyester skeleton and having a radically polymerizable functional group at at least one end, The storage modulus (G') of the subsequent adhesive layer at -20° C. and 1 Hz exceeded 30 kPa, indicating poor foldability.

Although specific parts of the present invention have been described in detail above, those with ordinary knowledge in the technical field to which the present invention pertains will understand that such specific descriptions are merely preferred embodiments, and that It is clear that the scope is not limited. Those with ordinary knowledge in the technical field 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 content.

Therefore, it can be said that the substantial scope of the invention is defined by the claims and their equivalents.

Claims (12)

An adhesive composition comprising a urethane oligomer having a polyester skeleton and a radically polymerizable functional group at at least one end, a diluent monomer, and a photoinitiator. The adhesive composition according to claim 1, which has a storage modulus (G') of 3 to 30 kPa at -20°C and 1 Hz after curing. The adhesive composition according to claim 1, wherein the radically polymerizable functional group is a (meth)acryloyloxy group or a vinyl group. The 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. The adhesive composition according to claim 4, wherein the polyester polyol is a compound represented by the following chemical 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. The pressure-sensitive adhesive composition according to claim 4, wherein the radically polymerizable compound having a hydroxy group includes a (meth)acrylate having a hydroxy group. The pressure-sensitive adhesive composition according to claim 1, wherein the diluent monomer includes a (meth)acrylate having a C ₆ -C ₃₀ alkyl group and a (meth)acrylic monomer having a polar functional group. The adhesive composition according to claim 7, wherein the (meth)acrylic monomer having a polar functional group is contained in an amount of 3 to 30% by weight based on 100% by weight of the total diluting monomer. The adhesive composition according to claim 1, wherein the mixing ratio of the urethane oligomer and diluent monomer is 1:9 to 5:5 on a weight basis. The 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 urethane oligomer and diluent monomer. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 10. The adhesive sheet according to claim 11, which is used for a foldable display.