adhesive

Abstract

The present application can provide a pressure-sensitive adhesive and its uses that can be applied to flexible devices to effectively handle repeated deformation and recovery, cause no defects before or after deformation (e.g., visible deformation marks), have excellent cuttability and workability, and do not induce lifting, peeling, and / or bubble formation.

Description

[Technical Field]

[0001] This application claims priority based on Korean Patent Application No. 10-2021-0026662, filed on February 26, 2021, and the contents disclosed in this Korean patent application are incorporated herein by reference.

[0002] The present application relates to pressure sensitive adhesives. [Background technology]

[0003] Flexible devices are a new concept of devices, and examples of such devices include so-called foldable devices and rollable devices.

[0004] The adhesive layer applied to the foldable device is stretched after repeated folding or unwound after wrapping.

[0005] Therefore, the layers applied to the foldable device are required to be able to effectively follow the repeated deformation and to recover to their original shape when the force applied during deformation is removed.

[0006] It is generally known that the lower the modulus of elasticity of a pressure-sensitive adhesive, particularly the modulus of elasticity at low temperatures, the more effectively it can follow the repeated deformations described above.

[0007] However, if the modulus of elasticity of the pressure-sensitive adhesive layer is too low, the recovery property when the force applied for deformation is removed decreases, resulting in problems such as reduced cuttability and workability.

[0008] Therefore, in consideration of cuttability and workability, it is preferable that the adhesive layer has an elastic modulus of at least a certain level, but it is not easy to obtain an adhesive layer that ensures desired levels of recovery, cuttability, workability, etc., while also effectively following deformation.

[0009] Furthermore, if the modulus of elasticity is increased in consideration of cuttability and workability, there is a problem in that the peel strength that is fundamentally required of the pressure-sensitive adhesive layer decreases.

[0010] Therefore, it is not an easy task to provide a pressure-sensitive adhesive layer with physical properties suitable for flexible devices. Summary of the Invention [Problem to be solved by the invention]

[0011] The present application relates to an adhesive. One object of the present application is to provide an adhesive suitable for foldable devices. In one example, the present application aims to provide an adhesive that can form an adhesive layer that exhibits a low modulus of elasticity suitable for foldable devices at low temperatures, a relatively high modulus of elasticity at high temperatures, and an appropriate level of adhesive strength (peel strength).

[0012] Another object of the present application is to provide an adhesive film or flexible device comprising the adhesive. [Means for solving the problem]

[0013] Unless otherwise specified, physical properties referred to in this specification are measured at room temperature when the measurement temperature affects the physical property.

[0014] As used herein, the term "room temperature" refers to a temperature in a state where the temperature is not particularly increased or decreased, and can mean any temperature within a range of about 10° C. to 30° C., for example, about 15° C. or higher, 18° C. or higher, 20° C. or higher, or about 23° C. or higher, and about 27° C. or lower. Unless otherwise specified, the unit of temperature referred to in this specification is ° C.

[0015] Of the physical properties referred to in this specification, unless otherwise specified in cases where the measurement pressure affects the physical property, the physical property is a physical property measured at normal pressure.

[0016] In this specification, the term "normal pressure" refers to pressure in a state where there is no particular increase or decrease in pressure, and generally refers to a pressure of approximately 740 mmHg to 780 mmHg, which is the atmospheric pressure level.

[0017] Unless otherwise specified, in cases where the humidity used to measure a physical property affects the physical property, the physical property is measured at the natural humidity at room temperature and pressure.

[0018] The present application relates to a pressure-sensitive adhesive. The pressure-sensitive adhesive of the present application may include an acrylic copolymer.

[0019] As used herein, the term copolymer refers to the result of a polymerization reaction of a mixture of monomers.

[0020] In this specification, the term "monomer unit" refers to the state of the monomer after the polymerization reaction.

[0021] As used herein, the term "acrylic copolymer" refers to a copolymer containing acrylic monomer units as a major component. The term "major component" refers to a copolymer in which the proportion of the acrylic monomer units in the acrylic copolymer is 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. There is no particular upper limit to the content of the acrylic monomer units in the acrylic copolymer. For example, the acrylic copolymer may contain 100% by weight or less, 99% by weight or less, 98% by weight or less, 97% by weight or less, 96% by weight or less, or 95% by weight or less of the acrylic monomer units.

[0022] As used herein, the term acrylic monomer refers to acrylic acid or methacrylic acid or a derivative of said acrylic acid or methacrylic acid (eg, an acrylate or methacrylate ester).

[0023] In this specification, the term (meth)acrylic means acrylic or methacrylic.

[0024] In the PSA of the present application, when the acrylic copolymer is crosslinkable, the acrylic copolymer may be in a pre-crosslinked state or a crosslinked state within the PSA, or may be in a crosslinked state appropriately. Therefore, the PSA may contain the crosslinked acrylic copolymer.

[0025] The pressure-sensitive adhesive may contain the acrylic copolymer as a major component. For example, the proportion of the acrylic copolymer in the pressure-sensitive adhesive may be 50% by weight or more, 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, 97% by weight or more, or 99% by weight or more. There is no particular upper limit to the content of the acrylic copolymer in the pressure-sensitive adhesive. For example, the acrylic copolymer may be contained in the pressure-sensitive adhesive at 100% by weight or less, 99% by weight or less, 98% by weight or less, 97% by weight or less, 96% by weight or less, or 95% by weight or less. When the pressure-sensitive adhesive contains a component that is not contained in the final pressure-sensitive adhesive layer, such as a solvent, the content of the acrylic copolymer refers to the content in the pressure-sensitive adhesive excluding the component that is not contained in the final pressure-sensitive adhesive layer.

[0026] The storage modulus and peel strength of the PSA referred to in this specification are the storage modulus and peel strength when the PSA composition is in a crosslinked state (i.e., when the acrylic copolymer contained in the PSA composition is crosslinked), and therefore may be the storage modulus and peel strength of the PSA or the PSA layer.

[0027] The pressure-sensitive adhesive of the present application can exhibit a low storage modulus at low temperatures.

[0028] In this specification, the storage modulus is the result measured by the method shown in the following examples.

[0029] For example, the pressure-sensitive adhesive may have a storage modulus of 100,000 Pa or less at −20° C. In other examples, the storage modulus of the pressure-sensitive adhesive at −20° C. may be 98,000 Pa or less, 96,000 Pa or less, 95,000 Pa or less, 94,000 Pa or less, 93,000 Pa or less, 92,000 Pa or less, 90,000 Pa or less, 88,000 Pa or less, 86,000 Pa or less, 85,000 Pa or less, 84,000 Pa or less, 83,000 Pa or less, or 82,000 Pa or less. , 80,000 Pa or less, 78,000 Pa or less, 76,000 Pa or less, 74,000 Pa or less, 72,000 Pa or less, 70,000 Pa or less, 68,000 Pa or less, 66,000 Pa or less, 64,000 Pa or less, 62,000 Pa or less, 60,000 Pa or less, 58,000 Pa or less, 56,000 Pa or less, or 54,000 Pa or less. The lower limit of the storage modulus at -20°C is not particularly limited, and may be, for example, 30,000 Pa or more, 40,000 Pa or more, 42,000 Pa or more, 44,000 Pa or more, 45,000 Pa or more, 46,000 Pa or more, 48,000 Pa or more, 50,000 Pa or more, 52,000 Pa or more, 54,000 Pa or more, 55,000 Pa or more, 56,000 Pa or more, 58,000 Pa or more, 60,000 Pa or more, 62,000 Pa or more, 64,000 Pa or more, 6 The pressure may be about 5,000 Pa or more, 66,000 Pa or more, 68,000 Pa or more, 70,000 Pa or more, 72,000 Pa or more, 74,000 Pa or more, 75,000 Pa or more, 76,000 Pa or more, 78,000 Pa or more, 80,000 Pa or more, 82,000 Pa or more, 84,000 Pa or more, 86,000 Pa or more, 88,000 Pa or more, 90,000 Pa or more, 92,000 Pa or more, 94,000 Pa or more, or 96,000 Pa or more.

[0030] Since the adhesive exhibits a storage modulus in the above range at a relatively low temperature of -20°C, it can be applied to flexible devices and effectively respond to repeated deformation and recovery.

[0031] The PSA of the present application exhibits the above-mentioned low storage modulus at low temperatures, and at relatively high temperatures, it can exhibit a high storage modulus above a certain level. The storage modulus of a PSA is a function dependent on temperature, and typically decreases as the temperature increases. Therefore, the storage modulus of a PSA at high temperatures is typically lower than its storage modulus at low temperatures. However, if a PSA has a low storage modulus at low temperatures, its storage modulus at high temperatures also decreases relatively. Therefore, the storage modulus of a PSA with a low storage modulus at low temperatures is lower than that of a PSA with a high storage modulus at low temperatures.

[0032] However, the pressure-sensitive adhesive of the present invention can exhibit a low storage modulus at low temperatures and a relatively high storage modulus at high temperatures, i.e., the pressure-sensitive adhesive of the present invention can exhibit a relatively gentle slope in a graph of storage modulus versus temperature.

[0033] For example, the pressure-sensitive adhesive of the present application may have a rate of change in elastic modulus according to the following equation 1 of 2500 or less.

[0034] [Number 1] Elastic modulus change rate = (M 20 -M 25 ) / 45

[0035] In equation 1, M 20 is the storage modulus (unit: Pa) of the pressure-sensitive adhesive at -20°C, and M 25 is the storage modulus (unit: Pa) of the pressure-sensitive adhesive at 25°C.

[0036] The rate of change in elastic modulus may be about 2400 or less, 2300 or less, 2200 or less, 2100 or less, 2000 or less, 1900 or less, 1800 or less, 1700 or less, 1600 or less, 1500 or less, 1400 or less, 1300 or less, 1200 or less, 1100 or less, 1000 or less, 900 or less, or 800 or less. The lower limit of the rate of change in elastic modulus is not particularly limited, and for example, the rate of change may be about 100 or more, 200 or more, 300 or more, 400 or more, 500 or more, 600 or more, 700 or more, 800 or more, 900 or more, 1000 or more, 1100 or more, 1200 or more, 1300 or more, or 1400 or more.

[0037] An adhesive layer exhibiting such a rate of change in elastic modulus effectively follows repeated deformation and recovery in a foldable device, and maintains excellent workability and cuttability. However, as described above, an adhesive with a low elastic modulus at low temperatures also exhibits a relatively low elastic modulus at high temperatures, making it difficult to achieve such a rate of change in elastic modulus. In the present application, the acrylic copolymer described below is used as the acrylic copolymer, thereby achieving such a rate of change in elastic modulus.

[0038] The pressure-sensitive adhesive may have a storage modulus at 25°C of 10,000 Pa or more. In other examples, the storage modulus at 25°C may be about 12,000 Pa or more, 13,000 Pa or more, 14,000 Pa or more, 15,000 Pa or more, 16,000 Pa or more, 17,000 Pa or more, 18,000 Pa or more, 20,000 Pa or more, 21,000 Pa or more, 22,000 Pa or more, 23,000 Pa or more, 24,000 Pa or more, 26,000 Pa or more, 28,000 Pa or more, 30,000 Pa or more, 32,000 Pa or more, 34,000 Pa or more, 36,000 Pa or more, 38,000 Pa or more, or 40,000 Pa or more. There is no particular upper limit to the storage modulus at 25°C, but the modulus may be, for example, about 100,000 Pa or less, 98,000 Pa or less, 96,000 Pa or less, 94,000 Pa or less, 92,000 Pa or less, 90,000 Pa or less, 88,000 Pa or less, 86,000 Pa or less, 84,000 Pa or less, 82,000 Pa or less, 80,000 Pa or less, 78,000 Pa or less, 76,000 Pa or less, 74,000 Pa or less, 72,000 Pa or less, 70,000 Pa or less, 68,000 Pa or less, 66,000 Pa or less, 64,000 Pa or less, 62,000 Pa or less, 60,000 Pa or less, The pressure may be about 58,000 Pa or less, 56,000 Pa or less, 54,000 Pa or less, 52,000 Pa or less, 50,000 Pa or less, 48,000 Pa or less, 46,000 Pa or less, 44,000 Pa or less, 42,000 Pa or less, 40,000 Pa or less, 38,000 Pa or less, 36,000 Pa or less, 35,000 Pa or less, 34,000 Pa or less, 32,000 Pa or less, 30,000 Pa or less, 28,000 Pa or less, 26,000 Pa or less, 25,000 Pa or less, 24,000 Pa or less, 22,000 Pa or less, 20,000 Pa or less, or 18,000 Pa or less.

[0039] The adhesive of the present application exhibits a relatively high high-temperature modulus as described above, and also exhibits a high peel strength. For example, the adhesive has a room-temperature peel strength of about 500 gf / inch from glass. (0.193 N / mm) It may be more than that.

[0040] The room temperature peel strength is a peel strength measured at about 25° C., and the method for measuring this peel strength is described in the Examples.

[0041] In another example, the peel force is 600 gf / inch (0.232 N / mm) More than 700gf / inch (0.270 N / mm) More than 800gf / inch (0.309 N / mm) More than 900gf / inch (0.347 N / mm) More than 1000gf / inch (0.386 N / mm) More than 1100gf / inch (0.425 N / mm) More than 1200gf / inch (0.463 N / mm) More than 1300gf / inch (0.502 N / mm) More than 1400gf / inch (0.541 N / mm) More than 1450gf / inch (0.560 N / mm) More than 1500gf / inch (0.579 N / mm) More than 1550gf / inch (0.598 N / mm) More than 1600gf / inch (0.618 N / mm) or more than 1700gf / inch (0.656 N / mm) There is no particular upper limit to the room temperature peel strength, and for example, the room temperature peel strength may be 5000 gf / inch (1.93 N / mm) Below, 4500gf / inch (1.74 N / mm) Below, 4000gf / inch (1.54 N / mm) Below, 3500gf / inch (1.35 N / mm) Below, 3000gf / inch (1.16 N / mm) Below, 2800gf / inch (1.08 N / mm) Below, 2600gf / inch (1.00 N / mm) Below, 2500gf / inch (0.965 N / mm) Below, 2400gf / inch (0.927 N / mm) Below, 2200gf / inch (0.849 N / mm) Below, 2000gf / inch (0.772 N / mm) Below, 1800gf / inch (0.695 N / mm) Below, 1600gf / inch (0.618 N / mm) or less than 1500gf / inch (0.579 N / mm) It may be about the same or less.

[0042] Such adhesives with a stable storage modulus and peel strength can be applied to flexible devices and effectively respond to repeated deformation and recovery, without causing defects before and after deformation (e.g., visible deformation marks), and have excellent cuttability and workability, without causing lifting, peeling, and / or bubble formation.

[0043] In the present application, a specific acrylic copolymer is used to form a pressure sensitive adhesive with the above-mentioned specific physical properties.

[0044] The acrylic copolymer may contain at least an alkyl (meth)acrylate unit, a unit of the following formula 1, and a polar functional group-containing unit. The copolymer may contain any monomer unit as needed, and may further contain a unit of the following formula 2.

[0045] The unit in the above means a monomer unit.

[0046] [C1] JPEG0007774192000001.jpg6244

[0047] In Chemical Formula 1, R1 represents hydrogen or an alkyl group, and R2 represents an alkyl group having 11 to 13 carbon atoms.

[0048] [C2] JPEG0007774192000002.jpg4448

[0049] In Chemical Formula 2, R1 represents hydrogen or an alkyl group, and R3 represents an aromatic ketone group or a (meth)acryloyl group.

[0050] An acrylic copolymer containing the above monomer units is effective in forming the desired adhesive.

[0051] The acrylic copolymer is formed as a so-called crystalline copolymer or has properties similar to a crystalline copolymer when the unit of Chemical Formula 1 and / or the polar functional group-containing unit are present in a predetermined ratio. As used herein, the term crystalline copolymer refers to a copolymer whose melting point is confirmed to be within a predetermined range in a DSC (Differential Scanning Calorimeter) measurement method described in the examples of the present specification.

[0052] Acrylic copolymers are known as amorphous copolymers. However, when the units of Chemical 1 are present in a certain ratio, and optionally when the units of Chemical 1 interact with polar functional groups present in a certain ratio, such copolymers can exhibit crystallinity or at least properties similar to crystallinity. When such a copolymer having crystallinity or properties similar to crystallinity is used, a pressure-sensitive adhesive having the aforementioned properties can be efficiently formed. Therefore, a pressure-sensitive adhesive layer having the aforementioned elastic modulus and peel force properties can be effectively formed through a pressure-sensitive adhesive using such a copolymer.

[0053] The alkyl(meth)acrylate unit contained in the copolymer may be, for example, a unit derived from an alkyl(meth)acrylate having an alkyl group having 1 to 10 carbon atoms. In other examples, the alkyl group may be an alkyl group having 2 to 20 carbon atoms, 3 to 10 carbon atoms, 4 to 10 carbon atoms, 4 to 9 carbon atoms, or 4 to 8 carbon atoms. The alkyl group may be linear or branched, and may be substituted or unsubstituted. In one example, the unit may be formed using an alkyl(meth)acrylate having a linear or branched, unsubstituted alkyl group as the alkyl group.

[0054] Examples of the alkyl (meth)acrylate include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, isononyl (meth)acrylate, n-octyl (meth)acrylate, and isooctyl (meth)acrylate.

[0055] The acrylic copolymer may contain the alkyl (meth)acrylate units in a proportion ranging from about 10 to 80% by weight. In other examples, the proportion of the alkyl (meth)acrylate units may be 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, or 55% by weight or more, or about 75% by weight or less, 70% by weight or less, 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, 45% by weight or less, 40% by weight or less, or 35% by weight or less. Within this range, a desired pressure-sensitive adhesive can be effectively formed.

[0056] The polar functional group-containing unit is a unit formed by a monomer having a polar functional group. Such a monomer usually contains both a polymerizable group (e.g., a carbon-carbon double bond) and a polar functional group.

[0057] Examples of the monomer having a polar functional group include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer. In the present application, it is particularly advantageous to apply a hydroxyl group-containing monomer, but the present invention is not limited thereto.

[0058] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxypolyethylene glycol (meth)acrylate, and 2-hydroxypolypropylene glycol (meth)acrylate. Examples of carboxyl group-containing monomers include (meth)acrylic acid, 2-(meth)acryloyloxyacetic acid, 3-(meth)acryloyloxypropyl acid, 4-(meth)acryloyloxybutyric acid, acrylic acid dimers, itaconic acid, maleic acid, and maleic anhydride. Examples of nitrogen-containing monomers include, but are not limited to, (meth)acrylamide, N-vinylpyrrolidone, and N-vinylcaprolactam. One or a mixture of two or more of the above may be used.

[0059] The polar functional group-containing units may be contained in the acrylic copolymer in a ratio of about 5 to 100 parts by weight per 100 parts by weight of the alkyl (meth)acrylate units, and at such a ratio, the durability, adhesiveness, and peel strength of the pressure-sensitive adhesive layer may be stably maintained. In other examples, the polar functional group-containing units may be contained in an amount of 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 35 parts by weight or more, 40 parts by weight or more, 45 parts by weight or more, or 50 parts by weight or more, or 95 parts by weight or less, 90 parts by weight or less, 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, 70 parts by weight or less, 65 parts by weight or less, 60 parts by weight or less, 55 parts by weight or less, 50 parts by weight or less, 45 parts by weight or less, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, 25 parts by weight or less, or 20 parts by weight or less, per 100 parts by weight of the alkyl (meth)acrylate units.

[0060] In Chemical Formula 1, the unit is a unit containing a long-chain alkyl group, and such units are contained in the copolymer in a certain proportion or more, and can interact with polar functional groups as needed to impart crystallinity or crystal-like properties to the copolymer.

[0061] In the unit of Chemical Formula 1, R1 may be hydrogen or an alkyl group having 1 to 4 carbon atoms, specifically hydrogen, a methyl group, or an ethyl group.

[0062] In Chemical Formula 1, R2 is an alkyl group having 11 to 13 carbon atoms, and such alkyl group may be linear or branched, and may be substituted or unsubstituted. In one example, R2 may be a linear or unsubstituted alkyl group. For example, lauryl (meth)acrylate and / or tetradecyl (meth)acrylate may be used to form the unit of Chemical Formula 1.

[0063] The units of Chemical Formula 1 may be contained in the acrylic copolymer in a ratio of about 50 to 300 parts by weight per 100 parts by weight of the alkyl (meth)acrylate units. In other examples, the ratio of the units of Chemical Formula 1 may be about 55 parts by weight or more, 60 parts by weight or more, 65 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, 100 parts by weight or more, 105 parts by weight or more, 110 parts by weight or more, 115 parts by weight or more, 120 parts by weight or more, 125 parts by weight or more, 130 parts by weight or more, 135 parts by weight or more, or 140 parts by weight or more, or 280 parts by weight or less, 260 parts by weight or less, 240 parts by weight or less, 220 parts by weight or less, 200 parts by weight or less, 180 parts by weight or less, 160 parts by weight or less, 140 parts by weight or less, 120 parts by weight or less, 100 parts by weight or less, 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or 65 parts by weight or less.

[0064] The unit of Chemical Formula 2 that may be contained as an optional monomer unit in the acrylic copolymer is a unit containing an aromatic ketone group or a (meth)acryloyl group in the side chain.

[0065] In the PSA, the aromatic ketone group or (meth)acryloyl group may exist as is, or may exist after undergoing a hydrogen elimination reaction or a radical reaction, which will be described later.

[0066] In the unit of formula 2, the aromatic ketone group means an aromatic ketone group or a substituent containing such an aromatic ketone group that induces hydrogen abstraction from the polymer chain when exposed to electromagnetic waves.

[0067] When exposed to electromagnetic waves, aromatic ketone groups can remove hydrogen atoms from other polymer chains or from other portions of the polymer chain. Such removal leads to the formation of radicals, which may form cross-links between polymer chains or within the same polymer chain. This category of aromatic ketone groups includes, for example, aromatic ketone groups such as derivatives of benzophenone, acetophenone, or anthroquinone.

[0068] Examples of monomers that derive the unit of formula 2 having an aromatic ketone group include, but are not limited to, 4-benzoylphenyl (meth)acrylate, 4-(meth)acryloyloxyethoxybenzophenone, 4-(meth)acryloyloxy-4'-methoxybenzophenone, 4-(meth)acryloyloxyethoxy-4'-methoxybenzophenone, 4-(meth)acryloyloxy-4'-bromobenzophenone, and / or 4-acryloyloxyethoxy-4'-bromobenzophenone.

[0069] In the unit of Chemical Formula 2, the (meth)acryloyl group refers to a (meth)acryloyl group or a substituent containing the same that induces free radical polymerization when exposed to electromagnetic waves in the presence of a suitable radical initiator. Such a (meth)acryloyl group can act similarly to the aromatic ketone group when irradiated with electromagnetic waves.

[0070] The unit of formula 2, in which R3 is a (meth)acryloyl group, may be formed, for example, by preparing a precursor copolymer and then further reacting it with an unsaturated reagent compound to introduce the (meth)acryloyl group. Typically, the introduction of the (meth)acryloyl group involves either (1) a reaction between a nucleophilic group on the precursor copolymer and an electrophilic group on the unsaturated reagent compound (i.e., the unsaturated reagent compound contains both an electrophilic group and a (meth)acryloyl group), or (2) a reaction between an electrophilic group on the precursor copolymer and a nucleophilic group on the unsaturated reagent compound (i.e., the unsaturated reagent compound contains both a nucleophilic group and a (meth)acryloyl group). These reactions between nucleophilic groups and electrophilic groups are typically ring-opening reactions, addition reactions, or condensation reactions.

[0071] In such cases, the precursor copolymer has hydroxy, carboxylic acid (-COOH), or anhydride (-O-(CO)-O-) groups. If the precursor copolymer has hydroxy groups, the unsaturated reagent compound has carboxylic acid (-COOH), isocyanate (-NCO), epoxy (i.e., oxiranyl), or anhydride groups in addition to the (meth)acryloyl groups. If the precursor copolymer has carboxyl groups, the unsaturated reagent compound has hydroxy, amino, epoxy, isocyanate, aziridinyl, azetidinyl, or oxazolinyl groups in addition to the (meth)acryloyl groups. If the precursor (meth)acrylate copolymer has anhydride groups, the unsaturated reagent compound has hydroxy or amine groups in addition to the (meth)acryloyl groups.

[0072] In one example, the precursor copolymer may have a carboxyl group and the unsaturated reagent compound may have an epoxy group. Exemplary unsaturated reagent compounds include, for example, glycidyl (meth)acrylate and 4-hydroxybutyl acrylate glycidyl ether. In another example, the precursor copolymer has an anhydride group, which reacts with an unsaturated reagent compound such as a hydroxy-substituted alkyl (meth)acrylate, e.g., 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, etc. In yet another example, the precursor copolymer has a hydroxy group and the unsaturated reagent compound has an isocyanate group and a (meth)acryloyl group. Such unsaturated reagent compounds include, but are not limited to, isocyanato alkyl (meth)acrylates, e.g., isocyanato ethyl (meth)acrylate.

[0073] In one example, the (meth)acryloyl group has the chemical formula CH2=CHR 1 It is represented by -(CO)-QL- (wherein L is a linking group and Q is oxy (-O-) or -NH-). In the above, L includes alkylene, arylene, or a combination thereof, and further includes -O-, -O-(CO)-, -NH-(CO)-, -NH-, or a combination thereof depending on the precursor copolymer and the specific unsaturated reagent compound that react to form a (meth)acryloyl group. In some specific examples, the (meth)acryloyl group is a group represented by the chemical formula -(CO)-OR of the precursor copolymer. 5 Hydroxy-containing groups represented by -OH and the chemical formula H2C=CHR 1 -(CO)-OR 6 H2C=CHR formed by reaction with an unsaturated reagent compound which is an isocyanato alkyl (meth)acrylate represented by -NCO 1- (CO)-OR 6 -NH-(CO)-OR 5 -O-(CO)-. 5 and R 6are each independently an alkylene group, for example, an alkylene group having 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. 1 is methyl or hydrogen.

[0074] In the unit of Chemical Formula 2, R1 may be hydrogen or an alkyl group having 1 to 4 carbon atoms, and specifically may be hydrogen, a methyl group, or an ethyl group.

[0075] When the unit of Chemical Formula 2 is contained, it may be contained in the acrylic copolymer in a ratio of about 0.001 to 5 parts by weight per 100 parts by weight of the alkyl (meth)acrylate unit, and at such a ratio, a desired adhesive layer can be effectively formed by irradiation with electromagnetic waves.

[0076] In other examples, the ratio of the units of Chemical Formula 2 is about 0.003 parts by weight or more, 0.005 parts by weight or more, 0.007 parts by weight or more, 0.009 parts by weight or more, 0.01 parts by weight or more, 0.015 parts by weight or more, 0.02 parts by weight or more, 0.025 parts by weight or more, 0.03 parts by weight or more, 0.035 parts by weight or more, 0.04 parts by weight or more, 0.045 parts by weight or more, 0.05 parts by weight or more, 0.055 parts by weight or more, 0.06 parts by weight or more, 0.065 parts by weight or more, 0.07 parts by weight or more, or 0.075 parts by weight, relative to 100 parts by weight of the alkyl (meth)acrylate units. or more, 0.08 parts by weight or more, 0.085 parts by weight or more, 0.09 parts by weight or more, 0.1 parts by weight or more, or about 4.5 parts by weight or less, 4 parts by weight or less, 3.5 parts by weight or less, 3 parts by weight or less, 2.5 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.1 parts by weight or less, 0.08 parts by weight or less, 0.06 parts by weight or less, 0.04 parts by weight or less, or 0.02 parts by weight or less, and by irradiation with electromagnetic waves at such a ratio, a desired pressure-sensitive adhesive layer can be effectively formed.

[0077] The acrylic copolymer may suitably contain other monomer units in addition to the monomer units mentioned above, as long as the other monomer units do not impair the purpose (for example, do not impair the crystallinity of the copolymer).

[0078] In one example, the acrylic copolymer contained in the pressure-sensitive adhesive may be a crystalline acrylic copolymer. As mentioned above, the term crystalline copolymer refers to a copolymer whose melting point is confirmed to be within a predetermined range when measured by a differential scanning calorimeter (DSC) as described in the Examples of this specification.

[0079] In one example, the acrylic copolymer may be a crystalline acrylic copolymer having a melting point of about -20°C or less, as determined by the above method. In other examples, the melting point of the crystalline acrylic copolymer may be about -25°C or less, -30°C or less, -35°C or less, or -40°C or less, or may be about -100°C or more, -95°C or more, -90°C or more, -85°C or more, -80°C or more, -75°C or more, -70°C or more, -65°C or more, -60°C or more, -55°C or more, -50°C or more, or -45°C or more. Acrylic copolymers having such melting points can effectively form desired adhesives.

[0080] The specific composition of the crystalline acrylic copolymer is not particularly limited. In one example, the crystalline acrylic copolymer may be a copolymer containing at least the three types of units described above (alkyl (meth)acrylate units, units of Chemical Formula 1, and polar functional group-containing units). However, not all of the acrylic copolymers described above exhibit crystallinity. In order for the acrylic copolymer to exhibit crystallinity, it is necessary for the units of Chemical Formula 1 to be contained in an amount of at least 60 parts by weight per 100 parts by weight of alkyl (meth)acrylate units. In other examples, the ratio of the units of Chemical Formula 1 in the crystalline acrylic copolymer may be 65 parts by weight or more, 70 parts by weight or more, 75 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, or 100 parts by weight or more, relative to 100 parts by weight of the alkyl (meth)acrylate units, and may be 2000 parts by weight or less, 1500 parts by weight or less, 1000 parts by weight or less, 900 parts by weight or less, 800 parts by weight or less, 700 parts by weight or less, 650 parts by weight or less, 600 parts by weight or less, 550 parts by weight or less, 500 parts by weight or less, 450 parts by weight or less, 400 parts by weight or less, 350 parts by weight or less, 300 parts by weight or less, 250 parts by weight or less, 200 parts by weight or less, or 150 parts by weight or less.

[0081] In the crystalline acrylic copolymer, the ratio (A / B) of the weight (A) of the units of Formula 1 to the weight (B) of the polar functional group-containing units may be 1.5 or greater. In other examples, the ratio (A / B) may be 1.7 or greater, 1.9 or greater, 2.1 or greater, 2.3 or greater, 2.5 or greater, 2.7 or greater, 2.9 or greater, 3.1 or greater, 3.3 or greater, 3.5 or greater, 3.7 or greater, or 3.9 or greater, or may be approximately 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2.5 or less, or 2 or less. Furthermore, in the crystalline acrylic copolymer, the polar functional group-containing units may be hydroxyl group-containing units. In one example, a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 3 or more carbon atoms or 4 or more carbon atoms may suitably form the crystalline acrylic copolymer. The reason for this is not clear, but it is believed that the interaction between the alkyl group (R2) in the unit of Chemical Formula 1 and the hydroxyalkyl group contributes to the development of crystallinity in the acrylic copolymer.

[0082] The crystalline acrylic copolymer may contain the alkyl (meth)acrylate units in a proportion ranging from about 20 to 70% by weight. In other examples, the proportion of the alkyl (meth)acrylate units may be 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, or 45% by weight or more, or about 65% by weight or less, 60% by weight or less, 55% by weight or less, 50% by weight or less, or 45% by weight or less. Within such a range, the desired pressure-sensitive adhesive layer can be effectively formed.

[0083] The reason for this is not clear, but it is believed that the interaction or regularity of the monomer units contained in the above ratio gives the acrylic copolymer crystallinity, which allows the melting point to be confirmed.

[0084] The acrylic copolymer may have a weight-average molecular weight of 1,000,000 or more. In this specification, the weight-average molecular weight refers to a polystyrene-equivalent value measured by GPC (gel permeation chromatography). Unless otherwise specified, the unit of the weight-average molecular weight is g / mol.

[0085] The weight average molecular weight of the copolymer may be, for example, 1.1 million or more, 1.2 million or more, 1.3 million or more, 1.4 million or more, 1.5 million or more, 1.6 million or more, 1.7 million or more, 1.8 million or more, 1.9 million or more, or 2 million or more, or may be about 5 million or less, 4 million or less, 3 million or less, 2.5 million or less, or 2 million or less.

[0086] The lower the weight-average molecular weight of the copolymer, the greater the change in physical properties after crosslinking, but if the weight-average molecular weight is too low, it is disadvantageous in terms of durability under high temperature and / or high humidity conditions. However, in the present application, by using the specific copolymer described above, it is possible to effectively form the desired pressure-sensitive adhesive layer while maintaining the weight-average molecular weight at an appropriate level.

[0087] The pressure-sensitive adhesive layer may further include a crosslinking agent, which may react with the acrylic copolymer to form a crosslinked structure.

[0088] The type of crosslinking agent is not particularly limited, and common crosslinking agents such as isocyanate compounds, epoxy compounds, aziridine compounds, and metal chelate compounds may be used. These types of crosslinking agents are so-called thermal crosslinking agents that form crosslinked structures by the application of heat and are different from the radical crosslinking agents described below. Specific examples of the isocyanate compounds include one or more selected from the group consisting of tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, and reaction products of any of the above with a polyol (e.g., trimethylolpropane). Specific examples of the epoxy compounds include one or more selected from the group consisting of ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N,N,N',N'-tetraglycidylethylenediamine, and glycerin diglycidyl ether. Specific examples of the aziridine compound include, but are not limited to, one or more selected from the group consisting of N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), triethylenemelamine, bisisoprothaloyl-1-(2-methylaziridine), and tri-1-aziridinylphosphine oxide. Specific examples of the metal chelate compound include, but are not limited to, compounds in which a polyvalent metal such as aluminum, iron, zinc, tin, titanium, antimony, magnesium, and / or vanadium is coordinated with acetylacetone or ethyl acetoacetate.

[0089] The crosslinking agent may be contained in the pressure-sensitive adhesive layer in an amount of 0.01 to 10 parts by weight or 0.01 to 5 parts by weight relative to 100 parts by weight of the acrylic copolymer, and may be adjusted within the above range in consideration of the cohesive strength and durability of the pressure-sensitive adhesive layer. In one example, the proportion of the crosslinking agent may be about 0.02 parts by weight or more, about 0.03 parts by weight or more, about 0.04 parts by weight or more, about 0.05 parts by weight or more, 0.06 parts by weight or more, 0.07 parts by weight or more, 0.08 parts by weight or more, or 0.09 parts by weight or more, or about 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, about 3 parts by weight or less, about 2 parts by weight or less, about 1 part by weight or less, about 0.8 parts by weight or less, about 0.6 parts by weight or less, about 0.4 parts by weight or less, about 0.2 parts by weight or less, about 0.15 parts by weight or less, about 0.1 parts by weight or less, 0.09 parts by weight or less, 0.08 parts by weight or less, or 0.07 parts by weight or less.

[0090] If the content of the crosslinking agent is selected so as to crosslink the acrylic copolymer at an appropriate level within the above content range, a desired adhesive can be effectively formed.

[0091] The pressure-sensitive adhesive layer may contain, as the crosslinking agent, a so-called radical crosslinking agent, which is a type of crosslinking agent different from the thermal crosslinking agent. Such a crosslinking agent realizes a crosslinked structure by a radical reaction. Examples of such radical crosslinking agents include so-called multifunctional acrylates, such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, and hydroxypivalic acid. acid) neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate, di(meth)acryloxyethyl isocyanurate, allylated cyclohexyl di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, ethylene oxide-modified hexahydrophthalic acid di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, neopentyl glycol-modified trimethylpropane di(meth)acrylate, adamantane di(meth)acrylate or 9,Difunctional acrylates such as 9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, trifunctional urethane (meth)acrylate, or tris(meth)acryloxyethyl isocyanurate, diglycerides Examples of the acrylate include, but are not limited to, tetrafunctional acrylates such as dipentaerythritol tetra(meth)acrylate or pentaerythritol tetra(meth)acrylate, pentafunctional acrylates such as propionic acid-modified dipentaerythritol penta(meth)acrylate, and hexafunctional acrylates such as dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, or urethane(meth)acrylate (e.g., a reaction product of an isocyanate monomer and trimethylolpropane tri(meth)acrylate).

[0092] The radical crosslinking agent may also be present in the adhesive layer in an appropriate ratio depending on the purpose, for example, in an amount of 0.01 to 10 parts by weight or 0.01 to 5 parts by weight per 100 parts by weight of the acrylic copolymer.

[0093] The radical crosslinking agent is not an essential component.

[0094] In addition to the above components, the adhesive may contain appropriate additive components as needed, such as a radical initiator, an ultraviolet absorber, a light stabilizer, a plasticizer, and / or a crosslinking catalyst.

[0095] In the present application, the method for forming the pressure-sensitive adhesive is not particularly limited. For example, the pressure-sensitive adhesive may be formed by applying an appropriate crosslinking method to a pressure-sensitive adhesive composition containing the components (copolymer, crosslinker, etc.) that form the pressure-sensitive adhesive, taking into account the type of acrylic copolymer and / or crosslinker used in the composition. For example, if the acrylic copolymer and / or crosslinker are of a type that crosslinks upon application of heat, a crosslinked product can be formed by applying appropriate heat. If they are of a type that crosslinks upon irradiation with electromagnetic waves, a crosslinked product can be formed by irradiating appropriate electromagnetic waves. Other crosslinking methods may also be used.

[0096] Such adhesives may exhibit the modulus and / or peel force properties described above.

[0097] The thickness of the adhesive of the present application is not particularly limited, and may have a normal adhesive thickness in consideration of the intended use.

[0098] For example, the adhesive may have a thickness of an appropriate level within the range of about 5 μm to 100 μm.

[0099] The present application further relates to a pressure-sensitive adhesive film or optical laminate including a base film and a pressure-sensitive adhesive layer formed on one or both sides of the base film. In the case of an optical laminate, the base film may be an optical film. The pressure-sensitive adhesive layer may include the pressure-sensitive adhesive described above.

[0100] The pressure-sensitive adhesive layer of the present application may be formed on one or both sides of a base film to form a pressure-sensitive adhesive film, or may be formed on one or both sides of the base film, which is an optical film, to form an optical laminate.

[0101] The type of the base film that can be used in this case is not particularly limited, and any base film that can be used to form a pressure-sensitive adhesive film may be used as the base film.

[0102] For example, the substrate film may include, but is not limited to, PET (poly(ethylene terephthalate)) film, PTFE (poly(tetrafluoroethylene)) film, PP (polypropylene) film, PE (polyethylene) film, polyimide film, polyamide film, COP (cyclic olefin polymer) film, polybutene film, polybutadiene film, vinyl chloride copolymer film, polyurethane film, ethylene-vinyl acetate film, ethylene-propylene copolymer film, ethylene-ethyl acrylate copolymer film, ethylene-methyl acrylate copolymer film, and / or polyimide film.

[0103] The thickness of the substrate film is not particularly limited, and may have an appropriate thickness within a range suitable for the purpose.

[0104] When an optical film is used as the substrate film, the type of the optical film is not particularly limited. For example, the optical film may be a polarizing film, a polarizing plate, or a retardation film. In such cases, the optical film may have a thickness within an appropriate range depending on the purpose.

[0105] The pressure-sensitive adhesive film or optical laminate may further include a release film or a protective film for protecting the pressure-sensitive adhesive layer before use, if necessary.

[0106] The present application further relates to a flexible device including a pressure-sensitive adhesive layer, a pressure-sensitive adhesive film, or an optical laminate containing the pressure-sensitive adhesive. In the device, there are no particular limitations on the application form of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive film, or the optical laminate containing the pressure-sensitive adhesive. For example, the pressure-sensitive adhesive layer may be used in the device as a so-called OCA (Optically Clear Adhesive) or OCR (Optically Clear Resin), and therefore the application form of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive film, or the optical laminate may be the same as the application form of a typical OCA or OCR.

[0107] In such a case, in one example, the flexible device may include a display panel and the adhesive layer, adhesive film, or optical laminate present on one or both sides of the display panel. In such a case, the display panel may be configured to be able to fold or roll about one or more folding or rolling axes.

[0108] There are no particular limitations on the other elements that constitute the flexible device described above, and known components of flexible devices may be used without limitation. [Effects of the Invention]

[0109] The present application can provide a pressure-sensitive adhesive that can be applied to flexible devices to effectively handle repeated deformation and recovery, does not cause defects before or after deformation (e.g., observation of deformation marks), has excellent cuttability and workability, and does not induce lifting, peeling, and / or bubble formation.

[0110] The present application may further provide an adhesive layer including the adhesive, an adhesive film or optical film including the same, and a flexible device such as a foldable device or a rollable device. [Brief explanation of the drawings]

[0111]

Figure 1

Figure 2

[0112] The present application will be described in detail below through examples, but the scope of the present application is not limited to the following examples.

[0113] 1. Evaluation of storage modulus The storage modulus was evaluated using an ARES G2 (Advanced Rheometric Expansion System G2) (TA Corporation). A test specimen was prepared by cutting a pressure-sensitive adhesive layer approximately 0.8 mm thick into a circle approximately 8 mm in diameter. The pressure-sensitive adhesive layer was prepared by stacking layers approximately 25 μm thick to a thickness of approximately 0.8 mm. The storage modulus of the test specimen at the measurement temperature was evaluated using a parallel plate fixture with a diameter of approximately 8 mm. The evaluation conditions were a frequency of 1 Hz and a strain of 5%.

[0114] 2. Evaluation of peeling force The PSA film (structure: release film / adhesive layer / base film) to be measured was cut into a rectangle approximately 25 mm wide and 100 mm long to prepare a test specimen. The release film was then peeled off, and the PSA layer was attached to soda lime glass using a 2 kg roller in accordance with JIS Z 0237, and left at room temperature for one day. The peel force was then measured using a Texture Analyzer (TA) (Stable Micro Systems) at room temperature while peeling the PSA layer at a peel angle of 180° and a peel speed of 0.3 m / min.

[0115] 3. Evaluation of melting point and glass transition temperature The melting point of the copolymer was measured by a measurement method using a conventional DSC (Differential Scanning Calorimeter) equipment. As the equipment, DSC-STAR3 equipment (Mettler Toledo) was used. Approximately 10 mg of the sample (copolymer) was filled into a dedicated pan, and the temperature increase condition was 10 °C / min, and the cooling condition was -10 °C / min. The heat absorption and heat generation amounts were confirmed according to the temperature in a nitrogen atmosphere, and the melting point and glass transition temperature were measured. The measurement temperature range was -120 °C to 200 °C. The conditions were first cooled from room temperature (about 30 °C) to -120 °C at a rate of about -10 °C / min, and then heated again to 200 °C at a heating rate of 10 °C / min (primary heating). Then, it was cooled again to -120 °C at a rate of about -10 °C / min, and then heated again to 200 °C at a heating rate of 10 °C / min (secondary heating).

[0116] The melting point and glass transition temperature were evaluated during the secondary heating.

[0117] 4. Evaluation of weight-average molecular weight The weight-average molecular weight (Mw) of the copolymer was measured using GPC (Gel Permeation Chromatograph), and the measurement conditions are as follows. When preparing the calibration curve during the measurement of the weight-average molecular weight, the measurement results were converted using standard polystyrene (manufactured by Aglient system).

[0118] <GPC measurement conditions> Measuring instrument: Aglient GPC (Aglient 1200 series, U.S.) Columns: Two PL Mixed B columns connected Column temperature: 40 °C Eluent: THF (Tetrahydrofuran) Flow rate: 1.0 μL / min Concentration: ~1 mg / mL (100 μl injection)

[0119] 5. Dynamic folding test The dynamic folding test was performed using a specimen as shown in FIG. 1. A laminate was prepared by sequentially laminating a polyimide film 200 (approximately 50 μm thick) with a hard coat layer 100 formed on both sides, a pressure-sensitive adhesive layer 300, a polarizing plate 400, another pressure-sensitive adhesive layer 300, and a display panel 500, as shown in FIG. 1. The laminate was then cut into a rectangular shape approximately 7.8 cm wide and 17 cm long to prepare a specimen. Next, as shown in FIG. 2, the specimen was folded between parallel plates spaced 5 mm apart at 25°C for 200,000 cycles. After the specimen was recovered, it was visually inspected for defects such as bubbles, lifting / peeling, and cracks in the hard coat layer. A test was evaluated as NG if any of the defects were observed, and PASS if none of the defects were observed.

[0120] Production Example 1. Production of Copolymer (A) 2-Ethylhexyl acrylate (2-EHA), lauryl acrylate (LA), and 4-hydroxybutyl acrylate (HBA) were added to the ethyl acetate solvent in a reactor in a weight ratio of 40:40:20 (2-EHA:LA:HBA), and approximately 500 ppm of a radical initiator (2,2'-Azobis(4-methoxy-2,4-dimethylvaleronitrile)) was added. The mixture was then polymerized at approximately 62°C for approximately 8 hours to produce a polymer (copolymer (A)).

[0121] The copolymer (polymer) (A) showed a melting point in the range of about -44°C.

[0122] Preparation Examples 2 to 11. Preparation of copolymers Copolymers (polymers) were prepared in the same manner as in Preparation Example 1, except that the weight ratios of the applied monomers and the weight average molecular weights of the polymers (copolymers) were as shown in Table 1 below.

[0123] [Table 1]

[0124] Example 1 A pressure-sensitive adhesive composition was prepared by blending 100 parts by weight of the copolymer (polymer) (A) of Preparation Example 1 with approximately 0.07 parts by weight of an isocyanate crosslinking agent (xylylene diisocyanate) and 0.005 parts by weight of a catalyst. The catalyst typically used promotes the urethane reaction between a hydroxy group and an isocyanate group. The pressure-sensitive adhesive composition prepared was applied to a substrate film (PET (poly(ethylene terephthalate)) film using a comma coater and heated to 140°C for approximately 3 minutes to form a pressure-sensitive adhesive layer with a thickness of approximately 25 μm.

[0125] Examples 2 to 11 and Comparative Examples 1 to 4 Pressure-sensitive adhesive compositions and pressure-sensitive adhesive layers were prepared in the same manner as in Example 1, except that the type of copolymer used and the ratio of the crosslinker and catalyst were changed as shown in Table 2 below. The same types of crosslinker and catalyst were used as in Example 1. In Table 2 below, the ratio of the crosslinker and catalyst is expressed in parts by weight relative to 100 parts by weight of the copolymer.

[0126] [Table 2]

[0127] The storage modulus, peel strength and dynamic folding test results evaluated for the pressure-sensitive adhesive layers of the Examples and Comparative Examples are summarized in Table 3 below.

[0128] In Table 3 below, the unit of storage modulus is Pa, and the unit of peel force is gf / inch. In addition, in Table 3 below, the rate of change in modulus of elasticity is a physical quantity confirmed by the above-mentioned equation 1.

[0129] [Table 3]

Claims

1. An adhesive, a crosslinked acrylic copolymer; the acrylic copolymer is a crystalline acrylic copolymer, The acrylic copolymer has a melting point of −30° C. or lower, The storage modulus at −20° C. is 30,000 Pa or more and 100,000 Pa or less, The room temperature peel strength to glass is 500 gf / inch (0.193 N / mm) or more, The storage modulus at 25°C is 10,000 Pa or more and 100,000 Pa or less, The rate of change in elastic modulus according to the following equation 1 is 2,500 Pa or less, [Equation 1] Elastic modulus change rate=(M 20 −M 25 ) / 45 In Equation 1, M 20 is the storage modulus (Pa) of the pressure-sensitive adhesive at −20° C., M 25 is the storage modulus (Pa) of the pressure-sensitive adhesive at 25° C., The acrylic copolymer includes an alkyl (meth)acrylate unit, a unit represented by the following Formula 1, and a polar functional group-containing unit: [Chemical formula 1] 【Chemistry 1】 The alkyl (meth)acrylate unit has a linear or branched alkyl group having 4 to 10 carbon atoms, The acrylic copolymer contains 50 to 200 parts by weight of the unit of Formula 1 based on 100 parts by weight of the alkyl (meth)acrylate unit, the acrylic copolymer contains 15 to 100 parts by weight of the polar functional group-containing unit per 100 parts by weight of the alkyl (meth)acrylate unit; In Chemical Formula 1, R １ represents hydrogen or an alkyl group, R ２ represents an alkyl group having 11 to 13 carbon atoms, Adhesive.

2. The pressure-sensitive adhesive according to claim 1 , wherein the polar functional group-containing unit is a unit derived from a hydroxy group-containing monomer.

3. 3. The pressure-sensitive adhesive according to claim 1, wherein the acrylic copolymer contains 25 to 65% by weight of the alkyl (meth)acrylate units.

4. 4. The pressure-sensitive adhesive according to claim 1, wherein the unit of Chemical Formula 1 is contained in the acrylic copolymer in an amount of 60 parts by weight or more per 100 parts by weight of the alkyl (meth)acrylate unit, and the ratio of the weight (A) of the unit of Chemical Formula 1 to the weight (B) of the polar functional group-containing unit is 1.5 or more.

5. A pressure-sensitive adhesive film comprising a base film and a pressure-sensitive adhesive layer formed on one or both surfaces of the base film, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive according to claim 1 .

6. A display panel configured to be foldable or rollable via one or more folding or rolling axes; and A flexible device comprising an adhesive layer present on one or both sides of the display panel, the adhesive layer comprising the adhesive of any one of claims 1 to 4.

Images