A laminated film with folding durability and a display device comprising the laminated film.

Abstract

The laminated film according to one embodiment comprises: a base film; an elastic layer comprising polyether block amide; and a primer layer disposed between the base film and the elastic layer, thus exhibiting not only flexibility but also adhesion between heterogeneous films, thereby demonstrating folding durability.

Description

Technical Field

[0001] The present invention relates to a laminated film with folding durability and a display device comprising the laminated film. Background Technology

[0002] Driven by the development of IT equipment and market demand, display technology continues to advance. Curved screen display technology has been commercialized. In recent years, flexible display devices that can be flexibly bent or folded to withstand external forces have gained favor in the field of mobile devices that require large screens and portability. In particular, foldable display devices have significant advantages, as they can be folded into a smaller size to enhance portability when not in use, and unfolded to form a larger screen when in use.

[0003] In such flexible displays, the cover window needs to possess flexible properties. In particular, in films used in foldable display devices, tensile loads are continuously applied to the film in the folded state. If sufficient flexibility and interlayer adhesion cannot be ensured, cracks or delamination may occur.

[0004] Korean Patent Publication No. 2017-0109746 discloses a technique for preparing a protective film, in which a soft layer using polyurethane acrylate resin and silicone rubber is formed on one side of a base layer, and this soft layer is applied to the cover window of a flexible display screen. However, since this protective film is prepared in the form of a thin film, it has limitations in performance and has the problem of different feel compared to the cover window.

[0005] Existing technical documents

[0006] (Patent Document 1) Korean Patent Publication No. 2017-0109746. Summary of the Invention

[0007] Technical issues

[0008] refer to Figure 1a For the inward-folding type (1a), the load is applied to the point where the fold is inward (p1). Reference Figure 1b For the outward folding type (1b), the load is applied to the point of outward folding (p2). If the cover window (10) fails to ensure sufficient flexibility and interlayer adhesion, cracks or interlayer delamination may occur due to the load applied during folding, resulting in performance degradation.

[0009] Through research, the inventors have discovered that when an elastic layer containing polyether block amide is laminated with a base film through a primer layer, not only flexibility can be ensured, but also adhesion between different types of films can be ensured, thereby achieving folding durability.

[0010] Therefore, the embodiments described below aim to provide a laminated film with excellent folding durability by ensuring interlayer adhesion, and a display device comprising the laminated film.

[0011] Solution to the problem

[0012] According to one embodiment, a laminated film is provided, the laminated film comprising a base film, an elastic layer comprising a polyether block amide, and a primer layer disposed between the base film and the elastic layer.

[0013] According to another embodiment, a process for preparing a laminated film is provided, the process comprising preparing a primer composition; coating the primer composition onto a base film and curing it to form a primer layer; and laminating the base film and an elastic layer through the primer layer to prepare a laminated film, wherein the elastic layer comprises a polyether block amide.

[0014] According to another embodiment, a display device is provided, the display device comprising a display panel and a laminate disposed on the front side of the display panel, wherein the laminate comprises a base film, an elastic layer comprising polyether block amide, and a primer layer disposed between the base film and the elastic layer.

[0015] Beneficial effects of the invention

[0016] In a laminated film according to one embodiment, an elastic layer containing polyether block amide is laminated to a base film through a primer layer; therefore, not only flexibility can be ensured, but also adhesion between different types of films can be ensured, thereby achieving folding durability.

[0017] Therefore, when the laminate according to this embodiment is applied to the panel of a flexible display device, such as the panel of an outward-folding or inward-folding device with the display exposed to the outside, it can have flexible properties and maintain excellent performance even after repeated folding. Attached Figure Description

[0018] Figure 1a and 1b The images show flexible display devices that are either folded inwards or folded outwards.

[0019] Figure 2 An exploded perspective view of a display device according to one embodiment is shown.

[0020] Figure 3 A cross-sectional view of a laminated film according to one embodiment is shown. Figure 2 (A-A' in the middle).

[0021] Figure 4 An example of a peel test method for laminated film samples is shown.

[0022] Figure 5 An example of a folding test method for laminated film samples is shown.

[0023] <Explanation of Figure Markers>

[0024] 1: Display device

[0025] 1a: Inward-folding flexible display device

[0026] 1b: Outward-folding flexible display device

[0027] 2: Peeling test device; 3: Folding tester

[0028] 10: Laminated film (covering window) 10a: Sample

[0029] 20: Display panel; 30: Circuit board

[0030] 40: Frame; 100: Base membrane

[0031] 200: Primer layer; 300: Elastic layer

[0032] N: Load; p1, p2: Folding points

[0033] a: Peeling angle Detailed Implementation

[0034] Best Implementation of the Invention

[0035] Various implementation schemes and examples will be described in detail below with reference to the accompanying drawings.

[0036] In the following description of the embodiments, detailed descriptions of relevant known components or functions will be omitted if they would obscure the subject matter. Furthermore, the sizes of the various elements in the accompanying drawings may be exaggerated or omitted for ease of description, and these elements may differ from their actual sizes.

[0037] In this specification, when describing a component forming on / under another component or being connected or coupled to each other, it covers situations where these components are formed, connected, or coupled directly or indirectly through another component. Furthermore, it should be understood that references to the upper / lower positions of the various components may vary depending on the orientation of the object being observed.

[0038] In this specification, the terms used to refer to the various components are for the purpose of distinguishing them from each other and are not intended to limit the scope of the embodiments. Furthermore, in this specification, unless the context otherwise requires, singular expressions are also construed as encompassing plural expressions.

[0039] In this specification, the term "comprising" is intended to specify a particular characteristic, region, step, process, element, and / or component. This term does not exclude the presence or addition of any other characteristic, region, step, process, element, and / or component unless expressly stated to the contrary.

[0040] In this specification, the terms first, second, etc., are used to describe various components. However, these components should not be limited by these terms. The use of terms is intended to distinguish one element from another.

[0041] The molecular weights of the compounds or polymers described in this specification, such as number-average molecular weight or weight-average molecular weight, are based on the relative mass of carbon-12, as is well known. Although their units are not described, they can be understood as the same numerical value of molar mass (g / mol) if necessary.

[0042] The embodiments described below provide a laminated film with excellent folding durability by ensuring interlayer adhesion, and a display device comprising the laminated film.

[0043] The display device according to one embodiment can be flexible. For example, the display device according to one embodiment can be a flexible display device. Specifically, it can be a foldable display device. More specifically, depending on the folding direction, the foldable display device can be an inward-folding type or an outward-folding type.

[0044] Figure 1a and 1b The images show inward-folding and outward-folding flexible display devices, respectively. (Reference) Figure 1a The display device can be an inwardly folding flexible display device (1a) with the screen located inside the folding direction. Alternatively, refer to... Figure 1b The display device can be an outward-folding flexible display device with the screen located on the outside of the folding direction (1b).

[0045] In such flexible displays, the cover window needs to be flexible. In inward-folding display devices where the display is located on the inside, and outward-folding display devices where the display is exposed on the outside, in addition to flexibility, excellent performance must be maintained even after repeated folding.

[0046] Figure 2 An exploded perspective view of a display device according to one embodiment is shown. (Reference) Figure 2 The display device (1) includes a cover window (10), a display panel (20), a circuit board (30), and a frame (40) protecting them. Furthermore, an adhesive layer may be provided between the cover window (10) and the display panel (20). For example, the adhesive layer may contain an optically transparent adhesive.

[0047] The display panel (20) may be a liquid crystal display (LCD) panel. Alternatively, the display panel (20) may be an organic light-emitting display (OLED) panel. The organic light-emitting display device may include a front polarizer and an organic light-emitting display panel. The front polarizer may be disposed on the front side of the organic light-emitting display panel. More specifically, the front polarizer may be bonded to the side of the organic light-emitting display panel that displays the image. The organic light-emitting display panel displays the image by means of self-emission of the pixel units. The organic light-emitting display panel includes an organic light-emitting substrate and a driving substrate. The organic light-emitting substrate includes a plurality of organic light-emitting units corresponding to each pixel. Each organic light-emitting unit includes a cathode, an electron transport layer, an emissive layer, a hole transport layer, and an anode. The driving substrate is operatively coupled to the organic light-emitting substrate. That is, the driving substrate may be coupled to the organic light-emitting substrate to apply a driving signal, such as a driving current. More specifically, the driving substrate may drive the organic light-emitting substrate by applying a current to each organic light-emitting unit.

[0048] According to one embodiment, the laminated film is used as a cover window (10) in the display device (1).

[0049] That is, the display device according to one embodiment includes a display panel; and a laminate disposed on the front side of the display panel.

[0050] The laminate according to one embodiment includes a base film; an elastic layer comprising a polyether block amide; and a primer layer disposed between the base film and the elastic layer.

[0051] When the laminated film according to one embodiment is cut to a size of 5 cm in length and 1 cm in width, and a 180° peel test is performed at room temperature at a speed of 300 mm / min, the adhesion between the base film and the elastic layer is 15 gf / inch or higher.

[0052] Figure 3 A cross-sectional view of a laminated film (covering window) according to one embodiment is shown. Figure 2 (A-A' in the middle).

[0053] refer to Figure 3 According to one embodiment, the laminate (10) includes a base film (100); an elastic layer (300) comprising a polyether block amide; and a primer layer (200) disposed between the base film (100) and the elastic layer (300).

[0054] In a laminated film according to one embodiment, an elastic layer containing polyether block amide is laminated to a base film through a primer layer; therefore, not only flexibility can be ensured, but also adhesion between different types of films can be ensured, thereby achieving folding durability.

[0055] Lamination process

[0056] The laminated film is prepared by the following process, which includes: (1) preparing a primer composition; (2) coating the primer composition onto a base film and curing it to form a primer layer; and (3) laminating the base film and the elastic layer through the primer layer to prepare the laminated film. When the laminated film is cut to a size of 5 cm in length and 1 cm in width and subjected to a 180° peel test at room temperature at a speed of 300 mm / min, the adhesion between the base film and the elastic layer is 15 gf / inch or higher.

[0057] Each step will be described in detail below.

[0058] In step (1), a primer composition is prepared.

[0059] The primer composition contains an adhesive resin. For example, it may contain a curable resin, specifically a UV-curable resin.

[0060] For example, the primer composition may contain polyester acrylate. Polyester acrylate resins have low viscosity, good processability, and good compatibility with a variety of oligomers or polymers.

[0061] Polyester acrylates can have a structure in which acrylate groups (or acryloyl groups) are substituted in the polyester backbone.

[0062] Polyester acrylates can be incorporating 1 to 6 acrylate groups as needed.

[0063] Polyester acrylates can be obtained by first preparing a polyester and then reacting both ends of the polyester with acrylic acid. Polyesters can be prepared by the polymerization of dicarboxylic acids and diols. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, diphenoxyethylenedicarboxylic acid, diphenyl sulfone dicarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyl adipic acid, trimethyl adipic acid, heptacyanic acid, azelaic acid, sebacic acid, octanoic acid, dodecanedicarboxylic acid, etc. In addition, examples of diols include ethylene glycol, propylene glycol, hexanediol, neopentyl glycol, 1,2-cyclohexanediethanol, 1,4-cyclohexanediethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, etc.

[0064] The reaction between polyester and acrylic acid can be carried out in the presence of an acidic catalyst.

[0065] Polyester acrylates can be in the form of oligomers or polymers. For example, the weight-average molecular weight (Mw) of polyester acrylates can be 1000 or higher, 2000 or higher, 2500 or higher, 3000 or higher, 3500 or higher, or 3800 or higher, and can also be 50000 or lower, 30000 or lower, 20000 or lower, 10000 or lower, 7000 or lower, 5000 or lower, 4500 or lower, or 4000 or lower. As a specific example, the weight-average molecular weight of polyester acrylates can be from 1000 to 7000.

[0066] As another example, the primer composition may contain an acrylamide-based compound. Because the primer composition contains an acrylamide-based compound, it can enhance not only the adhesion of the primer layer to the base film but also its adhesion to the elastic layer.

[0067] As another example, acrylamide-based compounds can be represented by the following formula I.

[0068] [Formula I]

[0069]

[0070] Here, R 1 and R 2 Each can be independently hydrogen, substituted or unsubstituted, with a single valence of C6-C. 30 Aliphatic cyclic group, substituted or unsubstituted, monovalent C4-C 30 Heterocyclic cycloids, substituted or unsubstituted, monovalent C6-C 30 Aromatic cycloalloys, substituted or unsubstituted, monovalent C4-C 30 heterocyclic cycloids, substituted or unsubstituted C1-C 30 Alkyl, substituted or unsubstituted C2-C 30 Alkenyl, or substituted or unsubstituted C2-C 30 Alkyne group.

[0071] As a specific example, an acrylamide-based compound could be dimethylacrylamide.

[0072] As another example, the primer composition may contain polyester acrylate and acrylamide-based compounds.

[0073] By adjusting the weight ratio of polyester acrylate to acrylamide-based compounds in the primer composition to a certain range, interlayer adhesion can be further enhanced.

[0074] For example, the primer composition may contain 1 or more, 5 or more, 10 or more, 15 or more, or 20 or more parts by weight of an acrylamide-based compound relative to 100 parts by weight of polyester acrylate. Furthermore, the primer composition may contain 60 or less, 50 or less, 40 or less, 30 or less, or 25 or less parts by weight of an acrylamide-based compound relative to 100 parts by weight of polyester acrylate.

[0075] Specifically, the primer composition may contain 5 to 40 parts by weight of an acrylamide-based compound relative to 100 parts by weight of polyester acrylate.

[0076] As another example, the primer composition may also contain other acrylic resins.

[0077] Acrylic resins are oligomers or polymers having repeating units derived from (meth)acrylic acid compounds. They can be formed by polymerizing (meth)acrylic acid compounds. (Meth)acrylic acid compounds can include (meth)acrylic acid and its derivatives. For example, derivatives of (meth)acrylic acid can include compounds based on (meth)acrylates. As described herein, "(meth)acrylic acid" encompasses both acrylic acid and methacrylic acid.

[0078] For example, a (meth)acrylate compound may comprise an ester compound in which (meth)acrylate is substituted with an alkyl group having 1 to 12 carbon atoms. For example, a (meth)acrylate compound may comprise a (meth)acrylate substituted with an alkyl group having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl. Preferably, the substituted alkyl group in the ester compound may have 1 to 8 carbon atoms.

[0079] As specific examples, (meth)acrylate compounds may include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, (meth)acrylic acid, (meth)acrylate, methyl acrylate, ethyl methacrylate, n-propyl acrylate, (meth)acrylate, isopropyl acrylate, n-butyl acrylate, (meth)acrylate, isobutyl acrylate, (meth)acrylate, tert-butyl acrylate, n-pentyl acrylate, (meth)acrylate, n-hexyl acrylate, (meth)acrylate, n-heptyl acrylate, (meth)acrylate, 2-ethylhexyl acrylate, (meth)acrylate, nonyl acrylate, (meth)acrylate, dodecyl acrylate, (meth)acrylate, tridecyl acrylate, (meth)acrylate, hexadecyl acrylate, (meth)acrylate, octadecyl acrylate, (meth)acrylate, dodecyl acrylate, (meth)acrylate, cyclohexyl acrylate, (meth)acrylate, etc. 4-tert-butylcyclohexyl acrylate, isobornyl methacrylate, dicyclofenac methacrylate, benzyl methacrylate, N,N-dimethylaminoethyl methacrylate, glycidyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxy-n-butyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxy-n-butyl methacrylate, 3-hydroxy-n-butyl methacrylate, 1,4-cyclohexanediol mono(meth)acrylate, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl methacrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, or lactone-modified (meth)acrylates with terminal hydroxyl groups. They can be used alone or in combination of two or more.

[0080] The primer composition may also contain a photoinitiator.

[0081] Examples of photoinitiators include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methyl benzoylcarbamate, α,α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. In addition, commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP 100F. Photoinitiators can be used alone or in combination of two or more.

[0082] The photoinitiator may be used in the primer composition in an amount of 1 to 10 parts by weight or 3 to 7 parts by weight relative to 100 parts by weight of the total weight of the adhesive resin (e.g., polyester acrylate and acrylamide-based compounds).

[0083] In step (2), the primer composition is applied to the base film and cured to form a primer layer.

[0084] The primer layer can be formed by applying a primer composition to a base film and then drying and curing it.

[0085] The primer composition may contain the above-mentioned adhesive resin and photoinitiator, other additives and / or solvents.

[0086] Examples of solvents include alcohol-based solvents such as methanol, ethanol, isopropanol, and butanol; alkoxy-based solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; ether-based solvents such as propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene, which can be used alone or in combination.

[0087] There are no particular limitations on the solvent content, as it can be adjusted in various ways without reducing the physical properties of the coating composition. For example, the use of solvent can result in a solids content in the primer composition ranging from 1% to 50% by weight, specifically from 1% to 30% by weight, and more specifically from 1% to 10% by weight. Within these ranges, the primer composition can exhibit suitable flowability and coatability.

[0088] The primer composition can be applied to the base film by methods such as stick coating, knife coating, roller coating, doctor blade coating, die coating, microgravure coating, comma coating, groove coating, lip coating, or solution casting, and then dried and cured to form a primer layer.

[0089] Solvents contained in the primer composition can be removed by a drying step. The drying temperature can be 70°C or higher, 90°C or higher, or 110°C or higher, for example, 70°C to 200°C or 90°C to 150°C. For example, the drying time can be 1 minute to 20 minutes, specifically 1 minute to 10 minutes or 3 minutes to 7 minutes.

[0090] The primer layer can be cured by light and / or heat. For example, the primer layer can be UV cured, and the light dose during the UV curing process can be 100mJ or more, 200mJ or more, or 300mJ or more, for example, 100mJ to 1000mJ or 300mJ to 700mJ.

[0091] Furthermore, curing can be partial or complete.

[0092] In step (3), the base film and the elastic layer are laminated through a primer layer to prepare a laminated film.

[0093] For example, an elastic layer can be prepared from the raw materials of the elastic layer, and then the base film and the elastic layer can be laminated through a primer layer to prepare a laminated film.

[0094] The elastic layer is prepared from a composition containing polyether block amides. For example, the elastic layer can be prepared from a composition containing polyether block amides by melt extrusion and casting. The melt extrusion temperature can be 200°C or higher, or 220°C or higher, for example, 200°C to 300°C. Subsequently, the cast elastic layer can be placed on a primer layer formed on a base film, and then laminated by applying pressure. The step of placing the elastic layer on the primer layer can be performed as a continuous process after the preparation of the elastic layer.

[0095] The lamination step can be performed using, for example, extrusion rollers. The lamination pressure can be from 0 kPa to 20000 kPa, specifically from 0 kPa to 15000 kPa, for example from 0 kPa to 10000 kPa. Alternatively, the lamination pressure can be 1500 kPa or higher, specifically 3000 kPa or higher, 5000 kPa or higher, or 10000 kPa or higher, for example from 3000 kPa to 7000 kPa. Furthermore, the lamination temperature, specifically the temperature of the extrusion rollers, can be 0°C or higher, 5°C or higher, or 10°C or higher, for example from 10°C to 120°C.

[0096] As another example, the lamination step can be performed using an extrusion lamination process. Specifically, the raw material for the elastic layer can be melt-extruded and then cast and laminated onto a primer layer formed on the base film in the previous step. Therefore, the entire process of preparing the laminated film can be carried out on a single production line, making it highly efficient. The extrusion temperature and lamination pressure described above can be applied to this extrusion lamination process.

[0097] A laminated film can be prepared by the above process, the laminated film comprising: a base film; an elastic layer comprising polyether block amide; and a primer layer disposed between the base film and the elastic layer.

[0098] Characteristics of laminated films

[0099] Since the laminated film is prepared by laminating an elastic layer containing polyether block amide with a base film treated with a primer, the adhesion between the base film and the elastic layer is excellent, and by combining different materials, both hardness and flexibility are achieved, thus ensuring folding durability.

[0100] According to one implementation scheme, when the laminated film is subjected to a 180° peel test, the adhesive force between the base film and the elastic layer is measured to reach or exceed a certain level.

[0101] Figure 4 An example of a peel test method for laminated film samples is shown. (Reference) Figure 4 One side of the laminated film sample (10a) is attached to the peel tester (20). When the opposite sides are peeled at an angle of 180° (a), the load (N) applied during the peeling process can be measured.

[0102] When performing a peel test, the laminated film sample can be cut into dimensions such as 5cm in length and 1cm in width. The peeling speed can be, for example, 300mm / minute, and the temperature can be room temperature (approximately 25°C).

[0103] When the laminated film according to one embodiment is cut to a size of 5 cm in length and 1 cm in width, and a 180° peel test is performed at room temperature at a speed of 300 mm / min, the adhesion between the base film and the elastic layer is 15 gf / inch or higher.

[0104] For example, the adhesive force between the base film and the elastic layer can be 15 gf / inch or higher, 20 gf / inch or higher, 25 gf / inch or higher, 28 gf / inch or higher, or 30 gf / inch or higher, and 100 gf / inch or lower, 50 gf / inch or lower, 45 gf / inch or lower, or 40 gf / inch or lower. As a specific example, the adhesive force between the base film and the elastic layer can be 15 gf / inch to 50 gf / inch, 15 gf / inch to 40 gf / inch, 15 gf / inch to 38 gf / inch, 20 gf / inch to 50 gf / inch, 25 gf / inch to 50 gf / inch, 25 gf / inch to 45 gf / inch, or 25 gf / inch to 40 gf / inch.

[0105] If the adhesive force between the base film and the elastic layer is within the above range, then when the laminated film is applied to the cover window of a foldable display, delamination will not occur even after repeated folding.

[0106] Referring to Figure 1, the interface where delamination occurs during the test can be, for example, the interface between the base film (100) and the primer layer (200), or the interface between the primer layer (200) and the elastic layer (300). Delamination may also occur partially at both interfaces. Specifically, the point where delamination occurs during the test can be the interface between the primer layer (200) and the elastic layer (300). Therefore, the adhesive strength range in the above example can be understood as the 180° peel strength of the interface between the primer layer and the elastic layer.

[0107] According to another implementation, even after long-term storage, the interlayer adhesion of the laminated film hardly deteriorates; therefore, its performance can be maintained at a certain level.

[0108] As a specific example, after the laminated film is stored at room temperature and 50% RH for 96 hours, the change in adhesive strength calculated by the following equation (1) may be 45% or less, or 40% or less. Specifically, after the laminated film is stored at room temperature and 50% RH for 96 hours, the change in adhesive strength calculated by the following equation (1) may be 35% or less.

[0109] Change in adhesive force (%) = [(A INT –A FIN ) / A INT]×100...(1)

[0110] Among them, A INT Under the above conditions, the adhesion force (gf / inch) between the base film and the elastic layer before storage, A FIN The adhesive force (gf / inch) between the base film and the elastic layer after storage under the above conditions is measured by cutting the laminated film into dimensions of 5cm in length and 1cm in width, and performing a 180° peel test at room temperature at a speed of 300mm / min to measure the load applied between the base film and the elastic layer.

[0111] As another specific example, after the laminated film is stored at room temperature and 50% RH for 240 hours, the change in adhesive strength calculated by the following equation (1) may be 80% or less, 70% or less, or 60% or less. Specifically, after the laminated film is stored at room temperature and 50% RH for 240 hours, the change in adhesive strength calculated by the following equation (1) may be 55% or less.

[0112] Change in adhesive force (%) = [(A INT –A FIN ) / A INT ]×100...(1)

[0113] Among them, A INT Under the above conditions, the adhesion force (gf / inch) between the base film and the elastic layer before storage, A FIN The adhesive force (gf / inch) between the base film and the elastic layer after storage under the above conditions is measured by cutting the laminated film into dimensions of 5cm in length and 1cm in width, and performing a 180° peel test at room temperature at a speed of 300mm / min to measure the load applied between the base film and the elastic layer.

[0114] According to another implementation, no cracks or delamination will occur in the laminate even after repeated folding.

[0115] Figure 5 An example of a folding test method for laminated film samples is shown. (Reference) Figure 5 The laminated film sample (10a) was fixed on the folding tester (3) and folded repeatedly at a constant folding speed (times / second) and curvature (R) to determine whether interlayer delamination or cracking occurred.

[0116] When conducting a folding test, the laminated film sample can be cut to a size of, for example, 12 cm in length and 4 cm in width. The folding speed can be, for example, 1 fold per second, and the curvature can be approximately 1.5R.

[0117] For example, when a laminated film is cut to a length of 12 cm and a width of 4 cm, and repeatedly folded at a folding speed of 1 fold per second at room temperature, while the base film is folded inward to achieve a radius of curvature of 1.5R, the number of folds until delamination occurs can be 100,000 or more. For example, the number of folds could be 100,000 or more, 150,000 or more, or 200,000 or more. Within these ranges, when the laminated film is applied to the panel of a flexible display device, such as the panel of an outward-folding or inward-folding device with the display exposed to the outside, it can possess flexible properties and maintain excellent performance even after repeated folding.

[0118] Specifically, if no delamination occurs in an inward-folding device even after 200,000 or more repeated foldings, and if no delamination occurs in an outward-folding device even after 100,000 or more repeated foldings, the laminate can be considered to be of excellent quality.

[0119] Base film (100)

[0120] The base film (100) serves as the base layer of the primer layer (200) and also imparts mechanical properties to the laminate (10).

[0121] The base film can be a polymer film or a glass substrate, specifically a reinforced glass substrate with a thickness of less than about 100 μm. For example, the base film can comprise a polymer film or ultrathin glass (UTG).

[0122] Specifically, the base film can be a polymer film. That is, the base film can contain a polymer resin.

[0123] Examples of polymeric resins contained in the base film include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; cellulose-based resins such as diacetylcellulose and triacetylcellulose; polycarbonate-based resins; acrylic resins such as poly(meth)acrylate and poly(meth)acrylate; styrene-based resins such as polystyrene and acrylonitrile-styrene copolymers; polyolefin resins such as polyethylene, polypropylene, polyolefins with cycloalkenes or norbornene structures, and ethylene-propylene copolymers; vinyl chloride resins; amide resins such as nylon and aromatic polyamides; imide-based resins; polyamide-imide-based resins; polyethersulfone resins; polyurethane resins; sulfone-based resins; polyetheretherketone-based resins; vulcanized polystyrene resins; vinyl alcohol-based resins; vinylidene chloride resins; vinyl butyral-based resins; allyl ester-based resins; polyoxymethylene-based resins; and epoxy-based resins. They can be used alone or in combination of two or more.

[0124] In addition to polymer resins, the base film may also contain fillers. For example, the base film may contain polyimide resins and fillers.

[0125] The filler can be at least one selected from the group consisting of barium sulfate, silica, and calcium carbonate. Because the base film contains filler, its roughness and rollability can be improved, as well as its sliding properties and scratch resistance during film preparation.

[0126] The particle size of the filler can be from 0.01 μm to less than 1.0 μm. For example, the particle size of the filler can be from 0.05 μm to 0.9 μm or from 0.1 μm to 0.8 μm, but is not limited thereto.

[0127] The amount of filler used can be from 0.01% to 3% by weight, depending on the total weight of the base membrane. For example, the amount of filler used can be from 0.05% to 2.5% by weight, 0.1% to 2% by weight, or 0.2% to 1.7% by weight, depending on the total weight of the base membrane, but is not limited thereto.

[0128] The thickness of the base film can be 20 μm or thicker, 30 μm or thicker, 40 μm or thicker, 50 μm or thicker, or 100 μm or thicker, and 500 μm or thinner, 400 μm or thinner, 300 μm or thinner, or 200 μm or thinner. As a specific example, the thickness of the base film can be from 20 μm to 500 μm, more specifically from 40 μm to 200 μm or from 50 μm to 200 μm.

[0129] The base film can have optical and mechanical properties that can be adjusted to a certain range.

[0130] The haze of the base film can be 3% or lower. For example, the haze of the base film can be 2% or lower, 1.5% or lower, or 1% or lower, but is not limited to these.

[0131] The yellowness index (YI) of the base film can be 5 or lower. For example, the yellowness index of the base film can be 4 or lower, 3.8 or lower, 2.8 or lower, 2.5 or lower, 2.3 or lower, or 2.1 or lower, but is not limited to these.

[0132] The modulus of the base film can be 5 GPa or higher. For example, the modulus of the base film can be 5.2 GPa or higher, 5.5 GPa or higher, 6.0 GPa or higher, 10 GPa or lower, 5 GPa to 10 GPa, or 7 GPa to 10 GPa, but is not limited to these.

[0133] The transmittance of the base film can be 80% or higher. For example, the transmittance of the base film can be 85% or higher, 88% or higher, 89% or higher, 80% to 99%, or 85% to 99%, but is not limited to these.

[0134] The compressive strength of the base film can be 0.4 kgf / μm or higher. Specifically, the compressive strength of the base film can be 0.45 kgf / μm or higher, or 0.46 kgf / μm or higher, but is not limited to these.

[0135] The surface hardness of the base film can be HB or higher. Specifically, the surface hardness of the base film can be H or higher, or 2H or higher, but is not limited to these.

[0136] The tensile strength of the base film can be 15 kgf / mm². 2 Or even higher. Specifically, the tensile strength of the base film can be 18 kgf / mm². 2 Or higher, 20 kgf / mm 2 Or higher, 21 kgf / mm 2 Or higher, or 22 kgf / mm 2 Or higher, but not limited to this.

[0137] The elongation of the base film can be 15% or higher. Specifically, the elongation of the base film can be 16% or higher, 17% or higher, or 17.5% or higher, but is not limited to these.

[0138] Polyimide resin

[0139] For example, the base film may comprise a polyimide-based resin. Specifically, the base film may be a transparent polyimide-based film. The polyimide-based resin can be prepared by reacting reactants comprising a diamine compound and a dianhydride compound simultaneously or sequentially. Specifically, the polyimide-based resin may comprise a polyimide-based polymer prepared by polymerizing a diamine compound and a dianhydride compound. The polyimide-based resin may comprise repeating imide units derived from the polymerization reaction of the diamine compound and the dianhydride compound. Furthermore, the polyimide-based resin may be polymerized by further comprising a dicarbonyl compound. Therefore, it may comprise a polyamide-imide-based polymer that also comprises repeating amide units derived from the polymerization reaction of the diamine compound and the dicarbonyl compound.

[0140] There are no particular limitations on the diamine compound, but it can be, for example, an aromatic diamine compound containing an aromatic structure. For example, the diamine compound can be a compound shown in Formula 1 below.

[0141] Formula 1

[0142] H2N-(E) e -NH2

[0143] In Equation 1, E is selected from substituted or unsubstituted divalent C6-C. 30 Aliphatic cyclic group, substituted or unsubstituted divalent C4-C 30 Heterocyclic cycloids, substituted or unsubstituted divalent C6-C 30Aromatic cycloyl groups, substituted or unsubstituted divalent C4-C 30 heterocyclic cycloids, substituted or unsubstituted C1-C 30 Alkylene, substituted or unsubstituted C2-C 30 alkenyl, substituted or unsubstituted C2-C 30 The following groups are used: -ynyne, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-. e is an integer selected from 1 to 5. When e is 2 or more, E can be the same or different from each other.

[0144] In this specification, the term "substitution" refers to a C1-C group selected from deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, amino, amide, hydrazine, hydrazone, ester, ketone, carboxyl, substituted or unsubstituted. 30 Alkyl, substituted or unsubstituted C2-C 30 alkenyl, substituted or unsubstituted C2-C 30 Alkyne, substituted or unsubstituted C1-C 30 Alkoxy, substituted or unsubstituted C6-C 30 Alicyclic organic groups, substituted or unsubstituted C4-C 30 Heterocyclic groups, substituted or unsubstituted C6-C 30 Aryl and substituted or unsubstituted C4-C 30 It is substituted by at least one substituent of the group consisting of heteroaryl groups. Two adjacent substituents may be linked to form a ring.

[0145] In Equation 1, (E) e It may be selected from the groups shown in formulas 1-1a to 1-14a below, but is not limited thereto.

[0146]

[0147] Specifically, (E) in Formula 1 e It may be selected from the groups shown in formulas 1-1b to 1-13b below, but is not limited thereto.

[0148]

[0149] More specifically, (E) in Equation 1 e It can be the group shown in Formula 1-6b above.

[0150] In one embodiment, the diamine compound may comprise a compound having a fluorinated substituent. Alternatively, the diamine compound may consist of a compound having a fluorinated substituent. In this case, the fluorinated substituent may be a fluorinated hydrocarbon group, specifically a trifluoromethyl group. However, it is not limited thereto.

[0151] In one embodiment, a diamine compound can be used as the diamine compound. That is, the diamine compound can consist of a single component.

[0152] For example, diamine compounds may contain, but are not limited to, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) as shown in the formula below.

[0153]

[0154] Diacid anhydride compounds have low birefringence values, which can help improve the optical properties of films containing polyimide resins, such as light transmittance.

[0155] There are no particular restrictions on the dianhydride compounds, but they can be aromatic dianhydride compounds containing aromatic structures. For example, an aromatic dianhydride compound can be a compound shown in Formula 2 below.

[0156] Formula 2

[0157]

[0158] In Equation 2, G can be selected from substituted or unsubstituted tetravalent C6-C. 30 Aliphatic cyclic group, substituted or unsubstituted tetravalent C4-C 30 Heterocyclic aliphatic cycloids, substituted or unsubstituted tetravalent C6-C 30 Aromatic cycloalloys, substituted or unsubstituted, tetravalent C4-C 30 The group consisting of aliphatic, heteroaliphatic, aromatic, or heteroaromatic cyclic groups can exist alone, can fuse together to form a fused ring, or can be derived from substituted or unsubstituted C1-C groups. 30 Alkylene, substituted or unsubstituted C2-C 30 alkenyl, substituted or unsubstituted C2-C 30 Linking groups include alkynyl, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2- and -C(CF3)2-.

[0159] In Formula 2 above, G can be selected from the groups shown in Formulas 2-1a to 2-9a below, but is not limited thereto.

[0160]

[0161] For example, G in Formula 2 above can be the group shown in Formula 2-8a above.

[0162] In one embodiment, the dianhydride compound may comprise a compound having a fluorinated substituent. Alternatively, the dianhydride compound may consist of a compound having a fluorinated substituent. In this case, the fluorinated substituent may be a fluorinated hydrocarbon group, specifically a trifluoromethyl group. However, it is not limited thereto.

[0163] In another embodiment, the dianhydride compound may consist of a single component or a mixture of two components.

[0164] For example, dianhydride compounds may contain, but are not limited to, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6-FDA) as shown in the formula below.

[0165]

[0166] Diamine compounds and dianhydride compounds can polymerize to form polyamic acid.

[0167] Subsequently, polyamic acid can be converted into polyimide through a dehydration reaction.

[0168] Polyimide may contain repeating units as shown in Formula A below.

[0169] Formula A

[0170]

[0171] In equation A, E, G, and e are as described above.

[0172] For example, polyimide may contain repeating units as shown in formula A-1, but is not limited thereto.

[0173] Formula A-1

[0174]

[0175] In equation A-1, n can be an integer from 1 to 400.

[0176] There are no particular restrictions on dicarbonyl compounds, but they can be, for example, compounds shown in Formula 3 below.

[0177]

Formula 3

[0178]

[0179] In Equation 3, J is selected from substituted or unsubstituted divalent C6-C. 30 Aliphatic cyclic group, substituted or unsubstituted divalent C4-C 30 Heterocyclic cycloids, substituted or unsubstituted divalent C6-C 30 Aromatic cycloyl groups, substituted or unsubstituted divalent C4-C 30 heterocyclic cycloids, substituted or unsubstituted C1-C30 Alkylene, substituted or unsubstituted C2-C 30 alkenyl, substituted or unsubstituted C2-C 30 The following groups are used: -ynyl group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-. j is an integer selected from 1 to 5. When j is 2 or more, j can be the same or different from each other. X is a halogen atom. Specifically, X can be F, Cl, Br, I, etc. More specifically, X can be Cl, but is not limited thereto.

[0180] In equation 3 above, (J) j It may be selected from the groups shown in formulas 3-1a to 3-14a below, but is not limited thereto.

[0181]

[0182] Specifically, in equation 3 above, (J) j It may be selected from the groups shown in formulas 3-1b to 3-8b below, but is not limited thereto.

[0183]

[0184] More specifically, (J) in Equation 3 j It can be the group shown in Formula 3-1b, the group shown in Formula 3-2b, or the group shown in Formula 3-3b.

[0185] In one embodiment, a mixture of at least two distinct dicarbonyl compounds can be used as the dicarbonyl compound. If two or more dicarbonyl compounds are used, at least two dicarbonyl compounds can be used as the dicarbonyl compound, wherein (J) in Formula 3 above... j Selected from the groups shown in formulas 3-1b to 3-8b above.

[0186] In another embodiment, the dicarbonyl compound may be an aromatic dicarbonyl compound containing an aromatic structure.

[0187] For example, a dicarbonyl compound may comprise a first dicarbonyl compound and / or a second dicarbonyl compound that is different from the first dicarbonyl compound.

[0188] The first dicarbonyl compound and the second dicarbonyl compound can be aromatic dicarbonyl compounds, respectively.

[0189] The first dicarbonyl compound and the second dicarbonyl compound can be different aromatic dicarbonyl compounds, but are not limited to this.

[0190] If the first and second dicarbonyl compounds are aromatic dicarbonyl compounds, then they contain benzene rings. Therefore, they can help improve the mechanical properties of films containing polyamide-imide resins, such as surface hardness and tensile strength.

[0191] Dicarbonyl compounds may include terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and 1,1'-biphenyl-4,4'-dicarbonyl dichloride (BPDC), or combinations thereof, as shown in the formula below. However, they are not limited to these.

[0192]

[0193] For example, the first dicarbonyl compound may contain BPDC, and the second dicarbonyl compound may contain TPC, but are not limited thereto.

[0194] Specifically, if BPDC is used as the first dicarbonyl compound and TPC as the second dicarbonyl compound in an appropriate combination, the resulting film containing polyamide-imide resin can have high antioxidant properties.

[0195] Alternatively, the first dicarbonyl compound may contain IPC (isophthaloyl chloride), and the second dicarbonyl compound may contain TPC, but is not limited thereto.

[0196] Specifically, if IPC is used as the first dicarbonyl compound and TPC as the second dicarbonyl compound in an appropriate combination, the resulting film containing polyamide-imide resin can have high antioxidant properties while reducing manufacturing costs.

[0197] Diamine compounds and dicarbonyl compounds can polymerize to form repeating units as shown in Formula B below.

[0198] Formula B

[0199]

[0200] In equation B, E, J, e, and j are as described above.

[0201] For example, diamine compounds and dicarbonyl compounds can be polymerized to form amide repeating units as shown in formulas B-1 and B-2 below.

[0202]

Form B-1

[0203]

[0204] In equation B-1, x is an integer from 1 to 400.

[0205]

Form B-2

[0206]

[0207] In equation B-2, y is an integer from 1 to 400.

[0208] Polyester base film

[0209] As another example, the base film may contain a polyester-based resin. Specifically, the base film may be a transparent polyester-based film.

[0210] Polyester-based resins can be homopolymer resins or copolymer resins formed by the polycondensation reaction of dicarboxylic acids and diols. Furthermore, polyester-based resins can be mixed resins formed by blending homopolymer resins or copolymer resins.

[0211] Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, biphenyl dicarboxylic acid, diphenoxyethylenedicarboxylic acid, diphenylsulfonedicarboxylic acid, anthracene dicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipic acid, pimelic acid, azelaic acid, sebacic acid, octanoic acid, dodecanedicarboxylic acid, etc.

[0212] In addition, examples of diols include ethylene glycol, propylene glycol, hexanediol, neopentyl glycol, 1,2-cyclohexanediethanol, 1,4-cyclohexanediethanol, decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, etc.

[0213] Preferably, the polyester-based resin can be an aromatic polyester-based resin with excellent crystallinity. For example, it can have polyethylene terephthalate (PET) resin as a main component.

[0214] When the base film is a polyester base film, the polyester base film may contain a polyester resin, specifically PET resin, in an amount of about 85% by weight or more, more specifically, 90% by weight or more, 95% by weight or more, or 99% by weight or more. As another example, the polyester base film may also contain polyester resins other than PET resin. Specifically, the polyester base film may also contain up to about 15% by weight of polyethylene naphthalate (PEN) resin. More specifically, the polyester base film may also contain about 0.1% by weight to 10% by weight or about 0.1% by weight to 5% by weight of PEN resin.

[0215] During the preparation of polyester-based films containing the above-mentioned components, the crystallinity can be improved and the mechanical properties, such as tensile strength, can be enhanced through processes such as heating and stretching.

[0216] Primer layer (200)

[0217] The primer layer (200) is disposed between the base film (100) and the elastic layer (300).

[0218] The primer layer contains an adhesive resin. For example, it may contain a curable resin, specifically a UV-curable resin.

[0219] For example, the primer layer may contain polyester acrylate. Polyester acrylate has low viscosity, good processability, and good compatibility with a variety of oligomers or polymers.

[0220] Polyester acrylates can have a structure in which acrylate groups (or acryloyl groups) are substituted in the polyester backbone.

[0221] For example, polyester acrylates can have 1 to 6 or 1 to 3 acrylate groups.

[0222] Polyester acrylates can be in the form of oligomers or polymers. For example, the weight-average molecular weight (Mw) of polyester acrylates can be 1000 or higher, 2000 or higher, 2500 or higher, 3000 or higher, or 3500 or higher, and can also be 50000 or lower, 30000 or lower, 20000 or lower, 10000 or lower, 7000 or lower, 5000 or lower, or 4500 or lower. As a specific example, the weight-average molecular weight of polyester acrylates can be from 1000 to 7000.

[0223] As another example, the primer layer may contain an acrylamide-based compound. Specifically, the acrylamide-based compound may be represented by the following formula I.

[0224] [Formula I]

[0225]

[0226] Here, R 1 and R 2 Each can be independently hydrogen, substituted or unsubstituted, with a single valence of C6-C. 30 Aliphatic cyclic group, substituted or unsubstituted, monovalent C4-C 30 Heterocyclic cycloids, substituted or unsubstituted, monovalent C6-C 30 Aromatic cycloalloys, substituted or unsubstituted, monovalent C4-C 30 heterocyclic cycloids, substituted or unsubstituted C1-C 30 Alkyl, substituted or unsubstituted C2-C 30 Alkenyl, or substituted or unsubstituted C2-C 30 Alkyne group.

[0227] As a specific example, an acrylamide-based compound could be dimethylacrylamide.

[0228] As another example, the primer layer may contain polyester acrylate and an acrylamide-based compound. Interlayer adhesion can be further enhanced by adjusting the weight ratio of polyester acrylate to acrylamide-based compound within a certain range in the primer layer.

[0229] For example, relative to 100 parts by weight of polyester acrylate, the primer layer may contain 1 part by weight or more, 5 parts by weight or more, 10 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more of an acrylamide-based compound. Furthermore, relative to 100 parts by weight of polyester acrylate, the primer layer may contain 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less of an acrylamide-based compound. Specifically, relative to 100 parts by weight of polyester acrylate, the primer layer may contain 5 to 40 parts by weight of an acrylamide-based compound.

[0230] As another example, the primer layer may also contain other acrylic resins, as specifically described in the preparation of the primer composition above.

[0231] In addition, the primer layer may also contain a photoinitiator, as specifically described in the preparation of the primer composition above.

[0232] The photoinitiator may be used in the primer layer in an amount of 1 to 10 parts by weight or 3 to 7 parts by weight relative to 100 parts by weight of the total weight of the adhesive resin (e.g., polyester acrylate and acrylamide-based compounds).

[0233] The thickness of the primer layer can range from 20 nm to 200 nm. Specifically, the thickness of the primer layer can be 20 nm to 190 nm, 20 nm to 180 nm, 20 nm to 160 nm, 20 nm to 130 nm, 20 nm to 120 nm, 20 nm to 110 nm, 20 nm to 80 nm, 30 nm to 200 nm, 30 nm to 190 nm, 30 nm to 180 nm, 30 nm to 160 nm, 30 nm to 130 nm, 30 nm to 120 nm, 30 nm to 110 nm, 30 nm to 100 nm, or 30 nm to 80 nm. Within the above thickness range, the adhesion between the base film and the elastic layer may increase.

[0234] Elastic layer (300)

[0235] The elastic layer (300) contains polyether block amide (PEBA).

[0236] Polyether block amides consist of two phases: polyamide segments (rigid segments) and polyether segments (flexible segments).

[0237] Rigid segments can be crystalline or semi-crystalline. Flexible segments can be amorphous. For example, amorphous segments can be the matrix, and crystalline segments can be distributed within the matrix.

[0238] Because polyether block amides contain both rigid and flexible segments, the elastic layer can have relatively high mechanical strength while also possessing flexible and / or elastic properties.

[0239] The elastic layer can have relatively high mechanical strength, while also having flexible and / or elastic properties.

[0240] The melting point of polyamide segments can be about 80°C or higher, specifically about 130°C to 200°C, about 150°C to 200°C, or 170°C to 200°C. They are essentially crystalline and constitute rigid segments. In contrast, the glass transition temperature of polyether segments can be about -40°C or lower, specifically -80°C to -40°C. They exist in the low-temperature region and can constitute essentially amorphous, flexible segments.

[0241] Polyether block amides can be polyethers composed of polyamides containing two or more carboxyl groups in the molecule and ethers containing two or more hydroxyl groups in the molecule.

[0242] The elastic layer may contain polyether block amides. The polyether block amide may contain at least one copolymer comprising polyether blocks and polyamide blocks. Therefore, the polyether block amide contains at least one polyether block and at least one polyamide block.

[0243] A copolymer containing polyether blocks and polyamide blocks (polyether block amide) can be a copolymer obtained by polycondensation reaction of polyether blocks containing reactive ends and polyamide blocks containing reactive ends.

[0244] For example, a polyether block amide can be a condensation polymer containing a polyamide block with a diamine end and a polyoxyalkylene block with a dicarboxylic acid end.

[0245] As another example, a polyether block amide can be a condensation polymer comprising a polyamide block with a dicarboxylic acid terminus and a polyoxyalkylene block with a diamine terminus.

[0246] Polyoxyalkylene blocks can be obtained by cyanoethylation and hydrogenation of aliphatic α,ω-dihydroxy polyoxyalkylene blocks known as polyether diols.

[0247] Polyether block amides can be condensation polymers comprising polyamide blocks with dicarboxylic acid terminals and polyether diol blocks. In this case, the polyether block amide is a polyether ester amide.

[0248] For example, polyamide blocks containing dicarboxylic acid chain ends can be included in condensation polymers of polyamide precursors in the presence of chain-limited dicarboxylic acids.

[0249] For example, polyamide blocks containing diamine chain ends can be included in condensation polymers of polyamide precursors in the presence of chain-limited diamines.

[0250] For example, polyamide blocks containing dicarboxylic acid chain ends may be included in condensation polymers of α,ω-aminocarboxylic acids, lactams, or dicarboxylic acids and diamines in the presence of chain-limited dicarboxylic acids.

[0251] Polyamide 12 or polyamide 6 is preferred as the polyamide block.

[0252] Polyether block polyamides may contain blocks with a randomly distributed unit structure.

[0253] Advantageously, the following three types of polyamide blocks can be used.

[0254] As a first type, the polyamide block may comprise a condensation polymer of a carboxylic acid and an aliphatic or aryliphatic diamine. The carboxylic acid may have 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms. The aliphatic or aryliphatic diamine may have 2 to 20 carbon atoms, preferably 6 to 14 carbon atoms.

[0255] Carboxylic acids, especially dicarboxylic acids, can be, for example, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexyldicarboxylic acid, 1,4-succinic acid, adipic acid, azelaic acid, octanoic acid, sebacic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and dimer fatty acids.

[0256] The diamine can be, for example, 1,5-tetramethylenediamine, 1,6-hexamethylenediamine, 1,10-decamethylenediamine, 1,12-dodecylmethylenediamine, trimethyl-1,6-hexamethylenediamine, 2-methyl-1,5-pentamethylenediamine, isomers of bis(3-methyl-4-aminocyclohexyl)methane (BMACM), 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), bis(p-aminocyclohexyl)methane (PACM), isophorone diamine (IPD), 2,6-bis(aminomethyl)norbornene (BAMN), piperazine (Pip), m-xylenediamine (MXD), and p-xylenediamine (PXD).

[0257] Specifically, the polyamide blocks of the first type may include PA 412, PA 414, PA 418, PA 610, PA 612, PA 614, PA618, PA912, PA1010, PA1012, PA1014, PA1018, MXD6, PXD6, MXD10, or PXD10.

[0258] As a second type, the polyamide block may comprise a condensation polymer of at least one α,ω-aminocarboxylic acid and / or at least one lactam, each having 6 to 12 carbon atoms, in the presence of a dicarboxylic acid or diamine having 4 to 12 carbon atoms. Examples of lactams include caprolactam, heptanolactam, and dodecanolactam. Examples of α,ω-aminocarboxylic acids include aminohexanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Specifically, the polyamide block of the second type may comprise polyamide 11, polyamide 12, or polyamide 6.

[0259] As a third type, the polyamide block may comprise a condensation polymer of at least one α,ω-aminocarboxylic acid (or at least one lactam), at least one diamine, and at least one dicarboxylic acid. In this case, the polyamide (PA) block can be prepared by a condensation reaction of a diamine, a diacid, and one (or more) comonomers.

[0260] As a diamine, for example, a linear aliphatic diamine, an aromatic diamine, etc., can be used. As a diacid, for example, an alicyclic diacid, an aliphatic diacid, an aromatic diacid, etc., can be used. As a diacid, for example, a dicarboxylic acid can be used. The comonomer can be selected from lactams, α,ω-aminocarboxylic acids, and mixtures comprising substantially equimolar amounts of one or more diamines and one or more dicarboxylic acids. Based on the total amount of the combined polyamide precursor monomers, the amount of comonomer can be 50% by weight or less, preferably 20% by weight or less, advantageously 10% by weight or less.

[0261] According to the third type of polycondensation reaction, it can be carried out in the presence of a chain restrictor selected from dicarboxylic acids. Specifically, dicarboxylic acids can be used as chain restrictors, and dicarboxylic acids can be introduced in stoichiometric excess relative to one or more diamines.

[0262] In another form of the third type, the polyamide block may comprise at least two α,ω-aminocarboxylic acids having 6 to 12 carbon atoms, or at least two lactams, or condensation polymers of lactams and aminocarboxylic acids having different numbers of carbon atoms, optionally in the presence of a chain restrictor. The aliphatic α,ω-aminocarboxylic acid may be, for example, aminohexanoic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid. The lactam may be, for example, caprolactam, heptanolactam, or dodecalactam.

[0263] Aliphatic diamines can be, for example, hexamethylenediamine, dodecamethyldiamine, or trimethylhexamethylenediamine.

[0264] Aliphatic dicarboxylic acids can be, for example, 1,4-cyclohexanedicarboxylic acid. Other aliphatic dicarboxylic acids can be, for example, succinic acid, adipic acid, azelaic acid, octanoic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acids (preferably with a dimer content of 98% or higher; preferably hydrogenated; sold under the trade name Pripol by Uniqema or Empol by Henkel) or polyoxyalkylene-α,ω-dicarboxylic acids.

[0265] Aromatic dicarboxylic acids can be, for example, terephthalic acid or isophthalic acid.

[0266] Alicyclic diamines can be isomers of, for example, bis(3-methyl-4-aminocyclohexyl)methane (BMACM) and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP) or bis(p-aminocyclohexyl)methane (PACM).

[0267] Other diamines include, for example, isophorone diamine (IPDI), 2,6-bis(aminomethyl)norbornene (BAMN), and piperazine.

[0268] Examples of arylita-diamines include, but are not limited to, m-xylenediamine (MXD) and p-xylenediamine (PXD).

[0269] Examples of the third type of polyamide blocks include PA 66 / 6, PA66 / 610 / 11 / 12, etc.

[0270] In PA 66 / 6, 66 represents the hexamethylenediamine unit condensed with adipic acid, and 6 represents the unit introduced by the condensation of caprolactam.

[0271] In PA66 / 610 / 11 / 12, 66 represents a hexamethylenediamine unit condensed with adipic acid, 610 represents a hexamethylenediamine unit condensed with sebacic acid, 11 represents a unit introduced by condensation with aminoundecanoic acid, and 12 represents a unit introduced by condensation with dodecanoic acid.

[0272] The number-average molecular weight of polyamide blocks can be from 400 to 20,000, specifically from 500 to 10,000.

[0273] The polyether block can be, for example, at least one polyalkylene ether polyol, such as polyalkylene ether glycol. Specifically, the polyether block can be selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene ether glycol (PO3G), polytetramethylene ether glycol (PTMG), mixtures thereof, and copolymers thereof.

[0274] The polyether block may comprise a polyoxyalkylene unit with an NH2 terminal. This unit can be introduced by cyanoacetylation of an aliphatic α,ω-dihydroxypolyoxyalkylene unit known as a polyether diol. Specifically, Jeffamine (e.g., Huntsman's Jeffamine) can be used. TM (D400, D2000, ED2003 or XTJ542).

[0275] At least one polyether block comprises, for example, at least one polyether selected from polyalkylene ether polyols such as PEG, PPG, PO3G and PTMG, polyethers with NH2 at the chain end and polyoxyalkylene sequences, copolymers (ether copolymers) arranged randomly and / or in block arrangement and mixtures thereof.

[0276] Based on the total weight of the copolymer, the amount of polyether block can be from 10% to 80% by weight, specifically from 20% to 60% by weight or from 20% to 40% by weight. The number average molecular weight of the polyether block can be from 200 to 1000, specifically from 400 to 800 or from 500 to 700.

[0277] The polyether block can be introduced from polyethylene glycol, polypropylene glycol or polytetramethylene ether glycol.

[0278] Polyether blocks can be copolymerized with polyamide blocks containing carboxyl ends to form polyether block amides.

[0279] Polyether blocks can be converted into polyether diamines through amination, and then condensed with polyamide blocks containing carboxyl ends to form polyether block amides.

[0280] Polyether blocks can be mixed with polyamide precursors and chain restrictors to form polyether block amides containing statistically dispersed units.

[0281] The polyether can be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene ether glycol (PTMG). Polytetramethylene ether glycol is also known as polytetrahydrofuran (PTHF). Polyether blocks can be introduced into the chain of the polyether block amide in the form of glycols or diamines, wherein the polyether blocks are referred to as PEG blocks, PPG blocks, and PTMG blocks, respectively.

[0282] Furthermore, even if the polyether block contains units other than those derived from ethylene glycol (-OC2H4-), propylene glycol (-O-CH2-CH(CH3)-) or tetramethylene ether glycol (-O-(CH2)4-), such polyether blocks should be understood as being within the scope of the embodiments.

[0283] The number-average molecular weight of the polyamide blocks can be from 300 to 15,000 or from 600 to 5,000. The number-average molecular weight of the polyether blocks can be from 100 to 6,000, preferably from 200 to 3,000.

[0284] Specifically, based on the total weight of the polyether block amide, the content of polyamide blocks contained in the polyether block amide can be 50% by weight or more. This may imply the possibility of a statistical distribution within the polymer chain. Specifically, the content of polyamide blocks can be from 50% by weight to 80% by weight. Furthermore, based on the total weight of the polyether block amide, the content of polyether blocks contained in the polyether block amide can be from 20% by weight to 50% by weight.

[0285] The number-average molecular weight ratio of the polyamide blocks to the polyether blocks in the copolymer can be, for example, from 1:0.25 to 1:1. Specifically, the number-average molecular weight ratio of the polyamide blocks to the polyether blocks in the copolymer can be 1000 / 1000, 1300 / 650, 2000 / 1000, 2600 / 650, or 4000 / 1000.

[0286] Polyether block amides can be prepared in a two-step process, involving the first step of preparing polyamide blocks and polyether blocks, and the second step of polycondensing the polyamide blocks and polyether blocks to prepare elastic polyether block amides. Alternatively, polyether block amides can be prepared by a one-step polycondensation reaction of monomers.

[0287] The Shore D hardness of polyether block amides can be, for example, 20 to 75, specifically 30 to 70.

[0288] The intrinsic viscosity of polyether block amides can be measured at 25°C using m-cresol and ranges from 0.8 dl / g to 2.5 dl / g. The intrinsic viscosity can be measured according to ISO 307:2019. Specifically, the intrinsic viscosity in solution can be measured at 25°C using an Ubbelohde viscometer in a 0.5 wt% m-cresol solution.

[0289] Examples of polyether block amides include Arkema's Pebax. TM and Pebax TM Rnew TM And Evonik's VESTAMID TM E, but not limited to this.

[0290] The optical properties of the elastic layer can be adjusted within a certain range. Therefore, it is advantageous for cover windows used in display devices.

[0291] The haze of the elastic layer can be, for example, 3% or lower, specifically 2% or lower, 1.5% or lower, or 1.2% or lower. Furthermore, the haze of the elastic layer can be 0.01% or higher, or 0.1% or higher.

[0292] The average visible light transmittance of the elastic layer can be, for example, 85% or more, specifically 88% or more, or 90% or more. Furthermore, the average visible light transmittance of the elastic layer can be 99.99% or lower.

[0293] The thickness of the elastic layer can be 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more, and 500 μm or less, 400 μm or less, 300 μm or less, or 200 μm or less. As a specific example, the thickness of the base film can be from 20 μm to 500 μm, more specifically from 50 μm to 200 μm.

[0294] Hard coating

[0295] According to one embodiment, the laminated film may optionally be further included in a hard coating on the base film (100).

[0296] The rigid coating can have an upper side and a lower side, where the lower side can face the base film and the upper side can be the outermost exposed side. Furthermore, the lower side of the rigid coating can directly contact one side of the base film, or be bonded to one side of the base film via an additional coating. For example, the rigid coating can be formed directly on one side of the base film.

[0297] Hard coatings can enhance the mechanical and / or optical properties of laminates. Furthermore, hard coatings can also incorporate anti-glare, anti-fouling, and antistatic properties.

[0298] Hard coatings may contain at least one of organic components, inorganic components, and organic-inorganic composite components as hard coating agents.

[0299] For example, a hard coating may comprise an organic resin. Specifically, the organic resin may be a curable resin. Therefore, a hard coating may be a curable coating. Furthermore, the organic resin may be an adhesive resin.

[0300] Specifically, the hard coating may comprise at least one selected from the group consisting of urethane acrylate compounds, acrylate compounds, and epoxy acrylate compounds. More specifically, the hard coating may comprise urethane acrylate compounds and acrylate compounds.

[0301] urethane acrylate compounds may contain urethane bonds as repeating units and may have multiple functional groups.

[0302] The urethane acrylate compound can be a compound in which the urethane compound formed by reacting a diisocyanate compound with a polyol has its terminal acrylate group substituted. For example, the diisocyanate compound can comprise at least one of a straight-chain, branched, or cyclic aliphatic diisocyanate compound having 4 to 12 carbon atoms and an aromatic diisocyanate compound having 6 to 20 carbon atoms. The polyol comprises 2 to 4 hydroxyl groups (-OH) and can be a straight-chain, branched, or cyclic aliphatic polyol compound having 4 to 12 carbon atoms or an aromatic polyol compound having 6 to 20 carbon atoms. The terminal substitution of the acrylate group is achieved by an acrylate compound having a functional group capable of reacting with an isocyanate group (-NCO). For example, an acrylate compound having hydroxyl or amino groups can be used, and hydroxyalkyl acrylates or aminoalkyl acrylates having 2 to 10 carbon atoms can be used.

[0303] ethyl carbamate acrylate compounds can contain 2 to 15 functional groups.

[0304] Examples of urethane acrylate-based compounds include, but are not limited to, difunctional urethane acrylate oligomers with a weight-average molecular weight of 1,400 to 25,000, trifunctional urethane acrylate oligomers with a weight-average molecular weight of 1,700 to 16,000, tetrafunctional urethane acrylate oligomers with a weight-average molecular weight of 500 to 2,000, hexafunctional urethane acrylate oligomers with a weight-average molecular weight of 818 to 2,600, nonfunctional urethane acrylate oligomers with a weight-average molecular weight of 2,500 to 5,500, decafunctional urethane acrylate oligomers with a weight-average molecular weight of 3,200 to 3,900, and pentafunctional urethane acrylate oligomers with a weight-average molecular weight of 2,300 to 20,000.

[0305] The glass transition temperature (Tg) of urethane acrylate compounds can be -80°C to 100°C, -80°C to 90°C, -80°C to 80°C, -80°C to 70°C, -80°C to 60°C, -70°C to 100°C, -70°C to 90°C, -70°C to 80°C, -70°C to 70°C, -70°C to 60°C, -60°C to 100°C, -60°C to 90°C, -60°C to 80°C, -60°C to 70°C, -60°C to 60°C, -50°C to 100°C, -50°C to 90°C, -50°C to 80°C, -50°C to 70°C, or -50°C to 60°C.

[0306] The acrylate compound may be at least one selected from the group consisting of substituted or unsubstituted acrylates and substituted or unsubstituted methacrylates. The acrylate compound may contain 1 to 10 functional groups.

[0307] Examples of acrylate-based compounds include, but are not limited to, trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxytriacrylate (TMPEOTA), glycerol propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

[0308] The weight-average molecular weight of acrylate-based compounds can be 500 to 6000, 500 to 5000, 500 to 4000, 1000 to 6000, 1000 to 5000, 1000 to 4000, 1500 to 6000, 1500 to 5000, or 1500 to 4000. The acrylate equivalent of acrylate-based compounds can be 50 g / equivalent to 300 g / equivalent, 50 g / equivalent to 200 g / equivalent, or 50 g / equivalent to 150 g / equivalent.

[0309] Epoxy acrylate compounds may contain 1 to 10 functional groups. Examples of epoxy acrylate compounds include, but are not limited to, monofunctional epoxy acrylate oligomers with a weight-average molecular weight of 100 to 300, difunctional epoxy acrylate oligomers with a weight-average molecular weight of 250 to 2000, and tetrafunctional epoxy acrylate oligomers with a weight-average molecular weight of 1000 to 3000. The epoxy equivalent of the epoxy acrylate compound may be from 50 g / equivalent to 300 g / equivalent, from 50 g / equivalent to 200 g / equivalent, or from 50 g / equivalent to 150 g / equivalent.

[0310] The content of organic resin can be from 30% to 100% by weight, depending on the total weight of the hard coating. Specifically, the content of organic resin can be from 40% to 90% by weight, or from 50% to 80% by weight, depending on the total weight of the hard coating.

[0311] The hard coating may optionally further comprise fillers. The fillers may be, for example, inorganic particles. Examples of fillers include silica, barium sulfate, zinc oxide, and alumina. The particle size of the filler may be from 1 nm to 100 nm. Specifically, the particle size of the filler may be from 5 nm to 50 nm or from 10 nm to 30 nm. The filler may comprise inorganic fillers with different particle size distributions. For example, the filler may comprise a first inorganic filler with a D50 of 20 nm to 35 nm and a second inorganic filler with a D50 of 40 nm to 130 nm. Based on the total weight of the hard coating, the filler content may be 25% by weight or more, 30% by weight or more, or 35% by weight or more. Furthermore, based on the total weight of the hard coating, the filler content may be 50% by weight or less, 45% by weight or less, or 40% by weight or less. Preferably, the hard coating does not contain inorganic fillers such as silica. In this case, for example, the adhesion between the base film and the hard coating in the above composition can be enhanced.

[0312] Hard coatings may also contain photoinitiators. Examples of photoinitiators include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methyl benzoylcarbamate, α,α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. In addition, commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP100F. Photoinitiators can be used alone or in combination of two or more.

[0313] Hard coatings may also contain antifouling agents. For example, hard coatings may contain fluorinated compounds. Fluorinated compounds can have antifouling properties. Specifically, fluorinated compounds may be acrylate compounds having a perfluoroalkyl group. Specific examples may include, but are not limited to, perfluorohexylethyl acrylate.

[0314] Hard coatings may also contain antistatic agents. Antistatic agents may contain ionic surfactants. For example, ionic surfactants may contain ammonium salts or alkyl quaternary ammonium salts, and ammonium salts and alkyl quaternary ammonium salts may contain halides, such as chlorides or bromides.

[0315] In addition, hard coatings may also contain additives such as surfactants, UV absorbers, UV stabilizers, anti-yellowing agents, leveling agents, and dyes to improve color values. For example, surfactants may be monofunctional to bifunctional fluoroacrylates, fluorosurfactants, or silicone-based surfactants. Surfactants may be present in the hard coating in dispersed or crosslinked forms. Furthermore, examples of UV absorbers include benzophenone compounds, benzotriazole compounds, and triazine compounds. Examples of UV stabilizers include tetramethylpiperidine, etc. The content of additives can be adjusted in various ways without impairing the physical properties of the hard coating. For example, the content of additives may be from 0.01% by weight to 10% by weight, but is not limited to this, based on the weight of the hard coating.

[0316] Hard coatings can consist of a single layer, two layers, or more. For example, a hard coating formed as a single layer can simultaneously increase the durability of the laminate and provide fingerprint or stain resistance.

[0317] The thickness of the hard coating can be 2 μm or thicker, 3 μm or thicker, 5 μm or thicker, or 10 μm or thicker, and as thin as 50 μm or thinner, 30 μm or thinner, 20 μm or thinner, or 10 μm or thinner. For example, the thickness of the hard coating can be from 2 μm to 20 μm. Specifically, the thickness of the hard coating can be from 5 μm to 20 μm. If the hard coating is too thin, it may not have sufficient surface hardness to protect the base film, resulting in deterioration of the durability of the laminate. If it is too thick, the flexibility of the laminate may deteriorate, and the overall thickness of the laminate may increase, which may be detrimental to film formation.

[0318] Therefore, the hard coating can be formed from a hard coating composition comprising at least one of an organic-based composition, an inorganic-based composition, and an organic-inorganic composite composition. For example, the hard coating composition may comprise at least one of an acrylate-based compound, a siloxane compound, and a silsesquioxane compound. Furthermore, the hard coating may also comprise inorganic particles. As a specific example, the hard coating can be formed from a hard coating composition comprising an urethane acrylate-based compound, an acrylate-based compound, and a fluorine-based compound.

[0319] Hard coatings can be formed by coating a hard coating composition onto a base film, followed by drying and curing.

[0320] The hard coating composition may contain the above-mentioned organic resin, photoinitiator, antifouling agent, antistatic agent, other additives and / or solvent.

[0321] Examples of organic solvents include alcohol-based solvents such as methanol, ethanol, isopropanol, and butanol; alkoxy-based solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; ether-based solvents such as propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene, which can be used alone or in combination.

[0322] There are no particular limitations on the content of the organic solvent, as it can be adjusted in various ways without impairing the physical properties of the hard coating composition. Organic solvents can be used such that the weight ratio of the solid content of the components in the coating composition to the organic solvent is from about 30:70 to about 99:1. If the content of the organic solvent is within the above range, the composition can have suitable flowability and coatability.

[0323] The hard coating composition may contain 10% to 30% by weight of an organic resin, 0.1% to 5% by weight of a photoinitiator, 0.01% to 2% by weight of an antifouling agent, and 0.1% to 10% by weight of an antistatic agent. According to this composition, the mechanical properties of the hard coating, as well as its antifouling and antistatic properties, can be simultaneously enhanced.

[0324] Hard coating compositions can be applied to a base film by rod coating, knife coating, roller coating, doctor blade coating, die coating, microgravure coating, comma coating, groove die coating, lip coating, or solution casting.

[0325] Subsequently, the organic solvent contained in the hard coating composition can be removed by a drying step. The drying step can be carried out at a temperature of 40°C to 100°C, preferably 40°C to 80°C, 50°C to 100°C, or 50°C to 80°C for about 1 minute to 20 minutes, preferably 1 minute to 10 minutes or 1 minute to 5 minutes.

[0326] Subsequently, the hard coating composition layer can be cured by light and / or heat.

[0327] Invention Model

[0328] The embodiments described below are intended to aid understanding and are not intended to limit the scope of implementation.

[0329] Preparation of primer composition

[0330] Preparation Example 1

[0331] Polyester acrylate resin (bifunctional, molecular weight: 3800 to 4000, Miramer PS2500, Miwon Corporation) and N,N-dimethylacrylamide (CAS2680-03-7) were mixed at a weight ratio of 100:20. Five parts by weight of photoinitiator (I-184, BASF) were added to 100 parts by weight of the mixture. Subsequently, the mixture was diluted to a solids content of 3% by weight using methyl isobutyl ketone (MIBK) as a solvent to obtain a primer composition (A-Primer 20).

[0332] Preparation Example 2

[0333] The primer composition (A-Primer 15) was obtained according to the steps of Preparation Example 1, except that the polyester acrylate resin and dimethacrylamide were mixed in a weight ratio of 100:15.

[0334] Comparative Preparation Example 1

[0335] The primer composition (F-Primer) was obtained by formulating the components shown in Table 1 below.

[0336] Table 1

[0337]

[0338] Preparation of laminated films

[0339] Example 1

[0340] Step (1) Primer treatment of the base film

[0341] The primer composition (A-Primer 20) obtained in Preparation Example 1 was coated onto one side of a transparent polyimide-based film (TPI, SKC) with a thickness of 50 μm, dried in an oven at 120°C for 5 minutes, and then UV cured at a light dose of about 500 mJ to form a primer layer with a thickness of about 100 nm.

[0342] Step (2) Extrusion lamination

[0343] polyether block amide resin (Arkema Pebax) TM Rnew TM 72R53 (Arkema) was fed into an extruder, extruded at approximately 240°C, and cast onto a primer layer previously formed on the base film for lamination. During lamination, a pressure of approximately 5000 kPa was applied. The final product was a laminated film in which a 50 μm thick PEBA layer was formed on the base film through the primer layer.

[0344] Example 2

[0345] Except for forming a primer layer using the primer composition (A-Primer 15) obtained in Preparation Example 2, a laminate was prepared according to the steps of Example 1.

[0346] Comparative Example 1

[0347] According to step (2) of Example 1, without any primer treatment, a 50 μm thick transparent polyimide-based film (TPI, SKC) is laminated with a PEBA film to prepare a laminated film.

[0348] Comparative Example 2

[0349] Except for forming a primer layer using the primer composition (F-Primer) obtained in Comparative Preparation Example 1, a laminate was prepared according to the steps of Example 1.

[0350] The layer configurations of the membranes prepared above are summarized in Table 2 below.

[0351] Table 2

[0352] Example 1 TPI(50μm) / A-Primer 20(100nm) / PEBA 72R53(50μm) Example 2 TPI(50μm) / A-Primer 15(100nm) / PEBA 72R53(50μm) Comparative Example 1 TPI (50μm) / PEBA 72R53 (50μm) Comparative Example 2 TPI(50μm) / F-Primer(100nm) / PEBA 72R53(50μm)

[0353] Test Example 1: Peel Test (Adhesive Strength)

[0354] Each laminated film sample was cut into 5cm long and 1cm wide sections, and its interlayer adhesion was measured by peeling at 180° on a peel tester. (Reference) Figure 4 The base film side of the laminated film sample (10a) was attached to the peel tester (20), and the PEBA film side was attached to the load sensor. Peeling was performed at an angle of 180° (a) along the longitudinal direction of the sample. The results showed that delamination mainly occurred at the interface between the primer layer formed on the base film and the PEBA film (or at the interface between the base film and the PEBA film if there is no primer layer). The load (N) applied to the load sensor during peeling was measured. The peel test was performed at an angle of 180°, a speed of 300 mm / min, and room temperature (approximately 25°C).

[0355] Test Example 2: Change in adhesive force over time

[0356] Each laminated film sample underwent a peel test to measure initial adhesion using the same method as in Test Example 1. Final adhesion was measured after storage at room temperature (approximately 25°C) and 50% RH for 96 hours (4 days) or 240 hours (10 days). Adhesion was measured for five samples. The average of the three values ​​was calculated, excluding the highest and lowest values. The results are shown in Table 3 below.

[0357] Change in adhesive force (%) = [(A INT –A FIN ) / A INT ]×100(A INT Under the above conditions, the adhesion force (gf / inch) between the base film and the elastic layer before storage, while A FIN This refers to the adhesion force (gf / inch) between the base film and the elastic layer after storage under the above conditions.

[0358] Test Example 3: Folding Test

[0359] Each laminated film sample was cut to a length of 12 cm and a width of 4 cm, then mounted on a folding tester, and the presence of interlayer delamination was checked during repeated folding. The folding test was performed by repeatedly folding inwards (base film folding inwards) or outwards (base film folding outwards) at a curvature radius of 1.5R and a folding speed of 1 fold / second. If no interlayer delamination occurred after more than 200,000 repeated inward folds, and no interlayer delamination occurred after more than 100,000 repeated outward folds, the result was considered excellent.

[0360] The results are shown in Table 3 below.

[0361] Table 3

[0362]

[0363] As shown in Table 3 above, the laminated films in the embodiments with adjusted lamination configurations and primer layer compositions exhibit excellent interlayer adhesion and repeated folding durability, indicating that these laminated films are suitable for use as cover windows in foldable displays. In contrast, the laminated films in the comparative examples have poor interlayer adhesion and lack repeated folding durability. Furthermore, compared to the laminated films in the comparative examples, the adhesive strength of the laminated films in the embodiments changes less over time.

Claims

1. A laminated film comprising a base film; an elastic layer comprising a polyether block amide; and a primer layer disposed between the base film and the elastic layer; The primer layer comprises 100 parts by weight of polyester acrylate; And 5 to 40 parts by weight of acrylamide-based compounds; A laminated film is prepared by laminating a base film and an elastic layer together with a primer layer.

2. The laminated film as described in claim 1, wherein, When the laminated film is cut to a size of 5cm in length and 1cm in width, and subjected to a 180° peel test at a speed of 300mm / min at room temperature, the adhesion between the base film and the elastic layer is 15gf / inch or higher.

3. The laminated film as described in claim 1, wherein, The weight-average molecular weight of the polyester acrylate is between 1,000 and 7,000.

4. The laminated film as described in claim 1, wherein, When the laminated film is stored at room temperature and 50% RH for 96 hours, the change in adhesive force calculated by the following equation (1) is 35% or less: Change in adhesive force (%) = [(A INT – A FIN ) / A INT ] × 100 ...(1) Among them, A INT The adhesion between the base film and the elastic layer before storage under the above conditions, A FIN The adhesive force between the base film and the elastic layer after storage under the above conditions is measured by cutting the laminated film into a size of 5 cm long and 1 cm wide, and performing a 180° peel test at a speed of 300 mm / min at room temperature to measure the load applied between the base film and the elastic layer; the unit of adhesive force is gf / inch.

5. The laminated film as claimed in claim 1, wherein, The laminated film comprises a polymer film or UTG.

6. A process for preparing a laminated film, the process comprising: Preparation of primer composition; The primer composition is applied to a base film and cured to form a primer layer; The primer composition comprises 100 parts by weight of polyester acrylate; And 5 to 40 parts by weight of acrylamide-based compounds; as well as, The base film and the elastic layer are laminated together using the primer layer to prepare a laminated film. The elastic layer comprises polyether block amide, and when the laminate is cut into a size of 5 cm long and 1 cm wide, and subjected to a 180° peel test at a speed of 300 mm / min at room temperature, the adhesion between the base film and the elastic layer is 15 gf / inch or higher.

7. A display device, the display device comprising a display panel; and a laminate disposed on the front side of the display panel, in, The laminated film comprises a base film; an elastic layer comprising a polyether block amide; and a primer layer disposed between the base film and the elastic layer; the primer layer comprising 100 parts by weight of polyester acrylate; And 5 to 40 parts by weight of acrylamide-based compounds; A laminated film is prepared by laminating a base film and an elastic layer together with a primer layer. When the laminated film is cut to a size of 5cm in length and 1cm in width, and subjected to a 180° peel test at a speed of 300mm / min at room temperature, the adhesion between the base film and the elastic layer is 15gf / inch or higher.

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