Laminated film with improved surface hardness and restorability and display device including same

Abstract

In one embodiment, the laminated film is formed by laminating an elastic layer containing a polyether-block-amide and a hard-coated substrate film, and the layer structure in which different materials are combined not only improves the surface hardness and resilience or elasticity at the same time, but also realizes excellent optical properties.

Description

[Technical Field]

[0001] The realization example relates to a laminated film having improved surface hardness and resilience, and a display device including the same. [Background technology]

[0002] Display technology continues to develop in response to the demands of the development of IT devices, with technologies such as curved displays and bent displays already being commercialized. In recent years, flexible display devices that can flexibly bend or fold in response to external forces have become popular in the mobile device field, where large screens and portability are both required. In particular, foldable display devices have the major advantage of being able to fold up when not in use to make them compact and portable, and then unfold to create a large screen when in use.

[0003] In such flexible displays, the cover window is required to be flexible and resilient. In the case of an outfolding type in which the flexible display is exposed to the outside, it is required to have not only flexibility but also a protective function against external forces.

[0004] Display devices typically use transparent polymer films such as polyimide or polyester or glass substrates for their cover windows, but polymer films are vulnerable to external scratches, and glass substrates lack flexibility.

[0005] To solve this problem, Patent Document 1 discloses a hard coat film that is manufactured by sequentially forming a high-flexibility layer and a high-hardness layer using a siloxane resin on a transparent substrate to improve scratch resistance and flexibility. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 2019-0026611 Summary of the Invention [Problem to be solved by the invention]

[0007] Previously developed display cover window films had limitations in achieving both surface hardness and resilience or elasticity at the same time. Furthermore, when a hard coating layer was formed to improve surface hardness, problems arose such as a significant decrease in flexibility and resilience, as well as a deterioration in the optical properties of the film.

[0008] As a result of research conducted by the present inventors, it was found that laminating an elastic layer containing a polyether-block-amide with a hard-coated substrate film not only improves the surface hardness and resilience or elasticity at the same time, but also achieves excellent optical properties, due to the layer configuration in which different materials are combined.

[0009] Therefore, the following embodiment aims to provide a laminated film having improved surface hardness and resilience or elasticity, and excellent optical properties, and a display device including the same. [Means for solving the problem]

[0010] According to one embodiment, there is provided a laminated film including a base film, a hard coat layer disposed on one side of the base film, and an elastic layer disposed on the other side of the base film, wherein the elastic layer includes a polyether-block-amide.

[0011] According to another embodiment, there is provided a display device including a display panel and a cover window disposed on a front surface of the display panel, the cover window including a substrate film, a hard coat layer disposed on one surface of the substrate film, and an elastic layer disposed on the other surface of the substrate film, the elastic layer including a polyether-block-amide. [Effects of the Invention]

[0012] The laminated film according to the above embodiment is formed by laminating an elastic layer containing a polyether-block-amide and a hard-coated substrate film, resulting in a layer structure in which different materials are combined, which not only improves surface hardness and resilience or elasticity at the same time, but also achieves excellent optical properties.

[0013] Therefore, the laminated film according to the above embodiment can be applied to the cover of a flexible display device, for example, an outfolding or infolding type device in which the display is exposed to the outside, and can have flexibility, protection performance for the display against external forces, and excellent optical properties. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 shows an exploded perspective view of a display device according to one implementation. [Figure 2] FIG. 2 shows a cross-sectional view of a laminated film according to one implementation (A-A' in FIG. 1). [Figure 3] Figure 3 shows the nanoindentation test results before (a) and after (b) indentation. [Figure 4] Figure 4 shows a cross-sectional view of the sample during (a) and (b) indentation by the indenter tip. [Figure 5a] FIG. 1a shows an in-folding type flexible display device. [Figure 5b] FIG. 1b shows an outfolding type flexible display device. DETAILED DESCRIPTION OF THE INVENTION

[0015] Various implementations and embodiments will now be described in detail with reference to the drawings. In the following description of the implementation examples, if it is determined that a detailed description of related known structures or functions may obscure the gist of the present invention, the detailed description will be omitted. In addition, the size of each component in the drawings may be exaggerated or omitted for the purpose of explanation, and may differ from the actual size.

[0016] In this specification, when a component is described as being formed above / below another component, or as being connected or coupled to each other, this includes being formed, connected or coupled between these components directly or indirectly via other components. It should also be understood that the reference to above / below each component may change depending on the direction from which the object is viewed.

[0017] In this specification, the terms used to refer to each component are used to distinguish it from other components and are not intended to limit the scope of the implementation. Furthermore, in this specification, the singular expression includes the plural expression unless the context clearly indicates a different meaning.

[0018] As used herein, the term "comprising" is intended to embody certain features, regions, steps, steps, elements and / or components, and does not exclude the presence or addition of other features, regions, steps, steps, elements and / or components, unless specifically stated to the contrary.

[0019] In this specification, terms such as "first" and "second" are used to describe various components, and the components should not be limited by these terms. These terms are used to distinguish one component from another.

[0020] The molecular weights of the compounds or polymers described herein, e.g., number average molecular weight or weight average molecular weight, are expressed as relative masses based on carbon-12, as is well known, without units, but may be understood to be molar masses (g / mol) of the same numerical value, if desired.

[0021] Fig. 1 shows an exploded perspective view of a display device according to an embodiment, and Fig. 2 shows a cross-sectional view of a laminated film (cover window) according to an embodiment (taken along line AA' in Fig. 1).

[0022] Referring to FIG. 2, a laminate film 10 according to one embodiment includes a substrate film 100, a hard coat layer 300 disposed on one side of the substrate film 100, and an elastic layer 300 disposed on the other side of the substrate film 100, the elastic layer 300 including a polyether-block-amide.

[0023] The laminated film according to the above embodiment is formed by laminating an elastic layer containing a polyether-block-amide and a hard-coated substrate film, resulting in a layer structure in which different materials are combined, which not only improves surface hardness and resilience or elasticity at the same time, but also achieves excellent optical properties.

[0024] [Surface hardness of laminated film] The surface hardness of the laminated film can be measured by a nanoindentation test.

[0025] Nanoindentation is an analytical technique that measures various mechanical properties such as hardness, elastic modulus, tensile properties, residual stress, etc. by analyzing the force-displacement curve obtained in the process of applying and removing a small force (load) of μN to mN level with an indenter with a specific geometric shape to the surface of a material.

[0026] The indenter tip may have a variety of geometric shapes, for example, a conical, pyramidal or triangular pyramid (Berkovich or Vickers triangular pyramid), or a cylindrical flat punch shape.

[0027] Figure 3 shows the sample before (a) and after (b) indentation in the nanoindentation test.

[0028] FIG. 4 shows a cross-sectional view of the sample during (a) and (b) indentation by the indenter tip.

[0029] 3 and 4, since a general polymer material is a viscoelastic body, when the tip 2a at the lower end of the indenter 2 is pressed into the sample 10a, the maximum depth (h max ), and then when the indenter 2 is removed and the indenter tip 2a is released, part of the deformation is restored due to the elasticity of the polymer, but the rest is not permanently restored and remains at a certain depth (h p ) leaving a dent 2b.

[0030] In such nanoindentation tests, stiffness (S), projected contact area (A p ), test force (F), maximum indentation depth at maximum force (h max ) and other parameters are measured to obtain a force-displacement curve. Based on these results, the indentation modulus (E IT ), indentation hardness (H IT ), Vickers hardness (HV), Martens hardness (HM), indentation creep (C IT ), elastic modulus (Recovery relation, ηIT The nanoindentation test can be performed based on, for example, the ISO 14577-1:2002(E) standard.

[0031] Martens hardness (HM), also known as composite hardness, is calculated based on the indentation depth at which the test force is applied. Unlike indentation hardness, it provides both plastic and elastic material properties. The Martens hardness of the laminated film according to the above embodiment is, for example, 250 N / mm 2 More than 260N / mm 2 More than 270N / mm 2 or more than 275N / mm 2 and above, and 400N / mm 2 Below, 350N / mm 2 Below, 330N / mm 2 Below, 310N / mm 2 or less than 290N / mm 2 As a specific example, the Martens hardness (HM) of the surface of the hard coat layer measured by a nanoindentation test based on the ISO 14577-1:2002(E) standard for the laminated film may be 250 N / mm 2 More specifically, 250N / mm 2 ~350N / mm 2 It could be.

[0032] Vickers hardness (HV) is the indentation hardness (H IT ) multiplied by 0.0945 (H IT × 0.0945) and can be measured, for example, based on the ISO 14577-1:2002(E) standard. From the Vickers hardness (HV), plastic properties such as ductility, malleability, and impact resistance can be known. The Vickers hardness (HV) of the laminated film according to the above embodiment is, for example, 40 N / mm 2 Over 45N / mm 2 Above, 48N / mm 2 or more than 49N / mm 2 and above 60N / mm 2 Below, 55N / mm 2 or less than 53N / mm2 As a specific example, the laminated film may have a Vickers hardness (HV) of 48 N / mm or less on the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E). 2 More specifically, 48N / mm 2 ~55N / mm 2 It could be.

[0033] The high Vickers hardness (HV) of the laminated film according to the embodiment may be due to the hard coat layer. For example, the laminated film has an HV increase (N / mm 2 ) is 1.5N / mm 2 More specifically, 2.0N / mm 2 or more, or 2.5N / mm 2 That is all. A more specific example is 1.5N / mm 2 ~7.0N / mm 2 It could be.

[0034] HV increase (N / mm 2 )=HV1(N / mm 2 )-HV2(N / mm 2 ) Here, HV1 is the Vickers hardness (HV) (N / mm 2 ), and HV2 is the Vickers hardness (HV) (N / mm 2 )

[0035] Indentation hardness (H IT ), also known as plastic hardness, is a measure of a material's resistance to permanent (plastic) deformation under maximum force, and it allows us to determine plastic properties such as ductility, malleability, and impact resistance. Specifically, indentation hardness (H IT ) is the maximum test force (F max ) is the contact projected area at the penetration depth (A p ) divided by (F max / A p) is calculated. The indentation hardness (H IT ) is, for example, 500N / mm 2 More than 505N / mm 2 More than 510N / mm 2 More than 515N / mm 2 More than 520N / mm 2 or more than 524N / mm 2 and above 550N / mm 2 Below, 545N / mm 2 Below, 540N / mm 2 or less than 535N / mm 2 As a specific example, the laminated film may have an indentation hardness (H IT ) is 505N / mm 2 More specifically, 505N / mm 2 ~550N / mm 2 The indentation hardness (H IT ) plastic properties such as impact resistance are realized, which may be advantageous for application to the cover window of a display device.

[0036] High indentation hardness (H IT ) may be due to the hard coat layer. For example, the laminated film may have a hard coat layer H calculated by the following formula: IT Increase (N / mm 2 ) is 10N / mm 2 More specifically, 15N / mm 2 More than 20N / mm 2 or more than 25N / mm 2 That is all. As a more specific example, 2 ~70N / mm 2 It could be.

[0037] H IT Increase (N / mm 2 )=H IT 1 (N / mm2 )-H IT 2 (N / mm 2 ) where H IT 1 is the indentation hardness (H IT )(N / mm 2 ) and H IT 2 is the indentation hardness (H IT )(N / mm 2 )

[0038] Indentation modulus (E IT The indentation modulus (E) is calculated using the Poisson's ratio between the sample and the indenter, the modulus of the indenter, and the reduced modulus of the indentation contact, and can be measured by a nanoindentation test, for example, according to the ISO 14577-1:2002(E) standard. IT ) can be used to determine elastic properties such as hardness and abrasion resistance. IT ) may be, for example, 3600 MPa or more, 3800 MPa or more, 4000 MPa or more, or 4200 MPa or more, and may be 5000 MPa or less, 4800 MPa or less, 4600 MPa or less, or 4500 MPa or less. As a specific example, the indentation modulus (E IT ) is 3800 MPa or more, and more specifically, can be 3800 MPa to 4800 MPa.

[0039] Indentation creep (C IT ) refers to the additional deformation of a material at a constant force. Indentation creep (C ITTo measure the indentation creep (C), the indenter is pressed into the sample with a constant force for a longer period of time (several minutes to several hours), and the increased indentation depth due to the sustained pressure can be measured and calculated. IT ) may be, for example, 3.0% or more, 3.3% or more, 3.5% or more, 3.6% or more, or 3.7% or more, and may be 4.5% or less, 4.3% or less, 4.1% or less, 4.0% or less, or 3.9% or less. As a specific example, the indentation creep (C IT ) may be 3.3% or more, and more specifically, 3.3% to 4.2%.

[0040] Elastic modulus (η IT ) is the total mechanical work of indentation (W) in the force-depth curve obtained when an indenter is pressed into the sample surface and then released. total ) for the total work at the time of release (elastic reserve deformation work, W elast ) percentage (i.e., (W elast / W total ) × 100%, and can be measured, for example, based on the ISO 14577-1:2002(E) standard. IT ) may be, for example, 60% or more, 65% or more, 68% or more, or 70% or more, and may be 85% or less, 80% or less, 78% or less, or 75% or less. As a specific example, the elastic modulus (η ) of the surface of the hard coat layer of the laminated film measured by a nanoindentation test based on ISO 14577-1:2002(E) standard is IT ) is 68% or more, and more specifically, can be 68% to 78%.

[0041] The recovery rate can be calculated using the following formula based on the value measured by a nanoindentation test. The recovery rate of the laminate film according to the embodiment can be, for example, 65% or more, 70% or more, 75% or more, 76% or more, or 78% or more, and 95% or less, 90% or less, 85% or less, or 83% or less. As a specific example, for the laminate film, the recovery rate of the hard coat layer surface measured by a nanoindentation test based on the ISO 14577-1:2002(E) standard can be 76% or more, more specifically 76% to 90%. The recovery rate is calculated using the following formula.

[0042] Recovery(%)=[(h max(@30mN) -h p ) / h max(@30mN) ] x 100 where h max(@30mN) is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure (creep) for 5 seconds, and h p is the indentation depth (μm) that remains unrecovered after the force is removed.

[0043] The high recovery rate of the laminated film according to the above embodiment may be due to the hard coat layer or the elastic layer. For example, the laminated film may have a recovery increase (%) calculated by the following formula of 2% or more, specifically 3% or more, or 5% or more, and more specifically, 3% to 20%.

[0044] Recovery Increase (%) = Recovery1 (%) - Recovery2 (%) Here, Recovery1 is the recovery rate (%) of the laminated film, and Recovery2 is the recovery rate (%) of a film having a layer structure in which only one of the hard coat layer and the elastic layer is removed from the laminated film.

[0045] [Optical properties of laminated film] The laminate film has a light transmittance, e.g., an average visible light transmittance, of a certain level or higher, making it advantageous for use as a cover window for a display device. For example, the average visible light transmittance of the laminate film may be 70% or higher, 75% or higher, 80% or higher, 82% or higher, 83% or higher, or 85% or higher. Meanwhile, the upper limit of the average visible light transmittance range of the laminate film is not particularly limited, but may be, for example, 100% or lower, 95% or lower, or 90% or lower. Such transmittance may be measured, for example, according to the ISO 13468 standard. As a specific example, the average visible light transmittance of the laminate film measured according to the ISO 13468 standard may be 80% or higher, or 85% or higher.

[0046] The laminated film may also have a transmittance increase effect due to the hard coating. For example, the laminated film may have a transmittance increase calculated by the following formula of 2% or more, specifically 2.5% or more, 3% or more, 4% or more, or 5% or more, and more specifically, 2% to 10%, or 3% to 10%.

[0047] Transmittance increase (%) = TT1 (%) - TT2 (%) Here, TT1 is the average visible light transmittance (%) of the laminate film, and TT2 is the average visible light transmittance (%) of a film having a layer structure in which only the hard coat layer is removed from the laminate film, and the average visible light transmittances are measured under the same conditions based on the ISO 13468 standard.

[0048] According to one embodiment, the laminated film may have an average visible light transmittance of 85% or more as measured according to the ISO 13468 standard, and the increase in transmittance calculated by the above formula may be 3% or more.

[0049] Furthermore, the laminate film has a haze of not more than a specific level, making it advantageous for use as a cover window for a display device. For example, the haze of the laminate film may be 5% or less, 4% or less, 3.5% or less, 3% or less, or 2% or less. Meanwhile, the lower limit of the haze range of the laminate film is not particularly limited, and may be, for example, 0% or more, 0.5% or more, or 1% or more. Such a haze may be measured, for example, according to the ISO 14782 standard. As a specific example, the haze of the laminate film measured according to the ISO 14782 standard may be 4% or less.

[0050] In one embodiment, the laminated film may have an average visible light transmittance of 80% or more as measured in accordance with the ISO 13468 standard, a haze of 4% or less as measured in accordance with the ISO 14782 standard, and an increase in transmittance calculated by the above formula of 2% or more.

[0051] Furthermore, the laminate film has a yellowness index (YI) of a specific level or less, which allows images emitted from a display to be perceived without distortion. For example, the yellowness index (YI) of the laminate film may be 2 or less, 1.5 or less, or 1 or less. Meanwhile, the lower limit of the yellowness index range of the laminate film is not particularly limited, but may be, for example, 0 or more, 0.3 or more, 0.5 or more, or 0.6 or more. The yellowness index (YI) can be measured using a spectrophotometer, for example, using a D65 light source, according to the ASTM-E313 standard. As a specific example, the yellowness index of the laminate film measured according to the ASTM-E313 standard at 10° using a D65 light source may be 1.5 or less.

[0052] Furthermore, the laminate film may have a yellowness reduction effect due to the hard coating. For example, the laminate film may have a yellowness reduction of 0.5 or more, more specifically 0.7 or more or 1.0 or more, and more specifically 0.5 to 5, calculated by the following formula:

[0053] Yellowness reduction (%)=YI2-YI1 Here, YI1 is the yellowness index of the laminated film, and YI2 is the yellowness index of a film having a layer structure obtained by excluding only the hard coat layer from the laminated film. The yellowness indexes are measured under the same conditions as those in ASTM-E313 at 10° using a D65 light source.

[0054] The laminate film also has a color that is adjusted to a specific range, allowing images emitted from a display to be perceived without distortion. For example, the L* value of the transmitted color of the laminate film in the CIE Lab color coordinate system may be 85 or more, 90 or more, or 93 or more, and 100 or less, 97 or less, or 95 or less. The a* value of the transmitted color of the laminate film in the CIE Lab color coordinate system may be -3 or more, -2 or more, -1.5 or more, or -1 or more, and 2 or less, 1 or less, 0 or less, -0.5 or less, or -0.9 or less. The b* value of the transmitted color of the laminate film in the CIE Lab color coordinate system may be -2 or more, -1 or more, 0 or more, or 0.5 or more, and 3 or less, 2 or less, 1.5 or less, or 1 or less. The transmitted color can be measured using a spectrophotometer, and a light source such as D65 can be used. As a specific example, the laminated film may have an L* value of 92 or more, an a* value of -2 to 1, and a b* value of -1 to 2 in the CIE Lab color coordinates of transmitted color measured using a D65 light source.

[0055] [Base film 100] The substrate film acts as a base layer for the hard coat layer 200 while providing mechanical properties to the laminate film 10 .

[0056] The substrate film may be a polymer film or a glass substrate, specifically a tempered glass substrate having a thickness of less than about 100 μm. For example, the substrate film may include a polymer film or ultra-thin glass (UTG).

[0057] Specifically, the substrate film may be a polymer film, that is, the substrate film may include a polymer resin.

[0058] Examples of polymer resins contained in the substrate film include polyester-based resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; cellulose-based resins such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based resins; acrylic-based resins such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrene-based resins such as polystyrene and acrylonitrile-styrene copolymers; polyolefin-based resins such as polyethylene, polypropylene, polyolefins having cyclo- or norbornene structures, and ethylene-propylene copolymers; vinyl chloride-based resins; amide-based resins such as nylon and aromatic polyamides; imide-based resins; polyamideimide-based resins; polyethersulfone-based resins; polyurethane-based resins; sulfone-based resins; polyetheretherketone-based resins; polyphenylene sulfide-based resins; vinyl alcohol-based resins; vinylidene chloride-based resins; vinyl butyral-based resins; arylate-based resins; polyoxymethylene-based resins; and epoxy-based resins. These may be used alone or in combination of two or more.

[0059] The base film may further include a filler in addition to the polymer resin. For example, the base film may include a polyimide resin and a filler.

[0060] The filler may be one or more selected from the group consisting of barium sulfate, silica, and calcium carbonate. By including the filler, the substrate film can improve roughness and winding properties, and further improve running properties and scratch prevention effects during film production.

[0061] The particle size of the filler may be 0.01 μm or more and less than 1.0 μm, for example, 0.05 μm to 0.9 μm or 0.1 μm to 0.8 μm, but is not limited thereto.

[0062] The filler may be included in an amount of 0.01 wt % to 3 wt % based on the total weight of the base film, for example, but not limited to, 0.05 wt % to 2.5 wt %, 0.1 wt % to 2 wt %, or 0.2 wt % to 1.7 wt % based on the total weight of the base film.

[0063] The thickness of the base film may be 20 μm or more, 30 μm or more, 40 μm or more, 50 μm or more, or 100 μm or more, and may be 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 may be 20 μm to 500 μm, more specifically 40 μm to 200 μm or 50 μm to 200 μm.

[0064] The optical and mechanical properties of the substrate film can be adjusted within a certain range.

[0065] The haze of the base film may be 3% or less. For example, the haze of the base film may be 2% or less, 1.5% or less, or 1% or less, but is not limited thereto.

[0066] The yellowness index (YI) of the base film may be 5 or less. For example, the yellowness index of the base film may be 4 or less, 3.8 or less, 2.8 or less, 2.5 or less, 2.3 or less, or 2.1 or less, but is not limited thereto.

[0067] The modulus of the base film may be 5 GPa or more, for example, 5.2 GPa or more, 5.5 GPa or more, 6.0 GPa or more, 10 GPa or less, 5 GPa to 10 GPa, or 7 GPa to 10 GPa, but is not limited thereto.

[0068] The light transmittance of the substrate film may be 80% or more, for example, 85% or more, 88% or more, 89% or more, 80% to 99%, or 85% to 99%, but is not limited thereto.

[0069] The compressive strength of the base film may be 0.4 kgf / μm or more. Specifically, the compressive strength of the base film may be 0.45 kgf / μm or more or 0.46 kgf / μm or more, but is not limited thereto.

[0070] The surface hardness of the substrate film may be HB or higher. Specifically, the surface hardness of the substrate film may be H or higher or 2H or higher, but is not limited thereto.

[0071] The base film has a tensile strength of 15 kgf / mm 2 Specifically, the tensile strength of the base film may be 18 kgf / mm or more. 2 Over 20kgf / mm 2 Above, 21kgf / mm 2 or more, or 22kgf / mm 2 It can be more than this, but is not limited to this.

[0072] The base film may have an elongation percentage of 15% or more. Specifically, the elongation percentage of the base film may be, but is not limited to, 16% or more, 17% or more, or 17.5% or more.

[0073] [Polyimide resin] For example, the substrate film may include a polyimide-based resin, and more specifically, the substrate film may be a transparent polyimide-based film. The polyimide-based resin may be formed by simultaneous or sequential reaction of reactants including a diamine compound and a dianhydride compound. More specifically, the polyimide-based resin may include a polyimide-based polymer formed by polymerization of the diamine compound and the dianhydride compound. The polyimide-based resin may include an imide repeating unit derived from polymerization of the diamine compound and the dianhydride compound. Furthermore, the polyimide-based resin may be polymerized by further including a dicarbonyl compound, and thus may include a polyamide-imide-based polymer further including an amide repeating unit derived from polymerization of the diamine compound and the dicarbonyl compound.

[0074] The diamine compound is not particularly limited, and may be, for example, an aromatic diamine compound having an aromatic structure, such as a compound represented by the following Formula 1:

[0075] [C1] JPEG0007746528000001.jpg754 In the above Chemical Formula 1, E is a substituted or unsubstituted divalent C6-C 30 Alicyclic groups, substituted or unsubstituted, divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C-C 30 Aromatic ring groups, substituted or unsubstituted, divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 Alkynylene groups are selected from -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-, where e is selected from integers of 1 to 5, and when e is 2 or greater, E may be the same or different.

[0076] As used herein, unless otherwise specified, the term "substituted" means deuterium, -F, -Cl, -Br, -I, a hydroxy group, a cyano group, a nitro group, an amino group, an amide group, a hydrazine group, a hydrazone group, an ester group, a ketone group, a carboxyl group, a substituted or unsubstituted C1-C 30 Alkyl groups, substituted or unsubstituted C2-C 30 Alkenyl groups, substituted or unsubstituted C2-C 30 Alkynyl groups, substituted or unsubstituted C1-C 30 Alkoxy groups, substituted or unsubstituted C6-C 30 Alicyclic organic groups, substituted or unsubstituted C4-C 30 Heterocyclic groups, substituted or unsubstituted C6-C 30 Aryl groups and substituted or unsubstituted C4-C 30 It refers to a group substituted with one or more substituents selected from the group consisting of heteroaryl groups, and two adjacent substituents may be linked to form a ring.

[0077] (E) of Chemical Formula 1 e can be selected from groups represented by the following chemical formulas 1-1a to 1-14a, but is not limited thereto. JPEG0007746528000002.jpg97153

[0078] Specifically, (E) of the above Chemical Formula 1 e can be selected from groups represented by the following chemical formulas 1-1b to 1-13b, but is not limited thereto. JPEG0007746528000003.jpg101150

[0079] More specifically, (E) of the above Chemical Formula 1 e can be a group represented by the above chemical formula 1-6b.

[0080] In one embodiment, the diamine compound may include a compound having a fluorine-containing substituent, or may be a compound having a fluorine-containing substituent, wherein the fluorine-containing substituent is a fluorinated hydrocarbon group, specifically, but not limited to, a trifluoromethyl group.

[0081] In one embodiment, the diamine compound may be one kind of diamine compound, i.e., the diamine compound may consist of a single component.

[0082] For example, the diamine compound may include, but is not limited to, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) having the following structure: JPEG0007746528000004.jpg4474

[0083] The dianhydride compound has a low birefringence value, and therefore can contribute to improving optical properties such as transmittance of a film containing the polyimide resin.

[0084] The dianhydride compound is not particularly limited, and may be an aromatic dianhydride compound having an aromatic structure, for example, the aromatic dianhydride compound may be a compound represented by the following formula 2: [Case 2] JPEG0007746528000005.jpg3451

[0085] In the above formula 2, G is a substituted or unsubstituted tetravalent C6-C 30 Alicyclic groups, substituted or unsubstituted, tetravalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted, tetravalent C-C 30 Aromatic ring groups, substituted or unsubstituted, tetravalent C4-C 30an aromatic heterocyclic group, wherein the alicyclic group, heteroalicyclic group, aromatic ring group, or aromatic heterocyclic group is present alone, or is bonded to each other to form a fused ring, or is a substituted or unsubstituted C-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 The alkynylene groups are linked by a linking group selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0086] G in the above Chemical Formula 2 can be selected from groups represented by the following Chemical Formulas 2-1a to 2-9a, but is not limited thereto. JPEG0007746528000006.jpg86148

[0087] For example, G in Chemical Formula 2 above can be a group represented by Chemical Formula 2-8a above.

[0088] In one embodiment, the dianhydride compound may include or consist of a compound having a fluorine-containing substituent, where the fluorine-containing substituent is a fluorinated hydrocarbon group, specifically, but not limited to, a trifluoromethyl group.

[0089] In other implementations, the dianhydride compound may consist of one single component or two mixed components.

[0090] For example, the dianhydride compound may include, but is not limited to, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) having the following structure: JPEG0007746528000007.jpg4076

[0091] The diamine compound and the dianhydride compound can be polymerized to form a polyamic acid.

[0092] The polyamic acid can then be converted to a polyimide by a dehydration reaction. The polyimide may include a repeating unit represented by the following chemical formula A: [Chemical A] JPEG0007746528000008.jpg4074 In the chemical formula A, the explanations for E, G, and e are as described above.

[0093] For example, the polyimide may include a repeating unit represented by the following chemical formula A-1, but is not limited thereto. [Chemical A-1] JPEG0007746528000009.jpg38128 In the chemical formula A-1, n can be an integer of 1 to 400.

[0094] The dicarbonyl compound is not particularly limited, and may be, for example, a compound represented by the following formula 3: [C3] JPEG0007746528000010.jpg2657

[0095] In the above formula 3, J is a substituted or unsubstituted divalent C-C 30 Alicyclic groups, substituted or unsubstituted, divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C-C 30 Aromatic ring groups, substituted or unsubstituted, divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30Alkynylene groups are selected from -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-, where j is an integer selected from 1 to 5, and when j is 2 or more, J's are the same or different, and X is a halogen atom. Specifically, X can be F, Cl, Br, I, or the like. More specifically, X can be Cl, but is not limited thereto.

[0096] JPEG0007746528000011.jpg100148 (J) of Chemical Formula 3 j can be selected from groups represented by the following chemical formulas 3-1a to 3-14a, but is not limited thereto.

[0097] Specifically, (J) of the above Chemical Formula 3 j can be selected from groups represented by the following chemical formulas 3-1b to 3-8b, but is not limited thereto. JPEG0007746528000012.jpg72149

[0098] More specifically, (J) of the above Chemical Formula 3 j can be a group represented by the chemical formula 3-1b, a group represented by the chemical formula 3-2b, or a group represented by the chemical formula 3-3b.

[0099] In one embodiment, the dicarbonyl compound may be a mixture of at least two different dicarbonyl compounds. When two or more dicarbonyl compounds are used, the dicarbonyl compound may be a compound represented by the formula (J) in Formula 3. j Two or more types selected from the groups represented by the chemical formulas 3-1b to 3-8b may be used.

[0100] In another implementation, the dicarbonyl compound can be an aromatic dicarbonyl compound that includes an aromatic structure.

[0101] For example, the dicarbonyl compound can include a first dicarbonyl compound and / or a second dicarbonyl compound that is different from the first dicarbonyl compound.

[0102] The first dicarbonyl compound and the second dicarbonyl compound can each be an aromatic dicarbonyl compound.

[0103] The first dicarbonyl compound and the second dicarbonyl compound may be, but are not limited to, different aromatic dicarbonyl compounds.

[0104] When the first dicarbonyl compound and the second dicarbonyl compound are each an aromatic dicarbonyl compound, they contain a benzene ring, which can contribute to improving the mechanical properties, such as the surface hardness and tensile strength, of the film containing the produced polyamide-imide resin.

[0105] The dicarbonyl compound may include, but is not limited to, terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), 1,1'-biphenyl-4,4'-dicarbonyl dichloride (BPDC), or a combination thereof, each having the following structure: JPEG0007746528000013.jpg24150

[0106] For example, the first dicarbonyl compound may include BPDC and the second dicarbonyl compound may include TPC, but is not limited thereto.

[0107] Specifically, when BPDC is used as the first dicarbonyl compound and TPC is used as the second dicarbonyl compound in combination, the resulting polyamide-imide resin film can have high oxidation resistance.

[0108] Alternatively, the first dicarbonyl compound may include IPC and the second dicarbonyl compound may include TPC, but is not limited thereto.

[0109] Specifically, when IPC is used as the first dicarbonyl compound and TPC is used as the second dicarbonyl compound in combination, the resulting polyamide-imide resin film can have high oxidation resistance and can reduce production costs.

[0110] The diamine compound and the dicarbonyl compound can be polymerized to form a repeating unit represented by the following chemical formula B. [Case B] JPEG0007746528000014.jpg3473 In the chemical formula B, the explanations for E, J, e, and j are as described above.

[0111] For example, the diamine compound and the dicarbonyl compound can be polymerized to form amide repeat units represented by chemical formulas B-1 and B-2.

[0112] [Case B-1] JPEG0007746528000015.jpg35128 In the chemical formula B-1, x is an integer of 1 to 400.

[0113] [Case B-2] JPEG0007746528000016.jpg39128 In the chemical formula B-2, y is an integer of 1 to 400.

[0114] [Polyester resin] As another example, the base film may include a polyester-based resin, and specifically, the base film may be a transparent polyester-based film.

[0115] The polyester-based resin may be a homopolymer resin or a copolymer resin obtained by polycondensation of a dicarboxylic acid and a diol, or a blend resin obtained by mixing the homopolymer resins or the copolymer resins.

[0116] Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfonedicarboxylic acid, anthracenedicarboxylic 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, trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, and dodecanedicarboxylic acid.

[0117] Examples of the diol include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0118] Preferably, the polyester resin is an aromatic polyester resin having excellent crystallinity, and may be composed primarily of, for example, polyethylene terephthalate (PET) resin.

[0119] When the substrate film is a polyester film, the polyester film may contain a polyester resin, specifically a PET resin, at about 85% by weight or more, more specifically, at 90% by weight or more, 95% by weight or more, or 99% by weight or more. As another example, the polyester film may further contain another polyester resin in addition to the PET resin. Specifically, the polyester film may further contain about 15% by weight or less of a polyethylene naphthalate (PEN) resin. More specifically, the polyester film may further contain about 0.1% by weight to 10% by weight, or about 0.1% by weight to 5% by weight of a PEN resin.

[0120] This composition increases the crystallinity of the polyester film during the manufacturing process, such as heating and stretching, and improves mechanical properties such as tensile strength.

[0121] The substrate film may have an in-plane retardation (Ro) of 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. When the Ro is within this range, the occurrence of rainbow unevenness can be minimized.

[0122] In addition, the substrate film has a minimum in-plane retardation (Ro min ) may be 200 nm or less or 150 nm or less. Specifically, the minimum in-plane retardation of the substrate film may be 120 nm or less, 100 nm or less, 85 nm or less, 75 nm or less, or 65 nm or less.

[0123] On the other hand, the lower limit of the in-plane retardation of the substrate film may be 0 nm, or in order to balance the optical properties and mechanical properties, the lower limit of the in-plane retardation (Ro) may be 10 nm or more, 30 nm or more, or 50 nm or more.

[0124] The substrate film may have a thickness direction retardation (Rth) of 4000 or more, 5,000 nm or more, or 5,500 nm or more.

[0125] In addition, the substrate film has a maximum thickness direction retardation (Rthmax ) may be 6000 nm or more, such as 6500 nm or more, for example 7500 nm or more, for example 8000 nm or more, for example 8500 nm or more.

[0126] The thickness direction retardation may be a value measured based on a thickness of 40 μm to 50 μm. When the thickness direction retardation is within the above range, the degree of molecular orientation is high, which promotes crystallization, and is preferable from the viewpoint of mechanical properties. Furthermore, the larger the thickness direction retardation (Rth), the larger the ratio (Rth / Ro) of the thickness direction retardation (Rth) to the in-plane retardation (Ro), and therefore rainbow unevenness can be effectively suppressed.

[0127] On the other hand, taking into consideration the thickness limit for eliminating rainbow unevenness from the substrate film and costs, the upper limit of the thickness direction retardation (Rth) can be set to 16,000 nm or less, 15,000 nm or less, or 14,000 nm or less.

[0128] The in-plane retardation (Ro) is a parameter defined by the product (Δnxy×d) of the refractive index anisotropy of two orthogonal axes in the plane of the film (Δnxy=|nx-ny|) and the film thickness (d), and is a measure of optical isotropy or anisotropy. min ) means the lowest measured value when the in-plane retardation (Ro) is measured at multiple points within the plane of the film.

[0129] The thickness direction retardation (Rth) is a parameter defined as the average of the retardations obtained by multiplying the two birefringences Δnxz (=|nx-nz|) and Δnyz (=|ny-nz|) by the thickness (d) of the film when viewed from the cross section in the thickness direction of the film. max ) means the highest measured value when the thickness direction retardation (Rth) is measured at multiple points within the plane of the film.

[0130] In addition, the substrate film may have a ratio (Rth / Ro) of thickness direction retardation (Rth) to in-plane retardation (Ro) of 10 or more, 15 or more, or 20 or more. Since a smaller in-plane retardation (Ro) and a larger thickness direction retardation (Rth) are more advantageous in preventing the occurrence of rainbow unevenness, it is preferable to maintain a large ratio of the two values ​​(Rth / Ro). In particular, the substrate film may have a minimum in-plane retardation (Ro min ) to the maximum thickness direction retardation (Rth max ) ratio (Rth max / Ro min ) may be 30 or more, 40 or more, 50 or more, or 60 or more.

[0131] The method for producing the base film can include the steps of: (1) extruding a composition containing a polyester-based resin to obtain an unstretched film; (2) stretching the unstretched film in the length direction and width direction; and (3) heat-setting the stretched film.

[0132] In the above-described manufacturing method, the base film is manufactured by extruding a raw material resin and then preheating, stretching, and heat setting the raw material resin. The composition of the polyester resin used as the base material film is as exemplified above. The extrusion can be performed at a temperature of 230°C to 300°C or 250°C to 280°C.

[0133] The base film is preheated at a certain temperature before stretching. The preheating temperature range can be determined so as to satisfy the range of Tg+5°C to Tg+50°C based on the glass transition temperature (Tg) of the polyester resin, and also satisfy the range of 70°C to 90°C. When the preheating temperature is within the range, the base film can be easily stretched with sufficient flexibility, and can effectively prevent breakage during stretching.

[0134] The stretching is carried out by biaxial stretching, and for example, the film can be stretched in two axes, the width direction (tenter direction, TD) and the length direction (machine direction, MD), by a simultaneous biaxial stretching method or a sequential biaxial stretching method. Preferably, the film is stretched first in one direction and then in the direction perpendicular to that direction, by a sequential biaxial stretching method.

[0135] The longitudinal stretch ratio may be in the range of 2.0 to 5.0, more specifically, in the range of 2.8 to 3.5. The transverse stretch ratio may be in the range of 2.0 to 5.0, more specifically, in the range of 2.9 to 3.7. Preferably, the longitudinal stretch ratio (d1) and the transverse stretch ratio (d2) are similar. Specifically, the ratio (d2 / d1) of the longitudinal stretch ratio (d2) to the transverse stretch ratio (d1) may be 0.5 to 1.0, 0.7 to 1.0, or 0.9 to 1.0. The stretch ratios (d1, d2) represent the length after stretching, assuming the length before stretching to be 1.0. The stretching speed may be 6.5 m / min to 8.5 m / min, but is not particularly limited.

[0136] The stretched sheet can be heat-set at 150° C. to 250° C., more specifically 160° C. to 230° C. The heat-setting can be carried out for 5 seconds to 1 minute, more specifically 10 seconds to 45 seconds.

[0137] After initiating heat setting, the film is relaxed in the length and / or width directions, which may be at a temperature ranging from 150°C to 250°C.

[0138] According to one embodiment, a laminate film including a polyester-based film as a substrate film can have improved surface hardness and elasticity at the same time.

[0139] The Martens hardness of the laminated film according to the above embodiment is, for example, 170 N / mm 2 More than 175N / mm 2 More than 180N / mm 2 Above, 181.25N / mm 2 or more, or 185N / mm 2 and above 250N / mm 2 Below, 200N / mm2 Below, 195N / mm 2 or less than 190N / mm 2 As a specific example, the laminated film may have a Martens hardness (HM) of 175 N / mm or less on the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E). 2 More specifically, 175N / mm 2 ~200N / mm 2 It could be.

[0140] The laminated film also has an HM increase (N / mm 2 ) is 5N / mm 2 More specifically, 7N / mm 2 or more than 10N / mm 2 That's all. A more specific example is 5N / mm 2 ~25N / mm 2 It could be.

[0141] HM increase (N / mm 2 )=HM1(N / mm 2 )-HM2(N / mm 2 ) Here, HV1 is the Martens hardness (HM) (N / mm 2 ), and HV2 is the Martens hardness (HM) (N / mm 2 )

[0142] The Vickers hardness (HV) of the laminated film according to the embodiment is, for example, 20 N / mm 2 More than 25N / mm 2 Above, 29N / mm 2 or more than 30N / mm 2 More than 50N / mm 2 Below, 45N / mm 2 Below, 40N / mm 2 or less than 35N / mm 2As a specific example, the laminated film may have a Vickers hardness (HV) of 29 N / mm or less on the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E). 2 More specifically, 29N / mm 2 ~50N / mm 2 It could be.

[0143] In addition, the laminated film has a HV increase (N / mm 2 ) is 1.5N / mm 2 More specifically, 2.0N / mm 2 or more, or 2.5N / mm 2 That is all. A more specific example is 1.5N / mm 2 ~7.0N / mm 2 It could be.

[0144] HV increase (N / mm 2 )=HV1(N / mm 2 )-HV2(N / mm 2 ) Here, HV1 is the Vickers hardness (HV) (N / mm 2 ), and HV2 is the Vickers hardness (HV) (N / mm 2 )

[0145] The indentation hardness (H IT ) is, for example, 250N / mm 2 More than 270N / mm 2 More than 290N / mm 2 More than 310N / mm 2 More than 320N / mm 2 or more than 330N / mm 2 and above 500N / mm 2 Below, 450N / mm 2 Below, 400N / mm 2 or less than 370N / mm 2As a specific example, the laminated film may have an indentation hardness (H IT ) is 310N / mm 2 More specifically, 310N / mm 2 ~450N / mm 2 The indentation hardness (H IT ) plastic properties such as impact resistance are realized, which may be advantageous for application to the cover window of a display device.

[0146] In addition, the laminated film has a H calculated by the following formula: IT Increase (N / mm 2 ) is 10N / mm 2 More specifically, 15N / mm 2 More than 20N / mm 2 or more than 25N / mm 2 That is all. As a more specific example, 2 ~70N / mm 2 It could be.

[0147] H IT Increase (N / mm 2 )=H IT 1 (N / mm 2 )-H IT 2 (N / mm 2 ) where H IT 1 is the indentation hardness (H IT )(N / mm 2 ) and H IT 2 is the indentation hardness (H IT )(N / mm 2 )

[0148] The indentation modulus (E IT) may be, for example, 2500 MPa or more, 2800 MPa or more, 2900 MPa or more, 2935 MPa or more, or 2950 MPa or more, and may be 4000 MPa or less, 3500 MPa or less, 3300 MPa or less, or 3100 MPa or less. As a specific example, the indentation modulus (E IT ) is 2900 MPa or more, and more specifically, can be 2900 MPa to 4000 MPa.

[0149] Indentation creep (C IT ) may be, for example, 3.0% or more, 3.5% or more, 3.7% or more, 4.0% or more, or 4.1% or more, and may be 6.0% or less, 5.5% or less, 5.0% or less, 4.5% or less, or 4.3% or less. As a specific example, the indentation creep (C IT ) is 3.5% or more, and more specifically, can be 3.5% to 5.0%.

[0150] The elastic modulus (η IT ) may be, for example, 50% or more, 55% or more, 60% or more, 61% or more, 63% or more, or 63.5% or more, and may be 85% or less, 80% or less, 75% or less, or 70% or less. As a specific example, the elastic modulus (η ) of the surface of the hard coat layer of the laminated film measured by a nanoindentation test based on ISO 14577-1:2002(E) standard is IT ) is 63.6% or more, and more specifically, can be 63.6% to 75%.

[0151] The recovery rate of the laminate film according to the above embodiment may be, for example, 60% or more, 65% or more, 70% or more, or 73.35% or more, and may be 90% or less, 85% or less, 80% or less, or 75% or less. As a specific example, the recovery rate of the hard coat layer surface of the laminate film measured by a nanoindentation test based on ISO 14577-1:2002(E) may be 65% or more, more specifically, 65% to 90%. The recovery rate is calculated using the following formula:

[0152] Recovery(%)=[(h max(@30mN) -h p ) / h max(@30mN )] × 100 where h max(@30mN) is the maximum indentation depth (μm) while the surface of the hard coat layer is pressed downward with a force of 30 mN for 15 seconds and then maintained (creep) for 5 seconds, and hp is the indentation depth (μm) that remains unrestored after the force is removed.

[0153] The laminated film has a recovery increase (%) calculated by the following formula of 5% or more, specifically 8% or more, or 9% or more, and more specifically, 5% to 15%.

[0154] Recovery Increase (%) = Recovery1 (%) - Recovery2 (%) Here, Recovery1 is the recovery rate (%) of the laminated film, and Recovery2 is the recovery rate (%) of a film having a layer structure in which only the hard coat layer is removed from the laminated film.

[0155] [Hard coat layer 200] The hard coat layer 200 is disposed on one surface of the substrate film 100 .

[0156] The hard coat layer may have an upper surface and a lower surface, the lower surface facing the substrate film and the upper surface being the outermost surface exposed to the outside. The lower surface of the hard coat layer may be in direct contact with one surface of the substrate film or may be bonded to one surface of the substrate film via an additional coating layer. For example, the hard coat layer may be formed directly on one surface of the substrate film.

[0157] The hard coat layer can improve the mechanical and / or optical properties of the laminate film, and can further have functions such as anti-glare, anti-fouling, and anti-static.

[0158] The hard coat layer may contain at least one of an organic component, an inorganic component, and an organic-inorganic composite component as a hard coat agent.

[0159] For example, the hard coat layer may include an organic resin. Specifically, the organic resin may be a curable resin. Thus, the hard coat layer may be a curable coat layer. Furthermore, the organic resin may be a binder resin.

[0160] Specifically, the hard coat layer may include one or more compounds selected from the group consisting of urethane acrylate compounds, acrylic ester compounds, acrylate compounds, and epoxy acrylate compounds. More specifically, the hard coat layer may include a urethane acrylate compound and an acrylic ester compound. Even more specifically, the hard coat layer may include, but is not limited to, a urethane acrylate compound, an acrylic ester compound, and an acrylate compound.

[0161] The urethane acrylate compound may contain a urethane bond as a repeating unit and may have multiple functional groups.

[0162] The urethane acrylate compound may be a urethane compound formed by reacting a diisocyanate compound with a polyol, with the terminal substituted with an acrylate group. For example, the diisocyanate compound may include at least one of a linear, 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 may contain 2 to 4 hydroxy groups (—OH) and may be a linear, 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 with an acrylate group may be performed using an acrylate compound having a functional group reactive with an isocyanate group (—NCO). For example, an acrylate compound having a hydroxy group, an amine group, or the like may be used, such as a hydroxyalkyl acrylate or an aminoalkyl acrylate having 2 to 10 carbon atoms.

[0163] The urethane acrylate compound may contain 2 to 15 functional groups.

[0164] Examples of the urethane acrylate compound include, but are not limited to, difunctional urethane acrylate oligomers having a weight average molecular weight of 1,400 to 25,000, trifunctional urethane acrylate oligomers having a weight average molecular weight of 1,700 to 16,000, tetrafunctional urethane acrylate oligomers having a weight average molecular weight of 500 to 2,000, hexafunctional urethane acrylate oligomers having a weight average molecular weight of 818 to 2,600, nonafunctional urethane acrylate oligomers having a weight average molecular weight of 2,500 to 5,500, 10-functional urethane acrylate oligomers having a weight average molecular weight of 3,200 to 3,900, and 15-functional urethane acrylate oligomers having a weight average molecular weight of 2,300 to 20,000.

[0165] The glass transition temperature (Tg) of the urethane acrylate compound may 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.

[0166] The acrylic ester compound may be one or more selected from the group consisting of substituted or unsubstituted acrylates and substituted or unsubstituted methacrylates, and may contain 1 to 10 functional groups.

[0167] Examples of the acrylic ester compound include, but are not limited to, trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxy triacrylate (TMPEOTA), glycerin propoxy triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

[0168] The weight average molecular weight of the acrylic ester compound may 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 the acrylic ester compound may be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0169] The acrylate compound may contain 1 to 10 functional groups. Examples of the acrylate compound include, but are not limited to, a monofunctional acrylate oligomer having a weight-average molecular weight of 100 to 300, a bifunctional acrylate oligomer having a weight-average molecular weight of 250 to 2000, or an acrylate oligomer having a weight-average molecular weight of 1000 to 3000.

[0170] The epoxy acrylate compound may contain 1 to 10 functional groups. Examples of the epoxy acrylate compound include, but are not limited to, monofunctional epoxy acrylate oligomers having a weight-average molecular weight of 100 to 300, difunctional epoxy acrylate oligomers having a weight-average molecular weight of 250 to 2000, and tetrafunctional epoxy acrylate oligomers having a weight-average molecular weight of 1000 to 3000. The epoxy equivalent of the epoxy acrylate compound may be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0171] The content of the organic resin may be 30% by weight to 100% by weight based on the total weight of the hard coat layer, specifically, 40% by weight to 90% by weight or 50% by weight to 80% by weight based on the total weight of the hard coat layer.

[0172] The hard coat layer may optionally further include a filler. The filler may be, for example, inorganic particles. Examples of the filler include silica, barium sulfate, zinc oxide, and alumina. The particle size of the filler may be 1 nm to 100 nm. Specifically, the particle size of the filler may be 5 nm to 50 nm or 10 nm to 30 nm. The fillers may include inorganic fillers having different particle size distributions. For example, the fillers may include a first inorganic filler having a D50 of 20 nm to 35 nm and a second inorganic filler having a D50 of 40 nm to 130 nm. The content of the filler may be 25 wt % or more, 30 wt % or more, or 35 wt % or more, based on the total weight of the hard coat layer. The content of the filler may be 50 wt % or less, 45 wt % or less, or 40 wt % or less, based on the total weight of the hard coat layer. Preferably, the hard coat layer does not include an inorganic filler such as silica. In this case, for example, the adhesive strength between the substrate film and the hard coat layer having the above-mentioned composition can be improved.

[0173] The hard coat layer may further include a photoinitiator. Examples of the photoinitiator include, but are not limited to, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methylbenzoyl formate, 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, or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Commercially available products include Irgacure 184, Irgacure® 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur® 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, Esacure® KIP 100F, etc. The photoinitiators may be used alone or in combination of two or more different types.

[0174] The hard coat layer may further include an antifouling agent. For example, the hard coat layer may include a fluorine-based compound. The fluorine-based compound may perform an antifouling function. Specifically, the fluorine-based compound is an acrylate-based compound having a perfluoroalkyl group, and a specific example thereof includes, but is not limited to, perfluorohexyl ethyl acrylate.

[0175] The hard coat layer may further include an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may include an ammonium salt or a quaternary alkyl ammonium salt, and the ammonium salt and the quaternary alkyl ammonium salt may include a halide such as a chloride or a bromide.

[0176] In addition, the hard coat layer may further contain additives such as surfactants, UV absorbers, UV stabilizers, anti-yellowing agents, leveling agents, or dyes for improving color value. For example, the surfactant may be a mono- or di-functional fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant. The surfactant may be dispersed or crosslinked within the hard coat layer. Examples of the UV absorber include benzophenone-based compounds, benzotriazole-based compounds, and triazine-based compounds, and examples of the UV stabilizer include tetramethylpiperidine. The content of these additives may be adjusted in various ways as long as they do not deteriorate the physical properties of the hard coat layer. For example, the content of the additives may be 0.01 wt % to 10 wt % based on the total weight of the hard coat layer, but is not limited thereto.

[0177] The hard coat layer may be composed of a single layer or two or more layers. For example, the hard coat layer may be formed as a single layer, which increases the durability of the laminated film and simultaneously serves to prevent fingerprints or stains.

[0178] The thickness of the hard coat layer may be 2 μm or more, 3 μm or more, 5 μm or more, or 10 μm or more, and may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. For example, the thickness of the hard coat layer may be 2 μm to 20 μm. Specifically, the thickness of the hard coat layer may be 5 μm to 20 μm. If the hard coat layer is too thin, it will not have sufficient surface hardness to protect the substrate film, resulting in reduced durability of the laminate film. If the hard coat layer is too thick, it will reduce flexibility of the laminate film and increase the overall thickness of the laminate film, which may be disadvantageous for thinning.

[0179] Therefore, the hard coat layer may be formed from a hard coat composition including at least one of an organic composition, an inorganic composition, and an organic-inorganic hybrid composition. For example, the hard coat composition may include at least one of an acrylate compound, a siloxane compound, or a silsesquioxane compound. The hard coat layer may further include inorganic particles. As a specific example, the hard coat layer may be formed from a hard coat composition including a urethane acrylate compound, an acrylic ester compound, and a fluorine-based compound.

[0180] The hard coat layer can be formed by applying a hard coat composition onto a substrate film, and then drying and curing the composition.

[0181] The hard coat composition may include the organic resin, photoinitiator, antifouling additive, antistatic agent, other additives and / or solvents described above.

[0182] Examples of the organic solvent include alcohol solvents such as methanol, ethanol, isopropyl alcohol, and butanol; alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; ether 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, diethyl glycol monoethyl ether, diethyl glycol monopropyl ether, diethyl glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene. These solvents may be used alone or in combination.

[0183] The content of the organic solvent is not particularly limited as it can be adjusted in various ways within a range that does not deteriorate the physical properties of the coating composition, but it may be included so that the weight ratio of solids to solvent relative to the solids of the components contained in the hard coat composition is about 30:70 to about 99:1. When the solvent is in this range, the composition can have appropriate fluidity and coatability.

[0184] The hard coat 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 additive, and 0.1 to 10% by weight of an antistatic agent. This composition may improve the mechanical properties, antifouling properties, and antistatic properties of the hard coat layer.

[0185] The hard coat composition can be applied onto a substrate film by bar coating, knife coating, roll coating, blade coating, die coating, microgravure coating, comma coating, slot die coating, lip coating, solution casting, or the like.

[0186] Thereafter, the organic solvent contained in the hard coat composition can be removed by a drying step, which 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.

[0187] The hardcoat composition may then be cured by light and / or heat.

[0188] [Elastic layer 300] The elastic layer 300 includes polyether-block-amide (PEBA).

[0189] The polyether-block-amide comprises two phases: a polyamide region, which is a rigid segment, and a polyether region, which is a soft segment.

[0190] The rigid region may be a crystalline region or a semi-crystalline region, and the soft region may be an amorphous region, for example, the amorphous region may be a matrix, and the crystalline region may be distributed in the matrix.

[0191] In this way, the polyether-block-amide may simultaneously contain stiff and soft domains, allowing the elastic layer to have relatively high mechanical strength, as well as flexible and / or elastomeric properties.

[0192] The polyamide domains have a melting point of about 80°C or higher, specifically about 130°C to 180°C, and can constitute hard domains with a substantially crystalline phase. The polyether domains have a glass transition temperature of about -40°C or lower, specifically about -80°C to -40°C, and can constitute soft domains in a low temperature range, which are substantially amorphous.

[0193] The polyether-block-amide may be a polyamide containing two or more carboxyl groups in the molecule bonded to an ether containing two or more hydroxyl groups in the molecule.

[0194] The elastic layer comprises a polyether-block-amide, which may comprise one or more copolymers comprising polyether blocks and polyamide blocks, such that the polyether-block-amide comprises one or more polyether blocks and one or more polyamide blocks.

[0195] A copolymer containing a polyether block and a polyamide block (polyether-block-amide) can be a condensation polymerization product of a polyether block containing a reactive end and a polyamide block containing a reactive end.

[0196] As an example, the polyether-block-amide may be a condensation polymer comprising a polyamide block containing diamine termini and a polyoxyalkylene block containing dicarboxyl termini.

[0197] As another example, the polyether-block-amide can be a condensation polymer comprising a polyamide block containing dicarboxyl termini and a polyoxyalkylene block containing diamine termini.

[0198] The polyoxyalkylene block may be obtained by cyanoethylation and hydrogenation of an aliphatic α,ω-dihydroxylated polyoxyalkylene block, known as a polyether diol.

[0199] The polyether-block-amide may be a condensation polymer comprising a polyamide block containing a dicarboxyl end group and a polyether diol block, in which case the polyether-block-amide is a polyetheresteramide.

[0200] Illustratively, polyamide blocks containing dicarboxylic chain ends may comprise condensation polymers of polyamide precursors in the presence of chain-limiting dicarboxylic acids.

[0201] Illustratively, polyamide blocks containing diamine chain ends may comprise condensation polymers of polyamide precursors in the presence of chain-limiting diamines.

[0202] Illustratively, polyamide blocks containing dicarboxylic chain ends may comprise condensation polymers of α,ω-aminocarboxylic acids, lactams or dicarboxylic acids and diamines in the presence of a chain-limiting dicarboxylic acid.

[0203] The polyamide block is preferably polyamide 12 or polyamide 6.

[0204] The polyether-block-polyamide may comprise blocks having randomly distributed unit structures.

[0205] Preferably, the following three types of polyamide blocks can be applied: As a first type, the polyamide block may comprise a condensation polymer of a carboxylic acid and an aliphatic or arylaliphatic diamine. The carboxylic acid may have 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms. The aliphatic or arylaliphatic diamine may have 2 to 20 carbon atoms, preferably 6 to 14 carbon atoms.

[0206] The carboxylic acid, specifically the dicarboxylic acid, may be, for example, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexyldicarboxylic acid, 1,4-butanedioic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, dimerized fatty acid, or the like.

[0207] Examples of the diamine include 1,5-tetramethylenediamine, 1,6-hexamethylenediamine, 1,10-decamethylenediamine, 1,12-dodecamethylenediamine, trimethyl-1,6-hexamethylenediamine, 2-methyl-1,5-pentamethylenediamine, and the isomers of bis(3-methyl-4-aminocyclohexyl)methane. bis(3-methyl-4-aminocyclohexyl)methan (BMACM), 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), bis(para-aminocyclohexyl)methane (PACM), isophoronediamine (IPD), 2,6-bis(aminomethyl)norbornane (BAMN), piperazine (Pip), meta-xylylenediamine (MXD), para-xylylenediamine (PXD), and the like.

[0208] Specifically, the first type of polyamide block may include PA 412, PA 414, PA 418, PA 610, PA 612, PA 614, PA 618, PA 912, PA 1010, PA 1012, PA 1014, PA 1018, MXD6, PXD6, MXD10, or PXD10.

[0209] As a second type, the polyamide block may comprise a condensation polymer of one or more α,ω-aminocarboxylic acids and / or one or more lactams having 6 to 12 carbon atoms in the presence of a dicarboxylic acid or diamine having 4 to 12 carbon atoms. Examples of the lactam include caprolactam, oenantholactam, and lauryllactam. Examples of the α,ω-aminocarboxylic acid include aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acids. Specifically, the second type of polyamide block may comprise polyamide 11, polyamide 12, or polyamide 6.

[0210] As a third type, the polyamide block may comprise a condensation polymer of one or more α,ω-aminocarboxylic acids (or one or more lactams), one or more diamines, and one or more dicarboxylic acids. In such a case, the polyamide (PA) block may be prepared by condensation polymerization of a diamine, a diacid, and a comonomer (or comonomers) such as those described below.

[0211] The diamine may be, for example, a linear aliphatic diamine or an aromatic diamine. The diacid may be, for example, an alicyclic diacid, an aliphatic diacid, or an aromatic diacid. The diacid may be, for example, a dicarboxylic acid. The comonomer may be selected from lactams, α,ω-aminocarboxylic acids, and mixtures of one or more diamines and one or more dicarboxylic acids in substantially equal molar amounts. The comonomer may be contained in an amount of 50% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less, based on the total amount of the combined polyamide precursor monomers.

[0212] The third type of condensation reaction may be carried out in the presence of a chain limiting agent selected from dicarboxylic acids. Specifically, a dicarboxylic acid may be used as the chain limiting agent, and the dicarboxylic acid may be introduced in a stoichiometric excess amount relative to the one or more diamines.

[0213] As an alternative to the third type, the polyamide block may comprise a condensation polymer of two or more α,ω-aminocarboxylic acids having 6 to 12 carbon atoms, or two or more lactams, or a lactam and an aminocarboxylic acid having different carbon atoms, optionally in the presence of a chain-limiting agent. The aliphatic α,ω-aminocarboxylic acid may be, for example, aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, etc. The lactam may be, for example, caprolactam, oenantholactam, lauryllactam, etc.

[0214] The aliphatic diamine may be, for example, hexamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, or the like.

[0215] The alicyclic diacid may be, for example, 1,4-cyclohexanedicarboxylic acid, and the aliphatic diacid may be, for example, butanedioic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, dodecanedicarboxylic acid, dimer fatty acid (preferably having a dimer ratio of 98% or more; preferably hydrogenated; sold under the trade name Pripol by Uniqema or the trade name Empol by Henkel), polyoxyalkylene-α,ω-diacid, etc.

[0216] The aromatic diacid may be, for example, terephthalic acid, isophthalic acid, or the like. The alicyclic diamine may be, for example, an isomer of bis(3-methyl-4-aminocyclohexyl)methane (BMACM) and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), bis(para-aminocyclohexyl)methane (PACM), or the like.

[0217] Other diamines include, for example, isophoronediamine (IPDI), 2,6-bis(aminomethyl)norbornene (BAMN), and piperazine.

[0218] Examples of arylaliphatic diamines include, but are not limited to, meta-xylylenediamine (MXD) and para-xylylenediamine (PXD).

[0219] Examples of the third type of polyamide block include PA66 / 6, PA66 / 610 / 11 / 12, etc.

[0220] In the PA66 / 6, the 66 represents a hexamethylenediamine unit condensed with adipic acid, and the 6 represents a unit introduced by condensation with caprolactam.

[0221] In the PA66 / 610 / 11 / 12, the 66 represents a hexamethylenediamine unit condensed with adipic acid, the 610 represents a hexamethylenediamine unit condensed with sebacic acid, the 11 represents a unit introduced by condensation of aminoundecanoic acid, and the 12 represents a unit introduced by condensation of lauryllactam.

[0222] The number average molecular weight of the polyamide block is 400 to 20,000, and specifically may be 500 to 10,000.

[0223] The polyether block may be, for example, one or more polyalkylene ether polyols, such as polyalkylene ether diols, specifically selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (PO3G), polytetramethylene glycol (PTMG), and mixtures or copolymers thereof.

[0224] The polyether block contains a polyoxyalkylene unit containing an NH chain terminal, and the unit can be introduced by cyanoacetylating an aliphatic α,ω-dihydroxypolyoxyalkylene unit known as a polyether diol. Specifically, Jeffamine (e.g., Jeffamine® D400, D2000, ED2003, or XTJ542, which are products of HUNTSMAN) can be used.

[0225] The one or more polyether blocks include one or more polyethers selected from polyalkylene ether polyols such as PEG, PPG, PO3G, and PTMG, polyethers containing NH2 at the chain end and containing polyoxyalkylene sequences, copolymers thereof in random and / or block arrangements (ether copolymers), and mixtures thereof.

[0226] The polyether block may be contained in an amount of 10 to 80% by weight, specifically 20 to 60% by weight, or 20 to 40% by weight, based on the total weight of the copolymer. The number average molecular weight of the polyether block may be 200 to 1,000, specifically 400 to 800, or 500 to 700.

[0227] The polyether blocks may be derived from polyethylene glycol, polypropylene glycol, or polytetramethylene glycol.

[0228] The polyether blocks may be copolymerized with polyamide blocks containing carboxyl termini to form polyether-block-amides.

[0229] The polyether blocks can be converted to polyetherdiamines via amination and then condensed with carboxyl-terminated polyamide blocks to form polyether-block-amides.

[0230] The polyether blocks may be mixed with polyamide precursors and chain limiters to form polyether-block-amides containing statistically dispersed units.

[0231] The polyether may be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene glycol (PTMG), etc. Polytetramethylene glycol is also known as polytetrahydrofuran (PTHF). The polyether block is introduced into the polyether-block-amide chain from the form of a diol or diamine, and the polyether block is called a PEG block, a PPG block, or a PTMG block, respectively.

[0232] It should also be understood that the polyether block may include units other than those derived from ethylene glycol (-OC2H4-), propylene glycol (-O-CH2-CH(CH3)-), or tetramethylene glycol (-O-(CH2)4-), and still be within the scope of the embodiment.

[0233] The number average molecular weight of the polyamide block may be, for example, 300 to 15,000, or 600 to 5,000. The number average molecular weight of the polyether block may be 100 to 6,000, preferably 200 to 3,000.

[0234] Specifically, the content of the polyamide blocks in the polyether-block-amide may be 50% by weight or more based on the total weight of the polyether-block-amide. This may mean that the polyamide blocks are statistically distributed within the polymer chain. Specifically, the content of the polyamide blocks may be 50% by weight to 80% by weight. In addition, the content of the polyether blocks in the polyether-block-amide may be 20% by weight to 50% by weight based on the total weight of the polyether-block-amide.

[0235] The ratio of the number average molecular weight of the polyamide block to the number average molecular weight of the polyether block of the copolymer may be, for example, 1:0.25 to 1:1. Specifically, the ratio of the number average molecular weight of the polyamide block to the number average molecular weight of the polyether block of the copolymer may be 1000 / 1000, 1300 / 650, 2000 / 1000, 2600 / 650, or 4000 / 1000.

[0236] The polyether-block-amides can be prepared in a two-step process, comprising a first step of preparing polyamide blocks and polyether blocks and a second step of condensation polymerizing the polyamide blocks and the polyether blocks to prepare an elastomeric polyether-block-amide, or they can be prepared in a single step by condensation polymerizing the monomers.

[0237] The polyether-block-amide may exhibit a Shore D hardness of, for example, 20-75, specifically 30-70.

[0238] The polyether-block-amide may have an intrinsic viscosity of 0.8 dL / g to 2.5 dL / g as measured in meta-cresol at 25°C. The intrinsic viscosity may be measured in accordance with ISO 307:2019. Specifically, the intrinsic viscosity in a solution may be measured in a meta-cresol solution having a concentration of 0.5 wt% at 25°C using an Ubbelohde viscometer.

[0239] Examples of the polyether-block-amide include, but are not limited to, Pebax® and Pebax® Rnew® from Arkema, and VESTAMID® E from Evonik.

[0240] The optical properties of the elastic layer can be adjusted within a certain range, which makes it advantageous for application to the cover window of a display device.

[0241] The haze of the elastic layer may be, for example, 3% or less, specifically 2% or less, 1.5% or less, or 1.2% or less, and may be 0.01% or more, or 0.1% or more.

[0242] The average visible light transmittance of the elastic layer may be, for example, 85% or more, specifically 88% or more, or 90% or more, or 99.99% or less.

[0243] The thickness of the elastic layer may 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 may be 20 μm to 500 μm, more specifically 50 μm to 200 μm.

[0244] [Display device] A display device according to one implementation includes the aforementioned laminated film in a cover. Specifically, the laminated film may form a cover window in the display device.

[0245] Referring to Figures 1 and 2, a display device 1 according to one embodiment includes a display panel 20 and a cover window 10 disposed on the front surface of the display panel 20, the cover window 10 including a base film 100, a hard coat layer 200 disposed on one surface of the base film 100, and an elastic layer 300 disposed on the other surface of the base film 100, the elastic layer 300 including a polyether-block-amide.

[0246] For example, the base film may include a polyimide-based resin, or a polyester-based resin.

[0247] The laminated film included in the display device has substantially the same configuration and properties as the laminated film described above.

[0248] The display device may be flexible. For example, the display device may be a flexible display device, specifically a foldable display device. More specifically, the foldable display device may be an in-folding type or an out-folding type depending on a folding direction.

[0249] 5a and 5b show in-folding and out-folding flexible display devices, respectively. Referring to Fig. 5a, the display device may be an in-folding flexible display device 1a in which the screen is located on the inside in the folding direction. Alternatively, referring to Fig. 5b, the display device may be an out-folding flexible display device 1b in which the screen is located on the outside in the folding direction.

[0250] Referring to FIG. 1, the display device 1 includes a cover window 10, a display panel 20, a substrate 30, and a frame 40 for protecting them, and the cover window 10 includes the aforementioned laminated film.

[0251] For example, the display panel 20 may be a liquid crystal display (LCD) panel. For another example, 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 surface of the organic light-emitting display panel. More specifically, the front polarizer may be attached to the surface of the organic light-emitting display panel where an image is displayed. The organic light-emitting display panel displays images by self-emitting light in pixels. 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, each corresponding to a pixel. Each of the organic light-emitting units includes a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and an anode. The driving substrate is drivingly coupled to the organic light-emitting substrate. That is, the driving substrate may be coupled to apply a driving signal, such as a driving current, to the organic light-emitting substrate. More specifically, the driving substrate may apply a current to each of the organic light-emitting units to drive the organic light-emitting substrate.

[0252] Also, an adhesive layer may be formed between the cover window 10 and the display panel 20. For example, the adhesive layer may include an optically transparent adhesive.

[0253] (Example) The examples described below are merely for ease of understanding and are not intended to limit the scope of possible implementations.

[0254] A. Laminated film containing polyimide film Various laminated films containing polyimide-based films were produced and evaluated.

[0255] (Example A1) Step 1) Formation of hard coat layer A hard coat composition having the composition shown in Table 1 below was coated onto one side of a 50 μm thick transparent polyimide film (TPI, manufactured by SKC) by die coating. The coating was then heat treated at 60°C for 3 minutes to dry the solvent, and then irradiated with 1 J of UV light to cure the coating, forming a hard coat layer with a thickness of approximately 5 μm.

[0256] [Table 1]

[0257] Step 2) Laminating the elastic layer A polyether-block-amide resin (Arkema Pebax Rnew 72R53, Arkema) was placed in an extruder, melt-kneaded at approximately 220°C, and then extruded as a single layer. This was then laminated with the substrate film having the hard coat layer formed thereon to produce a laminated film in which a 50 μm-thick PEBA layer was formed on the substrate film having the hard coat layer formed thereon.

[0258] (Example A2) A laminated film was produced in the same manner as in Example A1, except that in step 2 of Example A1, a polyether-block-amide resin (Arkema Pebax Rnew 55R53, ARKEMA) was used to produce the PEBA film.

[0259] (Comparative Example A1) A polyether-block-amide resin (Arkema Pebax Rnew 72R53, ARKEMA) was placed in an extruder, melt-kneaded at approximately 220°C, and then extruded as a single layer. This was then laminated with a 50 μm-thick transparent polyimide film (TPI, SKC) to obtain a laminated film with a 50 μm-thick PEBA layer formed on the base film.

[0260] (Comparative example A2) A laminated film was produced in the same manner as in Comparative Example A1, except that a polyether-block-amide resin (Arkema Pebax Rnew 55R53, Arkema) was used to produce the PEBA film.

[0261] (Comparative example A3) A film having a hard coat layer was manufactured by repeating the same procedure as in step 1) of Example A1, except that a transparent polyimide film (TPI, SKC) having a thickness of 100 μm was used.

[0262] The layer structure of the film produced as above is summarized in Table 2 below.

[0263] [Table 2]

[0264] (Test example A1: Nanoindentation test) Nanoindentation tests were performed on film samples produced in the examples and comparative examples. The film samples were cut to A4 size and stored at 25±5°C and 50±5% RH without any additional pretreatment before testing. The film samples were then evaluated using a nanoindentation surface analyzer (Fischerscope HM2000, Fischer). Specifically, the laminated film sample was positioned on a glass test plate (Fischerscope Part no. 600-028) with a thickness of approximately 3T as a sample holder, with the surface of the hard coat layer (or the surface of the substrate film if no hard coat layer was present) facing upward (i.e., as the indentation surface). Nanoindentation tests were then performed using a diamond tip at room temperature, pressing downward with a force of 30 mN for 15 seconds, maintaining this pressure for 5 seconds, and then raising the sample upward again. Vickers hardness (HV), indentation hardness (HV), and surface hardness (HV) were measured. IT ), recovery rate (Recovery), and maximum indentation depth (h) at maximum force (30 mN) max(@30mN)The nanoindentation test was performed based on ISO 14577-1:2002(E) and 14577-2:2002(E). The recovery rate was calculated using the following formula:

[0265] Recovery(%)=[(h max(@30mN) -h p ) / h max(@30mN) ] x 100 (where h max(@30mN) is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure for 5 seconds, and h p is the indentation depth (μm) that remains unrecovered after the force is removed) The results are shown in Table 3 below.

[0266] [Table 3]

[0267] As shown in Table 3 above, the films of the examples were excellent in both surface hardness and recovery, whereas the films of the comparative examples were relatively poor in at least one of these properties.

[0268] (Test Example A2: Optical Properties and Color) The optical properties and hue of the film samples were measured. The average visible light transmittance of the film samples was measured according to ISO 13468 using a haze meter (NDH-5000W, Nippon Denshoku Industries Co., Ltd.), and the haze was measured according to ISO 14782. The yellowness index (YI) of the film samples was measured according to ASTM-E313 using a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) with a D65 illuminant at 10°. The transmitted color of the film samples was also measured using a spectrophotometer (CM3700A, Minolta Corporation) with a D65 illuminant. The results are shown in Table 4 below.

[0269] [Table 4]

[0270] As shown in Table 4 above, the films of the examples were excellent in all of transmittance, haze, and transmitted color, whereas the films of the comparative examples were relatively poor in at least one of these properties.

[0271] B. Laminated film containing polyester film A variety of laminated films, including polyester-based films, were produced and evaluated.

[0272] Example B1 Step 1) Formation of hard coat layer A hard coat composition having the composition shown in Table 5 below was coated onto one side of a 50 μm thick transparent polyester film (NRF, SKC) by die coating. The coating was then heat treated at 60°C for 3 minutes to dry the solvent, and then irradiated with 1 J of UV light to harden the film, forming a hard coat layer with a thickness of approximately 5 μm.

[0273] [Table 5]

[0274] Step 2) Lamination of the elastic layer A polyether-block-amide resin (Arkema Pebax Rnew 72R53, Arkema) was placed in an extruder and melt-kneaded at approximately 220°C. The resin was then extruded as a single layer and laminated with the previously prepared substrate film having a hard coat layer to produce a laminated film in which a 50 μm-thick PEBA layer was formed on the substrate film having a hard coat layer.

[0275] (Example B2) A laminated film was produced in the same manner as in Example B1, except that in step 2 of Example B1, a polyether-block-amide resin (Arkema Pebax Rnew 55R53, Arkema) was used to produce the PEBA film.

[0276] (Comparative Example B1) A polyether-block-amide resin (Arkema Pebax Rnew 72R53, Arkema) was placed in an extruder and melt-mixed at approximately 220°C. The resulting extruded layer was then laminated with a 50 μm-thick transparent polyester film (NRF, SKC) to produce a laminated film with a 50 μm-thick PEBA layer formed on the base film.

[0277] (Comparative example B2) A laminated film was produced in the same manner as in Comparative Example B1, except that a polyether-block-amide resin (Arkema Pebax Rnew 55R53, Arkema) was used to produce the PEBA film. The layer structure of the film produced as above is summarized in Table 6 below.

[0278] [Table 6]

[0279] (Test example B1: Nanoindentation test) Nanoindentation tests were performed on film samples produced in the examples and comparative examples. The film samples were cut into A4 size pieces and stored at 25±5°C and 50±5% RH without any additional pretreatment before testing. The film samples were then evaluated using a nanoindentation surface analyzer (Fischerscope HM2000, Fischer). Specifically, the laminated film sample was positioned on a glass test plate (Fischerscope Part no. 600-028) with a thickness of approximately 3T as a sample holder, with the surface of the hard coat layer (or the surface of the substrate film if no hard coat layer was present) facing upward (i.e., as the indentation surface). Then, a diamond tip was used at room temperature to perform a nanoindentation test, pressing downward with a force of 30 mN for 15 seconds, maintaining this pressure for 5 seconds, and then raising the sample upward again. The Martens hardness (HM), indentation modulus (E IT ), elastic modulus (η IT ), indentation creep (C IT ), maximum strain at 30 mN force (h max(@30mN) The nanoindentation test was performed based on ISO 14577-1:2002(E) and 14577-2:2002(E). The recovery was calculated using the following formula:

[0280] Recovery(%)=[(h max(@30mN) -h p ) / h max(@30mN) ] x 100 (where h max(@30mN) is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure for 5 seconds, and h p is the indentation depth (μm) that remains unrecovered after the force is removed. The results are shown in Table 7 below.

[0281] (Test Example B2: Optical Properties) The average visible light transmittance of the film sample was measured using a haze meter (NDH-5000W, Nippon Denshoku Industries Co., Ltd.) in accordance with the ISO 13468 standard, and the results are shown in Table 7 below.

[0282] [Table 7]

[0283] As shown in Table 7, the films of the examples had the indentation test results (HM, E IT , η IT , C IT Specifically, the film of the example was excellent in both modulus of elasticity (η IT ) and has excellent resistance to permanent deformation during press-fitting (E IT ) is good, which reduces creep deformation (C IT Even when the film thickness is large, it has excellent recovery rate and little permanent deformation after folding. Furthermore, the films of the examples have excellent transmittance and can be used as cover windows for mobile phones. In contrast, the films of the comparative examples showed relatively poor results in at least one of the test items. [Explanation of symbols]

[0284] 1: Display device 1a: In-folding type flexible display device 1b: Outfolding type flexible display device 2: Indenter 2a: Indenter tip 2b: Dent left after release of press fit 10: Laminated film (cover window) 10a: Sample 20: Display panel 30: Circuit board 40: Frame 100: Base film 200: Hard coat layer 300: Elastic layer A p :Contact projected area F: Test force F max : Maximum test force h max : Maximum indentation depth at maximum test force h p : Indentation depth after removing the test force

Claims

1. A laminated film, A base film; a hard coat layer disposed on one surface of the substrate film; an elastic layer disposed on the other surface of the base film, the elastic layer comprises a polyether-block-amide; The laminated film is applied to a cover window of a foldable display device, The laminated film has a recovery rate (Recovery) of the hard coat layer surface measured by a nanoindentation test based on ISO 14577-1:2002(E) standard of 73.35% or more, and the recovery rate is calculated by the following formula: The other surface of the base film is a surface of the base film that faces a display panel included in a display device. Recovery (%) = [(h max (@30 mN) - h p ) / h max (@30 mN) ] × 100 (wherein h max (@30 mN) is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure (creep) for 5 seconds; h p is the indentation depth (μm) that remains unrecovered after the force is removed.

2. Regarding the laminated film, The Vickers hardness (HV) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard is 48 N / mm ２ or more, and the indentation hardness (H ＩＴ ) is 505N / mm ２ The laminated film according to claim 1 .

3. Regarding the laminated film, The laminate film according to claim 1, wherein the recovery rate of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) is 76% or more, and the recovery rate is calculated by the following formula: Recovery(%)=[(h ｍａｘ（＠３０ｍＮ） -h ｐ ) / h ｍａｘ（＠３０ｍＮ） ]×100 where: h ｍａｘ（＠３０ｍＮ） is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure (creep) for 5 seconds; h ｐ is the indentation depth (μm) that remains unrecovered after the force is removed.

4. Regarding the laminated film, The average transmittance of visible light measured based on the ISO 13468 standard is 80% or more, The haze measured according to the ISO 14782 standard is 4% or less, The laminated film according to claim 1, wherein the increase in transmittance calculated by the following formula is 2% or more: Transmittance increase (%) = TT1 (%) - TT2 (%) where: TT1 is the average visible light transmittance (%) of the laminated film, TT2 is the average visible light transmittance (%) of a film having a layer structure obtained by excluding only the hard coat layer from the laminate film, The average visible light transmittance is measured under the same conditions based on the ISO 13468 standard.

5. Regarding the laminated film, The yellowness index (YI) measured according to the ASTM-E313 standard at 10° using a D65 light source is 1.5 or less, The laminated film according to claim 1, wherein the yellowness reduction calculated by the following formula is 0.5 or more: Reduction in yellowness = YI2 - YI1 where: YI1 is the yellowness index of the laminated film, YI2 is the yellowness index of a film having a layer structure obtained by excluding only the hard coat layer from the laminate film, The yellowness index is measured under the same conditions as those in ASTM-E313 standard at 10° using a D65 light source.

6. Regarding the laminated film, 2. The laminate film according to claim 1, wherein the L* value is 92 or more, the a* value is -2 to 1, and the b* value is -1 to 2 in the CIE Lab color coordinates of transmitted color measured using a D65 light source.

7. The laminate film of claim 1 , wherein the substrate film comprises a polymer film or ultra-thin glass (UTG).

8. The laminate film according to claim 1 , wherein the substrate film comprises a polyester-based resin.

9. Regarding the laminated film, The Martens hardness (HM) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard is 175 N / mm ２ The laminated film according to claim 8, wherein the above-mentioned

10. Regarding the laminated film, The indentation modulus (E) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard ＩＴ 9. The laminated film according to claim 8, wherein the modulus of elastic modulus is 2900 MPa or more.

11. Regarding the laminated film, The elastic modulus (η) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard ＩＴ 9. The laminated film according to claim 8, wherein the modulus of elasticity is 63.6% or more.

12. Regarding the laminated film, The indentation creep (C) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard. ＩＴ 9. The laminated film according to claim 8, wherein the tensile strength is 3.5% or more.

13. Regarding the laminated film, The average transmittance of visible light measured based on the ISO 13468 standard is 85% or more, The laminated film according to claim 8, wherein the increase in transmittance calculated by the following formula is 3% or more: Transmittance increase (%) = TT1 (%) - TT2 (%) where: TT1 is the average visible light transmittance (%) of the laminated film, TT2 is the average visible light transmittance (%) of a film having a layer structure obtained by excluding only the hard coat layer from the laminate film, The average visible light transmittance is measured under the same conditions based on the ISO 13468 standard.

14. 9. The laminate film according to claim 1, wherein the hard coat layer comprises at least one compound selected from the group consisting of a urethane acrylate compound, an acrylic ester compound, an acrylate compound, and an epoxy acrylate compound.

15. The laminate film according to claim 14 , wherein the hard coat layer further contains a fluorine-based compound.

16. A display panel; a cover window disposed on a front surface of the display panel; The cover window is A base film; a hard coat layer disposed on one surface of the substrate film; an elastic layer disposed on the other surface of the base film, the elastic layer comprises a polyether-block-amide; Regarding the cover window, a recovery rate (Recovery) of the surface of the hard coat layer measured by a nanoindentation test based on ISO 14577-1:2002(E) standard is 73.35% or more, and the recovery rate is calculated by the following formula: The other surface of the base film is a surface of the base film facing a display panel included in the display device. Recovery (%) = [(h max (@30 mN) - h p ) / h max (@30 mN) ] × 100 (wherein h max (@30 mN) is the maximum indentation depth (μm) while pressing the surface of the hard coat layer downward with a force of 30 mN for 15 seconds and maintaining the pressure (creep) for 5 seconds; h p is the indentation depth (μm) that remains unrecovered after the force is removed.

17. The display device according to claim 16 , wherein the substrate film comprises a polyester-based resin.

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