Thin films, transparent laminates, cover films, and multilayer electronic devices

Abstract

Examples relate to thin films, transparent laminates, applications as cover films, and multilayer electronic devices incorporating the thin film, which possess excellent optical properties such as refractive index, haze, and yellowness, as well as excellent mechanical properties. The thin film includes an elastic layer with a refractive index of 1.48 to 1.58 and a low-temperature damage index (the difference between tensile modulus and tensile strength at a specific temperature), wherein the low-temperature damage index of the elastic layer at -40°C is below 1300 MPa.

Description

Technical Field

[0001] Examples include thin films, transparent laminates, applications as cover films, and multilayer electronic devices that incorporate them, all possessing excellent optical properties such as refractive index, haze, and yellowness, as well as excellent mechanical properties. Background Technology

[0002] Display devices are diversifying in form and their required functions are constantly evolving, with an ongoing evolution towards thinner and wider screens. The form factor of displays is also shifting from traditional flat panels to curved surfaces, and then gradually to foldable, bendable, and flexible forms. In other words, recent displays can change shape in ways such as folding or bending, offering different form variations compared to existing designs that primarily focus on larger screen sizes.

[0003] Polyethylene terephthalate (PET) films, with their excellent mechanical properties, chemical resistance, and moisture resistance, are widely used as protective films for displays. Examples include polyester fiber protective films (Korean License No. 10-1730854) with improved optical properties suitable for polarizing plates, and protective films (Korean License No. 10-1746170) suitable for touch panels. However, due to its high modulus, PET films may not meet the properties required for curved surfaces or bends, which may be one reason why the film may float in multi-layered display devices.

[0004] Furthermore, compared to the hard glass previously used to protect the display modules of display devices installed on portable electronic devices, PET film has weaker impact resistance (the function of protecting internal devices such as display modules from external impacts), thus limiting its ability to provide sufficient protection.

[0005] The background information described above is technical information that the inventor possessed or acquired in the process of deriving examples of the present invention, and cannot be said to necessarily be known technology that was disclosed to the general public before this application. Summary of the Invention

[0006] The problem the invention aims to solve

[0007] The purpose of these examples is to provide thin films, laminates, transparent laminates, cover films, etc., with excellent optical properties such as appropriate refractive index, low haze, high transmittance, and low phase difference.

[0008] Another example aims to provide a light-transmitting laminate or cover film that, because it includes the thin film, has excellent optical properties and excellent mechanical properties due to its relatively constant elastic properties over a wide temperature range, thus being advantageous for use as a cover window for multilayer electronic devices, etc.

[0009] Another example aims to provide the film for use as a cover window in foldable displays, bendable displays, flexible displays, etc.

[0010] Another example aims to provide a multilayer electronic device including the aforementioned cover film, which has excellent optical properties, such as appropriate refractive index, low haze, high transmittance, low phase difference, etc., and does not experience interlayer separation when repeatedly bent or rolled, and is resistant to external impacts.

[0011] Another example aims to provide the use of the aforementioned thin film as a cover film in multilayer electronic devices.

[0012] means for solving problems

[0013] To achieve the aforementioned objective, one example discloses a thin film comprising an elastic layer, wherein the elastic layer has a low-temperature damage index of less than 1300 MPa at -40°C.

[0014] At a specific temperature, the low-temperature damage index is the difference between the tensile modulus and the tensile strength.

[0015] The tensile strength of the elastic layer at -40℃ can be below 150MPa.

[0016] The tensile modulus of the elastic layer at -40℃ can be below 2000MPa.

[0017] The tensile modulus of the elastic layer at -10℃ can be below 3000MPa.

[0018] The energy storage modulus of the elastic layer at -40°C can be below 2300 MPa.

[0019] The elastic layer can have an elongation of over 200% at -10°C.

[0020] The refractive index of the elastic layer can be from 1.48 to 1.58.

[0021] The phase difference Re of the elastic layer can be below 300 nm.

[0022] The haze of the elastic layer can be below 3%.

[0023] The light transmittance of the elastic layer can be above 85%.

[0024] The roughness reference value is the larger of the surface roughness Ra1 of one surface and the surface roughness Ra2 of the other surface.

[0025] The elastic layer may have a roughness reference value of less than 0.5 μm.

[0026] The elastic layer may contain amide residues.

[0027] The elastic layer may comprise a polymer resin containing amide residues.

[0028] The elastic layer may contain a polymer resin with more than 50% by weight of amide residues as repeating units.

[0029] The film may include the elastic layer and a hardening layer disposed on one surface of the elastic layer.

[0030] The refractive index of the elastic layer may be less than that of the hard layer.

[0031] The difference between the refractive index of the elastic layer and the refractive index of the hard layer can be less than 0.2.

[0032] An adhesive layer may be further provided on the other surface of the elastic layer or between one surface of the elastic layer and the hard layer.

[0033] The refractive index of the elastic layer may be less than that of the adhesive layer.

[0034] The difference in refractive index between the adhesive layer and the elastic layer can be less than 0.2.

[0035] The difference in refractive index between the adhesive layer and the hardening layer can be less than 0.2.

[0036] The hardening layer may include a polyimide film or a glass layer.

[0037] The total thickness of the film can be less than 3000 μm.

[0038] According to another example, the light-transmitting laminate includes the thin film as described above.

[0039] The light-transparent laminate may further include a glass layer disposed on one or the other surface of the elastic layer.

[0040] The glass layer can be tempered glass with a thickness of less than 200 μm.

[0041] According to yet another example, the covering film includes the thin film as described above.

[0042] Another example is the use of the film as a covering film, as described above.

[0043] Another example is the use of the light-transmitting laminate as a cover film, as described above.

[0044] The covering film may also include a glass layer disposed on one or the other surface of the elastic layer.

[0045] The glass layer can be tempered glass with a thickness of less than 200 μm.

[0046] According to yet another example, a multilayer electronic device includes a thin film as described above.

[0047] According to another example, a multilayer electronic device includes a light-emitting functional layer and a thin film, the light-emitting functional layer having a display area that emits light or does not emit light according to an external signal, the thin film being disposed on the upper surface or the back surface of the display area. The thin film described above is applicable to the thin film.

[0048] According to another example, a multilayer electronic device includes a light-emitting functional layer and a thin film. The light-emitting functional layer has a display area that emits light or does not emit light according to an external signal. The thin film is disposed on a surface of the light-emitting functional layer and covers at least a portion of the display area. The thin film described above is applicable to the thin film.

[0049] Invention Effects

[0050] Examples of thin films, transparent laminates, and their preparation methods can provide thin films with excellent optical properties such as appropriate refractive index, low haze, high transmittance, and low phase difference, while also having excellent mechanical properties such as practically low storage modulus change over a wide temperature range and excellent elastic recovery. Efficient preparation methods for thin films are also provided.

[0051] Examples of cover films, multilayer electronic devices, etc., include the thin film, and therefore have excellent optical properties such as appropriate refractive index, low haze, high transmittance, and low phase difference, while also having excellent bending and rolling properties over a wide temperature range, excellent elastic recovery, and excellent effect in suppressing damage caused by external impacts. Attached Figure Description

[0052] Figure 1 (a), (b), and (c) are conceptual diagrams describing the thin film according to the example in a cross-sectional manner.

[0053] Figure 2 (a), (b), and (c) are conceptual diagrams describing the thin film according to the example, using cross-sections.

[0054] Figure 3 This is a conceptual diagram illustrating a method for preparing thin films.

[0055] Figure 4 This is a conceptual diagram illustrating the configuration of a multilayer electronic device based on an example, presented in a cross-sectional manner.

[0056] Figure 5 (a), (b), and (c) are conceptual diagrams describing the configuration of a multilayer electronic device based on an example in a cross-sectional manner.

[0057] Figure 6 This is a conceptual diagram illustrating the configuration of a multilayer electronic device based on an example, presented in a cross-sectional manner. Detailed Implementation

[0058] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art can readily implement the present invention. However, the present invention can be implemented in various different forms and is not limited to the embodiments described herein. Throughout the specification, similar portions are referred to by the same reference numerals.

[0059] In this document, when a component “includes” another component, it means, unless otherwise stated, that other components may be included, rather than excluded.

[0060] In this article, when one component is "connected" to another component, this includes not only the case of "direct connection" but also the case of "connection through other components".

[0061] In this article, "B is located on A" means that B is located on A in direct contact with A, or in a state where other components are disposed in between, and is not to be interpreted as limited to B being located on the surface of A in direct contact with A.

[0062] In this document, the term "combination of them" included in the Markush form of expression refers to a mixture or combination of more than one of the groups of components described in the Markush form of expression, and means including more than one of the groups of the structural elements described.

[0063] In this document, the description of "A and / or B" means "A, B, or A and B".

[0064] In this document, unless otherwise stated, terms such as “first”, “second” or “A”, “B” are used to distinguish the same terms.

[0065] In this document, unless otherwise stated, singular expressions are to be interpreted as including the meaning of singular or plural as interpreted in the context.

[0066] In this document, unless otherwise stated, the refractive index is expressed as a result measured at a wavelength of 550 nm.

[0067] In this paper, unless otherwise stated, the in-plane phase difference Re or the thickness-direction phase difference Rth is described based on the results measured at a wavelength of 550 nm using a 100 μm thick thin film sample.

[0068] In this paper, the storage modulus is described based on measurement using the DMAQ800 model from TA Instruments, in accordance with ASTM D4065. The device measures the storage modulus E' in MPa at 1 Hz and 2 °C / min over a temperature range of -40 °C to 80 °C in Dynamic Mechanical Analysis (DMA) tension mode.

[0069] In this article, room temperature is based on approximately 20°C and ambient temperature on approximately 25°C.

[0070] In this paper, the in-plane phase difference Re is a parameter defined as the product of the anisotropy of the in-plane orthogonal biaxial refractive index of the thin film (ΔNxy = |Nx - Ny|) and the film thickness d (nm) (ΔNxy × d), and is a measure of optical isotropy or anisotropy.

[0071] In this paper, the thickness direction Retardation (Rth) is defined as the average of the phase differences obtained by multiplying the two birefringences ΔNxz (=|Nx-Nz|) and ΔNyz (=|Ny-Nz|) when viewed from a cross section in the thickness direction of the film by the film thickness d.

[0072] In this article, the hardness layer refers to a layer with a surface hardness of H or higher.

[0073] In this document, the letters and / or numbers listed with the name of a compound refer to the abbreviation of the compound name.

[0074] In this document, for ease of description, the relative dimensions, thicknesses, etc. of the components shown in the accompanying drawings may be magnified.

[0075] The following is a more detailed description of the example.

[0076] The inventors of this example have confirmed that by forming the elastic layer into a thin film shape, a thin film can be provided that exhibits excellent tensile properties at low temperatures while also possessing excellent optical properties such as high light transmittance, low haze, suitable refractive index, phase difference characteristics, and ultraviolet (UV) durability, and this is presented as an example. It has been confirmed that the thin film of this example possesses a relatively constant storage modulus over a wide temperature range, thus providing relatively constant elastic properties under various temperature environments, and enabling the provision of a thin film with excellent optical properties and excellent mechanical properties from low to high temperatures, and this is presented as an example.

[0077] Figure 1 (a), (b), and (c) are conceptual diagrams describing the thin film based on the example, using cross-sections. Figure 2 (a), (b), and (c) are conceptual diagrams describing the thin film based on the example, using cross-sections. Figure 3 This is a conceptual diagram illustrating a thin film preparation method. (Reference) Figures 1 to 3 This describes the elastic layer, the film itself, and the method for preparing the film.

[0078] To achieve the stated purpose, according to one example, the film 190 includes an elastic layer 100.

[0079] elastic layer

[0080] The elastic layer 100 has excellent mechanical properties, especially excellent physical properties at low temperatures.

[0081] The low-temperature damage index (unit: MPa) is the difference between the tensile modulus (MPa) and the tensile strength (MPa) measured at low temperatures (a specific temperature below 0°C).

[0082] The low-temperature damage index of elastic layer 100 at -40℃ can be below 1300MPa or below 1200MPa. The low-temperature damage index of elastic layer 100 at -40℃ can be above 300MPa. Elastic layers with these characteristics can maintain excellent mechanical properties even at relatively low temperatures and can substantially suppress the occurrence of film rupture.

[0083] The low-temperature damage index of elastic layer 100 at -10℃ can be below 1300MPa or below 1200MPa. The low-temperature damage index of elastic layer 100 at -40℃ can be above 200MPa. Elastic layers with these characteristics can maintain excellent mechanical properties even at low temperatures.

[0084] The tensile modulus of the elastic layer 100 at -40℃ can be below 2000MPa, below 1500MPa, below 1000MPa, or above 500MPa. The tensile modulus of the elastic layer 100 at -10℃ can be below 3000MPa, below 1400MPa, below 1200MPa, below 700MPa, below 500MPa, or above 350MPa.

[0085] When the tensile modulus of the elastic layer 100 is too high at low temperatures, it may easily crack when repeatedly bent at low temperatures or subjected to external impacts.

[0086] When the tensile modulus of the elastic layer 100 is as described above, the occurrence of cracking or damage caused by external impact can be significantly reduced when repeatedly bent at low temperatures.

[0087] The difference TM of the low-temperature tensile modulus of the elastic layer 100 as shown in Formula 2 below. -40-20 It can be below 1000 MPa. The difference in low-temperature tensile modulus TM -40-20 It refers to the difference between the tensile modulus value at -40℃ and the tensile modulus value at 20℃.

[0088] [Equation 2]

[0089] TM -40-20 =TM -40 -TM 20

[0090] In Equation 2, TM -40-20 For low-temperature tensile modulus, TM n This is the tensile modulus measured at n℃.

[0091] The elastic layer 100 may have a strength of less than 700 MPa, less than 500 MPa, or more than 1 MPa. -40-20 .

[0092] When the elastic layer 100 has TM-40-20 as described above, the elastic properties of the elastic layer can be substantially maintained in good condition in the range of low temperature to room temperature. In particular, when the elastic layer is laminated together with other layers, it can substantially suppress the occurrence of peeling, lifting and other phenomena even at low temperatures.

[0093] The elastic layer 100 has an elongation of over 200% at -40°C. The elastic layer 100 has an elongation of over 200% at -10°C. The elastic layer 100 has an elongation of over 200% at 20°C. The upper limit of the elongation of the elastic layer at each temperature has not been measured, but is considered to be below 400%.

[0094] When the elongation of the elastic layer 100 is as described above, it exhibits excellent ductility at room temperature, ambient temperature, and low temperatures. When the elastic layer is applied to flexible displays, it exhibits excellent repeated bending ability at both ambient and low temperatures without cracking.

[0095] The elastic layer 100 has a tensile strength of 10 MPa or more and 20 MPa or more at -40°C. The elastic layer 100 has a tensile strength of 200 MPa or less and 150 MPa or less at -40°C. The elastic layer 100 has a tensile strength of 5 MPa or more and 10 MPa or more at -10°C. The elastic layer 100 has a tensile strength of 400 MPa or less and 150 MPa or less at -10°C. The elastic layer 100 has a tensile strength of 5 MPa or more, 10 MPa or more, and 10 MPa or more at 20°C. The elastic layer 100 has a tensile strength of 300 MPa or less and 150 MPa or less at 20°C. This elastic layer 100 possesses these characteristics, exhibiting tensile strength exceeding a predetermined level over a wide temperature range, and suitable mechanical properties over a wide temperature range suitable for use as a cover film for displays.

[0096] The elastic layer 100 can have excellent optical properties.

[0097] The refractive index of the elastic layer 100 can be from 1.48 to 1.58, or from 1.50 to 1.55. The elastic layer may have a refractive index from 1.505 to 1.53. When using an elastic layer with this refractive index as a protective layer for a display device, it is beneficial to achieve a clearer display.

[0098] The haze of the elastic layer 100 can be less than 3% or less than 2%. The haze of the elastic layer 100 can be less than 1.5% or less than 1.2%. The haze of the elastic layer 100 can be more than 0.01% or more than 0.1%. When the elastic layer has the haze described above, it is suitable for application to the display area of ​​a display device.

[0099] The visible light transmittance of the elastic layer 100 can be 85% or more, 88% or more, or 90% or more. The visible light transmittance of the elastic layer can be 99.99% or less. The elastic layer 100, or the film 190 including it, having these properties, is suitable for use as a protective layer (or cover window) for electronic devices.

[0100] The in-plane phase difference Re of the elastic layer 100 can be below 300 nm, below 200 nm, or below 100 nm. The in-plane phase difference Re of the elastic layer can be below 50 nm or below 45 nm. The in-plane phase difference Re of the elastic layer can be above 1 nm. Elastic layers with this in-plane phase difference characteristic can simultaneously impart shock mitigation and polarization properties to the thin film without the need for a separate polarizing layer or when used in conjunction with a polarizing layer.

[0101] The thickness-direction phase difference Rth of the elastic layer 100 can be less than 3000 nm, less than 1500 nm, or less than 1000 nm. The thickness-direction phase difference Rth of the elastic layer can be less than 800 nm, less than 400 nm, or less than 300 nm. The thickness-direction phase difference Rth of the elastic layer can be greater than 1 nm. Elastic layers with this thickness-direction phase difference characteristic can simultaneously impart shock-reducing and polarizing properties to the thin film, either without the need for a separate polarizing layer or when used in conjunction with a polarizing layer.

[0102] The elastic layer 100 can essentially be a layer where no cloudiness was observed. In fact, the area of ​​the elastic layer where no cloudiness was observed may be less than 1% of the total area. In this case, the total area is based on the total film area applied to the product. The cloudiness can be objectively measured by haze measurement; a haze measurement value greater than 1% can be considered cloudiness. The degree of cloudiness can be adjusted by the degree of gelation, molecular weight distribution, etc., of the resin used to prepare the elastic layer.

[0103] The elastic layer 100 can have excellent energy storage modulus related properties.

[0104] The energy storage modulus index of the elastic layer 100 is 20 MPa to 350 MPa, as expressed by Equation 1 below.

[0105] [Formula 1]

[0106]

[0107] In Equation 1, K SM SM is the energy storage modulus index of the elastic layer. n The storage modulus (MPa) of the elastic layer is measured at a temperature of n °C.

[0108] For example, SM -40 The storage modulus (MPa) of the elastic layer was measured at -40°C. 20 SM represents the storage modulus (MPa) of the elastic layer measured at 20°C. 80 The storage modulus (MPa) of the elastic layer was measured at 80°C.

[0109] When the elastic layer has a storage modulus index as described above, it can have stable elastic properties over a relatively wide temperature range because it has a relatively stable degree of change in storage modulus over a relatively wide temperature range.

[0110] The energy storage modulus of the elastic layer 100 at room temperature or ambient temperature can be below 3 GPa. The energy storage modulus of the elastic layer at room temperature or ambient temperature can be below 2 GPa.

[0111] Compared to PET films, the elastic layer 100 has a lower storage modulus value at room temperature or ambient temperature. These properties allow the elastic layer, or the film comprising it, to have more stable bending characteristics and further mitigate the transmission of externally applied impacts to objects positioned on the other side.

[0112] The high-temperature energy storage modulus ratio R of the elastic layer 100 80 / 20 It can be above 0.08. The high-temperature energy storage modulus ratio R... 80 / 20 It is the ratio of the energy storage modulus at 80℃ to the energy storage modulus at 20℃, and is expressed by the following formula 1-a.

[0113] [Equation 1-a]

[0114]

[0115] In equation 1-a, R 80 / 20 For high-temperature energy storage modulus ratio, SM n The storage modulus (MPa) of the elastic layer is measured at a temperature of n °C.

[0116] The elastic layer 100 R 80 / 20 The value can be greater than 0.08, greater than 0.10, or greater than 0.15. The R of the elastic layer... 80 / 20 It can be 0.20 or higher, or 0.25 or higher. The R of the elastic layer... 80 / 20 It can be below 1 or below 0.85. The R of the elastic layer... 80 / 20 It can be below 0.7 or below 0.55.

[0117] R with this range 80 / 20 The elastic layer is advantageous for applications such as flexible cover windows that undergo repeated bending over a wide temperature range. This characteristic is even more advantageous when the elastic layer is layered with other layers besides the elastic layer. Specifically, when an elastic layer with the aforementioned characteristics is applied, the degradation of physical properties caused by differences in energy storage modulus due to temperature differences between layers can be controlled more easily. Furthermore, the elastic layer exhibits excellent elastic properties within a controllable range not only at room temperature or room temperature but also at high temperatures.

[0118] R of elastic layer 10080 / 20 It can be from 0.15 to 0.55. The R of the elastic layer... 80 / 20 It can be from 0.25 to 0.55. In this case, after using an adhesive layer or the like to bond the elastic layer to other structures, it is possible to substantially control the occurrence of peeling, lifting, etc., at both room temperature and high temperature while maintaining stable physical properties of the elastic layer.

[0119] The low-temperature energy storage modulus ratio of elastic layer 100 to R -40 / 20 It can be 1.15 or higher. The cryogenic energy storage modulus ratio R... -40 / 20 It is the ratio of the energy storage modulus at -40℃ to the energy storage modulus at 20℃, and is expressed by the following formula 1-b.

[0120] [Equation 1-b]

[0121]

[0122] In Equation 1-b, R -40 / 20 For low-temperature energy storage modulus ratio, SM n The storage modulus (MPa) of the elastic layer is measured at a temperature of n °C.

[0123] R of elastic layer 100 -40 / 20 It can be 1.20 or higher, or 1.33 or higher. The R value of the elastic layer... -40 / 20 It can be below 20 or below 10. The R of the elastic layer... -40 / 20 It can be below 4.9 or below 4.5.

[0124] R with this range -40 / 20 The elastic layer is advantageous for applications such as flexible cover windows that undergo repeated bending over a wide temperature range. This characteristic is even more advantageous when the elastic layer is layered with other layers besides the elastic layer. Specifically, when an elastic layer with the aforementioned characteristics is applied, the degradation of physical properties caused by differences in the storage modulus based on the temperature between the layers can be controlled more easily. Furthermore, the elastic layer exhibits excellent elastic properties within a controllable range not only at room temperature or room temperature but also at low temperatures.

[0125] R of elastic layer 100 -40 / 20 The value can be from 1.22 to 4.50. The R of the elastic layer... -40 / 20 The value can be from 1.22 to 3.8. The R of the elastic layer... -40 / 20 The value can be from 1.22 to 3.0. In this case, by using an adhesive layer or the like to bond the elastic layer to other structures, it is possible to substantially control the occurrence of peeling, lifting, and other phenomena at both room temperature and low temperature while maintaining stable physical properties of the elastic layer.

[0126] The difference in low-temperature energy storage modulus is the difference between the energy storage modulus at -40℃ and the energy storage modulus at 20℃, and is expressed by the following formula 1-c.

[0127] [Equation 1-c]

[0128] D -40-20 =SM -40 -SM 20

[0129] In the above formula 1-c,

[0130] D -40-20 The difference is due to the low-temperature energy storage modulus.

[0131] SM n The storage modulus (MPa) of the elastic layer is measured at a temperature of n °C.

[0132] D of elastic layer 100 -40-20 The pressure can range from -1500MPa to 1500MPa. The D of the elastic layer... -40-20 It can be -1000MPa to 1000MPa. When the D of the elastic layer... -40-20 At pressures greater than 1500 MPa, the difference between the storage modulus at room temperature and at low temperatures is significant. Therefore, the elastic properties may be insufficient at low temperatures, potentially leading to irreversible deformation such as cracking and tearing due to bending or other deformations. Preferably, the D of the elastic layer... -40-20 It can be below 1000MPa.

[0133] The energy storage modulus of the elastic layer 100 at -40℃ can be below 2300MPa and below 2000MPa. Alternatively, the energy storage modulus of the elastic layer at -40℃ can be above 200MPa, above 400MPa, or above 500MPa.

[0134] The energy storage modulus of the elastic layer 100 at 0°C can be below 2500 MPa and below 2000 MPa. The energy storage modulus of the elastic layer at 0°C can be above 20 MPa and above 150 MPa. The energy storage modulus of the elastic layer at 0°C can be between 180 MPa and 1200 MPa.

[0135] The energy storage modulus of the elastic layer 100 at 40°C can be above 10 MPa or above 90 MPa. The energy storage modulus of the elastic layer at 40°C can be below 3000 MPa or below 2000 MPa. The energy storage modulus of the elastic layer at 40°C can be between 100 MPa and 1200 MPa.

[0136] The energy storage modulus of the elastic layer 100 at 80°C can be above 4 MPa or above 20 MPa. The energy storage modulus of the elastic layer at 80°C can be below 2000 MPa or below 1000 MPa. The energy storage modulus of the elastic layer at 80°C can be from 40 MPa to 950 MPa or from 60 MPa to 350 MPa.

[0137] The elastic layer 100 may have a difference between its energy storage modulus at 80°C and its energy storage modulus at -40°C, the difference being between -1000 MPa and 1000 MPa. For convenience, the difference can be expressed as an absolute value by subtracting the smaller value from the larger value, and in this case, the difference may be less than 1000 MPa. The elastic layer having this characteristic exhibits a small difference in energy storage modulus over a wide temperature range from high to low, thus demonstrating stable energy storage modulus characteristics over a considerably wide temperature range.

[0138] The elastic layer 100, which has the energy storage modulus characteristics described above at each temperature, has an appropriate energy storage modulus value and / or degree of variation not only at room temperature or ambient temperature, but also over a fairly wide temperature range from low to high temperature.

[0139] Even when the elastic layer 100 is applied alone or together with other layers to a product (such as a multilayer electronic device), it exhibits excellent cyclic recovery characteristics and provides adequate protection against external impacts when subjected to repeated bending, rolling, and other deformations.

[0140] The elastic layer 100 may have excellent recovery / impact resistance properties, etc.

[0141] The restoring force index Rv of the elastic layer 100 can be greater than 50, as shown in Equation 3 below.

[0142] Formula 3

[0143]

[0144] In Equation 3, Xo is the length (mm) of the initial elastic layer, X 2％ Xf is the length (mm) of the elastic layer after being stretched by 2%, and Xf is the length (mm) of the elastic layer after 100 cycles. One cycle consists of stretching the elastic layer by 2% at a speed of 50 mm / min and then restoring it to its original length at a speed of 50 mm / min.

[0145] To test the resilience index, clamps or other fixing components used to secure the elastic layer are applied to both ends of the elastic layer. The initial elastic layer length and the length of the elastic layer after cycles actually refer to the length of repeated stretching; therefore, the aforementioned Xo and X... 2％ Xf and Xf are the lengths of the elastic layer between the fixed parts, respectively.

[0146] The Rv of the elastic layer 100 can be 55 or higher, 60 or higher, or 68 or higher. The Rv of the elastic layer can be less than 100 or less than 99. The Rv of the elastic layer can be less than 95 or less than 90.

[0147] When the Rv of the elastic layer is within the above range, the elastic layer can also have excellent recovery characteristics after repeated stretching. In particular, even in repeated stretching-recovery with a relatively short length, such as bending, it has elastic recovery durability that can substantially maintain the physical properties and length of the initial elastic layer.

[0148] The Rv value of the elastic layer is based on the result of evaluating the elastic layer in the form of a 100 μm thick film after it has been individually fixed to the fixing part (e.g., a clamp) of the evaluation device without the use of a separate carrier film or support layer. However, it is not limited to this, and the measurement value of the evaluation that is deemed to be equivalent to this can also be accepted as the Rv value.

[0149] Elastic layer 100 can have 2500kJ / m 2 Above, 3500kJ / m 2 Above, 4500kJ / m 2 The above impact strength. Elastic layer 100 can have 5000 kJ / m. 2 The above impact strength can reach 10000 kJ / m 2 The following impact strength. An elastic layer with this property can absorb external impacts well and is not easily broken or damaged, making it ideal for use as a cover film.

[0150] The elastic layer 100 can have an absorbed energy of 1.4 J or more, or 1.5 J or more. It can also have an absorbed energy of 1.6 J or more, or less than 2.0 J. This type of elastic layer effectively absorbs external impacts, mitigating the transmission of impacts to the protected internal structures while ensuring the film itself is not easily damaged. Therefore, it is ideally suited for use as a cover film.

[0151] The impact strength and the absorbed energy are respectively based on the results of evaluating the tensile-impact strength of the elastic layer according to the JIS K 7160 standard, and the specific measurement conditions are as given in the experimental examples below.

[0152] Dynamic bending assessment results show that elastic layer 100 has excellent durability.

[0153] The dynamic bending assessment was conducted in accordance with the IEC 62715-6-1 standard. After the elastic layer was subjected to 200,000 dynamic bending tests at -40°C with a curvature radius of 2 mm and a bending degree of 2 seconds / cycle, it was confirmed whether cracks appeared in the elastic layer.

[0154] According to IEC 62715-6-1 standard, the elastic layer 100 can have excellent durability, which can withstand 200,000 dynamic bending tests at -40°C with a curvature radius of 2 mm and a bending degree of 2 seconds / cycle without substantially cracking.

[0155] This means that, considering the characteristic that elasticity at low temperatures is relatively lower than that at normal or high temperatures, the elastic layer also exhibits excellent elasticity in repeated bending tests over a wide temperature range.

[0156] The elastic layer 100 can have excellent properties such as thickness control and surface roughness control.

[0157] The elastic layer 100 can essentially be in the form of a thin film with a thickness controlled to be constant.

[0158] The elastic layer 100 can essentially be in the form of an extruded film with a thickness controlled to a constant thickness.

[0159] The elastic layer 100 may be laminated together with other layers described later and included in the laminated film.

[0160] In the above text, "the thickness is controlled to be (substantially) constant" means that the thickness is adjusted to a range of -5% to +5% of a preset thickness.

[0161] The elastic layer 100 may have a thickness of less than 2000 μm. The thickness of the elastic layer may be less than 1500 μm or less than 1000 μm. The thickness of the elastic layer may be greater than 1 μm. The thickness of the elastic layer may be from 20 μm to 300 μm, or from 50 μm to 300 μm.

[0162] The elastic layer 100 in the form of a thin film having the thickness described above has both the energy storage modulus characteristics described above and excellent optical properties, and is therefore suitable for use as a cover film for display devices.

[0163] The surface of the elastic layer 100 has a low surface roughness below a predetermined level.

[0164] The surface roughness of the elastic layer may have its own technical meaning, but it may also be related to other properties such as optical properties, thus affecting the physical properties of the elastic layer. The inventors have demonstrated that the surface roughness of the elastic layer can affect the optical properties of the film, and in particular, it can affect the haze properties, keeping them below a predetermined level.

[0165] The roughness reference value is the larger of the surface roughness Ra1 of one surface and the surface roughness Ra2 of the other surface.

[0166] The roughness reference value of the elastic layer 100 can be below 0.5 μm.

[0167] The roughness reference value of the elastic layer 100 can be less than 0.5 μm, less than 0.2 μm, or less than 0.1 μm. The roughness reference value of the elastic layer can be greater than 0 μm, greater than 0.0001 μm, or greater than 0.001 μm.

[0168] When the roughness reference value of the elastic layer is controlled below a predetermined level, the optical properties of the elastic layer, especially the haze properties, can be further improved.

[0169] The roughness reference value of the elastic layer 100 can be from 0.001 μm to 0.1 μm. The roughness reference value of the elastic layer can be from 0.0015 μm to 0.05 μm. Elastic layers with such roughness reference values ​​exhibit superior optical properties such as haze and are also very suitable for use as optical thin films.

[0170] For example, one surface of the elastic layer is the surface that contacts the carrier film 92 described later, and the other surface of the elastic layer can be a separate sheet protective film 94 or a surface that contacts the roller device (e.g., extrusion roller) during the preparation process.

[0171] Ra1 and Ra2 can be controlled by adjusting the surface roughness of the carrier film and the roller device (or sheet protective film) that are in contact with one or the other surface of the elastic sheet during the preparation of the elastic layer.

[0172] For example, when the surface roughness Ra of the carrier film is in the range of 0.8 μm to 1.2 μm, the surface roughness Ra value Ra1 of one surface of the elastic layer can be 0.8 μm to 1.2 μm.

[0173] For example, when the surface roughness Ra of the roller device is in the range of 0.01 μm to 0.5 μm, the surface roughness Ra value Ra2 of the other surface of the elastic layer can be in the range of 0.01 μm to 0.5 μm.

[0174] For example, when the surface roughness Ra of the sheet protective film is in the range of 0.01 μm to 0.5 μm, the surface roughness Ra value Ra2 of the other surface of the elastic layer can be in the range of 0.01 μm to 0.5 μm.

[0175] The carrier membrane 92 may be made of polyethylene terephthalate (PET) film, but is not limited thereto.

[0176] The sheet protective film 94 can be applied to polyethylene (PE) films, but is not limited thereto.

[0177] The elastic layer 100 may have a Shore D hardness of 20 to 75 or 30 to 70. This exhibits appropriate strength for use as a cover film and helps to impart elastic properties and excellent impact resistance to the film.

[0178] According to ISO 307:2019, the intrinsic viscosity of the elastic layer 100, measured with cresol, can be from 0.8 to 2.5 at 25°C.

[0179] The yellow index (YI) of the elastic layer 100 can be less than 1. The yellow index can be a value measured using a color meter ultrascanpro manufactured by Hunterlab in YI E313 (D65 / 10) mode.

[0180] For the elastic layer 100, the difference between the yellowness before and after exposure to ultraviolet light with wavelengths from 280 nm to 360 nm at a 3.0 W output for 72 hours can be less than 2. For the elastic layer, the difference between the yellowness before and after exposure to ultraviolet light with wavelengths from 280 nm to 360 nm at a 3.0 W output for 72 hours can be less than 1. For the elastic layer, the difference between the yellowness before and after exposure to ultraviolet light with wavelengths from 280 nm to 360 nm at a 3.0 W output for 72 hours can be greater than 0.1. Elastic layers with these characteristics exhibit excellent ultraviolet (UV) durability, wherein even when exposed to ultraviolet light, yellowing of the coating layer is minimal or almost nonexistent.

[0181] The elastic layer 100 may contain amide residues as repeating units.

[0182] The elastic layer 100 may contain a polymer resin with amide residues as repeating units.

[0183] The elastic layer 100 can be a plastic film containing a polymer resin having amide residues as repeating units.

[0184] The elastic layer 100 can be an elastomer film containing a polymer resin having amide residues as repeating units.

[0185] Based on the total amount of polymer resin included in the elastic layer, the amide residues can be 30% or more by weight, 50% or more by weight, or 60% or more by weight. Based on the total amount of polymer resin included in the elastic layer, the amide residues can be 80% or less by weight or 70% or less by weight. When a polymer resin having these properties is applied to the elastic layer, an elastic layer with superior mechanical properties can be provided.

[0186] Based on the total amount of polymer resin included in the elastic layer, the amide residues can be from 92 mol% to 97 mol%. When this polymer is applied to the elastic layer, an elastic layer with excellent strength and elastic properties can be provided in a substantially wide range.

[0187] The elastic layer 100 may comprise a polymer, which may include rigid and soft regions in the chain.

[0188] The rigid region can be represented as a rigid segment or a semi-crystalline region. The soft region can be represented as a soft segment or an amorphous region.

[0189] The polymer includes both rigid and soft regions, giving the elastic layer relatively strong mechanical strength while also possessing flexible and / or elastomeric properties.

[0190] The elastic layer may have polymer chain regions (homologous regions) comprising monomers classified as substantially the same type. By adjusting the degree of partial bonding or chain alignment within these polymer chain regions (homologous regions), the elastic layer can simultaneously possess the desired strength and elastic properties. In the elastic layer, monomers classified as substantially different types may also be bonded to the polymer chain regions (homologous regions). The elastic layer may simultaneously have partially rigid regions with high strength and partially soft regions with flexible properties to impart flexibility to the polymer.

[0191] The elastic layer may contain elastic polyamide (long chain polyamide).

[0192] The elastic polyamide may include an amorphous region as a soft region and a crystalline region as a rigid region, and may be in a state in which the amorphous region is used as a matrix and the crystalline region is distributed in the matrix.

[0193] Compared to the soft region, the rigid region may contain more hydrogen-bonded C=O molecules. Compared to the rigid region, the soft region may contain more non-hydrogen-bonded free C=O bonds. The content of hydrogen-bonded C=O molecules in the rigid and soft regions can be confirmed by measuring FT-IR spectra.

[0194] The elastic polyamide may contain semicrystalline polyamide. The elastic polyamide may contain amorphous polyamide. The elastic polyamide may contain a mixture of semicrystalline and amorphous polyamides. Preferably, based on the total elastic polyamide, the elastic polyamide contains more than 50% by weight of semicrystalline polyamide.

[0195] Elastic polyamides can be homopolymers, polyamide copolymers, or mixtures thereof. Homopolymers can be prepared by polymerizing one monomer selected from a mixture of amino acids, lactams, or diacids and diamines. Polyamide copolymers can be prepared by polymerizing two or more monomers selected from a mixture of amino acids, lactams, or diacids and diamines.

[0196] Elastic polyamides can be prepared by combining a molecule with an amide group at one end with another molecule with a carboxyl group at one end.

[0197] Examples of monomers used to prepare elastic polyamides are shown below, but are not limited to these.

[0198] Aliphatic diacids can be, for example, adipic acid (6), azelaic acid (9), sebacic acid (10), dodecanedioic acid (12), etc., but are not limited to these.

[0199] Aromatic diacids can be, for example, terephthalic acid (T) and isophthalic acid (I), but are not limited to these.

[0200] Aliphatic diamines may have, for example, butylenediamine (4), hexamethylene-diamine (6 or HMDA), isomers of trimethylhexamethylenediamine (TMHMDA), octamethylenediamine (8), decamethylenediamine (10), dodecamethylenediamine (12), etc., but are not limited to these.

[0201] Aromatic diamines can be, for example, meta-xylenediamine (MXD), but are not limited to this.

[0202] Alicyclic diamines can be, for example, bis(3,5-dialkyl-4-aminocyclohexyl)methane, bis(3,5-dialkyl-4-aminocyclohexyl)ethane, bis(3,5-dialkyl-4-aminocyclohexyl)propane, bis(3,5-dialkyl-4-aminocyclohexyl)butane, and bis(3,5-dialkyl-4-aminocyclohexyl)propane. Bis(3-methyl-4-aminocyclohexyl)methane (BMACM, MACM or B), bis(p-aminocyclohexyl)methane (PACM), isopropylidenedi(cyclohexylamine) (PACP), isophoronediamine (IPD), 2,6-bis(aminomethyl)norbornane (BAMN), piperazine, or mixtures thereof, but not limited thereto.

[0203] Other diamines may include, but are not limited to, isophoronediamine (IPDA), 2,6-bis-(aminomethyl)norbornane (BAMN), etc.

[0204] The lactam can be, for example, caprolactam (L6) or laurylactam (L12), but is not limited to these.

[0205] The amino acid can be, for example, 11-aminoundecanoic acid (11), 11-(N-heptyl-amino)undecanoic acid (NHAU), etc., but is not limited to these.

[0206] The elastic polyamide may comprise an aliphatic polyamide. The elastic polyamide may be made from an aliphatic polyamide.

[0207] The elastic polyamide may contain semi-aromatic polyamides. The elastic polyamide may be made from semi-aromatic polyamides.

[0208] Aliphatic polyamides can be, for example, polycaprolactam (PA6), polyundecanamide (PA11), polylauryllactam (PA12), polybutylene adipamide (PA46), polyhexamethylene adipamide (PA66), polyhexamethylene azelamide (PA69), polyhexamethylene sebacamide (PA610), polyhexamethylene dodecanediamide (PA612), polydecamethylene dodecanediamide (PA1012), polydecamethylene sebacamide (PA1010), and polydodecamethylene dodecanediamide (PA1010). 1212), which are polyamide copolymers such as PA 11 / NHUA, PA BACM6, PA BACM10, PABACM12, PA 6 / 66, PA 6 / 12, or mixtures thereof, but are not limited thereto. According to examples, the polyamide copolymer can be PA 6 / 66, PA 6 / 610, PA 6 / 12, or mixtures thereof.

[0209] The semi-aromatic polyamide can be, for example, PA 6 / 6T, PA 66 / 6T, PA 6T / 6I, PA 66 / 6T / 6I, PA 11 / 6T, PA 12 / 6T, PA MXD6, PA MXD10 or mixtures thereof, but is not limited thereto.

[0210] The amorphous polyamide can be, for example, polyhexamethylene isophthalamide (PA 6I), polytrimethylhexamethylene terephthalamide (PA TMHMDAT), PA BACM12 as a polyamide; PA 6 / BMACPI, PA 6 / BAMNT, PA11 / BMACMI, PA 11 / BMACMT / BMACMI, PA 11 / BACM.I / IPDA.I, PA 12 / BMACM.I, PA 12 / BACMT / BACMI, PA 12 / BMACMT / BACMI, PA 12 / BACMI / IPDAI, PA 6T / 6I / BACMI, PA 6T / 6I / BACMT / BACMI; or mixtures thereof, but not limited thereto.

[0211] Preferably, the polyamide is a semi-crystalline polyamide. In this document, semi-crystalline polyamide can essentially refer to a linear aliphatic polyamide. Preferably, the semi-crystalline polyamide can be any one selected from PA6, PA11, PA12, PA10.10, PA10.12, PA6.10, PA6.12, and combinations thereof.

[0212] For example, the elastic polyamide can be from Arkema, France. And so on, but not limited to these.

[0213] The elastic layer 100 may comprise a polyether block amide (PEBA). The polyether block amide comprises two phases: a polyamide region serving as a rigid region and a polyether region serving as a flexible region. The polyamide region has a melting point above approximately 80°C, specifically approximately 130°C to 180°C, and is substantially capable of forming a hard region as a crystalline phase. The polyether region has a glass transition temperature below approximately -40°C, specifically existing in a low-temperature region from -80°C to -40°C, and is substantially capable of forming a soft, amorphous region.

[0214] Polyether block amides can be formed by combining polyamides containing two or more carboxyl groups in their molecules with ethers containing two or more hydroxyl groups in their molecules.

[0215] The elastic layer 100 may comprise a polyether block amide, which may comprise at least one copolymer comprising a polyether block and a polyamide block. The polyether block amide comprises at least one polyether block and at least one polyamide block.

[0216] A copolymer containing polyether blocks and polyamide blocks (polyether block amide) can be formed by polycondensation of polyether blocks containing reactive ends and polyamide blocks containing reactive ends.

[0217] Polyether block amides can be condensation polymers containing polyamide blocks with diamine ends and polyoxyethylene blocks with dicarboxyl ends.

[0218] The polyether block amide can be a condensation polymer comprising a polyamide block with a dicarboxyl terminus and a polyoxyethylene block with a diamine terminus. The polyoxyethylene block can be obtained by cyanoethylation and hydrogenation of an aliphatic α,ω-dihydroxylated polyoxyalkylene block known as a polyether diol.

[0219] Polyether block amides can be condensation polymers comprising polyamide blocks with dicarboxylic acid ends and polyether glycol blocks. In this case, the polyether block amide is a polyether ester amide.

[0220] For example, a polyamide block containing a dicarboxyl group end may comprise a condensation polymer of a polyamide precursor in the presence of a chain-restricted dicarboxylic acid. For example, a polyamide block containing a diamine end may comprise a condensation polymer of a polyamide precursor in the presence of a chain-restricted diamine.

[0221] For example, in the presence of a chain-restricted dicarboxylic acid, the polyamide block containing a dicarboxylic acid end may comprise a condensation polymer of an α,ω-aminocarboxylic acid, a lactam, or a dicarboxylic acid and a diamine. Polyamide 12 or polyamide 6 is preferred as the polyamide block.

[0222] Polyether block polyamides may contain blocks with a randomly distributed unit structure.

[0223] Advantageously, the following three types of polyamide blocks can be applied.

[0224] 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.

[0225] The dicarboxylic acid can be, for example, 1,4-cyclohexanedicarboxylicacid, 1,2-cyclohexyldicarboxylic acid, 1,4-butanedioic acid, adipic acid, azelaic acid, subericacid, sebacic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, terephthalic acid, isophthalic acid, haphthalenedicar boxylic acid, and dimerized fatty acid.

[0226] The diamine may be, for example, 1,5-tetramethylenediamine, 1,6-hexamethylenediamine, 1,10-decamethylenediamine, 1,12-dodecamethylenediamine, trimethyl-1,6-hexamethylenediamine, 2-methyl-1,5-pentamethylenediamine, theisomers of bis(3-methyl-4-aminocyclohexyl)methan (BMACM), 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACM). Other examples include hydroxyl propane (BMACP), bis(para-aminocyclohexyl)methane (PACM), isophoronediamine (IPD), 2,6-bis(aminomethyl)norbornane (BAMN), piperazine (Pip), meta-xylylenediamine (MXD), and para-xylylenediamine (PXD).

[0227] Advantageously, 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.

[0228] In the presence of a dicarboxylic acid or diamine having 4 to 12 carbon atoms, the second type of polyamide block may comprise a condensation polymer of at least one α,w-aminocarboxylic acid and / or at least one lactam having 6 to 12 carbon atoms.

[0229] Examples of the lactams include caprolactam, heptanolactam, laurolactam, etc.

[0230] Examples of the α,ω-aminocarboxylic acids include aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acids.

[0231] Preferably, the second type of polyamide block may include polyamide 11, polyamide 12 or polyamide 6.

[0232] The third type of polyamide block may contain a condensation polymer of at least one α,ω-aminocarboxylic acid (or at least one lactam), at least one diamine, and at least one dicarboxylic acid.

[0233] In this case, polyamide (PA) blocks can be prepared by polycondensation of diamine, diacid and comonomer (or comonomer).

[0234] As the diamine, examples such as linear aliphatic diamines, aromatic diamines, and diamines having X carbon atoms can be used. As the diacid, examples such as dicarboxylic acids and acids having Y carbon atoms can be used. The comonomer or multiple comonomers {Z} can be comonomers selected from lactams having Z carbon atoms, α,ω-aminocarboxylic acids, and mixtures containing at least one diamine having X1 carbon atoms and at least one dicarboxylic acid having Y1 carbon atoms in substantially equal molar amounts. However, (X1, Y1) is different from (X, Y).

[0235] Based on the total amount of the combined polyamide precursor monomers, the comonomer or multiple comonomers {Z} can be less than 50% by weight, preferably less than 20% by weight, and advantageously less than 10% by weight.

[0236] The condensation reaction of the third type can be carried out in the presence of a chain restrictor selected from dicarboxylic acids.

[0237] Advantageously, as a chain limiting agent, a dicarboxylic acid having Y carbon atoms can be used, which is introduced in stoichiometric excess relative to the at least one diamine.

[0238] As a third type of alternative, the polyamide block may optionally comprise, in the presence of a chain restrictor, two or more α,ω-aminocarboxylic acids, or two or more lactams, or condensates of lactams and aminocarboxylic acids having 6 to 12 carbon atoms.

[0239] The aliphatic α,ω-aminocarboxylic acid can be, for example, aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid, etc.

[0240] The lactam can be, for example, caprolactam, heptanolactam, laurolactam, etc.

[0241] The aliphatic diamine can be, for example, hexamethylenediamine, dodecamethylenediamine, trimethylhexamethylenediamine, etc.

[0242] The alicyclic diacid can be, for example, 1,4-cyclohexanedicarboxylic acid.

[0243] The aliphatic diacid can be, for example, succinic acid, adipic acid, azelaic acid, octanoic acid, sebacic acid, dodecanecarboxylic acid, dimer fatty acids (preferably, the dimer ratio is 98% or more; preferably, they are hydrogenated and commercially available under the trademark name "Pripol" of Uniqema, UK, or "Empol" of Henkel, Germany), polyoxyethylene-α,ω-diacid, etc.

[0244] The aromatic diacid can be, for example, terephthalic acid (T), isophthalic acid (I), etc.

[0245] The alicyclic diamine can be, for example, an isomer of bis(3-methyl-4-aminocyclohexyl)methane (BMACM) and 2,2-bis(3-methyl-4-aminocyclohexyl)propane (BMACP), bis(p-aminocyclohexyl)methane (PACM), etc.

[0246] Other diamines can be, for example, isophorone diamine (IPD), 2,6-bis(aminomethyl)norbornene (BAMN), piperazine, etc.

[0247] Examples of aryl aliphatic diamines include, but are not limited to, m-phenylenediamine (MXD) and p-phenylenediamine (PXD).

[0248] Examples of the third type of polyamide blocks include PA 66 / 6, PA 66 / 610 / 11 / 12, etc.

[0249] In PA 66 / 6, 66 represents a hexamethylenediamine unit condensed with adipic acid, and 6 represents a unit introduced by the condensation of caprolactam.

[0250] In PA 66 / 610 / 11 / 12, 66 represents a hexamethylenediamine unit condensed with adipic acid, 610 represents a hexamethylenediamine unit condensed with sebacic acid, 11 represents a unit introduced by condensation with aminoundecanoic acid, and 12 represents a unit introduced by condensation with laurolactam.

[0251] The number-average molar mass (Mn) of the polyamide block can be from 400 g / mol to 20000 g / mol, preferably from 500 g / mol to 10000 g / mol.

[0252] As a polyether (PE) block, for example, at least one polyalkylene ether polyol, particularly as a polyalkylene ether glycol, preferably selected from polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (PO3G), polybutane glycol (PTMG), and mixtures thereof or copolymers thereof. The polyether block may comprise an NH2-terminated polyoxyethylene arrangement introduced by cyanoacetylation of an aliphatic α,ω-dihydroxy polyoxyethylene arrangement known as a polyether glycol. Specifically, JEFFAMINE (e.g., JEFFAM, a product of Huntsman Corporation) can be used. D2000, ED2003 or XTJ542).

[0253] Preferably, the at least one polyether block comprises at least one polyether selected from, for example, polyalkylene ether polyols selected from PEG, PPG, PO3G, PT MG, etc., polyethers containing NH2 at the chain end and containing polyoxyethylene arrangements, copolymers (ether copolymers) of these randomly arranged and / or block-arranged, and mixtures thereof.

[0254] The polyether block may contain 10% to 80% by weight relative to the total weight of the copolymer, preferably 20% to 60% by weight, and more preferably 20% to 40% by weight.

[0255] The number-average molecular weight of the polyether blocks can be from 200 g / mol to 1000 g / mol (excluding the critical point), preferably from 400 g / mol to 800 g / mol (including the critical point), and more preferably from 500 g / mol to 700 g / mol.

[0256] Polyether blocks can be introduced from polyethylene glycol. Polyether blocks can be introduced from polypropylene glycol. Polyether blocks can be generated from polybutane glycol. Polyether blocks can be copolymerized with polyamide blocks containing carboxyl-terminated groups to form polyether block amides. After amination of the polyether blocks to polyether diamine, they condense with polyamide blocks containing carboxyl-terminated groups to form polyether block amides. Polyether blocks can be mixed with polyamide precursors and chain limiting agents to form polyether block amides containing statistically dispersed units.

[0257] Examples of polyethers include polyethylene glycol (PEG), polypropylene glycol (PPG), or polybutanediol (PTMG). Polybutanediol is also known as polytetrahydrofuran (PTHF). Polyether blocks can be introduced into the chain of polyether-blocked amides in the form of diols or diamines, and these polyether blocks are referred to as PEG blocks, PPG blocks, or PTMG blocks, respectively.

[0258] Even if the polyether block contains units other than those derived from ethylene glycol (-OC2H4-), propylene glycol (-O-CH2-CH(CH3)-), or butanediol (-O-(CH2)4-), the corresponding polyether block is included within the scope of the examples.

[0259] The number-average molar mass of the polyamide blocks can advantageously be from 300 to 15,000, preferably from 600 to 5,000. The number-average molar mass of the polyether blocks can be from 100 to 6,000, preferably from 200 to 3,000.

[0260] Advantageously, based on the total polyether block amide, the content of polyamide blocks contained in the polyether block amide can be 30% by weight or more, or 50% by weight or more. This implies a statistical distribution probability within the polymer chain. Preferably, the content of the polyamide is 30% by weight to 80% by weight, or 50% by weight to 80% by weight. Preferably, based on the total polyether block amide, the content of polyether contained in the polyether block amide is 20% by weight to 70% by weight, or 20% by weight to 50% by weight.

[0261] Preferably, the number-average molar mass ratio of the polyamide block to the polyether block of the copolymer can be from 1:0.25 to 1, and the number-average molar masses of the polyamide block and the polyether block of the copolymer can be 1000 / 1000, 1300 / 650, 2000 / 1000, 2600 / 650 or 4000 / 1000, respectively.

[0262] Polyether block amides can be prepared by a method comprising a first step and a second step, wherein the first step is the preparation of polyamide blocks and polyether blocks, and the second step is the preparation of elastic polyether block amides by polycondensation of the prepared polyamide blocks and polyether blocks. Polyether block amides can also be prepared by polycondensation of monomers in a single step.

[0263] Polyether block amides can exemplarily exhibit a Shore D hardness of 20 to 75, and advantageously 30 to 70. The intrinsic viscosity of polyether block amides, measured with cresol at 25°C, can be from 0.8 to 2.5. The intrinsic viscosity is measured according to ISO 307:2019. Specifically, the intrinsic viscosity in solution is measured using a Ubbelohde viscometer in a cresol solution at 25°C, representing 0.5% by weight of the total solution.

[0264] For example, the polyether block amide is manufactured by Arkema, France. Evonik GmbH, Germany E, etc., but not limited to these.

[0265] The elastic layer 100 may contain thermoplastic polyurethane (TPU), which may contain copolymers of polyurethane blocks (PU) and polyether blocks (PE), also known as polyether polyurethane.

[0266] TPU can be a condensation polymer comprising a polyether glycol or polyester glycol (e.g., poly(butyl adipate) or polycarbolide diol) as a flexible PE block and a rigid PU block. The PU and PE blocks can be linked by bonds formed by a reaction between the isocyanate groups of the polyether and the hydroxyl groups of the polyether glycol.

[0267] In this document, polyurethane refers to the product of the reaction of at least one diisocyanate, selected from aromatic diisocyanates (e.g., MDI, TDI) and / or aliphatic diisocyanates (e.g., hexamethylenediisocyanate (HDI)), with at least one diol having a short chain length (e.g., butanediol, ethylene glycol).

[0268] The elastic layer may contain polyether ester copolymer (COPE).

[0269] COPE may comprise a thermoplastic elastomer containing at least one polyether block (PE) and at least one polyester fiber block (homopolymer or ester copolymer).

[0270] COPE may comprise flexible PE blocks derived from polyether glycols and rigid polyester fiber blocks formed by the reaction between at least one dicarboxylic acid and at least one short-chain extender glycol unit. The PES and PE blocks may be linked by ester bonds introduced by the reaction of the acid group of the dicarboxylic acid with the hydroxyl group of the polyether glycol. The short-chain extender glycol may be selected from neopentyl glycol and the chemical formula HO(CH2). n The aliphatic diol of OH, wherein n is an integer from 2 to 10.

[0271] The chains of the polyether and the diacid form flexible blocks, while the chains of the diacid and the diol or butanediol form rigid blocks of the polyether ester copolymer. Preferably, the diacid can be an aromatic dicarboxylic acid having 8 to 14 carbon atoms. Up to 50 mol% of the total aromatic dicarboxylic acid can be replaced by at least one other aromatic dicarboxylic acid having 8 to 14 carbon atoms and / or up to 20 mol% of the total aromatic dicarboxylic acid can be replaced by an aliphatic dicarboxylic acid having 2 to 14 carbon atoms.

[0272] Aromatic dicarboxylic acids can be, for example, terephthalic acid, isophthalic acid, biphenyl zoicacid, naphthalene dicarboxylic acid, 4,4'-diphenylenedicarboxylic acid, bis(p-carboxyphenyl)methaneacid, ethylene bis p-benzoic acid, 1,4-tetramethylene bis(p-oxybenzoic acid), ethylene bisacid(p-oxybenzoic) acid, 1,3-trimethylene bis(p-oxybenzoic) acid, etc.

[0273] Examples of diols include ethylene glycol, 1,3-trimethylenediol, 1,4-butanediol, 1,6-hexamethylenediol, 1,3-propanediol, 1,8-octamethylenediol, and 1,10-decamethylenediol.

[0274] COPE may comprise polyether units derived from polyether glycols such as polyethylene glycol (PEG), polypropylene glycol (PPG), polytrimethylene glycol (PO3G), or polybutane glycol (PTMG), and polyester fiber units introduced through a reaction between a dicarboxylic acid (e.g., terephthalic acid) and a glycol (e.g., ethanediol, 1,4-butanediol). Disclosures of such polyether ester copolymers are found in European Patents EP402883 and EP405227, the contents of which are incorporated herein by reference.

[0275] The elastic layer may comprise the polyamide, the PEBA, the TPU, the COPE, or a mixture thereof.

[0276] The method for preparing the elastic layer using polymer resins will be described below.

[0277] Thin film, applications of thin film

[0278] According to another example, the film 190 includes an elastic layer 100.

[0279] According to another example, the light-transmitting laminate includes an elastic layer 100.

[0280] According to another example, the covering film includes an elastic layer 100.

[0281] For a specific description of the elastic layer 100, the above description shall apply, and detailed descriptions shall be omitted to avoid repetition.

[0282] The film 190 may include a laminate, which further includes a carrier located on a surface 100a of the elastic layer. Membrane 92.

[0283] As a carrier film 92, a film with a thickness of 50 μm can be used. When considering factors such as chemical resistance and dimensional stability, PET film can be used.

[0284] For example, the carrier membrane 92 can be a PET film with a thickness of 50 μm to 250 μm.

[0285] The carrier membrane 92 can also perform the function of the release membrane 150 described below.

[0286] One surface of the carrier membrane 92 can be in direct contact with the elastic layer 100.

[0287] During the preparation of the elastic layer 100, the surface roughness of one surface of the carrier film 92 can be transferred to the layered surface in contact with it.

[0288] The surface roughness Ra of one surface of the carrier film 92 can be less than 0.5 μm or less than 0.2 μm. The surface roughness Ra of one surface of the carrier film 92 can be greater than 0 μm, greater than 0.0001 μm, or greater than 0.001 μm.

[0289] The surface roughness Ra of one surface of the carrier film 92 can be from 0.001 μm to 0.1 μm. A carrier film with this roughness can provide an elastic layer with a lower haze value by controlling the surface roughness of the elastic layer.

[0290] The film 190 may include a film laminate comprising the elastic layer 100 and the carrier film 92. The carrier film may be used as a release film.

[0291] The film 190 may include a laminate that further includes an elastic layer 100 and a sheet protective film 94 located on the elastic layer.

[0292] The film 190 may also include a sheet protective film 94 located on another surface 100b of the elastic layer.

[0293] For example, PE film or PET film may be used for the sheet protective film 94. The thickness of the sheet protective film is not particularly limited.

[0294] One surface of the sheet protective film can be in direct contact with the other surface 100b of the elastic layer. When the sheet protective film is used in the preparation of the elastic layer, the surface roughness of one surface of the sheet protective film can control the surface roughness of the other surface of the elastic layer.

[0295] The surface roughness Ra of one surface of the sheet protective film 94 can be less than 0.5 μm or less than 0.2 μm. The surface roughness Ra of one surface of the sheet protective film 94 can be greater than 0 μm or greater than 0.0001 μm or greater than 0.001 μm.

[0296] The surface roughness Ra of one surface of the sheet protective film can be from 0.001 μm to 0.1 μm. Sheet protective films with this roughness can provide elastic layers with lower haze values ​​by controlling the surface roughness of the elastic layer.

[0297] The film 190 may include a laminate comprising an elastic layer 100 and a sheet protective film 94 located on the elastic layer.

[0298] The film 190 may include a laminate comprising a carrier film 92, an elastic layer 100 on the carrier film, and a sheet protective film 94 on the elastic layer.

[0299] The laminate can be a light-transmitting laminate. In this document, a light-transmitting laminate refers to a laminate with a light transmittance of 85% or more.

[0300] The film 190 may include a hard layer 120 disposed on the elastic layer 100.

[0301] The elastic layer 100 can be disposed on the hardness layer 120.

[0302] The film 190 may include an adhesive layer 130 located between the hard layer 120 and the elastic layer 100. The specific details of the adhesive layer 130 will be described below.

[0303] The film 190 may not include a separate adhesive layer between the elastic layer 100 and the hard layer 120. In this case, the elastic layer 100 may be attached to the hard layer 120 by welding.

[0304] Hardness layer 120 is a layer with a surface hardness of H or higher.

[0305] The surface hardness of layer 120, measured by the pencil hardness method, can be H or higher, 3H or higher, or 4H or higher.

[0306] The hardness layer 120 can be a polyimide film, a glass layer, or a laminate thereof.

[0307] Polyimide films can be layers made of polyamide-imide polymers. Layers thus prepared contain repeating imide units and therefore can be broadly categorized as polyimide films.

[0308] The polyamide-imide polymer comprises a polymer formed by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound. Specifically, the polyamide-imide polymer can be obtained by polymerizing an aromatic diamine compound, an aromatic dianhydride compound, and a dicarbonyl compound in an organic solvent.

[0309] The aromatic diamine compound may include 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (HFBAPP), 4,4'-diamino-2,2'-bis(trifluoromethyl)diphenyl ether (BTFDPE), 2,2-bis(4-(4-amino-2-(trifluoromethyl)phenoxy)phenyl)hexafluoropropane (HFFAPP), or 3,5-diaminobenzotrifluoro (DATF).

[0310] Specifically, the aromatic diamine compound can be a compound represented by the following chemical formula 1-1.

[0311] [Chemical Formula 1-1]

[0312]

[0313] The aromatic dianhydride compound may contain 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6-FDA), 4,4'-oxophthalic anhydride (ODPA), or 2,3,3',4'-biphenyltetracarboxylic dianhydride (BPDA).

[0314] Specifically, the aromatic dianhydride compound can be a compound represented by the following chemical formula 2-1.

[0315] [Chemical Formula 2-1]

[0316]

[0317] The aromatic diamine compound and the aromatic dianhydride compound can react in a molar ratio of 1:0.95 to 1.05 to form a polymer.

[0318] The dicarbonyl compound may be a compound represented by the following chemical formula 3-1 or chemical formula 3-2.

[0319] [Chemical Formula 3-1]

[0320]

[0321] [Chemical Formula 3-2]

[0322]

[0323] The aromatic diamine compound and the dicarbonyl compound can react in a molar ratio of 1:0.95 to 1.05 to form a polymer.

[0324] The polyimide film may contain at least one repeating unit represented by the following chemical formulas 4-1 to 4-3.

[0325] [Chemical Formula 4-1]

[0326]

[0327] In the chemical formula 4-1, n is an integer from 1 to 400.

[0328] [Chemical Formula 4-2]

[0329]

[0330] In the chemical formula 4-2, x is an integer from 1 to 400.

[0331] [Chemical Formula 4-3]

[0332]

[0333] In the chemical formula 4-3, y is an integer from 1 to 400.

[0334] Polyimide films can contain imide repeating units and amide repeating units in a molar ratio of 1:1 to 4.

[0335] Polyimide films can possess excellent mechanical properties, chemical resistance, heat resistance, and other characteristics, as well as excellent transparency.

[0336] Based on a thickness of 50 μm, the modulus of polyimide films can be above 5.0 GPa.

[0337] Based on a thickness of 50 μm, the yellowness of a polyimide film can be below 5.

[0338] Based on a thickness of 50 μm, the haze of a polyimide film can be below 2%.

[0339] Polyimide films can be transparent polyimide films.

[0340] Based on a thickness of 50 μm, the transmittance of a polyimide film measured at 550 nm can be above 85%.

[0341] Based on a thickness of 50 μm, the tensile strength of a polyimide film can reach 15 kgf / mm². 2 above.

[0342] Based on a thickness of 50 μm, the elongation of a polyimide film can be above 15%.

[0343] The polyimide film may also include a hard coating on the polyimide layer.

[0344] The hard coating can be applied without limitation to hard coatings of polyimide films.

[0345] As the glass layer, ultra-thin glass (UTG) with heat resistance, insulation, and a small radius of curvature can be used. The ultra-thin glass can be, but is not limited to, cover window products from companies such as Dow Corning, DowooInsys, and SCHOTT. For example, the thickness of the glass layer can be less than 100 μm, and the radius of curvature can be less than 2 mm.

[0346] The film 190 may also include an adhesive layer 130' disposed facing the elastic layer 100 and with the hard layer 120 in between. A description of the adhesive layer 130' will be given below, therefore its detailed description is omitted.

[0347] The film 190 may also include a release film 150, which is disposed facing the rigid layer 120 and with the adhesive layer 130' in between. When the film also includes a release film, it can facilitate the adhesion process with other layers. Since the description of the release film is repeated above, its description will be omitted.

[0348] If necessary, the film 190 may also include an adhesive layer 130 on one or the other surface of the elastic layer.

[0349] An optically transparent adhesive layer with excellent light transmittance and / or transparency may be applied to adhesive layer 130. Exemplarily, adhesive materials including optically clear adhesive (OCA), pressure-sensitive adhesive (PSA), or combinations thereof may be applied.

[0350] The adhesive layer 130 may have a storage modulus at 80°C and a storage modulus at -40°C, wherein the difference between the two storage moduli may be -100 kPa to 100 kPa or -80 kPa to 80 kPa. The value of the adhesive layer 130 subtracting the storage modulus at 80°C from the storage modulus at -40°C may be 0.01 kPa to 100 kPa, 0.1 kPa to 80 kPa, or 1 kPa to 50 kPa. When the adhesive layer 130 with this storage modulus characteristic is applied to the thin film 10, the elastic recovery and elastic durability of the thin film can be further improved, which is particularly useful when applied to the window cover of flexible or rollable displays.

[0351] The elastic layer 100 can be disposed on the release film 150. An adhesive layer can be disposed between the elastic layer and the release film. In this case, the film 190 can be a laminate of the release film 150, the adhesive layer 130, and the elastic layer 100 stacked in sequence.

[0352] For example, PET film can be used in release film 150, but is not limited thereto. Furthermore, the carrier film 92 or sheet protective film 94 as described above can also be used as release film 150.

[0353] Optical properties of the layers included in thin film 190

[0354] Not only the elastic layer included in the thin film 190, but also other layers can have excellent optical properties.

[0355] The refractive index of the elastic layer 100 can be less than that of the hard layer 120.

[0356] The refractive index of the elastic layer 100 can be less than that of the adhesive layers 130 and 130'.

[0357] The difference between the refractive index of the elastic layer 100 and the refractive index of the hard layer 120 can be less than 0.2, less than 0.1, or greater than 0.00001.

[0358] The difference between the refractive index of the elastic layer 100 and the refractive index of the adhesive layers 130 and 130' can be less than 0.2, less than 0.1, or more than 0.00001.

[0359] The refractive index of the hardness layer 120 can be from 1.55 to 1.75. The refractive index of the hardness layer 120 can be from 1.55 to 1.70, 1.58 to 1.68, 1.60 to 1.68, 1.62 to 1.66, or 1.62 to 1.65.

[0360] To adjust the refractive index, the hardening layer may also contain additives such as fillers. For example, the filler may be particles with an average particle size of less than 160 nm, or it may be barium sulfate particles.

[0361] The haze of hardness layer 120 can be less than 1%. The haze of hardness layer 120 can be less than 0.8%, less than 0.6%, or less than 0.5%.

[0362] The light transmittance of the hardness layer 120 can be 80% or more. For example, the light transmittance of the hardness layer can be 85% or more, 88% or more, 89% or more, 80% to 99%, 80% to 99%, 85% to 99%, or 88% to 99%.

[0363] The yellow index of hardness layer 120 is 5 or less. For example, the yellow index can be 4 or less, 3.5 or less, or 3 or less.

[0364] The tensile strength of the 120 hardness layer can be 14 kgf / mm². 2 That's all. Specifically, the tensile strength can be 16 kgf / mm. 2 Above, 18kgf / mm2 and above, 20kgf / mm 2 Above, 21 kgf / mm 2 Above or 22 kgf / mm 2 above.

[0365] The thin film 190 may also optionally include a hard coating layer, a polarizing layer, and a sensing layer disposed above or below the elastic layer. wait.

[0366] The film 190 may also include a hard coating 140 disposed on the elastic layer.

[0367] The hard coating applied to the display can be applied to hard coating 140 and can be applied without restriction, as long as no lifting or other issues occur in the bending test or other tests described below.

[0368] The thin film 190 may also include a polarizing layer 360.

[0369] The polarizing layer 360 may be disposed below one surface 100a of the elastic layer. In this case, the film 190 may include a laminate of the polarizing layer 360 and the elastic layer 100. Furthermore, the film 190 may include a laminate of the polarizing layer 360, the hardness layer 120, and the elastic layer 100 sequentially stacked. In this case, adhesive layers 130, 130' may be disposed between the polarizing layer and the elastic layer, between the polarizing layer and the hardness layer, and / or between the hardness layer and the elastic layer. Furthermore, when the adhesive layer is not disposed, adjacent layers may be bonded by hot-melt bonding.

[0370] The thin film 190 may also include a sensing layer 340.

[0371] The thin film 190 may include a laminate containing a sensing layer 340 and an elastic layer 100. Furthermore, the thin film 190 may include a laminate containing a sensing layer 340, a polarizing layer 360, and an elastic layer 100 stacked sequentially. The thin film 190 may also include a laminate containing a sensing layer 340, a hardness layer 120, and an elastic layer 100 stacked sequentially. In this case, adhesive layers 130 and 130' are respectively provided between the sensing layer and the elastic layer, between the sensing layer and the polarizing layer, between the sensing layer and the hardness layer, between the polarizing layer and the hardness layer, and / or between the hardness layer and the elastic layer. Furthermore, when the adhesive layers are not provided, adjacent layers can be bonded by welding.

[0372] Thin film 190 may have properties such as impact resistance.

[0373] Film 190 can be manufactured according to IEC 62715-6-1 standard. After undergoing 200,000 dynamic bending tests at -40°C with the elastic layer at a radius of curvature of 2 mm and a bending frequency of 2 seconds per cycle, no lifting phenomenon may occur at the interface where the elastic layer 100 is bonded to other layers. This means that, considering the relatively lower elasticity at low temperatures compared to at room or high temperatures, the elastic layer exhibits excellent resilience even in repeated bending tests over a wide temperature range.

[0374] Thin film 190 can have 2500 kJ / m 2 The above impact strength. Thin film 190 can have 3500 kJ / m. 2 The above impact strength can reach 4500 kJ / m 2 The above impact strength. Thin film 190 can have 5000 kJ / m. 2 The above impact strength can reach 10000 kJ / m 2The following impact strength. Films with this property can absorb external impacts well and are not easily broken or damaged, making them ideal for use as cover films.

[0375] Thin film 190 can have an absorbed energy of 1.4 J or more. Thin film 190 can have an absorbed energy of 1.5 J or more. Thin film 190 can have an absorbed energy of 1.6 J or more, and can have an absorbed energy of less than 2.0 J. Thin films with these properties can effectively absorb external impacts and mitigate the transmission of impacts to the internal parts that need protection, without easily damaging the film itself. Therefore, they are very suitable for use as covering films.

[0376] For film 190, the difference in yellowness before and after irradiation with 3.0W at UVB (280nm to 360nm) for 72 hours can be less than 2 and less than 1. Furthermore, the yellowness difference of the film can be less than 0.8 and less than 0.6. The yellowness difference of the film can be from 0.01 to 0.6 and from 0.01 to 0.45. Film 190 with these characteristics will not yellow even after prolonged exposure to strong UV light and can maintain excellent optical properties.

[0377] The haze of film 190 can be less than 2% or less than 1%. The haze of film 190 can be less than 0.8% or less than 0.7%. The haze of film 190 can be greater than 0.01%. When film 190 has these haze characteristics, it can possess excellent optical properties and transparency.

[0378] The light-transparent laminate has the properties of the film 190 as described above. A detailed description of the light-transparent laminate is repeated above, therefore its description is omitted.

[0379] The covering film has the characteristics of the film 190 as described above. A detailed description of the covering film is repeated above, therefore its description is omitted.

[0380] Thin film 190 can be used as a cover window for multi-layer electronic devices.

[0381] The thin film 190 can be used as a cover layer for display devices.

[0382] A cover layer is a layer that forms an outline on at least a portion of a device and serves to protect the internal components; it is not necessarily limited to being located on the outermost part of the device. In particular, when a cover layer is located on the display area of ​​a monitor, it is called a cover window.

[0383] The film 190 can be used as a cover layer for flexible or foldable multilayer electronic devices where part of the device can be folded.

[0384] The film 190 can be used as a cover layer for a rollable device that can be reversibly rolled up or unrolled, either as part or all of the device.

[0385] The thin film 190 may be included in the protective film of the display.

[0386] When the thin film 190 is used as a protective film for the display, it has an appropriate level of energy storage modulus over a wide temperature range, and thus, together with stable bending or flexible properties over a wide temperature range, it can further mitigate the degree of impact transmitted to the product by the elastic layer.

[0387] Thin film 190 also exhibits excellent durability and resilience in repeated bending or flexible environments.

[0388] By using an elastic layer 100 with a relatively stable degree of change in energy storage modulus over a wide temperature range, the thin film 190 can suppress phenomena such as buoyancy between layers in direct contact with the elastic layer. Buoyancy can occur due to modulus differences between layers in direct contact with the elastic layer during repeated bending, folding, etc. The elastic layer, while possessing excellent optical properties suitable for displays, suppresses such buoyancy to a considerable level by controlling its energy storage modulus characteristics.

[0389] The thin film 190 can be disposed on the light source at a position further out than the polarizing layer and serves as a protective layer for the light-emitting layer 320 (display device).

[0390] The thin film 190 can be disposed on the light source to protect the light-emitting layer 320 (display device) and to serve as a polarizing layer.

[0391] The thin film 190 may be disposed on one side of the light-emitting functional layer 300, which includes a light-emitting layer 320 having a light-emitting function and / or a sensing layer 340 having a sensing function such as a touch sensor in a multilayer electronic device 900. The thin film 190 may be used for the purpose of protecting the light-emitting functional layer 300.

[0392] The thin film 190 is set as a support layer for the light source and can also serve as a heat-resistant support layer.

[0393] The thin film 190 can be used as a support layer for display devices.

[0394] A support layer is a layer that forms at least a portion of the shape of a device and is used to support light source devices, etc., and is not necessarily limited to being located on the outermost part of the device.

[0395] The thin film 190 can be used as a support layer for a flexible or foldable multilayer electronic device, where part of the device can be folded.

[0396] The film 190 can be used as a support layer for a rollable device that can be reversibly rolled up or unrolled, either as part or all of the device.

[0397] The light-transparent laminate has the use of the film 190 as described above.

[0398] The covering film has the uses of the film 190 as described above.

[0399] Figure 4 A conceptual diagram illustrating the configuration of a multi-layer electronic device based on an example, using cross-sections. Figure 5 (a), (b), and (c) are conceptual diagrams describing the configuration of a multi-layer electronic device based on an example, using cross-sections. Figure 6 This is a conceptual diagram illustrating the configuration of a multilayer electronic device based on an example, using cross-sections. (Reference) Figures 4 to 6 Specifically, it describes multi-layered electronic devices, etc.

[0400] Multi-layer electronic equipment 900

[0401] In other instances, the multilayer electronic device 900 includes a resilient layer 100.

[0402] In other examples, the multilayer electronic device 900 includes a thin film 190.

[0403] In other instances, the multilayer electronic device 900 includes a light-transmitting laminate.

[0404] The multilayer electronic device 900 can be a display device, such as a large-area display device, a foldable display device, a bendable display device, or a flexible display device. The multilayer electronic device 900 can also be a bendable mobile communication device (e.g., a mobile phone) or a bendable laptop computer.

[0405] The specific details of the elastic layer 100 and the film 190 overlap with those described above, and therefore their description is omitted.

[0406] According to one example, a multilayer electronic device 900 includes a light-emitting functional layer and a thin film. The light-emitting functional layer has a display area that emits light or does not emit light according to an external signal. The thin film may be disposed on the upper surface or the back surface of the display area.

[0407] According to one example, a multilayer electronic device 900 includes a light-emitting functional layer and a thin film. The light-emitting functional layer has a display area that emits light or does not emit light according to an external signal. The thin film is disposed on a surface of the light-emitting functional layer and can cover at least a portion of the display area.

[0408] The multilayer electronic device 900 may include a thin film 190 disposed above or below the light-emitting functional layer 300.

[0409] The light-emitting functional layer 300 includes a light-emitting layer 320.

[0410] The light-emitting layer 320 includes a device that emits light according to a signal in the display device. For example, the light-emitting layer 320 may include: a signal transmission layer 322 that transmits external electrical signals to the color display layer; a color display layer 324 disposed on the signal transmission layer and displaying colors according to a given signal; and an encapsulation layer 326 that protects the color display layer. The signal transmission layer 322 may include thin-film transistors (TFTs), such as LTPS, a-Si TFTs, or Oxide TFTs, but is not limited thereto. Thin-film encapsulation (TFE) may be applied to the encapsulation layer 326, but is not limited thereto.

[0411] The light-emitting layer 320 may be disposed on the support layer 380. A layer with insulating and heat-resistant properties may be applied to the support layer 380; for example, a polyimide film, a glass layer, etc., may be used. The film 190 described above may be used as the support layer.

[0412] The light-emitting functional layer 300 may also include a sensing layer 340. As the sensing layer 340, a touch sensor or the like can be applied.

[0413] The light-emitting functional layer 300 may also include a polarizing layer 360. The polarizing layer 360 may be disposed on the light-emitting layer 320 or on the sensing layer 340.

[0414] In the multilayer electronic device 900, the elastic layer 100 or the thin film 190 may be bonded to the light-emitting functional layer 300.

[0415] In the multilayer electronic device 900, the elastic layer 100 or the thin film 190 can be used as a cover film to protect the light-emitting layer 320 (display device). Furthermore, the elastic layer 100 or the thin film 190 possesses excellent optical properties, excellent elastic recovery over a wide temperature range, and excellent durability, thus suppressing phenomena such as lifting during repeated bending and folding to a considerable level. Therefore, it has excellent practicality as a window cover or protective film.

[0416] Furthermore, the elastic layer 100 supplements the protective function (the function of protecting the inside of the cover film from external impacts) that is insufficient when using polyimide film alone as a hard layer, and maintains the protective function of the cover window using existing glass, etc., while possessing the rolling and bending durability that has been evaluated as lacking in existing glass and other cover windows. Therefore, it has excellent practicality as a cover layer, protective film, etc. for multi-layer electronic devices.

[0417] Method for preparing elastic layer 100 or film 190

[0418] The method for preparing the elastic layer 100 according to the example includes the steps of forming a polymer resin into an elastic sheet; and the step of passing an assembly of the elastic sheet 80 disposed on a carrier film 92 between rollers to provide the elastic layer 100.

[0419] The polymer resin may contain amides or their residues as repeating units. The specific descriptions of the repeating units, polymerization, etc., of the polymer resin are the same as those in the description of the elastic layer described above, therefore their descriptions are omitted.

[0420] The method for preparing the film 190 according to the example includes the steps of forming a polymer resin into an elastic sheet; and the step of passing the assembly of the elastic sheet 80 disposed on a carrier film 92 between rollers to provide an elastic layer 100.

[0421] When the film 190 further includes an additional layer as an adhesive layer 130, 130', a hardness layer 120, and / or a polarizing layer 360 in addition to the elastic layer 100, the method for preparing the film 190 further includes the step of laminating the elastic layer 100 and the additional layer.

[0422] As the polymer resin, an elastomer forming amide residues as repeating units can be used. The polymer resin can be an elastic polyamide resin or a polyether block amide resin. The elastic polyamide resin can be PA11, PA12, PA1012, PA1010, PA610, PA612, etc. The polyether block amide resin can be from Arkema, France. Evonik GmbH, Germany E, etc.

[0423] The polymer resin can be molded into an elastic sheet. Any method applicable to film preparation can be used to mold this elastic sheet, such as melt extrusion. When the elastic layer or a film (or laminate) including it is prepared using the melt extrusion method, a high-quality elastic layer can be prepared more effectively.

[0424] When the polymer resin is melt-extruded to form an elastic sheet, the melt-extruded temperature can be between 200°C and 300°C. When melt-extruded within this temperature range, the polymer resin is given fluidity without damaging the properties of the resin itself, thus allowing it to be smoothly formed into a sheet.

[0425] The elastic sheet 80 can be disposed on the carrier membrane 92.

[0426] A sheet laminate 90, including the carrier film and an elastic sheet disposed on the carrier film, is passed through a roller to be processed into an elastic layer 100 in the form of a thin film.

[0427] The rollers may be a first roller 40 and a second roller 60, with the sheet laminate 90 spaced apart. The first roller 40 may be a casting roller, and the second roller 60 may be an extrusion roller.

[0428] One surface of the sheet laminate is in contact with a casting roller, and the other surface of the sheet laminate is in contact with an extrusion roller, and can be processed into a predetermined thickness by applying pressure.

[0429] As needed, during the processing, the sheet laminate may further include a sheet protective film 94. Specifically, the sheet laminate may include a carrier film 92, an elastic sheet (or elastic layer) disposed on the carrier film, and a sheet protective film 94 disposed on the elastic sheet.

[0430] The method for preparing the elastic layer involves preparing an elastic sheet of predetermined thickness and passing it between rollers, and can provide an elastic layer controlled to have a preset thickness. Any method used in film preparation, such as controlling the thickness of the elastic sheet or passing it between rollers and controlling the thickness of the elastic layer, can be used, and its detailed description is omitted. Furthermore, the specific description of the elastic layer thickness is redundant with the above description, and therefore is also omitted.

[0431] The surface roughness of the elastic layer is controllable during its passage between the rollers. The surface roughness of one surface of the elastic layer can be controlled by the roughness of the carrier film in direct contact with that surface. The surface roughness of the other surface of the elastic layer can be controlled by the surface roughness of the scraper roller or the sheet protective film in direct contact with that surface. The descriptions of the surface roughness of the elastic layer, the carrier film, the sheet protective film, and the scraper roller are repetitive with the above description and are therefore omitted.

[0432] In the method for preparing the thin film, the elastic layer can be prepared either as a component together with a carrier film or by removing the elastic layer itself, such as the carrier film.

[0433] If necessary, the method for preparing the thin film may further include the step of removing the carrier film from the component.

[0434] If necessary, the method for preparing the film may further include the step of further depositing an adhesive layer on one or another surface of the elastic layer.

[0435] If necessary, the method for preparing the film may further include the step of depositing a hardening layer on one or another surface of the elastic layer. The hardening layer may be a polyimide layer or a glass layer.

[0436] The hardening layer can be directly bonded to the elastic layer or bonded to the elastic layer through a separately provided adhesive layer.

[0437] The method for preparing the thin film may further include applying a hard coating layer to one or the other surface of the elastic layer. The hard coating formation process can be applied without limitation to any method that forms a hard coating layer on a display protective film.

[0438] The method for preparing the thin film may further include a polarizing plate disposed on one or another surface of the elastic layer. An adhesive layer and a hardening layer may be disposed between the elastic layer and the polarizing plate, or the adhesive layer and the hardening layer may be disposed together.

[0439] The specific descriptions of films, elastic layers, and their uses are repeated above, so they are omitted.

[0440] The following detailed description, through specific embodiments, further illustrates the invention. These embodiments are merely examples to aid understanding of the invention, and the scope of the invention is not limited thereto.

[0441] Example: Preparation and Physical Property Evaluation of the Elastic Layer

[0442] Preparation of polymer resin

[0443] The following are examples or comparative examples of resins prepared for application to films including elastic layers.

[0444] - Polyether block amide (PEBA) resin

[0445] The following resin was obtained from Arkema, a French company, and used in the experiments described below: Arkema 2533 (PEBA resin 1), Arkema 5533 (PEBA resin 2), Arkema 7033 (PEBA resin 3), Arkema 55R53 (PEBA resin 4), Arkema 63R53 (PEBA resin 5), Arkema 70R53 (PEBA resin 6), Arkema 72R53 (PEBA resin 7), Arkema 80R53 (PEBA resin 8), etc.

[0446] - Polyamide (PA) resin

[0447] The following resins were obtained from Arkema, France, and used in the tests described below: PA610 (PA resin 1), PA612 (PA resin 2), PA1010 (PA resin 3), PA1012 (PA resin 4), PA12 (PA resin 5), AESNOTL (PA resin 6), PA11 (PA resin 7), etc.

[0448] -Thermoplastic polyurethane elastomer (TPU) film, polyethylene terephthalate (PET) film

[0449] The TPU used is 46510 film (aliphatic TPU) purchased from Argotec, Inc. in the United States. The PET film used is NRF PET film manufactured by SKC Corporation in South Korea.

[0450] Preparation of elastic layer

[0451] The prepared resins were placed in an extruder, melt-kneaded, and the elastic sheet was extruded into a single-layer sheet. In the case of PEBA resin 7, the applicable melt-kneading temperature was approximately 220°C, and the melt-kneading temperature was controlled within the range of approximately 200 to 300°C depending on the resin. The resulting single-layer elastic sheet was then continuously deposited onto a carrier film (a PET film with a thickness of 50 μm to 250 μm; the Ra of the PET film was 0.001 μm to 0.01 μm) to form an assembly. This assembly was then processed between casting rolls and extrusion rolls heated to 10°C to 120°C to create a laminate including the elastic layer. Next, after removing the carrier film, the approximately 100 μm thick elastic layer was used as a film in the following examples for physical property evaluation. Each film is indicated by the same name as the resin described above.

[0452] In the absence of a carrier membrane, a film prepared using the same method and thickness as described above was used as a comparative example, and its physical properties were evaluated.

[0453] Example: Physical performance evaluation of elastic layers

[0454] Assessment of the low-temperature damage index of the elastic layer, etc.

[0455] Tensile strength, elongation, and other parameters were measured according to ASTM D882 standards using a Universal Material Testing Machine (UTM) from Instron, UK, at a travel speed of 50 mm / min. However, a temperature control chamber was connected to the UTM, and temperatures were controlled and measured at +20°C, -10°C, and -40°C. The measured tensile strength, elongation, and tensile modulus are shown in Table 1 below.

[0456] The low-temperature damage index was evaluated using film samples of PEBA resin 5 and PEBA resin 6, and the PET film and TPU film prepared as comparative examples were evaluated together.

[0457] Table 1

[0458]

[0459] *The low-temperature damage index (MPa) is the value obtained by subtracting the tensile strength (MPa) from the tensile modulus (MPa) measured at low temperatures (e.g., below -10°C).

[0460] *Difference in low-temperature tensile modulus™ -40-20 It is expressed as follows.

[0461] Mode

[0462] TM -40-20 =TM -40 -TM 20

[0463] In the formula, TM -40-20 For low-temperature tensile modulus, TM n This is the tensile modulus measured at n℃.

[0464] Referring to Table 1, PEBA film exhibits excellent elongation across the entire temperature range and also displays low tensile modulus at low temperatures, thus indicating a lower incidence of low-temperature breakage compared to PET or TPU. Furthermore, in the case of the low-temperature damage index, which represents the difference between tensile strength and tensile modulus, PEBA film shows values ​​below 1300 MPa at both -10°C and -40°C, suggesting a considerably low incidence of damage at both high and low temperatures. In contrast, PET film exhibits high values ​​exceeding 4000 MPa, indicating a higher likelihood of breakage at low temperatures. TPU film also shows a relatively high value at low temperatures, a difference from the examples.

[0465] Evaluation of the energy storage modulus of the elastic layer

[0466] The storage modulus E' was evaluated using a DMAQ800 instrument from TA Instruments, in accordance with ASTM D4065. The results, measured in MPa at 1 Hz and 2 °C / min in Dynamic Mechanical Analysis (DMA) tension mode over a temperature range of -40 °C to +80 °C, are shown in Table 2. The amplitude was 5 μm, and the preforce was 0.01 N.

[0467] Together with the above, the results of evaluating the storage modulus using PET film and TPU film at temperatures expressed in the same manner as above are shown. The PET film is a 50 μm thick NRF film prepared by SKC Corporation of South Korea, and the TPU is a 100 μm thick monolayer film of 46510 from Argotec Corporation of the United States.

[0468] All sample films were evaluated as described above after 15 days of acclimatization at 23°C and 50% RH.

[0469] Table 2

[0470]

[0471]

[0472]

[0473] *The energy storage modulus index KSM is represented by the following formula 1.

[0474] [Formula 1]

[0475]

[0476] The high-temperature energy storage modulus ratio R80 / 20 is expressed by the following formula 1-a.

[0477] [Equation 1-a]

[0478]

[0479] The low-temperature energy storage modulus ratio R-40 / 20 is expressed by the following formula 1-b.

[0480] [Equation 1-b]

[0481]

[0482] The difference in low-temperature energy storage modulus is represented by the following formula 1-c.

[0483] [Equation 1-c]

[0484] D -40-20 =SM -40 -SM 20

[0485] In the formula, SM n The storage modulus (MPa) is measured at a temperature of n °C.

[0486] Measurement of surface roughness, yellowness, and yellowing degree of the elastic layer

[0487] Surface roughness was evaluated using a MITUTOYO SJ-310 caliber from Japan, in accordance with ASTM D4417.

[0488] Haze was measured using a Nippon Denshoku NDH-7000N haze meter according to ISO 14782 standard. Transmittance was also measured using the same equipment, and a transmittance of 85% or higher was confirmed for all samples.

[0489] Yellow Index (YI) was measured using a Hunterlab Colormeter Ultra ScanPro in YI E313 (D65 / 10) mode. A value below 1 was rated "Pass", and a value above 1 was rated "Fail".

[0490] Delta-YI was measured using a UVB lamp (SANKYO DENKI G15T8E, 280–360 nm wavelength) before and after exposure to ultraviolet light at an output of 3.0 W for 72 hours. The result is shown as the difference between the YI before and after exposure.

[0491] Table 3

[0492]

[0493] Restoring force and dynamic bending assessment of elastic layer

[0494] An 80mm × 25mm film was fixed at 15mm intervals at both ends using jigs, with the stressed film length set to 50mm × 25mm. The film was stretched by 2% at a speed of 50mm / min, then restored to its original length at 50mm / min, repeating this cycle for 100 cycles. The length between the jigs (Xf) of the film after 100 cycles was measured and compared to the initial length between the jigs (Xo, 50mm), and the recovery index was evaluated according to Formula 3.

[0495] Formula 3

[0496]

[0497] In Equation 3, Xo is the length (mm) of the initial elastic layer, X 2％ Xf is the length (mm) of the elastic layer after stretching by 2%. Xf is the length (mm) of the elastic layer after stretching by 2% at a speed of 50 mm / min and then restoring to the original length at a speed of 50 mm / min, and so on, which is taken as one cycle and performed for 100 cycles.

[0498] A dynamic folding test was performed according to the IEC 62715-6-1 standard. The film was subjected to 200,000 dynamic folding tests at -40°C with a curvature radius of 2 mm and a folding frequency of 2 seconds per cycle to determine if cracks appeared. If cracks appeared, the evaluation was "Fail"; if no cracks were observed visually, the evaluation was "Pass".

[0499] Table 4

[0500] Recovery Index* Dynamic bending assessment PA resin 7 60 pass PEBA resin 2 88 pass PEBA resin 4 82 pass PEBA resin 7 75 pass Other resin 1 (PET) 50 fail Other resin 2 (TPU) 90 fail Comparative example 72 pass

[0501] Referring to Tables 2 to 4, compared with the elastic layers of the comparative examples, the prepared elastic layers all exhibited low haze values, which is considered to be related to the surface roughness values ​​to some extent.

[0502] In Delta-YI, the examples using PA or PEBA showed significantly superior results compared to other resins. In particular, the results of the examples were also superior compared to other resins 1 used as PET films, but significantly superior compared to other resins 2 using TPU. Furthermore, considering that the TPU used as another resin was an aliphatic TPU known to have superior UV durability than aromatic TPUs, the UV durability was evaluated as significantly superior, along with the films of the examples.

[0503] In the dynamic bending evaluation conducted at -40°C, both other resins 1 and 2 were rated as "fail", thus confirming that the films of other resins are insufficient for bending or folding applications over a wide temperature range, including low temperatures.

[0504] With respect to the recovery index, physical properties may vary depending on the resin used, but overall, the examples as PEBA films or PA films show excellent results, with PEBA films showing better results than PA films.

[0505] Regarding the recovery index, the films of the embodiments exhibit slightly lower, or at the same or higher, physical properties compared to other resin 2 films using TPU films. Conversely, compared to TPU films, the films of the embodiments show superior results in ultraviolet (UV) durability (yellowing properties) and dynamic bending evaluation at low temperatures.

[0506] Considering these characteristics, the elastic layer of the example, or the film including the elastic layer, is considered to be of excellent practicality in foldable displays and the like, which can be repeatedly bent or folded over a wide temperature range from low to high temperatures.

[0507] Refractive index and phase difference measurement of elastic layer

[0508] The refractive index was measured using the DR-A1-plus model from ATAGO Corporation of Japan at a temperature of 23 degrees Celsius and a wavelength of 550 nm.

[0509] The in-plane phase difference and the thickness direction phase difference were measured using the results from an Otsuka ReT S-100 at a wavelength of 550 nm.

[0510] For the refractive index, the polymer resins described below were used, and individual samples were tested using the same method as described above. The names of the resins used to prepare each sample are shown in Table 5, and the degree of crystallinity for PA resins is also shown.

[0511] For in-plane phase difference, samples of different thicknesses were prepared and tested, and the results are shown in Table 6. The comparative sample was used in the same manner as the sample described above.

[0512] All resins were supplied and used by Arkema, a French company.

[0513] Table 5

[0514]

[0515] Table 6

[0516] Thickness (μm) Re(nm) Rth(nm) PEBA4 100 191.4 1558.5 PEBA7 100 42.1 250.5 PEBA7 50 20.4 212.7 PET(NRF) 40 427.1 6574

[0517] Referring to Tables 5 and 6, the desired level of refractive index can be obtained, and the phase difference is confirmed to be at a level suitable for optical applications.

[0518] Example: Thin film preparation and physical property evaluation

[0519] Thin film preparation

[0520] Preparation of the cover film test piece: On a 50 μm thick transparent polyimide film (prepared by SKC, Korea), a 100 μm thick commercially available OCA from 3M (USA) with a storage modulus difference of -100 kPa to +100 kPa between -40°C and +80°C was used as an adhesive layer. A 100 μm thick elastic layer (a film prepared with PEBA resin 7) prepared above was then laminated onto the adhesive layer to prepare the cover film test piece of Example 1. Figure 2 (b) structure).

[0521] Covering film test pieces were prepared in the same manner as the covering film of Example 1, but the types of elastic layers used were as shown in Table 4 below, and they were used as Example 2 and Comparative Example 1, respectively.

[0522] Measurement of physical properties of thin films

[0523] 1) Evaluation of tensile impact strength

[0524] The tensile-impact strength of the elastic layer was evaluated according to JIS K 7160 standard. The measurement temperature was 23℃, 50%RH, and the measurement conditions were a 4.0J pendulum with a resonance angle of 150°. The impact strength and absorbed energy were measured, and the results are shown in Table 7 below.

[0525] 2) Bending / bending assessment and droplet assessment of thin films as laminates

[0526] Dynamic folding test: Using a protective film test piece, according to IEC 62715-6-1 standard, a curvature radius of 2 mm and a bending degree of 2 seconds / cycle were applied, and a total of 200,000 tests were conducted. If folding occurs, it is indicated as "X"; if folding does not occur, it is indicated as "O". The results are shown in Table 8 below.

[0527] Static bending test: Using a protective film test piece, the test is conducted according to IEC 62715-6-1 standard with a curvature radius of 2 mm. If the film floats up after 24 hours, it is marked as "X"; if it does not float up, it is marked as "O". The results are shown in Table 8 below.

[0528] Pen droplet evaluation: Approximately 5.4g of ballpoint pen (Bick Corporation, USA) was used. A drop was placed on the film sample, which was a laminate, with the tip of the pen cap 9 cm above the surface. If the film surface was in good condition, it was evaluated as "pass"; if cracks appeared on the film surface, it was evaluated as "fail". The results are shown in Table 8 below.

[0529] Transmittance / Haze: Transmittance and haze were measured using an NDH7000 (manufactured by Nippon Densh Oku). A haze of less than 1% was rated "pass," and a haze greater than 1% was rated "fail." For transmittance, a visible light transmittance of 90% or more was rated "pass," and a transmittance less than 90% was rated "fail." The results are shown in Table 8 below.

[0530] Table 7

[0531] <![CDATA[Impact strength (kJ / m 2 )]]> Absorbed energy (J) Other resin 1 (PET) 2900 1.43 Other resin 2 (TPU) 1900 1.05 PEBA resin 7 5400 1.66

[0532] Table 8

[0533]

[0534] Referring to Table 7, the impact strength of the film using PEBA resin 7 is significantly higher than that of films using other resins 2 (TPU) or PET, thus confirming its very strong impact resistance. Regarding energy absorption, the film using PEBA resin 7 exhibits significantly superior performance compared to films using other resins (TPU) or PET.

[0535] This indicates that TPU outperforms PET in terms of energy storage modulus, but TPU is inferior to PET in terms of tensile impact strength. Furthermore, these results also demonstrate that PEBA films exhibit excellent energy storage modulus and tensile impact strength properties.

[0536] Referring to Table 8, the laminate of Example 1, which uses the PEBA resin 7 prepared above, received a "Pass" rating in all aspects of dynamic bending evaluation at low and high temperatures, static bending evaluation at low and high temperatures, droplet evaluation, light transmittance, and haze, and was rated as excellent in all measured physical properties. Conversely, Example 2, which uses the same adhesive layer and PI film as Example 1 but uses TPU instead of PEBA resin 7, has excellent properties, but was rated "Fail" in the low-temperature dynamic bending evaluation, indicating that it may float up when repeatedly bent at low temperatures. Conversely, Comparative Example 1, which uses PET, was rated "Fail" in both dynamic and static bending evaluations, and was therefore assessed as having physical properties that make it difficult to use as a flexible or rollable cover film. Comparative Example 1 is the result of testing the polyimide film alone, and was rated "Fail" in the droplet evaluation, indicating that it is difficult to obtain the impact protection effect as a cover film using only the polyimide film alone.

[0537] The preferred embodiments of the present invention have been described in detail above, but the scope of protection of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts of the present invention as defined in the appended claims are also within the scope of the present invention.

[0538] Explanation of reference numerals in the attached figures

[0539] 100: Elastic layer; 100a: Elastic layer - surface

[0540] 100b: The other surface of the elastic layer; 120: The hard layer.

[0541] 130, 130': Adhesive layer; 140: Hard coating layer

[0542] 150: Release film; 80: Elastic sheet

[0543] 92: Carrier membrane; 94: Sheet protective film

[0544] 40: First roll, casting roll; 60: Second roll - extrusion roll

[0545] 90: Sheet laminate 190: Film-film laminate

[0546] 300: Light-emitting functional layer; 320: Light-emitting layer

[0547] 322: Signal transmission layer; 324: Color development layer

[0548] 326: Encapsulation layer; 340: Sensing layer

[0549] 360: Polarizing layer; 380: Support layer

[0550] 900: Multilayer electronic equipment

Claims

1. A thin film, wherein, The film includes an elastic layer. The elastic layer is an extruded film prepared by melt extrusion of polyether block amide resin. The polyether block amide resin comprises two phases: a polyamide region as a rigid region and a polyether region as a flexible region. The polyamide region is a hard region of a crystalline phase with a melting point of 130°C to 180°C. The polyether block is derived from polyethylene glycol, polypropylene glycol, or polybutane glycol. The refractive index of the elastic layer is 1.48 to 1.

58. The low-temperature damage index is the difference between the tensile modulus and the tensile strength at a specific temperature. The elastic layer has a low-temperature damage index of less than 1300 MPa at -40°C. The elastic layer has a strength of 2500 kJ / m 2 Above and 10000 kJ / m 2 The following impact strengths, The elastic layer has an absorbed energy of more than 1.4J and less than 2.0J.

2. The thin film according to claim 1, wherein, The elastic layer has a tensile modulus of less than 3000 MPa at -10°C.

3. The thin film according to claim 1, wherein, The in-plane phase difference Re of the elastic layer is less than 300 nm.

4. The film according to claim 1, wherein, The elastic layer has a storage modulus of less than 2300 MPa at -40°C.

5. The film according to claim 1, wherein, The roughness reference value is the larger of the surface roughness Ra1 of one surface and the surface roughness Ra2 of the other surface. The elastic layer has a roughness reference value of less than 0.5 μm.

6. A thin film, wherein, The film includes an elastic layer and a hard layer disposed on one surface of the elastic layer. The elastic layer is an extruded film prepared by melt extrusion of polyether block amide resin. The polyether block amide resin comprises two phases: a polyamide region as a rigid region and a polyether region as a flexible region. The polyamide region is a hard region of a crystalline phase with a melting point of 130°C to 180°C. The polyether block is derived from polyethylene glycol, polypropylene glycol, or polybutane glycol. The elastic layer has a tensile modulus of less than 2000 MPa and more than 500 MPa at -40°C. The elastic layer has a strength of 2500 kJ / m 2 Above and 10000 kJ / m 2 The following impact strengths, The elastic layer has an absorbed energy of 1.4 J or more and 2.0 J or less. The refractive index of the elastic layer is less than that of the hard layer.

7. The film according to claim 6, wherein, The elastic layer has an elongation of over 200% at -10°C.

8. The film according to claim 6, wherein, The hardening layer includes a polyimide film or a glass layer. The total thickness of the film is less than 3000 μm.

9. The film according to claim 6, wherein, The elastic layer has a light transmittance of over 85% and a haze of less than 3%.

10. A light-transmitting laminate comprising the thin film according to claim 1 or 6.

11. A method for preparing a thin film, used to prepare the thin film according to claim 1 or 6, in, include: The step of forming an elastic sheet from a polymer resin containing amides or their residues as repeating units; and The step of passing the first component of the elastic sheet disposed on the carrier film between the rollers to provide a second component including an elastic layer located on the carrier film.

12. A covering film comprising the film according to claim 1 or 6.

13. The covering film according to claim 12, wherein, The covering film also includes a glass layer disposed on one or the other surface of the elastic layer. The glass layer is tempered glass with a thickness of less than 200 μm.

14. A multilayer electronic device, wherein, The multilayer electronic device includes a light-emitting functional layer and a thin film. The light-emitting functional layer has a display area that emits light or does not emit light according to external signals. The film is the film according to claim 1 or 6. The thin film is disposed on the upper surface or the back surface of the display area.

15. A multilayer electronic device, wherein, Including a light-emitting functional layer and a thin film, The light-emitting functional layer has a display area that emits light or does not emit light according to external signals. The film is the film according to claim 1 or 6. The thin film is disposed on one surface of the light-emitting functional layer and covers at least a portion of the display area.

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