Polyamide film, method for manufacturing the same, and cover window and display device containing the same

Abstract

To provide a polyamide-based film excellent in optical characteristics and mechanical characteristics, and a manufacturing method therefor.SOLUTION: The polyamide-based film comprises a polyamide-based polymer and has a first IR peak having a maximum value in a section where the wavenumber is 2,950 cm-1 to 2,900 cm-1 and a second IR peak having a maximum value in a section where the wavenumber is 2,875 cm-1 to 2,825 cm-1, on an IR spectrum, wherein the area of the first IR peak may be 1.4 times or less relative to the area of the second IR peak.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] Examples of implementations include polyamide films with excellent optical and mechanical properties, methods for manufacturing the same, and cover windows and display devices containing the same. [Background technology]

[0002] Polyamide polymers exhibit excellent resistance to friction, heat, and chemicals, and are used in primary electrical insulation materials, coatings, adhesives, extrusion resins, heat-resistant paints, heat-resistant plates, heat-resistant adhesives, heat-resistant fibers, and heat-resistant films.

[0003] Polyamides are used in a variety of fields. For example, polyamides are made in powder form and used as coatings for metals or magnetic wires, and are mixed with other additives depending on the application. Polyamides are also used in combination with fluoropolymers as coatings for decoration and corrosion prevention, and play a role in bonding the fluoropolymers to metal substrates. Furthermore, polyamides are used to coat kitchen utensils, and due to their heat and chemical resistance, they are also used as membranes in gas separation, and are used in equipment to filter contaminants such as carbon dioxide, hydrogen sulfide, and impurities in natural gas wells.

[0004] Recently, polyamide films have been developed that are less expensive while possessing excellent optical, mechanical, and thermal properties, by forming polyamides into films. Such polyamide films can be applied to display materials such as organic light-emitting diodes (OLEDs) or liquid crystal displays (LCDs), and can be used as anti-reflective films, compensating films, or phase difference films when achieving phase difference properties.

[0005] When applying such polyamide films to foldable displays, flexible displays, and other applications, optical properties such as transparency and colorlessness, as well as mechanical properties such as flexibility and hardness, are required. However, optical properties and mechanical properties generally have a trade-off relationship; improving mechanical properties may reduce optical properties.

[0006] Therefore, there is a continuing need for research into polyamide films that have improved mechanical and optical properties. [Overview of the project] [Problems that the invention aims to solve]

[0007] The practical application aims to provide a polyamide-based film with excellent optical and mechanical properties, a method for manufacturing the same, and a cover window and display device containing the same. [Means for solving the problem]

[0008] One example of a polyamide film contains a polyamide polymer, and the 2θ value on the XRD (X-ray diffraction) graph includes a first XRD peak having a maximum value in the interval between 10° and less than 20°, and the full width at half maximum of the first XRD peak may be 6° or less.

[0009] A cover window for a display device according to one implementation example includes a polyamide film and a functional layer, wherein the polyamide film includes a first XRD peak having a maximum value in the interval between 10° and less than 20° of the 2θ value on the XRD graph, and the full width at half maximum of the first XRD peak may be 6° or less.

[0010] A display device according to one embodiment includes a display unit and a cover window disposed on the display unit, the cover window includes a polyamide film and a functional layer, the polyamide film includes a first XRD peak having a maximum value in the interval between 10° and less than 20° of the 2θ value on the XRD graph, and the full width at half maximum of the first XRD peak may be 6° or less.

[0011] One example of a method for producing a polyamide film includes the steps of: polymerizing a diamine compound and a dicarbonyl compound in an organic solvent to prepare a polymer solution containing a polyamide polymer; casting the polymer solution to produce a gel sheet; and heat-treating the gel sheet.

[0012] One example of a polyamide film contains a polyamide polymer and has a wavenumber of 2950 cm⁻¹ on the IR spectrum. -1 ~2900cm -1 The first IR peak, which has the maximum value in the section, and wavenumber 2875 cm -1 ~2825cm -1 The interval includes a second IR peak with a maximum value, and the area of ​​the first IR peak may be 1.4 times or less the area of ​​the second IR peak.

[0013] A cover window for a display device according to one implementation example includes a polyamide film and a functional layer, wherein the polyamide film has a wavenumber of 2950 cm⁻¹ on the IR spectrum. -1 ~2900cm -1 The first IR peak, which has the maximum value in the section, and wavenumber 2875 cm -1 ~2825cm -1 The area of ​​the first IR peak may be 1.4 times or less the area of ​​the second IR peak, and the area of ​​the first IR peak may include a second IR peak having a maximum value in the interval.

[0014] A display device according to one embodiment includes a display unit and a cover window disposed on the display unit, the cover window includes a polyamide film and a functional layer, the polyamide film has a wavenumber of 2950 cm⁻¹ on the IR spectrum.-1 ~2900 cm -1 A first IR peak having a maximum value in the range and a wavenumber of 2875 cm -1 cm -1 ~, 2825 cm -1 A second IR peak having a maximum value in the range, and the area of the first IR peak can be 1.4 times or less that of the second IR peak.

[0015] A method for producing a polyamide film according to one embodiment includes a step of polymerizing a diamine compound and a dicarbonyl compound on an organic solvent to prepare a polymer solution containing a polyamide polymer, a step of casting the polymer solution to produce a gel sheet, and a step of heat-treating the gel sheet.

Advantages of the Invention

[0016] When separating the XRD peaks of the XRD graph, a polyamide film according to one embodiment has a half-value width of the first XRD peak located in the range of 2θ values of 10° or more and less than 20° of 6° or less, and the crystal plane spacing of the crystalline component corresponding to the first XRD peak is relatively uniform. Therefore, while having excellent optical properties (low yellowness and haze and high light transmittance), mechanical properties (modulus, scratch resistance, etc.) can be improved.

[0017] For example, the percentage of the half-value width of the first XRD peak with respect to the sum of the half-value width of the first XRD peak and the half-value width of the second XRD peak is 40% or less, and the crystal plane spacing of the wide-spacing crystal form is relatively uniform. As a result, the modulus, transmittance, and scratch resistance of the polyamide film can be improved, and the haze and yellowness can be reduced.

[0018] A polyamide film according to one embodiment has an area of a first IR peak located in the range of wavenumbers 2950 cm -1 ~2900 cm -1 and an area of a second IR peak located in the range of wavenumbers 2875 cm -1 ~2825 cm -1It is 1.4 times or less the second IR peak located in the interval, and may have excellent modulus, transmittance, and low haze and yellowness.

[0019] In some examples of implemented polyamide films, the area of ​​the first IR peak is 0.6 or more relative to the area of ​​the second IR peak. Because the difference between the areas of the first and second IR peaks is small, the chemical bonds corresponding to the first IR peak and the chemical bonds corresponding to the second IR peak exist in a ratio that does not show a large difference, and properties such as modulus, transmittance, haze, and yellowness can all be improved.

[0020] Furthermore, the polyamide-based films used in the real-world examples possess excellent mechanical and optical properties, making them useful for application in cover windows for display devices and foldable / flexible display devices. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 shows a cross-sectional view of a display device based on one implementation example. [Figure 2] Figure 2 shows a schematic flowchart of a method for manufacturing a polyamide film based on one example. [Figure 3] Figure 3 is a schematic flowchart illustrating the manufacturing steps of a polyamide polymer solution based on some implementation examples. [Figure 4] Figure 4 shows the XRD analysis graph (diffractogram) for the polyamide film of Example 1. [Figure 5] Figure 5 shows the FT-IR analysis spectra of polyamide films for the examples and comparative examples. [Figure 6] Figure 6 shows the FT-IR analysis spectrum for the polyamide film of Example 7. [Figure 7] Figure 7 shows the FT-IR analysis spectrum for the polyamide film of Comparative Example 5. [Figure 8]Figure 8 shows the FT-IR analysis spectrum of the polyamide film of Comparative Example 6. [Modes for carrying out the invention]

[0022] Hereinafter, examples of implementations will be described in detail with reference to the accompanying drawings, so that those with ordinary skill in the art to which the present invention pertains can easily carry them out. However, the examples of implementation may be carried out in various different forms and are not limited to those described herein.

[0023] In this specification, when a film, window, panel, or layer is described as being formed "on" or "under" another film, window, panel, or layer, "on" and "under" include all those formed "directly" or "indirectly" through other components. The criteria for on / under each component are explained based on the drawings. Note that the sizes of components in the drawings may be exaggerated for illustrative purposes and do not represent the actual sizes applied. Throughout the specification, the same reference numeral refers to the same component.

[0024] In this specification, when a part is said to "include" a component, unless otherwise stated, it means that it may include other components rather than excluding them.

[0025] In this specification, singular expressions are interpreted as including singular or plural, as interpreted in the context, unless otherwise specified.

[0026] Furthermore, all figures and expressions describing the amounts of components, reaction conditions, etc., as described herein should be understood to be modified by the term "approximately" unless otherwise specified.

[0027] In this specification, terms such as "first," "second," etc., are used to describe various components, and such components are not limited to those components. The terms are used solely to distinguish one component from another.

[0028] Furthermore, in this specification, "substituted" means, unless otherwise specified, that the molecule is substituted with one or more substituents selected from the group consisting of deuterium, -F, -Cl, -Br, -I, hydroxyl group, cyano group, nitro group, amino group, amidino group, hydrazine group, hydrazone group, ester group, ketone group, carboxyl group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkoxy group, substituted or unsubstituted alicyclic organic group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted aryl group, and substituted or unsubstituted heteroaryl group, and the aforementioned substituents may bond to each other to form a ring.

[0029] [Polyamide film] One example provides a polyamide film that not only has excellent optical properties such as high transmittance, low haze, and low yellowness, but also excellent scratch resistance and / or modulus.

[0030] One example of a polyamide-based film includes a polyamide-based polymer.

[0031] The polyamide film may contain XRD peaks corresponding to crystalline phase components on an XRD graph. The XRD peaks may be a single XRD peak or a combined XRD peak containing multiple single XRD peaks, and the multiple XRD peaks contained in the combined XRD peak may be separated into individual single XRD peaks by an XRD analysis method and program. In some implementations, the single XRD peaks and combined XRD peaks may include a first XRD peak having a maximum value in the interval between 10° and less than 20° for the 2θ value.

[0032] For example, the maximum value or highest point of the first XRD peak may be located in the interval between 10° and less than 20° for the 2θ value.

[0033] In some implementations, the combined XRD peak may further include a second XRD peak. In some implementations, the combined XRD peak may consist of the sum of the first XRD peak and the second XRD peak.

[0034] For example, the second XRD peak may have its maximum value in the interval between 20° and 25° for the 2θ value. The maximum value or highest point of the second XRD peak may be located in the interval between 20° and 25° for the 2θ value.

[0035] The first XRD peak and the second XRD peak can then be added together to form a combined XRD peak. In some implementations, the combined XRD peak may be located in the range of 2θ values ​​from 2° to 40°, preferably from 5° to 35°.

[0036] As used herein, "XRD peak" may mean an XRD pattern or its shape that deviates from a particular regression, for example, when an XRD pattern outside the interval in which the XRD peak is located on an XRD graph has a specific regression that can be expressed by a function.

[0037] The aforementioned function is, for example, y=ae x It can be an exponential function represented by +b, where a and b can be constants.

[0038] The aforementioned specific regression can be defined as the baseline on the XRD graph. For example, the baseline may correspond to the XRD pattern of the amorphous component in the polyamide polymer or film, and the XRD peaks may correspond to the XRD pattern of the crystalline component.

[0039] In this case, the XRD peak may be defined as the portion where the intensity value is greater than that of the baseline (the portion located above the baseline). The baseline may be provided as the bottom of the XRD peak.

[0040] In some implementations, the full width at half maximum (FWHM) of the XRD peak can be measured. For example, the FWHM can be defined as the width in the direction parallel to the tangent line, when the maximum distance (maximum height) of the XRD peak from the XRD pattern is derived from the tangent line to any point on the baseline in a direction perpendicular to the tangent line.

[0041] Among the various crystal forms with interplane spacings that appear in XRD patterns, those with relatively wide interplane spacings can be defined as wide-spacing crystal forms, and those with relatively narrow interplane spacings can be defined as narrow-spacing crystal forms.

[0042] In some implementations, the crystalline component corresponding to the first XRD peak may contain a high proportion of widely spaced crystal forms with relatively wide interplane spacing, while the crystalline component corresponding to the second XRD peak may contain a high proportion of narrowly spaced crystal forms with relatively narrow interplane spacing.

[0043] The full width at half maximum (FWHM) of the first XRD peak may be 6° or less. In this case, the variation in the interplane spacing of the crystalline component corresponding to the first XRD peak may be small. For example, the uniformity of the interplane spacing of widely spaced crystals may increase, improving both the mechanical properties of the polyamide film, such as scratch resistance and modulus, and the optical properties, such as transmittance, haze, and yellowness. Preferably, the FWHM of the first XRD peak may be 5.8° or less or 5.6° or less. Alternatively, the FWHM of the first XRD peak may be 5.0° or more, 5.2° or more, 5.4° or more, or 5.5° or more.

[0044] In some implementations, the percentage of the full width at half maximum (FWHM) of the first XRD peak relative to the sum of the FWHM of the second XRD peak and the FWHM of the first XRD peak may be 40% or less. In this case, for example, the uniformity between crystal planes of the wide-spaced crystal form may be higher than the uniformity between crystal planes of the narrow-spaced crystal form. In this case, the wide-spaced crystal form may have relatively uniform inter-crystal plane spacing. Therefore, both the mechanical properties of the polyamide film, such as scratch resistance and modulus, and the optical properties, such as transmittance, haze, and yellowness, may be improved. Preferably, the percentage of the FWHM of the first XRD peak may be 38% or less or 36% or less.

[0045] Polyamide films, based on some realization examples, show a wavenumber of 3000 cm⁻¹ in the IR spectrum. -1 ~2800cm -1 The interval may include the first IR peak and the second IR peak.

[0046] In some implementation examples, the first IR peak is at wavenumber 2950 cm⁻¹. -1 ~2900cm -1 This may include the maximum value within the interval. For example, the highest point of the first IR peak is at wavenumber 2950 cm. -1 ~2900cm -1 It can be located within the section.

[0047] The aforementioned second IR peak is at wavenumber 2875 cm⁻¹. -1 ~2825cm -1 This may include the maximum value within the interval. For example, the highest point of the second IR peak is wavenumber 2875 cm. -1 ~2825cm -1 It can be located within the section.

[0048] In some implementation examples, the first IR peak is at a wavenumber of approximately 2960 cm⁻¹. -1 ~2895cm -1 Appearing in this section, the aforementioned second IR peak has a wavenumber of approximately 2890 cm⁻¹. -1 ~2820cm -1 It can appear in the section.

[0049] The amide groups (-C(=O)NH-) contained in the polyamide polymer can form hydrogen bonds with adjacent amide groups (other amide groups within the molecule) that become close when the polymer is bent, provided the polymer has sufficient length. These hydrogen bonds are formed between the oxygen and hydrogen of the amide group, and may also be formed between the nitrogen and hydrogen.

[0050] Alternatively, amide groups contained in different polyamide polymers may form hydrogen bonds (intermolecular hydrogen bonds) with each other. Therefore, at least four types of hydrogen bonds may be formed, including intramolecular oxygen-hydrogen bonds, intramolecular nitrogen-hydrogen bonds, intermolecular oxygen-hydrogen bonds, and intermolecular nitrogen-hydrogen bonds.

[0051] In the implementation example, the first IR peak and the second IR peak may be due to the hydrogen bonding. For example, of the four types of hydrogen bonding, some (hereinafter referred to as the first hydrogen bond group) may correspond to the first IR peak, and the remainder (hereinafter referred to as the second hydrogen bond group) may correspond to the second IR peak.

[0052] For example, one of the intramolecular hydrogen bonds and intermolecular hydrogen bonds may correspond to the first IR peak, and the other to the second IR peak. Alternatively, one of the oxygen-hydrogen bonds and nitrogen-hydrogen bonds may correspond to the first IR peak, and the other to the second IR peak.

[0053] In some implementation examples, the polyamide polymer is C sp3 -H bonds are not included. Therefore, the IR spectrum is at wavenumber 3000 cm⁻¹. -1 ~2800cm -1 In the section, C sp3 - May not contain IR peaks caused by H, wavenumber 3000 cm -1 ~2800cm -1 In this section, IR peaks caused by the aforementioned hydrogen bonding may appear.

[0054] The area of ​​the first IR peak may be 1.4 times or less than the area of ​​the second IR peak. In this case, since the difference in the proportion of the first hydrogen bond group and the second hydrogen bond group is not large, the optical properties such as light transmittance, haze, and yellowness, and the mechanical properties such as modulus of the polyamide film can be improved. Preferably, the area of ​​the first IR peak may be 1.3 times or less, 1.2 times or less, or 1.1 times or less than the area of ​​the second IR peak.

[0055] In some implementation examples, the area of ​​the first IR peak may be 0.6 times or more, 0.7 times or more, 0.8 times or more, or 0.9 times or more than the area of ​​the second IR peak.

[0056] In some implementations, the area of ​​the first IR peak may be 0.8 times or more and 1.2 times or less the area of ​​the second IR peak. In this case, the first hydrogen bond group and the second hydrogen bond group are present in substantially equal amounts, which can improve the optical and mechanical properties of the polyamide film. Preferably, the area of ​​the first IR peak may be 0.9 times or more and 1.1 times or less the area of ​​the second IR peak.

[0057] The area of ​​the IR peak can be obtained by subtracting the noise area from the total area of ​​the interval in the IR spectrum where the IR peak appears. For example, a straight line connecting the start and end points of the IR peak is defined as the baseline, and the region below the baseline (the region with low absorbance) may correspond to the noise.

[0058] Refractive index (n) in the x-direction of polyamide films based on implementation examples. x ) could be 1.60-1.70, 1.61-1.69, 1.62-1.68, 1.64-1.68, 1.64-1.66, or 1.64-1.65.

[0059] Furthermore, the refractive index (n) in the y direction of the polyamide film. y) could be 1.60-1.70, 1.61-1.69, 1.62-1.68, 1.63-1.68, 1.63-1.66, or 1.63-1.64.

[0060] Furthermore, the refractive index (n) in the z direction of the polyamide film z ) could be 1.50-1.60, 1.51-1.59, 1.52-1.58, 1.53-1.58, 1.54-1.58, or 1.54-1.56.

[0061] When the refractive index values ​​of the polyamide film in the x, y, and z directions are within the aforementioned range, the film, when applied to a display device, can achieve excellent visibility not only from the front but also from the side, and a wide viewing angle.

[0062] In-plane phase difference (R) of polyamide film based on implementation examples o The in-plane phase difference (R) of the polyamide film may be 800 nm or less. Specifically, the in-plane phase difference (R) of the polyamide film o ) may be 700nm or less, 600nm or less, 550nm or less, 100nm to 800nm, 200nm to 800nm, 200nm to 700nm, 300nm to 700nm, 300nm to 600nm, or 300nm to 540nm.

[0063] Furthermore, the phase difference in the thickness direction of the polyamide film (R) in the implementation example. th ) may be 5000 nm or less. Specifically, the phase difference in the thickness direction of the polyamide film (R th ) may be below 4800nm, below 4700nm, below 4650nm, 1000nm-5000nm, 1500nm-5000nm, 2000nm-5000nm, 2500nm-5000nm, 3000nm-5000nm, 3500nm-5000nm, 4000nm-5000nm, 3000nm-4800nm, 3000nm-4700nm, 4000nm-4700nm, or 4200nm-4650nm.

[0064] Here, the in-plane phase difference (in-plane retardation, Ro ) is the anisotropy of the refractive index of two orthogonal axes in the plane of the film (△n xy =|n x -n y |) and the product of the film thickness (d) (△n xy The parameter defined in ×d) is a measure of optical isotropy or anisotropy.

[0065] Note that the thickness direction phase difference (thickness direction retardation, R) th ) is the two birefringences Δn when viewed from a cross-section in the thickness direction of the film. xz (=|n x -n z |) and △n yz (=|n y -n z This parameter is defined by the average of the phase differences obtained by multiplying each of the |) values ​​by the film thickness (d).

[0066] When the in-plane phase difference and thickness-direction phase difference values ​​of the polyamide film are within the aforementioned range, optical distortion and color distortion can be minimized when the film is applied to a display device, and light leakage from the sides can also be minimized.

[0067] The polyamide film may further contain a filler in addition to the polyamide polymer.

[0068] The average particle size of the filler may be 60 nm to 180 nm. Specifically, the average particle size of the filler may be, but is not limited to, 80 nm to 180 nm, 100 nm to 180 nm, 110 nm to 160 nm, 120 nm to 160 nm, or 130 nm to 150 nm.

[0069] When the average particle size of the filler is within the aforementioned range, no deterioration in optical properties occurs even when a relatively large amount is added compared to other inorganic fillers.

[0070] The refractive index of the filler may be between 1.55 and 1.75. Specifically, the refractive index of the filler may be between 1.60 and 1.75, 1.60 and 1.70, 1.60 and 1.68, or 1.62 and 1.65, but is not limited to these values.

[0071] The refractive index of the filler satisfies the range, n x , n y , n z The birefringence values ​​related to this can be appropriately adjusted, improving the brightness of the film at various angles.

[0072] On the other hand, if the refractive index of the filler falls outside the range, the presence of the filler may become visible to the naked eye on the film, or the filler may cause an increase in haze.

[0073] The filler content may range from 100 ppm to 3000 ppm based on the total weight of the polyamide polymer solids. Specifically, the filler content may range from 100 ppm to 2500 ppm, 100 ppm to 2200 ppm, 200 ppm to 2500 ppm, 200 ppm to 2200 ppm, 250 ppm to 2100 ppm, or 300 ppm to 2000 ppm based on the total weight of the polyamide polymer solids, but is not limited to these ranges.

[0074] If the filler content falls outside the range, the film haze increases rapidly, and the fillers aggregate on the film surface, which can lead to a visible foreign body texture, problems during running in the manufacturing process, and reduced winding performance.

[0075] The filler may include, but is not limited to, silica and barium sulfate.

[0076] The filler may be included in particulate form. Furthermore, the filler may be in a state where no special coating treatment is applied to its surface, and may be uniformly dispersed throughout the entire film.

[0077] By including the filler in the polyamide film, the film can ensure a wide viewing angle without a decrease in optical properties.

[0078] The residual solvent content in the polyamide film may be 1500 ppm or less. For example, the residual solvent content may be 1200 ppm or less, 1000 ppm or less, 800 ppm or less, or 500 ppm or less, but is not limited to these values.

[0079] The residual solvent refers to the amount of solvent that remains in the final manufactured film without volatilizing during the film manufacturing process.

[0080] If the residual solvent content in the polyamide film exceeds the aforementioned range, the film's durability may decrease, and its brightness may also be affected.

[0081] In the example, a polyamide film with a thickness of 50 μm can withstand more than 200,000 folding cycles before breaking when folded to a radius of curvature of 3 mm.

[0082] The number of folding operations is defined as bending the film so that its radius of curvature is 3 mm, and then unfolding it once.

[0083] The aforementioned polyamide film can be usefully applied to foldable display devices and flexible display devices by satisfying the aforementioned range of folding cycles.

[0084] The surface roughness of the polyamide film in the implemented examples may be 0.01 μm to 0.07 μm. Specifically, the surface roughness may be, but is not limited to, 0.01 μm to 0.07 μm or 0.01 μm to 0.06 μm.

[0085] The surface roughness of the polyamide film satisfying the aforementioned range is advantageous for achieving high brightness even when the angle from the normal direction of the surface light source is large.

[0086] One example of a polyamide film includes a polyamide polymer, and the polyamide polymer includes amide repeating units and may selectively include imide repeating units.

[0087] In some implementations, the polyamide polymer may contain only the amide repeating units and not the imide repeating units. In this case, the modulus of the polyamide film is increased, allowing it to be effectively applied to foldable / flexible display devices, improving transmittance and reducing yellowness and haze.

[0088] The polyamide film comprises a polyamide polymer, which can be formed by the simultaneous or sequential reaction of a reaction product containing a diamine compound and a dicarbonyl compound. Specifically, the polyamide polymer can be formed by the polymerization of a diamine compound and a dicarbonyl compound.

[0089] Alternatively, the polyamide polymer may be formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound. In this case, the polyamide polymer may contain imide repeating units derived from the polymerization of the diamine compound and the dianhydride compound, and amide repeating units derived from the polymerization of the diamine compound and the dicarbonyl compound.

[0090] In some implementations, the polyamide polymer may be polymerized without containing the dianhydride compound. In this case, the polyamide polymer does not need to contain imide repeating units.

[0091] One example of a polyamide film may include a polyamide polymer in which a diamine compound and a dicarbonyl compound polymerize to form an amide bond. The polyamide polymer may also include a polyamide-imide polymer in which a dianhydride compound is selectively further polymerized to form an imide bond.

[0092] In some implementations, the polyamide polymer may not include the polyamide-imide polymer. In this case, the modulus of the polyamide film increases, allowing it to be effectively applied to foldable / flexible display devices, improving transmittance and potentially reducing yellowness and haze.

[0093] The diamine compound is a compound that forms a copolymer by bonding with the dianhydride compound via an imide bond and with the dicarbonyl compound via an amide bond.

[0094] The diamine compound is not particularly limited, but for example, it may be an aromatic diamine compound containing an aromatic structure. For example, the diamine compound may be a compound of the following chemical formula 1. [C1] JPEG0007856708000001.jpg863

[0095] In the above chemical formula 1, E is a substituted or unsubstituted divalent C6-C 30 Alicyclic group, substituted or unsubstituted divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C6-C 30 Aromatic ring group, substituted or unsubstituted divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene group, substituted or unsubstituted C2-C 30 Alkenylene group, substituted or unsubstituted C2-C 30 The group can be selected from alkynylene, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0096] e is selected from integers between 1 and 5, and if e is 2 or greater, E can be the same or different from each other.

[0097] (E) of the aforementioned chemical formula 1 eThe group can be selected from, but is not limited to, the groups represented by the following chemical formulas 1-1a to 1-14a. JPEG0007856708000002.jpg89141

[0098] Specifically, (E) of the above chemical formula 1 e The group can be selected from, but is not limited to, the groups represented by the following chemical formulas 1-1b to 1-13b. JPEG0007856708000003.jpg88131

[0099] More specifically, (E) of the above chemical formula 1 e This may be a group represented by chemical formula 1-6b or a group represented by chemical formula 1-9b.

[0100] In one example, the diamine compound may include a compound having a fluorine-containing substituent or a compound having an ether group (-O-).

[0101] The diamine compound may consist of a compound having a fluorine-containing substituent. In this case, the fluorine-containing substituent is a fluorinated hydrocarbon group, and may specifically be a trifluoromethyl group, but is not limited to this.

[0102] In other realizations, the diamine compound may be a single type of diamine compound; that is, the diamine compound may consist of a single component.

[0103] For example, the diamine compound may include, but is not limited to, 2,2'-Bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), which has the structure shown below. JPEG0007856708000004.jpg66117

[0104] The dicarbonyl compound is not particularly limited, but for example, it may be a compound of the following chemical formula 3. [C3] JPEG0007856708000005.jpg2657

[0105] In the above chemical formula 3, J is a substituted or unsubstituted divalent C6-C 30 Alicyclic group, substituted or unsubstituted divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C6-C 30 Aromatic ring group, substituted or unsubstituted divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene group, substituted or unsubstituted C2-C 30 Alkenylene group, substituted or unsubstituted C2-C 30 The group can be selected from alkynylene, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0106] j is selected from integers between 1 and 5, and if j is 2 or greater, J can be the same or different from each other. X is a halogen atom. Specifically, X can be F, Cl, Br, I, etc. More specifically, X can be Cl, but is not limited to this.

[0107] JPEG0007856708000006.jpg96144 (J) of the above chemical formula 3 j The group can be selected from, but is not limited to, the groups represented by the following chemical formulas 3-1a to 3-14a.

[0108] Specifically, (J) of the above chemical formula 3 j The group can be selected from, but is not limited to, the groups represented by the following chemical formulas 3-1b to 3-8b. JPEG0007856708000007.jpg74150

[0109] More specifically, (J) of the above chemical formula 3 jThis can be the group represented by chemical formula 3-1b, the group represented by chemical formula 3-2b, the group represented by 3-3b, or the group represented by 3-8b.

[0110] In one implementation example, the dicarbonyl compound may be a mixture of at least two different dicarbonyl compounds. When two or more dicarbonyl compounds are used, the dicarbonyl compounds are (J) in the chemical formula 3. j Two or more groups selected from the groups represented by the chemical formulas 3-1b to 3-8b may be used.

[0111] In other realizations, the dicarbonyl compound may be an aromatic dicarbonyl compound containing an aromatic structure.

[0112] The dicarbonyl compound may include, but is not limited to, terephthaloyl chloride (TPC), 1,1'-biphenyl-4,4'-dicarbonyl dichloride (BPDC), isophthaloyl chloride (IPC), or a combination thereof, having the following structures. JPEG0007856708000008.jpg2657JPEG0007856708000009.jpg2874JPEG0007856708000010.jpg3446

[0113] In one implementation example, the polyamide polymer may contain two or more amide repeating units.

[0114] For example, the two or more amide repeating units may include a first amide repeating unit and a second amide repeating unit. The first amide repeating unit may be formed by the reaction of a first dicarbonyl compound and the diamine compound, and the second amide repeating unit may be formed by the reaction of a second dicarbonyl compound and the diamine compound.

[0115] The first dicarbonyl compound and the second dicarbonyl compound may be different compounds from each other.

[0116] The first dicarbonyl compound and the second dicarbonyl compound may each contain two carbonyl groups. The angle between the two carbonyl groups in the first dicarbonyl compound may be greater than the angle between the two carbonyl groups in the second dicarbonyl compound.

[0117] In the exemplary embodiment, the first dicarbonyl compound and the second dicarbonyl compound may be structural isomers of each other. By using two structurally isomeric dicarbonyl compounds, a polyamide polymer satisfying the aforementioned interplanar spacing can be formed, thereby improving the optical and mechanical properties of the polyamide polymer.

[0118] The first dicarbonyl compound and the second dicarbonyl compound may each be an aromatic dicarbonyl compound.

[0119] For example, the first dicarbonyl compound and the second dicarbonyl compound may be different aromatic dicarbonyl compounds, but are not limited thereto.

[0120] If the first dicarbonyl compound and the second dicarbonyl compound are both aromatic dicarbonyl compounds, they contain a benzene ring, which can contribute to improving the mechanical properties of the film containing the manufactured polyamide polymer, such as surface hardness and tensile strength.

[0121] For example, the angle between the two carbonyl groups in the first dicarbonyl compound may be 160° to 180°, and the angle between the two carbonyl groups in the second dicarbonyl compound may be 80° to 140°.

[0122] For example, the dicarbonyl compound may include a first dicarbonyl compound and / or the second dicarbonyl compound.

[0123] For example, the first dicarbonyl compound may include TPC, and the second dicarbonyl compound may include IPC, but is not limited thereto.

[0124] When TPC is used as the first dicarbonyl compound and IPC as the second dicarbonyl compound in an appropriate combination, the resulting film containing the polyamide polymer can have high oxidation resistance, productivity, light transmittance, transparency, modulus, etc., and may have low haze.

[0125] The diamine compound and the dicarbonyl compound may polymerize to form a repeating unit represented by the following chemical formula B. [Case B] JPEG0007856708000011.jpg3679 In the above chemical formula B, the explanations for E, J, e, and j are as described above.

[0126] For example, the diamine compound and the dicarbonyl compound may polymerize to form amide repeating units represented by chemical formulas B-1 and B-2.

[0127] [Case B-1] JPEG0007856708000012.jpg38128 In the above chemical formula B-1, y is an integer from 1 to 400.

[0128] [Case B-2] JPEG0007856708000013.jpg40128 In the above chemical formula B-2, y is an integer from 1 to 400.

[0129] In some implementations, the molar ratio of the first amide repeating unit to the second amide repeating unit may be 10:90 to 90:10. By setting the molar ratio of the first and second amide repeating units within the aforementioned range, the interplanar spacing of the polyamide polymer can be adjusted to the aforementioned range. Therefore, physical properties such as haze, transmittance, yellowness, and modulus of the polyamide film can be improved. Preferably, the molar ratio of the first amide repeating unit to the second amide repeating unit may be 25:75 to 80:20, 40:60 to 80:20, or 50:50 to 75:25.

[0130] In some implementations, the polyamide film may have a thickness deviation of 4 μm or less, based on a thickness of 50 μm. This thickness deviation may refer to the deviation between the maximum or minimum values ​​of the average thickness measured at 10 random locations on the film. In this case, since the polyamide film has a uniform thickness, the optical and mechanical properties at each point may be uniform.

[0131] The haze of the polyamide film may be 1% or less. For example, the haze may be 0.5% or less or 0.4% or less, but is not limited to these values.

[0132] The transmittance of the polyamide film may be 80% or higher. For example, the transmittance may be 82% or higher, 85% or higher, 88% or higher, 89% or higher, 80% to 99%, 88% to 99%, or 89% to 99%, but is not limited to these values.

[0133] The yellow index of the polyamide film may be 3.5 or less. For example, the yellow index may be 3 or less, 2.5 or less, or 2 or less, but is not limited to these.

[0134] The modulus of the polyamide film may be 5 GPa or higher. Specifically, the modulus may be 5.5 GPa or higher, or 6.0 GPa or higher, but is not limited to these values.

[0135] The compressive strength of the polyamide film may be 0.4 kgf / μm or higher. Specifically, the compressive strength may be 0.45 kgf / μm or higher or 0.46 kgf / μm or higher, but is not limited to these values.

[0136] When the aforementioned polyamide film is perforated in UTM compression mode using a 2.5 mm spherical tip at a speed of 10 mm / min, the maximum perforation diameter (mm) including cracks is 60 mm or less. Specifically, the maximum perforation diameter may be, but is not limited to, 5 mm to 60 mm, 10 mm to 60 mm, 15 mm to 60 mm, 20 mm to 60 mm, 25 mm to 60 mm, or 25 mm to 58 mm.

[0137] The polyamide film may have a surface pencil hardness of HB or higher. Specifically, the surface pencil hardness may be H or higher or 2H or higher, but is not limited to these.

[0138] The aforementioned polyamide film has a tensile strength of 15 kgf / mm². 2 It may be the above. Specifically, the tensile strength is 18 kgf / mm 2 Above 20 kgf / mm 2 Above, 21kgf / mm 2 or above, or 22 kgf / mm² 2 The above are possible, but not limited to them.

[0139] The polyamide film may have an elongation of 15% or more. Specifically, the elongation may be 16% or more, 17% or more, or 17.5% or more, but is not limited to these values.

[0140] The polyamide-based films, as demonstrated in this example, possess excellent optical properties such as low haze, low yellowness, and high transmittance, as well as excellent scratch resistance and / or modulus, making them effectively applicable to flexible / foldable display devices, for example.

[0141] The physical properties of the aforementioned polyamide film are based on a thickness of 40 μm to 60 μm. For example, the physical properties of the aforementioned polyamide film are based on a thickness of 50 μm.

[0142] The characteristics of the constituent components and physical properties of the aforementioned polyamide films can be combined with each other.

[0143] For example, the polyamide film may contain a polyamide polymer, have a transmittance of 80% or more, a haze of 1% or less, and a yellowness of 3.5 or less or 3 or less.

[0144] Furthermore, the aforementioned XRD patterns and IR spectral characteristics and properties of the polyamide film may be the result of the combined process conditions at each stage of the manufacturing method of the polyamide film, as described later, along with the chemical and physical properties of the components constituting the polyamide film.

[0145] For example, all factors, such as the composition and content of the components constituting the polyamide film, and the polymerization and heat treatment conditions in the film manufacturing process, can be combined to achieve the desired characteristics on the XRD and IR patterns.

[0146] In some implementations, the molecular structure of the polyamide polymer may change depending on the amount of the first dicarbonyl compound and the second dicarbonyl compound used and the polymerization conditions. In this case, the ratio of the first hydrogen bond group to the second hydrogen bond group may change, thereby adjusting the ratio of the area of ​​the first IR peak to the area of ​​the second IR peak.

[0147] [Cover window for display device] A cover window for a display device according to one implementation example includes a polyamide film and a functional layer.

[0148] The polyamide film according to some implementation examples includes a polyamide polymer and includes a first XRD peak having a maximum value in a range of 2θ values on the XRD graph from 10° or more to less than 20°, and the full width at half maximum of the first XRD peak can be 6° or less.

[0149] The specific description of the polyamide film is as described above. The cover window for the display device can be usefully applied to the display device.

[0150] Due to the positions and full widths at half maximum of the peaks on the XRD analysis pattern of the polyamide film having the above characteristics, it can have excellent optical and mechanical properties.

[0151] The polyamide film according to some implementation examples includes a polyamide polymer, and includes a first IR peak having a maximum value in the range of wavenumbers 2950 cm -1 ~2900 cm -1 and a second IR peak having a maximum value in the range of wavenumbers 2875 cm -1 cm -1 ~2825 cm -1 on the IR spectrum, and the area of the first IR peak can be 1.4 times or less the area of the second IR peak.

[0152] Due to the area ratio of the peaks located in the range of wavenumbers 3000 cm -1 ~2800 cm -1 on the IR spectrum of the polyamide film having the above characteristics, it can have excellent optical and mechanical properties.

[0153] [Display Device] A display device according to one implementation example includes a display unit and a cover window disposed on the display unit, and the cover window includes a polyamide film and a functional layer.

[0154] A polyamide film according to some embodiments includes a polyamide polymer and includes a first XRD peak having a maximum value in the range of 2θ values on the XRD graph of 10° or more and less than 20°, and the full width at half maximum of the first XRD peak can be 6° or less.

[0155] A polyamide film according to some embodiments includes a polyamide polymer, and has a first IR peak having a maximum value in the range of wavenumbers 2950 cm -1 ~2900 cm -1 on the IR spectrum, and a second IR peak having a maximum value in the range of wavenumbers 2875 cm -1 cm -1 ~2825 cm -1 on the IR spectrum, and the area of the first IR peak can be 1.4 times or less the area of the second IR peak.

[0156] Specific descriptions of the polyamide film and the cover window are as described above.

[0157] FIG. 1 shows a cross-sectional view of a display device according to an embodiment.

[0158] Specifically, FIG. 1 illustrates a display device in which a display unit 400, a polyamide film 100 having a first surface 101 and a second surface 102 on the display unit 400, and a cover window 300 including a functional layer 200 are disposed, and an adhesive layer 500 is disposed between the display unit 400 and the cover window 300.

[0159] The display unit 400 can display an image and can have flexible characteristics.

[0160] The display unit 400 can be a display panel for displaying an image. For example, it can be a liquid crystal display panel or an organic electroluminescence display panel. The organic electroluminescence display panel can include a front polarizing plate and an organic EL panel.

[0161] The front polarizing plate may be placed on the front surface of the organic EL panel. Specifically, the front polarizing plate may be bonded to the surface on which the image is displayed in the organic EL panel.

[0162] The organic EL panel can display images by self-illumination on a pixel-by-pixel basis. The organic EL panel may include an organic EL substrate and a drive substrate. The organic EL substrate may include a plurality of organic electroluminescent units, each corresponding to a pixel. Specifically, each may include a cathode, an electron transport layer, an emissive layer, a hole transport layer, and an anode. The drive substrate may be connected to the organic EL substrate in a driving manner. That is, the drive substrate can drive the organic EL substrate by applying a drive signal, such as a drive current, to each of the organic electroluminescent units.

[0163] Furthermore, an adhesive layer 500 may be included between the display unit 400 and the cover window 300. The adhesive layer may be an optically transparent adhesive layer and is not particularly limited.

[0164] The cover window 300 may be positioned on the display unit 400. The cover window may be located on the outermost casing of the display device in the embodiment, and may protect the display unit.

[0165] The cover window 300 may include a polyamide film and a functional layer. The functional layer may be one or more selected from the group consisting of a hard coating layer, a reflectivity reduction layer, an anti-fouling layer, and an anti-glare layer. The functional layer may be coated on at least one surface of the polyamide film.

[0166] In the case of polyamide films as demonstrated in the implementation examples, they can be easily applied as a film to the outside of a display device without changing the display driving method, color filters inside the panel, or the laminated structure, providing a display device with excellent scratch resistance, light transmittance, transparency, and / or low haze. Furthermore, since excessive process changes and cost increases are unnecessary, there is also the advantage of reducing production costs.

[0167] The polyamide films demonstrated in this example not only possess excellent optical properties such as high transmittance, low haze, and low yellowness, but may also have excellent scratch resistance and / or modulus.

[0168] Furthermore, the polyamide-based film used in the real-world example minimizes optical distortion by having in-plane phase difference and thickness-direction phase difference below a specific level, and can also reduce light leakage from the sides.

[0169] In particular, when the screen size of a display device increases, or when a cover window is flexible for a flexible / foldable display, excellent mechanical properties such as surface strength are required. The polyamide film, as demonstrated in the examples, has excellent scratch resistance, modulus, and / or optical properties, making it effectively applicable to large-area or foldable / flexible display devices.

[0170] [Method for manufacturing polyamide films] One example of implementation is the provision of a method for manufacturing polyamide films.

[0171] One example of a method for producing a polyamide film includes the steps of: polymerizing a diamine compound and a dicarbonyl compound to prepare a polymer solution containing a polyamide polymer on an organic solvent; casting the polymer solution to produce a gel sheet; and heat-treating the gel sheet.

[0172] Referring to Figure 2, a method for producing a polyamide film according to one example includes the steps of: preparing a polymer solution containing a polyamide polymer by polymerizing a diamine compound and a dicarbonyl compound in an organic solvent (S100); producing a gel sheet by casting the polymer solution (S200); and heat-treating the gel sheet (S300).

[0173] The polyamide film is a film whose main component is a polyamide polymer, and the polyamide polymer is a resin containing amide repeating units as structural units. Selectively, the polyamide polymer may also contain imide repeating units.

[0174] In the method for producing the polyamide film, the polymer solution for preparing the polyamide polymer can be prepared by simultaneously or sequentially mixing a diamine compound and a dicarbonyl compound in an organic solvent in a reactor and reacting the mixture (S100).

[0175] In one implementation example, the polymer solution can be prepared by simultaneously adding a diamine compound and a dicarbonyl compound to an organic solvent and allowing them to react.

[0176] In other realizations, the step of preparing the polymer solution may include the step of mixing and reacting the diamine compound and the dicarbonyl compound in a solvent to prepare a polyamide (PA) solution. The polyamide solution is a polymer solution having amide repeating units.

[0177] In one embodiment, the step of preparing the polymer solution may be carried out using two different dicarbonyl compounds as the dicarbonyl compounds. In this case, the two dicarbonyl compounds may be mixed and reacted simultaneously or sequentially. Preferably, the first dicarbonyl compound and the diamine compound react to form a prepolymer, and the prepolymer and the second dicarbonyl compound react to form the polyamide polymer. In this case, polyamide polymers and polyamide films can be effectively produced in which the peaks of the XRD pattern have the aforementioned positions and full widths at half maximum, or the peaks in a specific section of the IR pattern have the aforementioned area ratios.

[0178] Figure 3 is a schematic flowchart illustrating the preparation steps of a polyamide polymer solution in some implementation examples. Referring to Figure 3, the dicarbonyl compound can be added in at least four steps (e.g., S120 to S150).

[0179] The step of preparing the polymer solution (S100) may include the steps of: adding a diamine compound to an organic solvent and dissolving it (S110); adding a first dicarbonyl compound and stirring to react it (S120); after step S120, adding a second dicarbonyl compound and stirring to prepare a first polymer solution (S130); further adding the first or second dicarbonyl compound and stirring to prepare a second polymer solution (S140); and further adding the first or second dicarbonyl compound and stirring to prepare a third polymer solution (S150).

[0180] For example, the approximate molecular structure and / or molecular weight of the polyamide polymer are determined in steps S110 to S130, and in steps S140 and S150, the viscosity of the polyamide polymer solution is adjusted, and the position of the peak on the XRD pattern, the full width at half maximum, and / or the wavenumber of the IR spectrum are determined. -1 ~2800cm -1The area ratio of peaks located within a given section can be precisely adjusted. This allows for the formation of polyamide films with desired optical and mechanical properties.

[0181] In one implementation example, the viscosity of the polymer solution can be adjusted to 200,000 cps to 350,000 cps at room temperature. In this case, the film-forming properties of the polyamide film can be improved, thereby improving thickness uniformity and / or scratch resistance.

[0182] In some implementations, different dicarbonyl compounds may be used in the step of preparing the second polymer solution (S140) and the step of preparing the third polymer solution (S150). For example, if the first dicarbonyl compound is used in the step of preparing the second polymer solution (S140), the second dicarbonyl compound may be used in the step of preparing the third polymer solution (S150). If the second dicarbonyl compound is used in the step of preparing the second polymer solution (S140), the first dicarbonyl compound may be used in the step of preparing the third polymer solution (S150). Preferably, after the reactants in step S120 react with the second dicarbonyl compound, the first dicarbonyl compound is used in step S130 to adjust the XRD and / or IR pattern characteristics of the polyamide polymer to the aforementioned range.

[0183] In the steps of preparing the first polymer solution, the second polymer solution, and the third polymer solution, the viscosities of the prepared polymer solutions may differ. For example, the viscosity of the second polymer solution may be higher than that of the first polymer solution, and the viscosity of the third polymer solution may be higher than that of the second polymer solution.

[0184] The stirring speed when preparing the first polymer solution, the stirring speed when preparing the second polymer solution, and the stirring speed when preparing the third polymer solution may differ from each other. For example, the stirring speed when preparing the first polymer solution may be faster than the stirring speed when preparing the second polymer solution and / or the third polymer solution.

[0185] The polymer contained in the polymer solution includes amide repeating units derived from the polymerization of the diamine compound and the dicarbonyl compound.

[0186] Alternatively, the polymer contained in the polymer solution may include imide repeating units derived from the polymerization of the diamine compound and the dianhydride compound, and amide repeating units derived from the polymerization of the diamine compound and the dicarbonyl compound.

[0187] In one implementation example, the step of preparing the polymer solution containing the polyamide polymer may be carried out under temperature conditions of -10°C to 25°C. For example, the mixing and reaction of the solvent, the diamine compound, and the dicarbonyl compound may be carried out under temperature conditions of -10°C to 25°C. Outside this temperature range, the position and full width at half maximum of the peaks on the XRD pattern may fall outside the aforementioned range.

[0188] In one implementation example, the step of preparing the polymer solution containing the polyamide polymer can be carried out under temperature conditions of -20°C to 25°C. For example, the mixing and reaction of the solvent, the diamine compound, and the dicarbonyl compound can be carried out under temperature conditions of -20°C to 25°C. Outside this temperature range, the wavenumber of the IR spectrum is 3000 cm⁻¹. -1 ~2800cm -1 The area ratio of the peaks located in the interval may fall outside the aforementioned range. Consequently, properties such as modulus and yellowness of the polyamide film may decrease. Furthermore, the viscosity of the polymer solution may not reach a predetermined range, which may increase the variation in the thickness of the fabricated film. Preferably, the step of preparing the polymer solution containing the polyamide polymer may be carried out under temperature conditions of -20°C to 20°C, -20°C to 15°C, -20°C to 10°C, -15°C to 20°C, -15°C to 15°C, -15°C to 10°C, -10°C to 20°C, -10°C to 15°C, -10°C to 10°C, -8°C to 20°C, -8°C to 15°C, -8°C to 10°C, -5°C to 20°C, -5°C to 15°C, or -5°C to 10°C.

[0189] The solid content in the polymer solution may be 10% to 30% by weight, but is not limited to this.

[0190] When the solid content in the polymer solution is within the specified range, a polyamide film can be effectively manufactured in the extrusion and casting processes. Furthermore, the manufactured polyamide film may have improved mechanical properties such as modulus and low optical properties such as yellowness.

[0191] In other realizations, the step of preparing the polymer solution may further include the step of adjusting the pH of the polymer solution. In this step, the pH of the polymer solution is adjusted to 4-7, for example, to 4.5-7.

[0192] The pH of the polymer solution is adjusted by adding a pH adjusting agent, which is not particularly limited but may include, for example, amine compounds such as alkoxyamines, alkylamines, or alkanolamines.

[0193] By adjusting the pH of the polymer solution within the aforementioned range, defects in the film produced from the polymer solution can be prevented, and desired optical and mechanical properties in terms of yellowness and modulus can be achieved.

[0194] The pH adjusting agent may be added in an amount of 0.1 mol% to 10 mol% based on the total number of moles of monomers in the polymer solution.

[0195] In some implementations, the molar ratio of the first dicarbonyl compound to the second dicarbonyl compound used to prepare the polymer solution may be 10:90 to 90:10. Preferably, it may be 25:75 to 80:20, 40:60 to 80:20, or 50:50 to 75:25. The molar ratio may be determined, for example, based on the total number of moles of the first and second dicarbonyl compounds added in each stage when the first and second dicarbonyl compounds are added in four or more stages.

[0196] In some implementations, the molar ratio of the first dicarbonyl compound to the second dicarbonyl compound used to prepare the polymer solution may be 10:90 to 79:21. Preferably, it may be 30:70 to 79:21, 40:60 to 79:21, or 50:50 to 75:25. The molar ratio may be determined, for example, based on the total number of moles of the first and second dicarbonyl compounds added in each stage when the first and second dicarbonyl compounds are added in four or more stages.

[0197] In some implementations, the content of the first or second dicarbonyl compound added in the step of preparing the second polymer solution (S140) may be 0.5 mol% to 15 mol% based on the total number of moles of dicarbonyl compounds. In this case, the position and full width at half maximum of the peaks on the XRD pattern and / or the area ratio of the peaks on the IR pattern of the polyamide polymer can be precisely adjusted to a desired range. Preferably, the amount of dicarbonyl compound added in the step of preparing the second polymer solution (S140) may be 0.5 mol% to 10 mol%, 0.5 mol% to 5 mol%, 1 mol% to 3 mol%, or 0.5 mol% to 3 mol%.

[0198] In some implementations, the content of the first or second dicarbonyl compound added in the step of preparing the third polymer solution (S150) may be 0.5 mol% to 15 mol% based on the total number of moles of dicarbonyl compounds. In this case, the position and full width at half maximum of the peaks on the XRD pattern and / or the area ratio of the peaks on the IR pattern of the polyamide polymer can be precisely adjusted to a desired range. Preferably, the amount of dicarbonyl compound added in the step of preparing the third polymer solution (S150) may be 0.5 mol% to 10 mol%, 0.5 mol% to 5 mol%, 1 mol% to 3 mol%, or 0.5 mol% to 3 mol%.

[0199] By using the first dicarbonyl compound and the second dicarbonyl compound in such proportions, polyamide polymers and films having the aforementioned characteristics in their XRD patterns and / or IR spectra can be produced, and the scratch resistance, modulus, haze, transmittance, yellowness, etc., of the polyamide film can be improved.

[0200] Outside the aforementioned range, optical properties such as luminance and haze, as well as mechanical properties such as scratch resistance and modulus, may decrease.

[0201] The descriptions of the diamine and dicarbonyl compounds are as stated above.

[0202] In one implementation example, the organic solvent may be one or more selected from the group consisting of dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), m-cresol, tetrahydrofuran (THF), and chloroform. The organic solvent used in the polymer solution may be, but is not limited to, dimethylacetamide (DMAc).

[0203] The polymer solution may be stored at -20°C to 20°C, -20°C to 10°C, -20°C to 5°C, -20°C to 0°C, or 0°C to 10°C.

[0204] Storing the polymer solution at the aforementioned temperature prevents deterioration, reduces its water content, and thereby prevents defects in the manufactured film.

[0205] In one implementation example, the polyamide polymer solution can be degassed. By removing water from the polymer solution through degassing and reducing impurities, the reaction yield can be increased, and a final film with excellent surface appearance and mechanical properties can be achieved.

[0206] The degassing may include vacuum degassing or inert gas purging. The vacuum degassing can be performed for 30 minutes to 3 hours after reducing the pressure of the reactor containing the polymer solution to 0.1 bar to 0.7 bar. By performing vacuum degassing under these conditions, air bubbles inside the polymer solution can be reduced, thereby preventing surface defects in the resulting film and achieving excellent optical properties such as haze.

[0207] Specifically, the purging can be performed by purging the internal pressure of the tank to 1 to 2 atmospheres using an inert gas. By performing the purging under these conditions, water is removed from the polymer solution and impurities are reduced, thereby increasing the reaction yield and enabling the realization of products with excellent optical properties such as haze and mechanical properties.

[0208] The inert gas may be one or more selected from the group consisting of nitrogen, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn), but is not limited thereto. Specifically, the inert gas may be nitrogen.

[0209] The vacuum degassing and the inert gas purging may be carried out in a separate step. For example, a vacuum degassing process may be performed, followed by a purging process with an inert gas, but this is not the only possible step.

[0210] By performing the vacuum degassing and / or the inert gas purging, the physical properties of the surface of the manufactured polyamide film can be improved.

[0211] As mentioned above, a polymer solution containing a polyamide polymer may be prepared on an organic solvent, and then the filler may be added to the solution.

[0212] The average particle size of the filler is 60 nm to 180 nm, its refractive index is 1.55 to 1.75, and its content is 100 ppm to 3000 ppm based on the total weight of the polyamide polymer solids. The filler may be silica or barium sulfate. A more detailed explanation of the aforementioned filler is provided above.

[0213] A gel sheet can be produced by casting the polymer solution (S200). For example, the polymer solution can be extruded, coated, and / or dried onto a support to form a gel sheet.

[0214] Furthermore, the casting thickness of the polymer solution can be 200 μm to 700 μm. By casting the polymer solution within this thickness range, appropriate thickness and thickness uniformity can be ensured when the final film is manufactured after drying and heat treatment.

[0215] As mentioned above, the viscosity of the polymer solution can be 200,000 cps to 350,000 cps at room temperature. By satisfying this viscosity range, the polymer solution can be cast to a uniform thickness without defects, and a polyamide film of substantially uniform thickness can be formed without local / partial thickness changes during the drying process.

[0216] After casting the polymer solution, a gel sheet can be produced by drying it at a temperature of 60°C to 150°C for 5 to 60 minutes. Specifically, a gel sheet can be produced by drying the polymer solution at a temperature of 70°C to 90°C for 15 to 40 minutes.

[0217] During the drying process, some or all of the solvent in the polymer solution may evaporate, thereby producing the gel sheet.

[0218] The dried gel sheet can be heat-treated to form a polyamide film (S300).

[0219] The heat treatment of the gel sheet can be carried out, for example, by a thermosetting apparatus. The aforementioned thermosetting apparatus can heat-treat the gel sheet using hot air.

[0220] When heat treatment is performed using hot air, the amount of heat can be applied evenly. If the amount of heat is not distributed evenly, a satisfactory surface roughness cannot be achieved, and in that case, the surface tension may become too high or too low.

[0221] The heat treatment of the gel sheet may be carried out at a temperature in the range of 60°C to 500°C for 5 minutes to 200 minutes. Specifically, the heat treatment of the gel sheet may be carried out at a temperature in the range of 80°C to 300°C while increasing the temperature at a rate of 1.5°C / min to 20°C / min for 10 minutes to 150 minutes.

[0222] In this case, the starting temperature for the heat treatment of the gel sheet may be 60°C or higher. Specifically, the starting temperature for the heat treatment of the gel sheet may be 80°C to 180°C.

[0223] Furthermore, the maximum temperature during heat treatment may be between 300°C and 500°C. For example, the maximum temperature during heat treatment may be between 350°C and 500°C, 380°C and 500°C, 400°C and 500°C, 410°C and 480°C, 410°C and 470°C, or 410°C and 450°C.

[0224] According to one implementation example, the heat treatment of the gel sheet can be carried out in two or more stages. Specifically, the heat treatment may include a first hot air treatment step performed at a temperature range of 60°C to 120°C for 5 to 30 minutes, and a second hot air treatment step performed at a temperature range of 120°C to 350°C for 10 to 120 minutes.

[0225] By heat-treating under these conditions, the gel sheet is cured to have appropriate surface hardness and modulus, and the cured film can simultaneously ensure high light transmittance, low haze, and an appropriate level of gloss.

[0226] According to one implementation example, the heat treatment may include a step of passing through an IR heater. The heat treatment with the IR heater may be performed for 1 to 30 minutes at a temperature range of 300°C or higher. Specifically, the heat treatment with the IR heater may be performed for 1 to 20 minutes at a temperature range of 300°C to 500°C.

[0227] The polyamide film, when manufactured by the aforementioned manufacturing method, can exhibit excellent optical and mechanical properties. Such a polyamide film can be applied to various applications requiring flexibility, transparency, and a specific level of brightness. For example, the polyamide film can be applied to solar cells, displays, semiconductor devices, sensors, and the like.

[0228] In particular, the polyamide film has excellent modulus, scratch resistance, and / or optical properties, making it useful for cover windows and display devices for display devices, and its excellent folding characteristics make it useful for foldable display devices and flexible display devices as well.

[0229] The description of the polyamide film manufactured by the manufacturing method described above is as stated above.

[0230] (Examples) The above content will be explained in more detail by the following examples. Note that the following examples are merely illustrative of the present invention, and the scope of the examples is not limited to these.

[0231] (Example 1) In a 1L glass reactor with a double jacket that allows for temperature control, 567g of the organic solvent dimethylacetamide (DMAc) was filled under a nitrogen atmosphere at 10°C. Then, 64.0g (0.200mol) of the aromatic diamine 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) was gradually added and dissolved.

[0232] Next, terephthaloyl chloride (TPC) was slowly added as the first dicarbonyl compound at a rate of 48.5 mol% based on the total number of moles of dicarbonyl compounds used in polymerization, while stirring for 1 hour. Subsequently, isophthaloyl chloride (IPC) was slowly added as the second dicarbonyl compound at a rate of 48.5 mol% based on the total number of moles of dicarbonyl compounds, while stirring for 1 hour, to prepare the first polymer solution.

[0233] TPC solution and IPC solution were prepared in DMAc organic solvents at a concentration of 10% by weight, respectively.

[0234] After adding 1 mL of the TPC solution to the first polymer solution, the process of stirring for 30 minutes was repeated to react with 1.5 mol% of TPC based on the total number of moles of the dicarbonyl compound to prepare the second polymer solution.

[0235] After adding 1 mL of the IPC solution to the second polymer solution, the process of stirring for 30 minutes was repeated to react with 1.5 mol% of IPC based on the total number of moles of the dicarbonyl compound to prepare the third polymer solution. At this time, the reaction temperature (polymerization temperature) of the first, second, and third polymer solutions was adjusted to approximately 10°C, and the reaction was terminated when the viscosity of the third polymer solution reached approximately 200,000 cps.

[0236] Viscosity was measured using a BH-II model viscometer from Toki Sangyo Co., Ltd., while maintaining the polymer solution (Varnish) at a temperature of 10°C. The RPM was set to 4, and the target viscosity was confirmed using spindle number 7.

[0237] The third polymer solution was applied to a glass plate and dried. After peeling the dried polyamide polymer from the glass plate, it was heat-treated to obtain a polyamide film with a thickness of 50 μm.

[0238] Regarding the content of diamine compounds (TFMB) and dicarbonyl compounds (IPC, TPC), the number of moles of dicarbonyl compounds and the order of addition are shown in Table 1 below, based on 100 moles of diamine compounds.

[0239] In the case of the dicarbonyl compound, the step of charging and stirring in the order described in Table 1 below (in the order from top to bottom) was performed. For example, in the case of Example 1, after performing the step of charging and dissolving the diamine compound in an organic solvent, the step of charging 48.5 mol% of TPC and stirring, the step of charging 48.5 mol% of IPC and stirring, the step of charging 1.5 mol% of TPC and stirring, and the step of charging 1.5 mol% of IPC and stirring were sequentially performed.

[0240] (Examples 2, 3 and Comparative Examples 1 to 3) As described in Table 1 below, except that the content of each reactant, the charging order and the charging amount of the dicarbonyl compound were changed, the film was produced in the same manner as in Example 1.

[0241] [Table 1]

[0242] <Evaluation Example> Regarding the films produced in the above Examples and Comparative Examples, the physical properties were measured and evaluated as follows, and the results are shown in Table 2 below.

[0243] (Evaluation Example 1: Measurement of film thickness) Using a digital micrometer 547-401 manufactured by Mitutoyo Corporation of Japan, the thicknesses at 10 random positions were measured, and the average value was taken as the thickness.

[0244] (Evaluation Example 2: Modulus measurement) Using a universal testing machine UTM5566A manufactured by Instron Corporation, the sample was cut at 10 cm or more in the direction perpendicular to the main shrinkage direction and 10 mm in the main shrinkage direction, and after being attached to clips at 10 cm intervals, a stress-strain curve was obtained while stretching at a speed of 12.5 mm / min at room temperature until breakage occurred. In the stress-strain curve, the slope of the load with respect to the initial deformation was taken as the modulus (GPa). The modulus was measured under the condition of room temperature (about 20 °C to 25 °C).

[0245] (Evaluation Example 3: Transmittance and Haze Measurement) Light transmittance and haze were measured using the NDH-5000W haze meter from Nippon Denshoku Industries Co., Ltd., in accordance with JIS K 7105, JIS K 7136, and JIS K 7161 standards.

[0246] (Evaluation example 4: Measurement of yellowness) Yellowness (YI) was measured using a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) under conditions of d65 and 10°, according to the ASTM-E313 standard.

[0247] (Evaluation Example 5: XRD (X-ray diffraction crystallography) analysis) XRD analysis was performed on the polyamide films of the examples and comparative examples. Rigaku's Ultima IV was used, and the analytical conditions were set as follows. -Scan source: Cu (40kV, 30mA) - Scan range (2θ): 5°~45° -Scan size: 0.02° - Scan speed: 0.24° / sec

[0248] Figure 4 shows the XRD analysis graph (diffractogram) for the polyamide film of Example 2. Referring to Figure 4, a combined XRD peak 10 was observed in the interval of 2θ values ​​from approximately 5° to 35°, where two XRD peaks were combined.

[0249] The combined XRD peak 10 was separated into a first XRD peak 11 and a second XRD peak 12. The first XRD peak 11 had its maximum value in the interval between 2θ values ​​of 10° or more and less than 20° (first interval), and the second XRD peak 12 had its maximum value in the interval between 2θ values ​​of 20° and 25° (second interval). The combined XRD peak 10 was separated such that the first XRD peak 11 and the second XRD peak 12 had the form of a normal distribution (Gaussian distribution) relative to the baseline 18.

[0250] The starting point (14; point where the 2θ value is approximately 5°) and ending point (15; point where the 2θ value is approximately 35°) of the combined XRD peak 10 are given by an exponential function (for example, y=ae x A baseline 18 was established by connecting arbitrary lines having the form (a and b are constants) and linking them with the XRD pattern of the section excluding the aggregated XRD peak.

[0251] For the first XRD peak 11 and the second XRD peak 12, the full width at half maximum (FWHM) of the portion with a higher intensity value than baseline 18 was analyzed using an analysis program.

[0252] Furthermore, Table 2 below shows the percentage of the full width at half maximum (FWHM) of the first XRD peak 11 relative to the sum of the FWHM of the first XRD peak 11 and the FWHM of the second XRD peak 12.

[0253] (Evaluation Example 6: Scratch Resistance Evaluation) We used KIPAE E&T's Pencil Hardness Tester and Mitsubishi's Pressure-Proofed Hi-Density Lead Pencil. The H-hardness pencil was positioned so that it formed a contact angle of approximately 45° with the film, and the film surface was evaluated by rubbing it five times over a 40mm measurement area at a speed of 300mm per minute while applying a load of 750g. A film surface without scratches was evaluated as "good," and a film surface with scratches was evaluated as "poor."

[0254] [Table 2]

[0255] As can be confirmed from Table 2 above, in the case of the examples where the half-value width of the first XRD peak is 6° or less on the XRD graph, it was confirmed that they have excellent properties such as modulus, transmittance, haze, and yellowness compared to the comparative examples.

[0256] On the other hand, in the case of the comparative examples where the half-value width of the first XRD peak is more than 6° on the XRD graph, it was confirmed that the properties such as yellowness, modulus, transmittance, and haze decreased.

[0257] Specifically, in the case of Comparative Example 1 where IPC reacted with the diamine compound prior to TPC and was formed, the half-value width of the first XRD peak was 6.2°, and the haze and yellowness increased relatively.

[0258] In the case of Comparative Example 2 where TPC was used in a relatively excessive amount at 95 mol% in the total molar amount of the dicarbonyl compound, the half-value width of the first XRD peak was shown to be 6.2°, the yellowness and haze increased significantly, and the transmittance decreased.

[0259] Also, in the case of Comparative Example 3 where TPC was used in a relatively small amount at 5 mol% in the total molar amount of the dicarbonyl compound, the half-value width of the first XRD peak was shown to be 6.1°, the modulus decreased, the yellowness increased, and particularly scratches occurred in the scratch resistance evaluation.

[0260] (Example 4) In a 1 L glass reactor with a double jacket capable of temperature adjustment, under a nitrogen atmosphere at 10°C, after filling it with 567 g of dimethylacetamide (DMAc), which is an organic solvent, 64.0 g (0.200 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), which is an aromatic diamine, was gradually added and dissolved while being introduced.

[0261] Next, terephthaloyl chloride (TPC) was slowly added as the first dicarbonyl compound at a rate of 38.8 mol% based on the total number of moles of dicarbonyl compounds used in polymerization, while stirring for 1 hour. Subsequently, isophthaloyl chloride (IPC) was slowly added as the second dicarbonyl compound at a rate of 58.2 mol% based on the total number of moles of dicarbonyl compounds, while stirring for 1 hour, to prepare the first polymer solution.

[0262] TPC solution and IPC solution were prepared in DMAc organic solvents at a concentration of 10% by weight, respectively.

[0263] After adding 1 mL of the TPC solution to the first polymer solution, the process of stirring for 30 minutes was repeated to react with 1.2 mol% of TPC based on the total number of moles of the dicarbonyl compound, thereby preparing the second polymer solution.

[0264] After adding 1 mL of the IPC solution to the second polymer solution, the process of stirring for 30 minutes was repeated to react with 1.8 mol% of IPC based on the total number of moles of the dicarbonyl compound, thereby preparing the third polymer solution. During this process, the reaction temperature (polymerization temperature) of the first, second, and third polymer solutions was adjusted to approximately 10°C, and the reaction was terminated when the viscosity of the third polymer solution reached approximately 250,000 cps.

[0265] Viscosity was measured using a BH-II model viscometer from Toki Sangyo Co., Ltd., while maintaining the polymer solution temperature at 10°C. The RPM was set to 4, and spindle number 7 was used to confirm whether the target viscosity was achieved.

[0266] The third polymer solution was applied to a glass plate and dried with hot air at 100°C for 30 minutes. After peeling the dried polyamide polymer from the glass plate, it was fixed to a pin frame and heated at a rate of 2°C / min in the temperature range of 80°C to 300°C to obtain a polyamide film with a thickness of 50 μm.

[0267] Regarding the content of diamine compounds (TFMB) and dicarbonyl compounds (IPC, TPC), Table 3 shows the number of moles of dicarbonyl compounds and the order of addition, based on 100 moles of diamine compounds.

[0268] In the case of dicarbonyl compounds, the steps of adding and stirring were performed in the order shown in Table 3 (from top to bottom). For example, in Example 4, this means that after adding the diamine compound to the organic solvent and dissolving it, the steps of adding 38.8 mol% TPC and stirring, adding 58.2 mol% IPC and stirring, adding 1.2 mol% TPC and stirring, and adding 1.8 mol% IPC and stirring were performed in sequence.

[0269] (Examples 5-8 and Comparative Examples 4-6) As shown in Table 3 below, the film was manufactured in the same manner as in Example 4, except that the content of each reactant was changed.

[0270] (Comparative Example 7) In Example 4, when preparing the first polymer solution, 70 mol% of TPC and 30 mol% of IPC were added based on the total dicarbonyl compounds to prepare the first polymer solution. The steps for preparing the second and third polymer solutions were omitted, and the first polymer solution was applied to a glass plate, dried, and heat-treated to produce a polyamide film.

[0271] (Comparative Example 8) A polyamide film was produced in the same manner as in Comparative Example 7, except that the first polymer solution was prepared by adding 75 mol% TPC based on the total dicarbonyl compounds and 25 mol% IPC.

[0272] The physical properties of the films produced in Examples 4-8 and Comparative Examples 4-6 were measured and evaluated, and the following FT-IR analysis was performed.

[0273] (Evaluation Example 7: FT-IR (Fourier-Transform Infrared Spectroscopy) Analysis) FT-IR analysis was performed on the polyamide films of the examples and comparative examples. A Thermo Fisher FT-IR spectrometer was used, and the analytical conditions were set as follows. -Detector: MIR TGA - Scan range: 4000 cm² -1 ~650cm -1 - Resolution: 4 -Number of scans: 16

[0274] Figure 5 shows the FT-IR analysis spectra of the polyamide films of the examples and comparative examples. Figures 6 to 8 show the FT-IR analysis spectra of the polyamide films of Example 7 and Comparative Examples 5 and 6, respectively.

[0275] The spectra in Figures 5-8 are at 4000 cm⁻¹. -1 ~650cm -1 In the spectrum against wavenumber, wavenumber approximately 3800 cm⁻¹ -1 ~2500cm -1 The section has been expanded.

[0276] The spectra in Figures 6-8 are at a wavenumber of approximately 3800 cm⁻¹. -1 ~2500cm -1 The largest IR peak in this section is wavenumber 1415cm. -1 The spectrum was normalized based on the height of the IR peak, and the spectrum shown in Figure 5 was obtained.

[0277] Referring to Figures 5-7, the wavenumber is approximately 2960 cm². -1 ~2895cm -1 A first IR peak was observed in the section, with a wavenumber of 2890 cm⁻¹. -1 1-2820cm -1 A second IR peak was observed in this section, and the highest point of the first IR peak was at a wavenumber of approximately 2924.43 cm. -1 Located at [location], the highest point of the second IR peak is approximately 2853.72 cm. -1 It was located there.

[0278] Regarding the first IR peak and the second IR peak, the starting point of the peak (2960 cm each) -1 and 2890cm -1 ) and the terminus (2895cm each) -1 and 2820cm -1 A straight line was drawn connecting the two points to set the baseline for the IR peaks. For each IR peak, the area of ​​the portion with an intensity value greater than the baseline was calculated by integrating the portion.

[0279] Then, the ratio of the area of ​​the first IR peak to the area of ​​the second IR peak (area ratio) was calculated and is shown in Table 3 below.

[0280] [Table 3]

[0281] Referring to Table 3 above, it was confirmed that the examples with an area ratio of 1.4 or less showed improvements in modulus, light transmittance, haze, and yellowness compared to the comparative examples.

[0282] For example, in comparative examples where the ratio of TPC to IPC used in polymerization was 5:95, 80:20, or 95:5, the area of ​​the first IR peak on the IR spectrum was more than 1.5 times larger than the area of ​​the second IR peak, resulting in a deterioration of modulus, light transmittance, haze, and / or yellowness.

[0283] Furthermore, in Comparative Examples 7 and 8, the viscosity of the first polymer solution fell significantly short of 250,000 cps, making it difficult to produce a polyamide film of a grade that was substantially usable as an optical film. The resulting polyamide films had significantly uneven thickness, and variations in properties such as modulus, light transmittance, haze, and yellowness increased in each region of the polyamide film, resulting in a significant decrease in their suitability as cover windows for display devices. [Explanation of Symbols]

[0284] 100: Polyamide film 101: 1st page 102:Second side 200: Functional Layer 300: Cover window 400:Display section 500: Adhesive layer

Claims

1. Contains polyamide polymers, Wavenumber 2950 cm⁻¹ on the IR spectrum －１ ~2900cm －１ The first IR peak, which has the maximum value in the section, and wavenumber 2875 cm －１ ~2825cm －１ Including the second IR peak which has the maximum value in the interval, The area of ​​the first IR peak is 1.4 times or less the area of ​​the second IR peak. The polyamide polymer comprises two or more amide repeating units, The two or more amide repeating units include a first amide repeating unit derived from a first dicarbonyl compound and a second amide repeating unit derived from a second dicarbonyl compound. The angle between the two carbonyl groups in the first dicarbonyl compound is 160° to 180°. A polyamide film in which the angle between the two carbonyl groups in the second dicarbonyl compound is 80° to 140°.

2. The polyamide film according to claim 1, wherein the area of ​​the first IR peak is 0.6 times or more the area of ​​the second IR peak.

3. The polyamide film according to claim 1, wherein the area of ​​the first IR peak is 0.8 to 1.2 times the area of ​​the second IR peak.

4. Based on a film thickness of 50 μm, Modulus is 5 GPa or higher, Transmittance of 80% or more, Haze is less than 1%, A polyamide film according to claim 1, wherein the yellowness is 3.5 or less.

5. A cover window for a display device, comprising the polyamide film and a functional layer as described in claim 1.

6. Display unit and The display unit includes a cover window positioned on the display unit, The cover window comprises the polyamide film and functional layer described in claim 1, in a display device.

7. The process involves polymerizing a diamine compound and a dicarbonyl compound in an organic solvent to prepare a polymer solution containing a polyamide polymer at a temperature of -20°C to 25°C, The steps include: casting the polymer solution to produce a gel sheet; The step includes heat treatment of the gel sheet, The dicarbonyl compound comprises a first dicarbonyl compound and a second dicarbonyl compound having a smaller angle between the two carbonyl groups than the first dicarbonyl compound. The step of preparing a polymer solution containing the polyamide polymer is as follows: The step of adding a diamine compound to an organic solvent and dissolving it, The first step involves adding a first dicarbonyl compound and stirring, then adding a second dicarbonyl compound and stirring to prepare a first polymer solution. The steps include: adding a first dicarbonyl compound or a second dicarbonyl compound and stirring to prepare a second polymer solution; The steps of adding the first or second dicarbonyl compound and stirring to prepare the third polymer solution are carried out sequentially. The content of the first dicarbonyl compound or the second dicarbonyl compound added in the step of preparing the second polymer solution is 0.5 mol% to 15 mol% based on the total number of moles of the dicarbonyl compounds. The content of the first dicarbonyl compound or the second dicarbonyl compound added in the step of preparing the third polymer solution is 0.5 mol% to 15 mol% based on the total number of moles of the dicarbonyl compounds. The method for producing a polyamide film according to claim 1, wherein the molar ratio of the first dicarbonyl compound to the second dicarbonyl compound is 10:90 to 79:

21.

8. A method for producing a polyamide film according to claim 7, wherein the first dicarbonyl compound is added in the step of preparing the second polymer solution, and the second dicarbonyl compound is added in the step of preparing the third polymer solution.

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