Polyamide film, its manufacturing method, and cover window and display device including same

Abstract

To provide a polyamide-based film that is excellent in solvent resistance and optical properties, a method for preparing the same, and a cover window for a display device comprising the same.SOLUTION: A polyamide-based film comprises a polyamide-based polymer. When 3D surface roughness of a first surface of the film is measured, volume (natural volume) between the surface and a reference plane placed at the highest peak of a surface parallel to a surface plane is 100 μm3 to 2,800 μm3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The implementation relates to polyamide-based films, methods for their manufacture, and cover windows and display devices containing same. [Background technology]

[0002] Polyamide resins such as poly(amide-imide) (PAI) have excellent resistance to friction, heat, and chemicals, and are used in primary electrical insulation materials, coating agents, adhesives, extrusion resins, heat-resistant paints, heat-resistant boards, heat-resistant adhesives, heat-resistant fibers, and heat-resistant films.

[0003] Polyamides are used in a variety of fields. For example, polyamides are made into powder form and used as coatings for metals or magnet wires, and are mixed with other additives depending on the application. Polyamides are also used as decorative and corrosion-resistant paints together with fluoropolymers, and serve to adhere the fluoropolymers to metal substrates. Polyamides are also used to coat kitchen utensils, and are used as membranes for gas separation, due to their heat and chemical resistance, and are also used in devices that filter contaminants such as carbon dioxide, hydrogen sulfide, and impurities in natural gas wells.

[0004] Recently, polyamide-based films have been developed that are cheaper and have excellent optical, mechanical, and thermal properties by forming polyamide into films. Such polyamide-based 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-reflection films, compensation films, or retardation films when retardation properties are realized.

[0005] When such polyamide-based films are applied to foldable displays, flexible displays, etc., optical properties such as transparency and colorlessness, and mechanical properties such as flexibility and hardness are required. However, optical properties and mechanical properties are generally in a trade-off relationship, and improving mechanical properties may result in a decrease in optical properties.

[0006] Therefore, there is a continuing need for research into polyamide-based films with improved mechanical and optical properties. Summary of the Invention [Problem to be solved by the invention]

[0007] Implementations provide polyamide-based films with excellent optical and mechanical properties, and cover windows and display devices containing same.

[0008] The implementation provides a method for producing polyamide-based films with excellent optical and mechanical properties. [Means for solving the problem]

[0009] The polyamide-based film according to the embodiment includes a polyamide-based polymer, and when measuring the 3D surface roughness of the first surface of the film, the volume (natural volume) between the surface and a reference plane located at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 It is.

[0010] A cover window for a display device according to an embodiment includes a polyamide-based film and a functional layer, the polyamide-based film includes a polyamide-based polymer, and when measuring the 3D surface roughness of a first surface of the polyamide-based film, the volume between the surface and a reference plane located at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 It is.

[0011] A method for producing a polyamide-based film according to an embodiment includes the steps of: polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent to prepare a polymer solution containing a polyamide-based polymer; casting and drying the polymer solution on a belt to produce a gel sheet; and heat-treating the gel sheet. Effect of the Invention

[0012] The polyamide-based film according to the embodiment includes a polyamide-based polymer, and when measuring the 3D surface roughness of the first surface of the film, the volume between the surface and a reference plane located at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 By adjusting the viscosity within this range, the solvent resistance is excellent, optical properties such as yellowness index and transmittance are improved, and smoothness and winding properties can be improved. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 shows a schematic perspective view of a display device according to one implementation. [Diagram 2] FIG. 2 shows a schematic exploded view of a display device according to one implementation. [Diagram 3] FIG. 3 shows a schematic cross-sectional view of a display device according to one implementation. [Figure 4] FIG. 4 shows a schematic flow chart of a method for producing a polyamide-based film according to one embodiment. [Diagram 5] FIG. 5 is a schematic conceptual diagram of a polyamide film processing facility according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be realized in various different forms and is not limited to the embodiments described herein.

[0015] In this specification, when it is described that each film, window, panel, or layer is formed "on" or "under" each film, window, panel, or layer, "on" and "under" include those formed "directly" or "indirectly through other components. In addition, the reference to the top / bottom of each component is described based on the drawings. Note that the size of each component in the drawings may be exaggerated for the purpose of explanation and does not represent the size actually applied. In addition, the same reference numerals refer to the same components throughout the specification.

[0016] In this specification, when a part is said to "comprise" a certain component, unless specifically stated to the contrary, it does not mean that it excludes other components, but that it may further include other components.

[0017] In this specification, the singular expressions are to be construed as including the singular or plural as the context requires, unless otherwise specified.

[0018] Also, all numbers and expressions expressing quantities of components, reaction conditions, and the like described herein should be understood to be modified in all instances by the term "about," unless otherwise specified.

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

[0020] In addition, unless otherwise specified, the term "substituted" in this specification means substituted with one or more substituents selected from the group consisting of deuterium, -F, -Cl, -Br, -I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, an ester group, a ketone group, a carboxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alicyclic organic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group, and the substituents listed above may be bonded to each other to form a ring.

[0021] [Polyamide film] The embodiment provides a polyamide-based film with excellent solvent resistance, improved optical properties such as yellowness index and transmittance, and improved slipperiness and windability.

[0022] A polyamide-based film according to one implementation includes a polyamide-based polymer.

[0023] In the 3D surface roughness measurement of the first surface of the polyamide-based film, the volume between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 It is.

[0024] The 3D surface roughness is data obtained by optically or contact-measuring the unevenness of an object surface, and may indicate topographical features of a given area in the planar direction of the object surface. The natural volume may refer to, for example, the amount of liquid required for a surface to be completely submerged. Specifically, the volume may be a value measured by using Bruker's CONTOUR GT-X, setting a measurement area for one measurement to 166 μm×220 μm, applying a 20x objective lens, and then applying a Gaussian filter.

[0025] For example, the volume of the first surface is 2800 μm 3 If the volume of the first surface is more than 100 μm, the haze change of the film after immersion in a solvent becomes very large, the optical properties deteriorate, and there is a possibility that a coating defect due to air bubbles may occur during surface treatment coating. 3 If it is less than this, blocking or the like may occur when the film is wound up, which may result in a decrease in the winding properties and slipperiness of the film.

[0026] According to an embodiment, the volume of the first surface is 100 μm 3 ~2800μm 3 When the temperature is controlled within this range, the solvent resistance of the film is excellent, and optical properties such as transmittance, haze, and yellowness are all improved. When the film is wound into a roll, defects such as lumps do not occur, and the wound film can be easily unwound.

[0027] Specifically, the volume of the first surface is 2800 μm 3 Below, 2700μm 3 Below, 2600μm 3 Below, 2500μm 3 Below, 2400μm 3 Below, 2000μm 3 Less than or equal to 1800μm 3 Less than or equal to 100m 3 More than 150μm 3 More than 200μm 3 or more, or 250μm 3 It could be more than that.

[0028] More specifically, the volume of the first surface is 100 μm 3 ~2500μm 3 , 100μm 3 ~2400μm 3 , 250μm 3 ~2800μm 3 , 250μm 3 ~2500μm 3 , or 250 μm 3 ~2400μm 3 It may be, but is not limited to this.

[0029] In one embodiment, the first surface may be the air surface of the film. The air surface means the surface that does not contact a support used in forming a polyamide-based film. Specifically, in the method for producing the film, the air surface may mean the surface that does not contact a belt on which a polyamide-based polymer solution is cast and dried.

[0030] In the 3D surface roughness measurement of the second surface of the polyamide film, the volume between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane is 5 μm 3 ~200μm 3 It could be.

[0031] Specifically, the volume of the second surface is 200 μm 3 Below, 180μm 3 Below, 150μm 3 Below, 120μm 3 Less than or equal to 100μm 3 Less than 5μm 3 More than 7μm 3 More than 10μm 3 or more, 12μm 3 or more, or 15μm 3 It could be more than that.

[0032] More specifically, the volume of the second surface is 5 μm 3 ~150μm 3 , 5 μm 3 ~100μm 3 , 10μm 3 ~200μm 3 , 10μm 3 ~150μm 3 , 10μm 3 ~100μm 3 , 12 μm 3 ~200μm 3 , 12 μm 3 ~150μm 3 , or 12 μm 3 ~100μm 3 It may be, but is not limited to this.

[0033] According to an embodiment, when the volume of the second surface is adjusted within the above range, the solvent resistance, optical properties, winding property, and slip property of the film can be improved.

[0034] In one embodiment, the second surface may be a belt surface of the film. The belt surface means a surface that contacts a support used in forming a polyamide-based film. Specifically, in the film manufacturing method, the belt surface may mean a surface that contacts a belt on which a polyamide-based polymer solution is cast and dried.

[0035] In some implementations, the polyamide-based film has a 3D surface roughness measurement of 4400 / mm2 or less, as measured by the following method: 2 It can be the following:

[0036] <Measurement method> Using Bruker's CONTOUR GT-X, the measurement area is set to 166 μm × 220 μm, and a 20x objective lens is used for measurement, after which a Gaussian filter is applied.

[0037] The vertex means, for example, a peak that is found at a point that is 5% or more higher than the mean plane in terms of surface height difference (Sz) during 3D surface roughness measurement. The vertex also means a peak that is separated from other vertices by a specific distance (1% of the sample side size). The peak may mean all points located above the nearest eight points. More specifically, the number of vertices per unit area (Sds) may be a value measured based on the standard set forth in EUR 15178 EN.

[0038] Specifically, the Sds is 4000 / mm 2 Below, 3900 / mm 2 Below, 3800 / mm 2 Below, 3500 / mm 2 Below, 3300 / mm 2or less than 3100 / mm 2 The Sds may be, but is not limited to, 500 / mm 2 More than 800 / mm 2 More than 1000 / mm 2 More than 1200 / mm 2 More than 1500 / mm 2 More than 1600 / mm 2 More than 1800 / mm 2 More than 2000 / mm 2 More than 2200 / mm 2 or more, or 2400 / mm 2 It can be more than this, but is not limited to this.

[0039] For example, the Sds is 1600 to 4400 / mm 2 , 1600~4000 / mm 2 , 1600~3900 / mm 2 , 1600~3500 / mm 2 , 1600~3100 / mm 2 , 2000~4400mm 2 , 2000~4000mm 2 , 2000~3900 / mm 2 , 2000~3500 / mm 2 , 2000~3100 / mm 2 , 2400~4400 / mm 2 , 2400~4000 / mm 2 , 2400~3900 / mm 2 , 2400~3500 / mm 2 , or 2400~3100 / mm 2 It could be.

[0040] In some implementations, the surface height difference (Sz) may be 320 nm or more. Preferably, but not limited to, the Sz may be 330 nm or more. Also, the Sz may be, but not limited to, 2000 nm or less, 1800 nm or less, 1500 nm or less, 1200 nm or less, 1000 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 550 nm or less.

[0041] The Sz (surface height difference) may mean the average difference value between the five highest peaks and the five lowest valleys. The peaks may mean all points located above the eight closest points, and the valleys may mean all points located below the eight closest points. Specifically, the Sz may be a S10z (ten point height of surface) value defined based on ISO 25178. More specifically, the Sz may be a value obtained by measuring a single measurement area of ​​166 μm×220 μm using a Bruker CONTOUR GT-X, applying a 20x objective lens, and then applying a Gaussian filter.

[0042] In some implementations, the mean curvature of the vertex (Ssc) may be 24-47 / mm, preferably 24-45 / mm, 24-42 / mm, 25-47 / mm, 25-45 / mm, or 25-42 / mm.

[0043] When the film satisfies the above Sds, Sz and / or Ssc properties, a film excellent in modulus, transmittance, haze, yellowness, pencil hardness, slipperiness and winding property can be realized.

[0044] The refractive index in the x direction (n x ) may be 1.60 to 1.70, 1.61 to 1.69, 1.62 to 1.68, 1.64 to 1.68, 1.64 to 1.66, or 1.64 to 1.65.

[0045] In addition, the refractive index in the y direction of the polyamide film (n y ) may be 1.60 to 1.70, 1.61 to 1.69, 1.62 to 1.68, 1.63 to 1.68, 1.63 to 1.66, or 1.63 to 1.64.

[0046] Furthermore, the z-direction refractive index (n z ) may be 1.50 to 1.60, 1.51 to 1.59, 1.52 to 1.58, 1.53 to 1.58, 1.54 to 1.58, or 1.54 to 1.56.

[0047] When the values ​​of the x-direction refractive index, y-direction refractive index, and z-direction refractive index of the polyamide-based film are within the above ranges, when the film is applied to a display device, excellent visibility can be achieved not only when viewed from the front but also from the side, and a wide viewing angle can be achieved.

[0048] In-plane retardation (R o ) may be 800 nm or less. Specifically, the in-plane retardation (R o ) can be 700 nm or less, 600 nm or less, 550 nm or less, 100 nm to 800 nm, 200 nm to 800 nm, 200 nm to 700 nm, 300 nm to 700 nm, 300 nm to 600 nm, or 300 nm to 540 nm.

[0049] In addition, the thickness direction retardation (R th ) may be 5000 nm or less. Specifically, the thickness direction retardation (R th ) can be 4800 nm or less, 4700 nm or less, 4650 nm or less, 1000 nm to 5000 nm, 1500 nm to 5000 nm, 2000 nm to 5000 nm, 2500 nm to 5000 nm, 3000 nm to 5000 nm, 3500 nm to 5000 nm, 4000 nm to 5000 nm, 3000 nm to 4800 nm, 3000 nm to 4700 nm, 4000 nm to 4700 nm, or 4200 nm to 4650 nm.

[0050] Here, the in-plane retardation (R o ) is the anisotropy of the refractive index along two perpendicular axes in the plane of the film (△n xy =|n x -n y |) and the film thickness (d) (△n xy × d) and is a measure of optical isotropy or anisotropy.

[0051] In addition, thickness direction retardation (R th ) are the two birefringences Δn xz (=|n x -n z |) and △n yz (=|n y -n z This parameter is defined as the average of the phase difference obtained by multiplying the phase difference (f,g) and the film thickness (d).

[0052] When the in-plane retardation and thickness direction retardation of the polyamide-based film are within the above ranges, optical distortion and color distortion can be minimized when the film is applied to a display device, and the light leakage phenomenon in which light leaks from the side can also be minimized.

[0053] The polyamide-based film may contain a filler. The filler can adjust the mechanical properties of the film, such as hardness, modulus, brittleness, flexibility, and the optical properties, such as transmittance, haze, yellowness, and the like, and can adjust the topographical properties of the film surface.

[0054] In some embodiments, the filler may be particles having a hardness of 2.5 to 6, but is not limited to these. When the filler has the above hardness, the hardness and modulus of the film can be improved without decreasing the flexibility. In addition, the optical properties of the film can be prevented from being deteriorated. Preferably, the hardness of the filler may be 2.5 to 5 or 2.5 to 4.

[0055] Preferably, the filler may include one or more selected from the group consisting of silica (SiO2), barium sulfate (BaSO4), aluminum oxide (Al2O3), and zirconium oxide (ZrO2).

[0056] The filler has a particle size distribution of 50% cumulative mass particle size distribution diameter (D 50Specifically, the 50% cumulative mass particle size distribution diameter (D 50 ) may be, but is not limited to, 30nm to 200nm, 30nm to 180nm, 30nm to 150nm, 30nm to 120nm, 30nm to 100nm, 40nm to 200nm, 40nm to 180nm, 40nm to 150nm, 40nm to 120nm, 40nm to 100nm, 50nm to 200nm, 50nm to 180nm, 50nm to 150nm, 50nm to 120nm, 50nm to 100nm, 60nm to 200nm, 60nm to 180nm, 60nm to 150nm, 60nm to 120nm, or 60nm to 100nm.

[0057] When the filler has the above particle size, the flexibility and optical properties of the film are not reduced, and the winding properties and slipperiness of the film can be improved.

[0058] In some implementations, the filler has a particle size distribution having a cumulative mass particle size distribution diameter (D 90 Specifically, the 90% cumulative mass particle size distribution diameter (D 90 ) may be, but is not limited to, 50nm to 900nm, 50nm to 800nm, 50nm to 700nm, 50nm to 600nm, 50nm to 500nm, 70nm to 1000nm, 70nm to 900nm, 70nm to 800nm, 70nm to 700nm, 70nm to 600nm, 70nm to 500nm, 90nm to 1000nm, 90nm to 900nm, 90nm to 800nm, 90nm to 700nm, 90nm to 600nm, 90nm to 500nm, 110nm to 1000nm, 110nm to 900nm, 110nm to 800nm, 110nm to 700nm, 110nm to 600nm, or 110nm to 500nm.

[0059] In some implementations, the filler has a particle size distribution having a 10% cumulative mass particle size distribution diameter (D 10 Specifically, the 10% cumulative mass particle size distribution diameter (D 10) may be, but is not limited to, 5 nm to 180 nm, 5 nm to 160 nm, 5 nm to 140 nm, 5 nm to 130 nm, 10 nm to 200 nm, 10 nm to 180 nm, 10 nm to 160 nm, 10 nm to 140 nm, 10 nm to 130 nm, 15 nm to 200 nm, 15 nm to 180 nm, 15 nm to 160 nm, 15 nm to 140 nm, 15 nm to 130 nm, 20 nm to 200 nm, 20 nm to 180 nm, 20 nm to 160 nm, 20 nm to 140 nm, or 20 nm to 130 nm.

[0060] The filler contained in the polyamide film may have a SPAN value of 0.5 to 20, as defined by the following formula 1:

[0061] <Expression 1> JPEG0007657857000001.jpg1133In the above formula 1, D 10 is the 10% cumulative mass particle size distribution diameter in the particle size distribution of the filler, D 50 is the 50% cumulative mass particle size distribution diameter in the particle size distribution of the filler, D 90 is the 90% cumulative mass particle size distribution diameter in the particle size distribution of the filler.

[0062] Specifically, the SPAN value can be, but is not limited to, 0.5 to 10, 0.5 to 5, 0.5 to 2, 0.7 to 20, 0.7 to 10, 0.7 to 5, 0.7 to 2, 0.8 to 20, 0.8 to 10, 0.8 to 5, 0.8 to 2, 0.9 to 20, 0.9 to 10, 0.9 to 5, or 0.9 to 2.

[0063] The content of the filler may be 200 ppm or more based on the total weight of the polyamide-based polymer. Specifically, the content of the filler may be 400 ppm or more, 600 ppm or more, 800 ppm or more, 1000 ppm or more, or 1500 ppm or more based on the total weight of the polyamide-based polymer. Also, the content of the filler may be 2500 ppm or less, 2300 ppm or less, 2100 ppm or less, 2000 ppm or less, or 1500 ppm or less based on the total weight of the polyamide-based polymer, but is not limited thereto. More specifically, the content of the filler may be 200 ppm to 2500 ppm based on the total weight of the polyamide-based polymer, but is not limited thereto.

[0064] If the content of the filler is out of the above range, the haze of the film increases rapidly, the fillers may aggregate on the film surface, causing a visually noticeable foreign body sensation, problems with running during the production process, and deterioration in winding properties. In addition, the mechanical properties of the film, such as hardness and flexibility, and the optical properties, such as transmittance and yellowness, may be comprehensively impaired.

[0065] For example, the particle size and content of the filler can be adjusted to adjust the surface properties such as the 3D surface roughness volume, Sds, Sz, and Ssc to a desired range.

[0066] The refractive index of the filler may be 1.55 to 1.75. Specifically, the refractive index of the filler may be, but is not limited to, 1.60 to 1.75, 1.60 to 1.70, 1.60 to 1.68, or 1.62 to 1.65.

[0067] When the refractive index of the filler satisfies the above range, n x , n y , n z By appropriately adjusting the birefringence values ​​associated with the .lambda., the brightness at various angles of the film can be improved.

[0068] On the other hand, if the refractive index of the filler is outside the above range, the presence of the filler may be visible to the naked eye on the film, or the filler may cause problems such as an increase in haze.

[0069] The filler may be uniformly dispersed throughout the film without any special surface coating treatment.

[0070] By including the filler in the polyamide-based film, the film can ensure a wide viewing angle without any deterioration in optical properties.

[0071] The residual solvent content in the polyamide film may be 1500 ppm or less. For example, the residual solvent content may be, but is not limited to, 1200 ppm or less, 1000 ppm or less, 800 ppm or less, or 500 ppm or less.

[0072] The residual solvent means the amount of solvent that is not evaporated during the film production and remains in the final film.

[0073] If the content of the residual solvent in the polyamide film exceeds the above range, the durability of the film may decrease and the brightness may be affected.

[0074] According to an embodiment, when a polyamide-based film having a thickness of 50 μm is folded to a curvature radius of 3 mm, the film can be folded more than 200,000 times before breaking.

[0075] The number of folding cycles is defined as one cycle of bending the film to a curvature radius of 3 mm and then unfolding it.

[0076] Since the polyamide-based film satisfies the folding number within the above range, it can be usefully applied to a foldable display device or a flexible display device.

[0077] According to an embodiment, the surface roughness of the polyamide-based film may be 0.01 μm to 0.07 μm. Specifically, the surface roughness may be 0.01 μm to 0.07 μm or 0.01 μm to 0.06 μm, but is not limited thereto.

[0078] When the surface roughness of the polyamide film satisfies the above range, it is advantageous to realize high brightness even when the angle from the normal direction of the surface light source is large.

[0079] In some implementations, the polyamide-based film may have a thickness deviation of 4 μm or less based on a thickness of 50 μm. The thickness deviation may refer to the deviation between the maximum or minimum value from the average thickness measured at 10 random positions on the film. In this case, the polyamide-based film has a uniform thickness, so that the optical and mechanical properties at each point may be uniform.

[0080] The polyamide film may have a transmittance of 80% or more. For example, the transmittance may be 82% or more, 85% or more, 88% or more, 89% or more, 80% to 99%, 88% to 99%, or 89% to 99%, but is not limited thereto.

[0081] The polyamide film may have a yellow index of 4 or less. For example, the yellow index may be 3.5 or less or 3 or less, but is not limited thereto.

[0082] The polyamide-based film may have a modulus of 5 GPa or more. Specifically, the modulus may be, but is not limited to, 5.5 GPa or more, 6.0 GPa or more, or 6.5 GPa or more.

[0083] The polyamide film may have a compressive strength of 0.4 kgf / μm or more. Specifically, the compressive strength may be 0.45 kgf / μm or more or 0.46 kgf / μm or more, but is not limited thereto.

[0084] When the polyamide film is perforated in UTM compression mode with a 2.5 mm spherical tip at a speed of 10 mm / min, the maximum diameter of the perforation including cracks (mm) is 60 mm or less. Specifically, the maximum diameter of the perforation 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.

[0085] The haze of the polyamide film may be 1% or less. Specifically, the haze may be 0.7% or less or 0.5% or less, but is not limited thereto.

[0086] The polyamide-based film may have a pencil hardness of HB or more. Specifically, the pencil hardness may be H or more, but is not limited thereto.

[0087] The polyamide film has a tensile strength of 15 kgf / mm 2 Specifically, the tensile strength may be 18 kgf / mm 2 Above 20kgf / mm 2 Above, 21kgf / mm 2 or more than 22kgf / mm 2 It may be more than this, but is not limited to this.

[0088] The polyamide film may have an elongation percentage of 15% or more. Specifically, the elongation percentage may be, but is not limited to, 16% or more, 17% or more, or 17.5% or more.

[0089] The above-mentioned physical properties of the polyamide film are based on a thickness of 40 μm to 60 μm, for example, based on a thickness of 50 μm.

[0090] For example, the polyamide-based film may include a polyamide-based polymer and may have a modulus of 5 GPa or more, a transmittance of 80% or more, a haze of 1% or less, a yellowness index of 3 or less, and a pencil hardness of F or more, based on a film thickness of 50 μm.

[0091] The film was immersed in MIBK (methyl isobutyl ketone) solvent for 5 seconds, then dried at 80°C for 2 minutes, and the haze was measured. The haze change (ΔHz M ) may be 2.0% or less.

[0092] Specifically, the haze change (ΔHz M ) may be, but is not limited to, 1.8% or less, 1.6% or less, 1.4% or less, 1.2% or less, or 1.0% or less.

[0093] The ΔHz M (%) is Hz M -Hz0, where Hz0 represents the initial haze (%) of the film, and Hz M indicates the haze (%) measured after the film was immersed in MIBK solvent for 5 seconds and then dried at 80° C. for 2 minutes.

[0094] The film is immersed in MIBK solvent for 5 seconds, then dried at 80°C for 2 minutes. The film surface is rubbed 3,000 times with a MINOAN abrasion test eraser having a hardness of 81 (type A durometer) and a load of 500 g, after which the water contact angle of the film surface can be 60° to 80°.

[0095] Specifically, the water contact angle of the film surface may be 65° to 80°, and preferably, the water contact angle of the film surface may be 70° to 80°.

[0096] The haze change amount (ΔHz M ) and the water contact angle of the film surface can be used as indicators for judging the solvent resistance of the film.

[0097] The polyamide-based film according to the embodiment includes a polyamide-based polymer, which may be formed by polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound.

[0098] For example, the polyamide polymer may be formed by polymerizing a diamine compound and a dicarbonyl compound, or may be formed by polymerizing a diamine compound, a dicarbonyl compound, and a dianhydride compound.

[0099] The polyamide-based polymer is a polymer containing an amide repeating unit, and may optionally further contain an imide repeating unit.

[0100] Specifically, the polyamide polymer contains an amide repeating unit derived from the polymerization of a diamine compound and a dicarbonyl compound, and optionally contains an imide repeating unit derived from the polymerization of a diamine compound and a dianhydride compound.

[0101] The diamine compound is a compound that forms an imide bond with the dianhydride compound and an amide bond with the dicarbonyl compound to form a copolymer.

[0102] The diamine compound is not particularly limited, and may be, for example, an aromatic diamine compound having an aromatic structure. For example, the diamine compound may be a compound represented by the following Formula 1: [C1] JPEG0007657857000002.jpg760

[0103] In the above Chemical Formula 1, E is a substituted or unsubstituted divalent C6-C 30 Alicyclic radicals, substituted or unsubstituted divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C6-C 30 Aromatic ring groups, substituted or unsubstituted divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 Alkynylene groups may be selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0104] e is selected from integers of 1 to 5, and when e is 2 or greater, E may be the same or different.

[0105] (E) of Chemical Formula 1 e can be selected from groups represented by the following chemical formulas 1-1a to 1-14a, but is not limited thereto. JPEG0007657857000003.jpg89141

[0106] Specifically, (E) of the above Chemical Formula 1 e can be selected from groups represented by the following chemical formulas 1-1b to 1-13b, but is not limited thereto. JPEG0007657857000004.jpg88131

[0107] More specifically, (E) of the above Chemical Formula 1 e may be a group represented by the above chemical formula 1-6b or a group represented by the above chemical formula 1-9b.

[0108] In one implementation, the diamine compound may include a compound having a fluorine-containing substituent or a compound having an ether group (-O-).

[0109] The diamine compound may be a compound having a fluorine-containing substituent, where the fluorine-containing substituent is a fluorinated hydrocarbon group, specifically, a trifluoromethyl group, but is not limited thereto.

[0110] In some implementations, the diamine compound may include one type of diamine compound, i.e., the diamine compound may consist of a single component.

[0111] For example, the diamine compound may include, but is not limited to, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB / TFDB) having the following structure: JPEG0007657857000005.jpg4778

[0112] The dianhydride compound has a low birefringence value, and therefore can contribute to improving optical properties such as transmittance of a film containing the polyamide-based polymer.

[0113] The dianhydride compound is not particularly limited, and may be, for example, an aromatic dianhydride compound having an aromatic structure. For example, the aromatic dianhydride compound may be a compound represented by the following formula 2: [Case 2] JPEG0007657857000006.jpg3654

[0114] In the above formula 2, G is a substituted or unsubstituted tetravalent C6-C 30 Alicyclic radicals, substituted or unsubstituted tetravalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted tetravalent C6-C 30 Aromatic ring groups, substituted or unsubstituted, tetravalent C4-C 30 an aromatic heterocyclic group, wherein the alicyclic group, the heteroalicyclic group, the aromatic ring group, or the aromatic heterocyclic group is present alone or is bonded to each other to form a fused ring, or is a substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 The alkynylene groups are linked by a linking group selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0115] G in the above Chemical Formula 2 may be selected from groups represented by the following Chemical Formulas 2-1a to 2-9a, but is not limited thereto. JPEG0007657857000007.jpg84143

[0116] For example, G in the above chemical formula 2 can be a group represented by the above chemical formula 2-2a, a group represented by the above chemical formula 2-8a, or a group represented by the above chemical formula 2-9a.

[0117] In one implementation, the dianhydride compound can include a compound having a fluorine-containing substituent, a compound having a biphenyl group, or a compound having a ketone group.

[0118] The fluorine-containing substituent is a fluorinated hydrocarbon group, and specifically may be, but is not limited to, a trifluoromethyl group.

[0119] In other implementations, the dianhydride compound may consist of one single component or two mixed components.

[0120] For example, the dianhydride compound may include, but is not limited to, one or more selected from the group consisting of 2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) having the following structures: JPEG0007657857000008.jpg8071

[0121] The diamine compound and the dianhydride compound can be polymerized to produce a polyamic acid.

[0122] The polyamic acid is then converted to a polyimide by a dehydration reaction, the polyimide comprising imide repeat units.

[0123] The polyimide may form a repeating unit represented by the following chemical formula A. [Chemical A] JPEG0007657857000009.jpg4074 In the above chemical formula A, the explanations for E, G, and e are as described above.

[0124] For example, the polyimide may include a repeating unit represented by the following formula A-1, but is not limited thereto. [Chemical A-1] JPEG0007657857000010.jpg41128 In the above chemical formula A-1, n is an integer of 1 to 400.

[0125] The dicarbonyl compound is not particularly limited, and may be, for example, a compound represented by the following formula 3: [C3] JPEG0007657857000011.jpg2657In the above Chemical Formula 3, J is a substituted or unsubstituted divalent C6-C 30 Alicyclic radicals, substituted or unsubstituted divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C6-C 30 Aromatic ring groups, substituted or unsubstituted divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 Alkynylene groups may be selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0126] j is selected from integers of 1 to 5, and when j is 2 or more, J may be the same or different. X is a halogen atom. Specifically, X can be F, Cl, Br, I, etc. More specifically, X can be Cl, but is not limited thereto.

[0127] (J) of the above Chemical Formula 3 j can be selected from groups represented by the following chemical formulas 3-1a to 3-14a, but is not limited thereto. JPEG0007657857000012.jpg102153

[0128] Specifically, (J) of the above Chemical Formula 3 j can be selected from groups represented by the following chemical formulas 3-1b to 3-8b, but is not limited thereto. JPEG0007657857000013.jpg74150

[0129] More specifically, (J) of the above Chemical Formula 3 j may be a group represented by the above chemical formula 3-1b, a group represented by the above chemical formula 3-2b, a group represented by the above chemical formula 3-3b, or a group represented by the above chemical formula 3-8b.

[0130] For example, (J) in Chemical Formula 3 j may be a group represented by the above chemical formula 3-1b, or a group represented by the above chemical formula 3-2b.

[0131] In one embodiment, the dicarbonyl compound may be a single dicarbonyl compound or a mixture of at least two different dicarbonyl compounds. When two or more dicarbonyl compounds are used, the dicarbonyl compound may be (J) in Formula 3. j may be used two or more selected from the groups represented by the chemical formulas 3-1b to 3-8b.

[0132] In another implementation, the dicarbonyl compound can be an aromatic dicarbonyl compound that includes an aromatic structure.

[0133] 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 structure: JPEG0007657857000014.jpg2657JPEG0007657857000015.jpg2874JPEG0007657857000016.jpg3446

[0134] The diamine compound and the dicarbonyl compound can be polymerized to form a repeating unit represented by the following chemical formula B. [Case B] JPEG0007657857000017.jpg3679In the above chemical formula B, the explanations for E, J, e, and j are as described above.

[0135] For example, the diamine compound and the dicarbonyl compound can be polymerized to form amide repeat units represented by formulas B-1 and B-2.

[0136] Alternatively, the diamine compound and the dicarbonyl compound may be polymerized to form amide repeat units represented by chemical formulas B-2 and B-3.

[0137] [Case B-1] JPEG0007657857000018.jpg38128In the chemical formula B-1, x is an integer of 1 to 400.

[0138] [Case B-2] JPEG0007657857000019.jpg39128 In the chemical formula B-2, y is an integer of 1 to 400.

[0139] [Case B-3] JPEG0007657857000020.jpg40128 In the chemical formula B-3, y is an integer of 1 to 400.

[0140] According to one embodiment, the polyamide-based polymer may include a repeating unit represented by the following chemical formula B, and may optionally include a repeating unit represented by the following chemical formula A: [Chemical A] JPEG0007657857000021.jpg48128

[0141] [Case B] JPEG0007657857000022.jpg41128In the above chemical formula A and chemical formula B, E and J are each independently a substituted or unsubstituted divalent C6-C 30 Alicyclic radicals, substituted or unsubstituted divalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted divalent C6-C 30 Aromatic ring groups, substituted or unsubstituted divalent C4-C 30 Aromatic heterocyclic groups, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 alkynylene groups selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-; e and j are each independently selected from integers of 1 to 5. When e is 2 or more, the 2 or more E's may be the same or different. When j is 2 or more, two or more Js may be the same or different. G is a substituted or unsubstituted tetravalent C6-C 30 Alicyclic radicals, substituted or unsubstituted tetravalent C4-C 30 Heteroalicyclic groups, substituted or unsubstituted tetravalent C6-C 30 Aromatic ring groups, substituted or unsubstituted, tetravalent C4-C 30an aromatic heterocyclic group, wherein the alicyclic group, the heteroalicyclic group, the aromatic ring group, or the aromatic heterocyclic group is present alone or is bonded to each other to form a fused ring, or is a substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 Alkenylene groups, substituted or unsubstituted C2-C 30 The alkynylene groups are linked by a linking group selected from among -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, -C(CH3)2-, and -C(CF3)2-.

[0142] The polyamide polymer may contain imide repeating units and amide repeating units in a molar ratio of 0:100 to 80:20. Specifically, the molar ratio of the imide repeating units to the amide repeating units may be, but is not limited to, 0:100 to 70:30, 0:100 to 60:40, 0:100 to 50:50, 0:100 to 45:55, 1:99 to 50:50, or 5:95 to 50:50.

[0143] When the molar ratio of the imide repeating unit to the amide repeating unit of the polyamide polymer is within the above range, the volume of the polyamide film and 3D surface roughness properties such as Sds, Sz, and Ssc can be effectively controlled, leading to a unique production method and improving the solvent resistance, optical properties, and mechanical durability of the film.

[0144] In the polyamide polymer, the molar ratio of the repeating unit represented by the chemical formula A to the repeating unit represented by the chemical formula B may be 0:100 to 80:20. Specifically, the molar ratio of the repeating unit represented by the chemical formula A to the repeating unit represented by the chemical formula B may be, but is not limited to, 0:100 to 70:30, 0:100 to 60:40, 0:100 to 50:50, 0:100 to 45:55, 1:99 to 50:50, or 5:95 to 50:50.

[0145] In addition to the polyamide-based polymer, the polyamide-based film according to the embodiment may further include one or more selected from the group consisting of a blue pigment and a UVA absorber.

[0146] The blue pigment may include, but is not limited to, OP-1300A from TOYO Corporation.

[0147] In some embodiments, the blue pigment may be contained in an amount of 50 ppm to 5000 ppm based on the total weight of the polyamide-based polymer. Preferably, the blue pigment is contained in an amount of 100 ppm to 5000 ppm, 200 ppm to 5000 ppm, 300 ppm to 5000 ppm, 400 ppm to 5000 ppm, 50 ppm to 3000 ppm, 100 ppm to 3000 ppm, 200 ppm to 3000 ppm, 300 ppm to 3000 ppm, 400 ppm to 3000 ppm, 50 It may be contained at, but is not limited to, ppm to 2000 ppm, 100 ppm to 2000 ppm, 200 ppm to 2000 ppm, 300 ppm to 2000 ppm, 400 ppm to 2000 ppm, 50 ppm to 1000 ppm, 100 ppm to 1000 ppm, 200 ppm to 1000 ppm, 300 ppm to 1000 ppm, or 400 ppm to 1000 ppm.

[0148] The UVA absorber may include absorbers used in the art that absorb electromagnetic waves with wavelengths of 10 nm to 400 nm. For example, the UVA absorber may include a benzotriazole-based compound, and the benzotriazole-based compound may include an N-phenolic benzotriazole-based compound. In some implementations, the N-phenolic benzotriazole-based compound may include an N-phenolic benzotriazole in which the phenol group is substituted with an alkyl group having 1 to 10 carbon atoms. The alkyl group may be substituted with two or more groups and may be linear, branched, or cyclic.

[0149] In some implementations, the UVA absorber may be included in an amount of 0.1% to 10% by weight based on the total weight of the polyamide-based polymer. Preferably, the UVA absorber may be included in an amount of 0.1% to 5% by weight, 0.1% to 3% by weight, 0.1% to 2% by weight, 0.5% to 10% by weight, 0.5% to 5% by weight, 0.5% to 3% by weight, 0.5% to 2% by weight, 1% to 10% by weight, 1% to 5% by weight, 1% to 3% by weight, or 1% to 2% by weight based on the total weight of the polyamide-based polymer, but is not limited thereto.

[0150] The above-mentioned physical properties of the polyamide film are based on a thickness of 40 μm to 60 μm, for example, based on a thickness of 50 μm.

[0151] The aforementioned features regarding the components and physical properties of the polyamide-based film may be combined with each other.

[0152] In addition, the polyamide film has the above-mentioned volume, 3D surface roughness characteristics such as Sds, Sz, and Ssc, and haze change (ΔHz M ) and solvent resistance such as water contact angle of the film after solvent immersion / abrasion, modulus, transmittance, haze, yellowness, etc. can be adjusted by adjusting the specific process conditions of each step in the method for producing the polyamide film described below, together with the chemical and physical properties of the components constituting the polyamide film.

[0153] For example, the composition and content of the components constituting the polyamide film, the particle size and content of the filler, the polymerization conditions in the film manufacturing process, the heat treatment conditions, and the amount of solvent evaporation per unit area are all taken into consideration to obtain the volume, Sds, Sz, Ssc, and ΔHz in the desired range. M , and the water contact angle of the film can be realized.

[0154] [Cover window for display device] A cover window for a display device according to one implementation includes a polyamide-based film and a functional layer.

[0155] When the 3D surface roughness of the first surface of the polyamide film was measured, the volume (natural volume) between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane was 100 μm 3 ~2800μm 3 It is.

[0156] The polyamide film is as described above. The cover window for a display device can be usefully applied to a display device.

[0157] The polyamide-based film can have excellent solvent resistance, optical properties, and windability / slip properties due to the aforementioned 3D surface roughness characteristics.

[0158] [Display device] A display device according to one implementation includes a display portion and a cover window disposed on the display portion, the cover window including a polyamide-based film and a functional layer.

[0159] In the 3D surface roughness measurement of the first surface of the polyamide-based film, the volume between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 It is.

[0160] The polyamide film and the cover window are described above in detail.

[0161] 1 to 3 are a schematic perspective view, an exploded view, and a cross-sectional view of a display device according to an embodiment.

[0162] Specifically, Figures 1 to 3 illustrate a display device in which a display unit 400 is disposed on the display unit 400, and a cover window 300 including a polyamide-based film 100 having a first surface 101 and a second surface 102 and a functional layer 200, and an adhesive layer 500 is disposed between the display unit 400 and the cover window 300.

[0163] The display unit 400 can display an image and can have a flexible characteristic.

[0164] The display unit 400 may be a display panel for displaying an image, such as a liquid crystal display panel or an organic electroluminescence display panel. The organic electroluminescence display panel may include a front polarizer and an organic EL panel.

[0165] The front polarizer may be disposed on a front surface of the organic electroluminescence panel. Specifically, the front polarizer may be attached to a surface of the organic electroluminescence panel on which an image is displayed.

[0166] The organic EL panel may display an image by self-luminescence in pixel units. The organic EL panel may include an organic EL substrate and a driving 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, a light-emitting layer, a hole transport layer, and an anode. The driving substrate may be drivingly connected to the organic EL substrate. That is, the driving substrate may be connected to the organic EL substrate so as to apply a driving signal such as a driving current to the organic EL substrate, thereby applying a current to each of the organic electroluminescent units to drive the organic EL substrate.

[0167] Also, 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.

[0168] The cover window 300 may be disposed on the display unit 400. The cover window may be located at the outermost periphery of a display device according to an embodiment, and may protect the display unit.

[0169] The cover window 300 may include a polyamide-based film and a functional layer. The functional layer may be at least one selected from the group consisting of a hard coating layer, a reflectance reducing layer, an antifouling layer, and an antiglare layer. The functional layer may be coated on at least one surface of the polyamide-based film.

[0170] In the case of the polyamide-based film according to the embodiment, it can be easily applied in film form to the outside of a display device without changing the display driving method, color filter inside the panel, or lamination structure, etc., and can provide a display device with uniform thickness, low haze, high light transmittance, and transparency. In addition, it has the advantage of reducing production costs because excessive process changes and cost increases are not required.

[0171] The polyamide-based film according to the embodiment not only has excellent optical properties such as high transmittance, low haze, and low yellowness, but also has excellent mechanical properties such as modulus and pencil hardness, and ease of handling such as smoothness and rollability, by adjusting Sds, Sz, and / or Ssc on the 3D surface roughness within a predetermined range.

[0172] In addition, the polyamide-based film according to the embodiment has an in-plane retardation and a thickness direction retardation below a specific level, thereby minimizing optical distortion and reducing the light leakage phenomenon in which light leaks from the sides.

[0173] When the first surface of the film is a polyamide-based film having a volume value within the above-mentioned range, the film has excellent solvent resistance and optical properties, as well as excellent slipperiness and windability. Therefore, even if the film is made large in area, it can be wound on a roll without being damaged, and then unwound and used, and can be effectively applied to rollable / flexible display devices.

[0174] [Method of manufacturing polyamide film] One implementation provides a method for producing a polyamide-based film.

[0175] The 3D surface roughness characteristics of the polyamide-based film may be a result of the chemical and physical properties of the components constituting the polyamide-based film as well as the process conditions of each step in the method for producing the polyamide-based film described below.

[0176] For example, the composition and content of the components constituting the polyamide film, the polymerization conditions in the film manufacturing process, the heat treatment conditions, etc. can be combined to realize the desired 3D surface roughness characteristics.

[0177] A method for producing a polyamide-based film according to one embodiment includes a step of preparing a polyamide-based polymer solution by polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent (S100), a step of casting and drying the polymer solution on a belt to produce a gel sheet (S200), and a step of heat-treating the gel sheet (S300) (see FIG. 4).

[0178] According to some implementations, the method for producing a polyamide-based film may further include a step of adjusting the viscosity of the polyamide-based polymer solution (S110), a step of maturing the polyamide-based polymer solution (S120), and / or a step of degassing the polyamide-based polymer solution (S130).

[0179] The polyamide-based film is a film containing a polyamide-based polymer as a main component, and the polyamide-based polymer is a polymer containing imide repeating units and amide repeating units as structural units in a predetermined molar ratio.

[0180] In the method for producing the polyamide-based film, the polymer solution for preparing the polyamide-based polymer may be prepared by simultaneously or sequentially mixing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent in a reactor and reacting the mixture (S100).

[0181] In one embodiment, the polymer solution can be prepared by simultaneously adding and reacting a diamine compound and a dicarbonyl compound in an organic solvent.

[0182] Specifically, the step of preparing the polymer solution may include a step of mixing and reacting a diamine compound and a dicarbonyl compound in an organic solvent to prepare a polyamide solution.

[0183] In another embodiment, the polymer solution can be prepared by simultaneously adding and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent.

[0184] Specifically, the step of preparing the polymer solution may include a step of first mixing and reacting the diamine compound and the dianhydride compound in a solvent to prepare a polyamic acid (PAA) solution, and a step of second mixing and reacting the dicarbonyl compound with the polyamic acid (PAA) solution to form amide bonds and imide bonds. The polyamic acid solution is a solution containing a polymer having polyamic acid repeat units.

[0185] Alternatively, the step of preparing the polymer solution may include a step of primarily mixing and reacting the diamine compound and the dianhydride compound in a solvent to prepare a polyamic acid solution, a step of dehydrating the polyamic acid solution to prepare a polyimide (PI) solution, and a step of secondary mixing and reacting the dicarbonyl compound with the polyimide (PI) solution to additionally form amide bonds. The polyimide solution is a solution containing a polymer having imide repeat units.

[0186] In one embodiment, the step of preparing the polymer solution may include a step of first mixing and reacting the diamine compound and the dicarbonyl compound in a solvent to prepare a polyamide (PA) solution, and a step of second mixing and reacting the dianhydride compound with the polyamide (PA) solution to additionally form imide bonds. The polyamide solution is a solution containing a polymer having amide repeat units.

[0187] The polymer solution thus prepared may be a solution containing a polymer including one or more repeating units selected from the group consisting of polyamic acid (PAA) repeating units, polyamide (PA) repeating units, and polyimide (PI) repeating units.

[0188] Alternatively, the polymer contained in the polymer solution contains an amide repeat unit derived from the polymerization of the diamine compound and the dicarbonyl compound, and optionally contains an imide repeat unit derived from the polymerization of the diamine compound and the dianhydride compound.

[0189] The diamine compound, the dianhydride compound and the dicarbonyl compound are as described above.

[0190] In some embodiments, the dianhydride compound and the dicarbonyl compound may be used in a molar ratio of 0:100 to 80:20. Specifically, the dianhydride compound and the dicarbonyl compound may be included in a molar ratio of 0:100 to 70:30, 0:100 to 60:40, 0:100 to 50:50, 1:99 to 50:50, or 5:95 to 50:50.

[0191] The solid content of the polymer solution may be 10% by weight to 30% by weight, or 15% by weight to 25% by weight, or 15% by weight to 20% by weight, but is not limited thereto.

[0192] When the solid content of the polymer solution is within the above range, a polyamide film can be effectively produced in the extrusion and casting processes.

[0193] In another implementation, preparing the polymer solution may further include dosing a catalyst.

[0194] In this case, the catalyst may include at least one selected from the group consisting of beta-picoline, acetic anhydride, isoquinoline (IQ) and pyridine-based compounds, but is not limited thereto.

[0195] The catalyst may be added in an amount of 0.01 to 0.5 molar equivalents, 0.01 to 0.4 molar equivalents, 0.01 to 0.3 molar equivalents, 0.01 to 0.2 molar equivalents, or 0.01 to 0.1 molar equivalents based on 1 mole of the polyamide polymer, but is not limited thereto.

[0196] The addition of the catalyst can increase the reaction rate and improve the chemical bonding strength between or within the repeating unit structures.

[0197] In one embodiment, the step of preparing the polymer solution may further include a step of adjusting the viscosity of the polymer solution (S110). The viscosity of the polymer solution may be adjusted to 80000cps to 500000cps, 100000cps to 500000cps, 150000cps to 500000cps, 150000cps to 450000cps, 200000cps to 450000cps, 200000cps to 400000cps, 200000cps to 350000cps, or 200000cps to 300000cps based on room temperature. In this case, the thickness uniformity may be improved by improving the film formability of the polyamide film.

[0198] Specifically, the step of preparing the polymer solution may include a step of simultaneously or sequentially mixing and reacting a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent to prepare a first polymer solution, and a step of additionally adding the dicarbonyl compound to prepare a second polymer solution having a target viscosity.

[0199] In the step of preparing the first polymer solution and the step of preparing the second polymer solution, the prepared polymer solutions have different viscosities, for example, the viscosity of the second polymer solution is higher than that of the first polymer solution.

[0200] The stirring speed when preparing the first polymer solution may be different from the stirring speed when preparing the second polymer solution, for example, the stirring speed when preparing the first polymer solution may be faster than the stirring speed when preparing the second polymer solution.

[0201] In another embodiment, the step of preparing the polymer solution may further include a step of adjusting the pH of the polymer solution, in which the pH of the polymer solution is adjusted to 4 to 7, for example, 4.5 to 7.

[0202] The pH of the polymer solution is adjusted by adding a pH adjuster, which is not particularly limited and may include, for example, an amine-based compound such as an alkoxyamine, an alkylamine, or an alkanolamine.

[0203] By adjusting the pH of the polymer solution within the above range, it is possible to prevent defects in the film produced from the polymer solution and to achieve the desired optical and mechanical properties in terms of yellowness index and modulus.

[0204] The pH adjuster may be added in an amount of 0.1 mol % to 10 mol % based on the total moles of monomers in the polymer solution.

[0205] In one embodiment, 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).

[0206] In another implementation, one or more selected from the group consisting of fillers, blue pigments, and UVA absorbers may be added to the polymer solution.

[0207] The specific contents of the filler, blue pigment, and UVA absorber, such as the type and content thereof, are as described above. The filler, blue pigment, and / or UVA absorber may be mixed with the polyamide-based polymer in the polymer solution.

[0208] 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.

[0209] Storage at this temperature can prevent deterioration of the polymer solution and reduce the moisture content, thereby preventing defects in the produced film.

[0210] In some implementations, the polymer solution or the viscosity adjusted polymer solution may be aged (S120).

[0211] The aging may be performed by leaving the polymer solution at rest for 24 hours or more at a temperature condition of -10°C to 10°C. In this case, the polyamide-based polymer or unreacted substances contained in the polymer solution may, for example, complete the reaction or reach chemical equilibrium, thereby homogenizing the polymer solution, and the mechanical and optical properties of the polyamide-based film thus formed may be substantially uniform over the entire area of ​​the film. Preferably, the aging may be performed at a temperature condition of -5°C to 10°C, -5°C to 5°C, or -3°C to 5°C, but is not limited thereto.

[0212] In one embodiment, the method may further include a step of degassing the polyamide-based polymer solution (S130), which removes moisture and reduces impurities in the polymer solution, thereby increasing the reaction yield and achieving excellent surface appearance and mechanical properties of the final film.

[0213] The degassing may include vacuum degassing or inert gas purging. The vacuum degassing may be carried out 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 carrying out the vacuum degassing under such conditions, it is possible to reduce the number of bubbles in the polymer solution, and as a result, it is possible to prevent surface defects in the film produced therefrom and realize excellent optical properties such as haze.

[0214] The purging can be performed by using an inert gas to set the internal pressure of the tank at 1 to 2 atm. By performing the purging under such conditions, the water content in the polymer solution can be removed and impurities can be reduced, thereby increasing the reaction yield and achieving excellent optical properties such as haze and excellent mechanical properties.

[0215] 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.

[0216] The vacuum degassing and the inert gas purging may be performed in separate steps. For example, a vacuum degassing step may be performed, followed by a purging step with an inert gas, but this is not limiting.

[0217] By carrying out the vacuum degassing and / or the inert gas purging, the physical properties of the surface of the produced polyamide-based film can be improved.

[0218] The polymer solution may be cast to produce a gel sheet (S200). For example, the polymer solution may be coated, extruded and / or dried onto a support to form a gel sheet. Specifically, the polymer solution may be cast onto a belt and dried to produce a gel sheet.

[0219] In addition, the casting thickness of the polymer solution may be 200 μm to 700 μm. By casting the polymer solution in this thickness range, it is possible to ensure an appropriate thickness and thickness uniformity when the polymer solution is manufactured into a final film through drying and heat treatment.

[0220] In some implementations, the polymer solution may be cast and dried on the belt at 50°C to 200°C. In this case, the amount of solvent evaporation may be effectively controlled. Preferably, the casting and drying temperature may be 60°C to 200°C, 70°C to 200°C, 50°C to 150°C, 60°C to 150°C, 70°C to 150°C, 50°C to 120°C, 60°C to 120°C, 70°C to 120°C, 50°C to 100°C, 60°C to 100°C, or 70°C to 100°C.

[0221] In some implementations, the drying time can be 5 minutes to 60 minutes, 10 minutes to 60 minutes, 15 minutes to 60 minutes, 5 minutes to 50 minutes, 10 minutes to 50 minutes, 15 minutes to 50 minutes, 5 minutes to 40 minutes, 10 minutes to 40 minutes, or 15 minutes to 40 minutes.

[0222] In some implementations, the step of drying the polymer solution to produce a gel sheet has a solvent evaporation rate per unit area of ​​0.5 kg / m 2 ~3.0kg / m 2 In this case, the surface roughness of the film can be effectively adjusted to a desired range, and a film having improved optical properties, mechanical properties, slip properties, and winding properties can be produced. Preferably, the amount of solvent evaporation per unit area is 0.5 kg / m 2 ~2.5kg / m 2 , 0.5kg / m 2 ~2.0kg / m 2 , 0.5kg / m 2 ~1.8kg / m 2 , 0.5kg / m 2 ~1.6kg / m 2 , 0.5kg / m 2 ~1.4kg / m 2 , 0.8kg / m 2 ~3.0kg / m 2 , 0.8kg / m 2 ~2.5kg / m 2 , 0.8kg / m 2 ~2.0kg / m 2 , 0.8kg / m 2 ~1.8kg / m 2 , 0.8kg / m 2 ~1.6kg / m 2 , 0.8kg / m 2 ~1.4kg / m 2 , 1.0kg / m 2 ~3.0kg / m 2 , 1.0kg / m 2 ~2.5kg / m 2 , 1.0kg / m 2 ~2.0kg / m 2 , 1.0kg / m 2 ~1.8kg / m 2 , 1.0kg / m 2~1.6kg / m 2 , 1.0kg / m 2 ~1.4kg / m 2 It can be adjusted to, but is not limited to,

[0223] For example, the moving distance of the belt may be 40 m to 60 m. The belt may move at a speed of 0.5 m / min to 15 m / min, specifically 1 m / min to 10 m / min.

[0224] During the drying, the solvent of the polymer solution may be partially or completely evaporated to produce the gel sheet.

[0225] According to one embodiment, the content of the residual solvent contained in the gel sheet after drying may be 1500 ppm or less, in which case the surface roughness characteristics of the film can be effectively adjusted to a target range, thereby producing a film with improved optical properties, mechanical properties, and smoothness and winding properties.

[0226] The dried gel sheet may be heat-treated to form a polyamide-based film (S300).

[0227] The heat treatment of the gel sheet may be performed, for example, by a heat treatment device (tenter). The heat treatment device may include at least one hot air fan and at least one heater. The heat treatment device may include only one of at least one hot air fan or at least one heater.

[0228] The step of heat-treating the dried gel sheet may include a first heat-treating step of heat-treating the gel sheet with hot air generated by at least one hot air blower, and a second heat-treating step of heat-treating the gel sheet with at least one heater.

[0229] The section in which the first heat treatment step is performed is referred to as a first heat treatment section, and the section in which the second heat treatment step is performed is referred to as a second heat treatment section.

[0230] The first heat treatment step and the second heat treatment step may be performed sequentially. The second heat treatment step may be performed after the first heat treatment step, or the first heat treatment step may be performed after the second heat treatment step, but is not limited thereto. Specifically, the first heat treatment step may be performed before the second heat treatment step.

[0231] The step of heat-treating the gel sheet may be performed by a support that moves continuously in a heat treatment device, specifically, the gel sheet may be placed on a support, and the support may move in a traveling direction, so that the film may also move in a length direction.

[0232] The step of heat-treating the gel sheet includes a step of fixing both ends in the width direction of the gel sheet (film) with a fixing member and a step of changing the width of the gel sheet using the fixing member. That is, the step of heat-treating the gel sheet may be performed by fixing both ends in the width direction of the gel sheet with a fixing member and changing the width of the fixed gel sheet. For example, both ends in the width direction of the film may be fixed with pins in the heat treatment device, and the width of the gel sheet may be changed by adjusting the positions of the pins when the film is moved by a support.

[0233] The step of fixing both ends of the gel sheet in the width direction with a fixing member and heat-treating the fixed gel sheet while changing the width of the gel sheet may be performed while the gel sheet passes through the first heat treatment zone and the second heat treatment zone.

[0234] In an embodiment, the step of changing the width of the gel sheet while the gel sheet passes through the first heat treatment zone in the length direction (travel direction) of the gel sheet may be performed while narrowing the width of the gel sheet.

[0235] In addition, in the step of changing the width of the gel sheet while the gel sheet passes through the second heat treatment section in the length direction (travel direction) of the gel sheet, the width of the gel sheet may be narrowed, or the width of the gel sheet may be repeatedly increased and decreased in the step of changing the width of the gel sheet.

[0236] The width of the gel sheet at the inlet of the first heat treatment section may be greater than the width of the gel sheet at the end of the first heat treatment section, and the width of the gel sheet at the inlet of the second heat treatment section may be greater than the width of the gel sheet at the end of the second heat treatment section.

[0237] Furthermore, the width of the gel sheet at the inlet of the first heat treatment section may be greater than the width of the gel sheet at the end of the second heat treatment section, but is not limited thereto.

[0238] The maximum width of the gel sheet in the first heat treatment section is Wa, the minimum width of the gel sheet in the first heat treatment section is Wb, and the minimum width of the gel sheet in the first heat treatment section and the second heat treatment section is Wc.

[0239] For example, the width of the gel sheet at the introduction portion of the first heat treatment section may be the maximum width (Wa) of the gel sheet in the first heat treatment section, and the width of the gel sheet at the end portion of the first heat treatment section may be the minimum width (Wb) of the gel sheet in the first heat treatment section.

[0240] In addition, the width of the gel sheet at the introduction portion of the first heat treatment section may be the maximum width (Wa) of the gel sheet in the first heat treatment section, and the width of the gel sheet at the end portion of the second heat treatment section may be the minimum width (Wc) of the gel sheet in the first heat treatment section and the second heat treatment section.

[0241] As another example, Wb may be equal to or greater than Wc, or equal to or less than Wc. Specifically, Wb may be greater than Wc. More specifically, Wa>Wb>Wc may be satisfied, but is not limited thereto.

[0242] In an embodiment, the Wb / Wa value is 0.955 to 0.990. For example, the Wb / Wa value may be 0.955 or more, 0.960 or more, 0.965 or more, 0.968 or more, or 0.969 or more, and 0.990 or less, 0.985 or less, 0.980 or less, or 0.975 or less, but is not limited thereto. As another example, the Wb / Wa value may be 0.955 to 0.980.

[0243] Also, the Wc / Wa value is 0.950 to 0.990. For example, the Wc / Wa value may be 0.950 or more, 0.953 or more, 0.955 or more, or 0.957 or more, and 0.990 or less, 0.985 or less, 0.980 or less, 0.975 or less, 0.970 or less, or 0.965 or less, but is not limited thereto. As another example, the Wc / Wa value may be 0.950 to 0.970.

[0244] In one implementation, the first heat treatment step using hot air generated by the at least one hot air blower can provide a uniform heat amount, if the heat amount is not distributed evenly, the surface roughness may not be satisfactory or the surface quality may be non-uniform, the surface energy may be too high or too low.

[0245] The heat treatment using hot air may be performed for 5 to 100 minutes at a temperature range of 100°C to 250°C. Specifically, the heat treatment of the gel sheet using hot air may be performed for 5 to 60 minutes at a temperature increase rate of 1.5°C / min to 20°C / min at a temperature range of 100°C to 250°C. More specifically, the heat treatment of the gel sheet may be performed at a temperature range of 140°C to 250°C.

[0246] At this time, the starting temperature of the heat treatment of the gel sheet by the hot air may be 100° C. or more. Specifically, the starting temperature of the heat treatment of the gel sheet by the hot air may be 100° C. to 180° C. In addition, the maximum temperature during the heat treatment by the hot air may be 150° C. to 250° C.

[0247] The temperature related to the heat treatment using hot air is the temperature in the heat treatment device in which the gel sheet exists, and corresponds to the temperature measured by a temperature sensor located in a first heat treatment section in the heat treatment device.

[0248] In one implementation, the step of heat treating the gel sheet may include a second heat treating step of heat treating with at least one heater, specifically a heat treating step of heat treating with multiple heaters.

[0249] The heaters may include a plurality of heaters spaced apart in the width direction (TD) of the gel sheet. The heaters are mounted on heater mounting parts, and two or more of the heater mounting parts may be disposed along the traveling direction (MD) of the gel sheet.

[0250] The at least one heater may include an IR heater. However, the type of the at least one heater is not limited to the above example and may be variously changed. Specifically, the plurality of heaters may include an IR heater.

[0251] The heat treatment by the at least one heater may be performed at a temperature range of 250° C. or more. Specifically, the heat treatment by the at least one heater may be performed at a temperature range of 250° C. to 400° C. for 1 minute to 30 minutes, or 1 minute to 20 minutes.

[0252] The temperature related to the heat treatment by the heater is the temperature in the heat treatment device where the gel sheet is present, and corresponds to the temperature measured by a temperature sensor located in a second heat treatment section in the heat treatment device.

[0253] Then, after the step of heat treating the gel sheet, a step of cooling the hardened film while moving the film may be performed.

[0254] The step of cooling the cured film while moving it may include a first temperature reduction step of reducing the temperature at a rate of 100°C / min to 1000°C / min, and a second temperature reduction step of reducing the temperature at a rate of 40°C / min to 400°C / min.

[0255] Specifically, the second temperature reducing step may be performed after the first temperature reducing step, and the temperature reducing rate of the first temperature reducing step may be faster than the temperature reducing rate of the second temperature reducing step.

[0256] For example, the maximum speed during the first temperature reduction stage is greater than the maximum speed during the second temperature reduction stage, or the minimum speed during the first temperature reduction stage is greater than the minimum speed during the second temperature reduction stage.

[0257] By performing the cooling step of the cured film in multiple stages in this manner, the physical properties of the cured film can be more stabilized, and the optical and mechanical properties of the film established during the curing process can be maintained more stably for a long period of time.

[0258] A step of winding the cooled, cured film with a winder may also be performed.

[0259] In this case, the ratio of the moving speed of the gel sheet on the belt during drying to the moving speed of the cured film during winding is 1:0.95 to 1:1.40. Specifically, the ratio of the moving speeds may be, but is not limited to, 1:0.99 to 1:1.20, 1:0.99 to 1:1.10, or 1:1.01 to 1:1.10.

[0260] If the ratio of the moving speeds is outside this range, the mechanical properties of the cured film may be impaired, and the flexibility and elasticity properties may decrease.

[0261] In the method for producing the polyamide-based film, the thickness deviation (%) according to the following formula 2 may be 3% to 30%. Specifically, the thickness deviation (%) may be 5% to 20%, but is not limited thereto. [Formula 2] Thickness deviation (%) = {(M1-M2) / M1} x 100 In the above formula 2, M1 is the thickness (μm) of the gel sheet, and M2 is the thickness (μm) of the cooled cured film when wound.

[0262] The polyamide-based film produced according to the above-mentioned production method not only has excellent solvent resistance and excellent optical and mechanical properties, but also has excellent recovery force when the bending force is released after a long period of bending, and hardly any wrinkles are observed even after a severe folding test. Furthermore, since the desired level of loop rigidity is still achieved not only at room temperature but also in an extremely low temperature environment, it can be applied to various applications requiring flexibility and mechanical durability. For example, the polyamide-based film can be applied not only to display devices but also to solar cells, semiconductor elements, sensors, etc.

[0263] The polyamide film produced by the above-mentioned production method is as described above.

[0264] (Example) The above contents will be explained in more detail with reference to 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 examples.

[0265] Example 1 A temperature-controllable double-jacketed 1 L glass reactor was filled with dimethylacetamide (DMAc), an organic solvent, under a nitrogen atmosphere at 10°C, and then the aromatic diamine 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) was gradually added and dissolved.

[0266] Then, the temperature inside the reactor was raised to 30° C., and the reaction solution was stirred for 2 hours while gradually adding 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6-FDA).

[0267] The temperature of the reactor was lowered to 10°C, and terephthaloyl chloride (TPC) was gradually added while stirring for 1 hour. Then, isophthaloyl chloride (IPC) (94 mol% based on the total amount added) was added and stirred for 1 hour to prepare a first polymer solution. The viscosity of the prepared first polymer solution was 1000cps to 10000cps.

[0268] Then, 1 mL of an IPC solution (DMAc solvent) with a concentration of 10% by weight was added, and the process of stirring for 30 minutes was repeated to prepare a second polymer solution with a viscosity of 180,000 cps to 220,000 cps.

[0269] In this case, the viscosity of the polymer solution was measured using an RM100 CP2000 PLUS device manufactured by LAMY rheology instruments under a constant temperature condition of 20°C and a shear rate of 4s. -1 The viscosity was measured under certain conditions to confirm whether the target viscosity was achieved.

[0270] Silica (Nissan Chemical, DMAc-ST-ZL) having a particle size (average particle size D50 by BET method) of about 83 nm dispersed in a DMAc solvent was added to the second polymer solution so that the amount was 1000 ppm relative to the total weight of the solids in the polymer solution, thereby preparing a polymer solution.

[0271] The polymer solution was cast onto a belt and applied at a rate of about 1.4 kg / m per unit area before being introduced into a heat curing device. 2 The film was moved while adjusting the injection speed on the belt, drying temperature, drying time, moving distance, moving speed, etc., so that DMAc of 100% was evaporated. During this process, drying was performed by blowing hot air onto the gel sheet.

[0272] The dried polyamide-based gel sheet was placed in a heat curing device that heated the sheet at a rate of 2°C / min in the temperature range of 80°C to 300°C, and then cooled and wound up to obtain a polyamide-based film having a thickness of 50 µm.

[0273] The specific composition and molar ratio of the polyamide polymer are as shown in Table 1 below.

[0274] (Examples 2 to 13 and Comparative Examples 1 to 6) In Examples 2 to 13 and Comparative Examples 1 to 6, polyamide films were obtained in the same manner as in Example 1, except that the monomer composition and molar ratio of the polyamide polymer, the amount of solvent evaporated per unit area in the drying stage, and the type, particle size and content of the filler were changed based on Table 1 below.

[0275] [Table 1]

[0276] <Evaluation example> The physical properties of the films prepared in the above examples and comparative examples were measured and evaluated as follows, and the results are shown in Table 2 below.

[0277] (Evaluation example 1: 3D surface roughness measurement) Measurements were performed using a Bruker CONTOUR GT-X. The measurement area was set to 166 μm × 220 μm, and a magnification of 20 was applied to the objective lens, after which a Gaussian filter was applied to perform basic correction. After repeating the same measurement five times, the average value was calculated by removing the maximum and minimum values ​​from the measured data. The volume (natural volume) between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane was measured for the air surface and the belt surface of the film, respectively, and is shown in Table 2 below. The measurements were performed based on ISO 25178.

[0278] (Evaluation Example 2: Transmittance and Haze Measurement) The light transmittance and haze were measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Industries Co., Ltd., based on the JIS K 7136 standard.

[0279] (Evaluation example 3: haze change measurement) The film was immersed in MIBK solvent for 5 seconds, then dried at 80° C. for 2 minutes, and the haze was measured again by the method of Evaluation Example 2. The amount of haze change (ΔHz M ) was calculated.

[0280] (Evaluation Example 4: Yellowness Measurement) Yellowness index (YI) was measured using a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) at d65 and 10° according to the ASTM-E313 standard.

[0281] (Evaluation Example 5: Slipperiness Evaluation) When the film was wound up on a roll, the static friction coefficient between one side and the other side of the film that were in contact with each other was measured, and a value of 0.3 or less was evaluated as good, and a value exceeding 0.3 was evaluated as poor.

[0282] The static friction coefficient was measured between the first and second surfaces of polyamide film samples cut to sizes of 130 mm x 250 mm and 63 mm x 63 mm, respectively, using a friction coefficient measuring device manufactured by Qmesys Co., Ltd., Korea, in accordance with the measurement standard ASTM D1894.

[0283] (Evaluation Example 6: Winding Property Evaluation) Both ends of the film were trimmed and a 500 m length with a width of 1,460 mm was continuously wound up to prepare a roll, after which the film was visually inspected to see whether or not there was a lump, which indicates a difference in light and dark across the entire width. If two or more of ten workers judged there to be a lump, the film was rated as poor, and if not, it was rated as good.

[0284] (Evaluation Example 7: Optical Performance Evaluation) If the haze of the film measured after immersion in the MIBK solvent in the above Evaluation Example 3 was 5% or less, it was evaluated as good, and if it exceeded 5%, it was evaluated as poor.

[0285] (Evaluation Example 8: Solvent Resistance Evaluation) The film was immersed in MIBK solvent for 5 seconds, then dried at 80°C for 2 minutes, and the film surface was rubbed 3000 times with a Minoan abrasion test eraser with a hardness of 81 (type A durometer) and a weight of 500g, and the water contact angle of the film surface was measured. At this time, if the water contact angle was 70° to 80°, it was evaluated as good, and otherwise it was evaluated as bad.

[0286] [Table 2]

[0287] Referring to Table 2, when measuring the 3D surface roughness of the first surface of the film, the volume (natural volume) between the surface and the reference plane placed at the highest point of the surface parallel to the surface plane is 100 μm 3 ~2800μm 3 In the case of the polyamide-based films according to Examples 1 to 13, the volume is controlled to 100 μm 3 Less than or equal to 2800μm 3 It was confirmed that the polyamide films according to the present invention had superior lubricity, winding property, optical properties, and solvent resistance, as compared with the polyamide films according to the comparative examples 1 to 6, which had superior lubricity, winding property, optical properties, and solvent resistance. [Explanation of symbols]

[0288] 10: Polymerization equipment 20: Tank 30: Belt 40:Thermosetting equipment 50: Winder 100: Polyamide film 101: 1st page 102:Second side 200: Functional layer 300: Cover window 400: Display section 500: Adhesive layer

Claims

1. A polyamide-based film, The composition includes a polyamide polymer and a filler, The content of the filler is 200 ppm to 2500 ppm based on the total weight of the polyamide-based polymer; When measuring the 3D surface roughness of the first surface of the film, the volume (natural volume) between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane is 100 μm ３ ~2800μm ３ and When measuring the 3D surface roughness of the second surface of the film, the volume between the surface and a reference plane located at the highest point of the surface parallel to the surface plane is 10 μm 3 to 150 μm 3 ; The first surface is an air surface that does not contact a support used in forming a polyamide-based film, The second surface is a belt surface that contacts a support used in forming a polyamide-based film, The volume is measured using a Bruker CONTOUR GT-X, with a measurement area set to 166 μm × 220 μm, a 20x objective lens, and a Gaussian filter. The polyamide-based film, wherein the filler has a SPAN value defined by the following formula 1 of 0.5 to 20. In the above formula 1, D 10 is the 10% cumulative mass particle size distribution diameter in the particle size distribution of the filler, The D50 is the 50% cumulative mass particle size distribution diameter in the particle size distribution of the filler, The D 90 is the 90% cumulative mass particle size distribution diameter in the particle size distribution of the filler.

2. The filler is silica (SiO ２ ), barium sulfate (BaSO ４ ), aluminum oxide (Al ２ O ３ ), and zirconium oxide (ZrO ２ The polyamide film according to claim 1 , comprising one or more selected from the group consisting of:

3. The filler has a 50% cumulative mass particle size distribution diameter (D ５０ 2. The polyamide film according to claim 1, wherein the thickness of the polyamide film is 30 nm to 250 nm.

4. The film was immersed in MIBK (methyl isobutyl ketone) solvent for 5 seconds, dried at 80° C. for 2 minutes, and then the haze was measured. The haze change (ΔHz Ｍ 2. The polyamide film according to claim 1, wherein the modulus of elasticity is 2.0% or less.

5. 2. The polyamide film according to claim 1, wherein the film is immersed in MIBK solvent for 5 seconds, dried at 80°C for 2 minutes, and the film surface is rubbed 3,000 times with a MINOAN abrasion test eraser having a hardness of 81 (type A durometer) and a load of 500 g, after which the water contact angle of the film surface is 70° to 80°.

6. The polyamide film includes a functional layer. The polyamide-based film comprises a polyamide-based polymer and a filler, The content of the filler is 200 ppm to 2500 ppm based on the total weight of the polyamide-based polymer; When measuring the 3D surface roughness of the first surface of the polyamide-based film, the volume (natural volume) between the surface and a reference plane placed at the highest point of the surface parallel to the surface plane is 100 μm ３ ~2800μm ３ and When measuring the 3D surface roughness of the second surface of the film, the volume between the surface and a reference plane located at the highest point of the surface parallel to the surface plane is 10 μm 3 to 150 μm 3 ; The first surface is an air surface that does not contact a support used in forming a polyamide-based film, The second surface is a belt surface that contacts a support used in forming a polyamide-based film, The volume is measured using a Bruker CONTOUR GT-X, with a measurement area set to 166 μm × 220 μm, a 20x objective lens, and a Gaussian filter. The cover window for a display device, wherein the filler has a SPAN value, as defined by the following formula 1, of 0.5 to 20. In the above formula 1, D 10 is the 10% cumulative mass particle size distribution diameter in the particle size distribution of the filler, The D50 is the 50% cumulative mass particle size distribution diameter in the particle size distribution of the filler, The D 90 is the 90% cumulative mass particle size distribution diameter in the particle size distribution of the filler.

7. preparing a polyamide-based polymer solution by polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent; casting and drying the polymer solution onto a belt to produce a gel sheet; and heat treating the gel sheet.

2. The method for producing a polyamide film according to claim 1, wherein in the step of producing a gel sheet by drying the polymer solution, the amount of solvent evaporated per unit area is adjusted to 0.5 kg / m 2 to 3.0 kg / m 2 .

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