Polyamide-imide-based film, preparation method thereof, and cover window and display device comprising the same

Abstract

The embodiment aims to provide a polyamide-imide film having excellent optical properties, mechanical properties and UV blocking rate, comprising a polyamide-imide polymer that does not contain fluorine atoms and having a modulus of 5 GPa or more based on a film thickness of 50 μm, a method for manufacturing the same, and a cover window and a display device including the same.

Description

Technology Field

[0001] An embodiment relates to a polyamide-imide-based film, a method for manufacturing the same, and a cover window and a display device including the same. Background Technology

[0002] Polyimide resins such as poly(amide-imide) (PAI) have excellent resistance to friction, heat, and chemicals, and are applied 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] Polyimide is utilized in various fields. For example, polyimide is produced in powder form and used as a coating agent for metals or magnetic wires, and is mixed with other additives depending on the application. Additionally, polyimide is used to coat kitchen cookware, and due to its heat and chemical resistance, it is used as a membrane for gas separation and in devices that filter contaminants such as carbon dioxide, hydrogen sulfide, and impurities from natural gas wells.

[0004] Recently, by converting polyimide into films, polyimide-based films are being developed that are more affordable while possessing excellent optical, mechanical, and thermal properties. These polyimide-based films can be applied as display materials for organic light-emitting diodes (OLEDs) or liquid-crystal displays (LCDs), and can also be used as anti-reflective films, compensation films, or phase difference films when realizing phase difference properties.

[0005] However, conventional polyimide-based films, specifically conventional polyamide-imide-based films, have a problem in that the polyamide-imide polymer necessarily contains fluorine atoms, which can be subject to environmental regulations. Therefore, there is a continuously increasing demand for the development of polyamide-imide films that possess excellent optical and mechanical properties while not containing fluorine atoms. The problem to be solved

[0006] The embodiment aims to provide a polyamide-imide-based film having excellent optical and mechanical properties, a method for manufacturing the same, and a cover window and display device including the same. means of solving the problem

[0007] A polyamide-imide film according to one embodiment comprises a polyamide-imide polymer that does not contain fluorine atoms, and has a modulus of 5 GPa or more based on a film thickness of 50 μm.

[0008] A cover window for a display device according to another embodiment comprises a polyamide-imide film and a functional layer, wherein the polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and the modulus is 5 GPa or more based on a film thickness of 50 μm.

[0009] A display device according to another embodiment includes a display unit; and a cover window disposed on the display unit; wherein the cover window comprises a polyamide-imide film and a functional layer, and the polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and the modulus is 5 GPa or more based on a film thickness of 50 μm.

[0010] A method for manufacturing a polyamide-imide film according to one embodiment comprises the steps of: preparing a polyamide-imide polymer solution by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent; preparing a gel sheet by casting and drying the solution; and heat-treating the gel sheet. Effects of the invention

[0011] The polyamide-imide film according to the embodiments has excellent optical and mechanical properties while the polyamide-imide polymer does not contain fluorine atoms.

[0012] In addition, the polyamide-imide film according to the embodiments does not contain fluorine atoms, so it can easily comply with environmental regulations, and

[0013] Furthermore, the polyamide-imide film according to the embodiments has an excellent UV blocking rate, so when applied to a display device, it prevents deterioration or damage caused by UV rays, thereby maintaining stable performance of the display device even during long-term use. Brief explanation of the drawing

[0014] FIG. 1 is a schematic exploded view of a display device according to one embodiment. FIG. 2 is a schematic perspective view of a display device according to one embodiment. FIG. 3 is a schematic cross-sectional view of a display device according to one embodiment. FIG. 4 shows a schematic flowchart of a method for manufacturing a polyamide-imide-based film according to one embodiment. Specific details for implementing the invention

[0015] Hereinafter, embodiments are described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, embodiments may be implemented in various different forms and are not limited to the embodiments described herein.

[0016] In this specification, where each film, window, panel, or layer is described as being formed "on" or "under" each film, window, panel, or layer, "on" and "under" include both being formed "directly" and being formed "indirectly" through other components. Furthermore, the reference for the top and bottom of each component is described based on the drawings. The size of each component in the drawings may be exaggerated for illustrative purposes and does not imply the actual size applied. Additionally, throughout the specification, the same reference numerals refer to the same component.

[0017] In this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0018] In this specification, singular expressions are interpreted to include singular or plural forms as interpreted in context unless otherwise specified.

[0019] In addition, all numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification should be understood as being modified by the term “about” in all cases unless otherwise specified.

[0020] In this specification, terms such as "first," "second," etc. are used to describe various components, and said components are not to be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another.

[0021] In addition, the term “substituted” in this specification means, unless otherwise specified, that it 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 listed substituents may be connected to each other to form a ring.

[0022] Polyamide-imide film

[0023] The embodiment provides a polyamide-imide-based film with excellent optical properties such as yellowness and haze, as well as mechanical properties and UV blocking rate.

[0024] The polyamide-imide film according to the embodiment comprises a polyamide-imide polymer that does not contain fluorine atoms, and has a modulus of 5 GPa or more based on a film thickness of 50 μm.

[0025] Specifically, fluorine atoms may not be detected in the polyamide-imide-based polymer when analyzed by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDS). For example, fluorine atoms may not be detected in the polyamide-imide-based polymer when analyzed by SEM-EDS using Bruker’s FlatQUAD XFlash150 instrument.

[0026] In one embodiment, the polyamide-imide film may not substantially contain fluorine atoms.

[0027] Specifically, the polyamide-imide film may contain fluorine atoms at a concentration of 500 ppm or less.

[0028] More specifically, the polyamide-imide film may contain fluorine atoms at a concentration of 400 ppm or less, 300 ppm or less, 200 ppm or less, 100 ppm or less, or 50 ppm or less.

[0029] For example, the above polyamide-imide film may not contain fluorine atoms, but is not limited thereto.

[0030] When a polyamide-imide film and / or a polyamide-imide polymer according to an embodiment does not contain fluorine atoms or contains them within the range described above, it is possible to provide an eco-friendly film by minimizing harmful substances contained in the film, improve chemical stability to extend the lifespan of the film, and be free from environmental regulations related to fluorine (PFAS).

[0031] In one embodiment, the polyamide-imide film may have a modulus of 5.2 GPa or more, 5.3 GPa or more, 5.4 GPa or more, 5.5 GPa or more, 5.6 GPa or more, 5.7 GPa or more, 5.8 GPa or more, 5.9 GPa or more, or 6 GPa based on a film thickness of 50 μm, and the modulus may be 8 GPa or less, 7.5 GPa or less, or 7 GPa or less.

[0032] Specifically, the polyamide-imide film may have a modulus of 5 to 8 GPa, 5 to 7 GPa, 5.4 to 8 GPa, 5.4 to 7 GPa, 6 to 8 GPa, or 6 to 7 GPa based on a film thickness of 50 μm, but is not limited thereto.

[0033] The above modulus may be a value measured by cutting the sample into lengths of 10 cm or more in a direction orthogonal to the main shrinkage direction and 10 mm in the main shrinkage direction, mounting it on clips spaced 10 cm apart, and then elongating it at a speed of 10 mm / min until fracture occurs at room temperature to obtain a stress-strain curve, wherein the slope of the load relative to the initial deformation in the stress-strain curve is the modulus (GPa). For example, the above modulus may be measured using the Instron Universal Testing Machine UTM 5566A, but is not limited thereto.

[0034] When the modulus of the polyamide-imide film according to the embodiment satisfies the above range, the mechanical strength and durability of the polyamide-imide film are improved, the heat resistance of the film is improved, and it may be suitable for use in electronic device components such as cover windows.

[0035] On the other hand, if the modulus of the polyamide-imide film according to the embodiment does not satisfy the above range, there is a possibility that the film may be deformed by heat or external force, or that the moldability during processing may be reduced.

[0036] In one embodiment, the polyamide-imide film may have a transmittance of 3% or less at a wavelength of 380 nm based on a film thickness of 50 μm. Specifically, the polyamide-imide film may have a transmittance of 2.5% or less, 2.3% or less, 2% or less, 1.7% or less, 1.5% or less, 1% or less, 0.7% or less, 0.5% or less, 0.4% or less, 0.35% or less, or 0.3% or less based on a film thickness of 50 μm.

[0037] For example, the transmittance at the above 380 nm wavelength can be measured using the JASCO V-670 ultraviolet / visible / near-infrared spectrophotometer, but is not limited thereto.

[0038] When the transmittance of the polyamide-imide film according to the embodiment at a wavelength of 380 nm satisfies the above range, the UV blocking rate is increased, the optical stability of the film is improved, and the film can be suitablely used for protecting electronic device components and displays sensitive to UV rays. On the other hand, when the transmittance of the polyamide-imide film according to the embodiment at a wavelength of 380 nm does not satisfy the above range, there is a possibility that discoloration of the material and degradation of physical properties due to UV rays may occur.

[0039] In one embodiment, the polyamide-imide-based film may not contain a UV blocker.

[0040] According to one embodiment, the total light transmittance of the polyamide-imide film measured in the visible light wavelength region may be 78% or more, or 80% or more. For example, the total light transmittance may be 82% or more, 84% or more, 85% or more, or 86% or more, and may be 100% or less, 99% or less, 95% or less, 90% or less, 89% or less, or 88% or less.

[0041] According to one embodiment, the transmittance of the polyamide-imide film at a wavelength of 550 nm may be 78% or more, or 80% or more. For example, the transmittance at a wavelength of 550 nm may be 82% or more, 84% or more, 85% or more, or 86% or more, and may be 100% or less, 99% or less, 95% or less, 90% or less, 89% or less, or 88% or less.

[0042] The haze of the above polyamide-imide film may be 1% or less. Specifically, the haze may be 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, or 0.25% or less, but is not limited thereto. The haze of the film may be a value measured in the visible light wavelength range (400 to 700 nm).

[0043] The above transmittance and haze values ​​may be values ​​measured according to the JIS K 7105 standard using the haze meter NDH-5000W of Tenshoku Kogyo Co., Ltd., Japan.

[0044] The yellow index of the above polyamide-imide film may be 5 or less. For example, the yellow index may be 4.8 or less, 4.5 or less, 4.3 or less, 4.2 or less, 4.1 or less, or 4.0 or less, but is not limited thereto.

[0045] The above yellowness may be a value measured according to ASTM-E313 standards under d65, 10° conditions by a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory).

[0046] In an embodiment, the thickness variation of the polyamide-imide film may be 3 μm or less or 2 μm or less based on a thickness of 50 μm. In addition, the thickness variation rate may be 5% or less, 4% or less, or 3% or less, but is not limited thereto.

[0047] In one embodiment, the polyamide-imide film may have a total light transmittance of 80% or more, a haze of 1% or less, and a yellowness of 5 or less, based on a film thickness of 50 μm, but is not limited thereto.

[0048] Specifically, the polyamide-imide film may have a modulus of 6 GPa or more, a total light transmittance of 85% or more measured in the visible light wavelength range, a haze of 0.5% or less, and a yellowness of 4.5 or less, based on a film thickness of 50 μm, but is not limited thereto.

[0049] The compressive strength of the above polyamide-imide film may be 0.4 kgf / ㎛ or higher. Specifically, the compressive strength may be 0.45 kgf / ㎛ or higher or 0.46 kgf / ㎛ or higher, but is not limited thereto.

[0050] When the above polyamide-imide film is perforated at a speed of 10 mm / min using a 2.5 mm spherical tip in UTM compression mode, the maximum perforation diameter (mm) including cracks is 60 mm or less. Specifically, the maximum perforation diameter may be 5 to 60 mm, 10 to 60 mm, 15 to 60 mm, 20 to 60 mm, 25 to 60 mm, or 25 to 58 mm, but is not limited thereto.

[0051] The pencil hardness of the surface of the above polyamide-imide film may be HB or higher. Specifically, the pencil hardness may be H or higher or 2H or higher, but is not limited thereto.

[0052] The above polyamide-imide film has a tensile strength of 15 kgf / mm 2 It may be more than that. Specifically, the tensile strength is 18 kgf / mm 2 Above, 20 kgf / mm 2 Above, 21 kgf / mm 2 ≥ or 22 kgf / mm 2 This may be the case, but is not limited to it.

[0053] The above polyamide-imide film may have an elongation of 15% or more. Specifically, the elongation may be 16% or more, 17% or more, or 18% or more, but is not limited thereto.

[0054] When the above polyamide-imide film is folded to a radius of curvature of 3 mm based on a thickness of 50 μm, the number of folding cycles before breaking may be 200,000 or more.

[0055] The above folding count is defined as bending and straightening the film so that the radius of curvature becomes 3 mm as one cycle.

[0056] The above polyamide-imide-based film can be usefully applied to a foldable display device or a flexible display device by satisfying the number of folding cycles within the range described above. Specifically, the film can be applied to a foldable phone, but is not limited thereto.

[0057] The surface roughness of the above polyamide-imide film may be 0.01 μm to 0.07 μm. Specifically, the surface roughness may be 0.01 μm to 0.06 μm, but is not limited thereto.

[0058] Since the surface roughness of the above polyamide-imide-based film satisfies the above range, it may be advantageous to realize brightness conditions or textures that are favorable for application to a display device.

[0059] The residual solvent content in the above polyamide-imide film may be 2,500 ppm or less. For example, the content of the residual solvent may be 2,200 ppm or less, 2,000 ppm or less, 1,500 ppm or less, 1,200 ppm or less, 1,000 ppm or less, 800 ppm or less, 500 ppm or less, or 300 ppm or less, but is not limited thereto.

[0060] The above residual solvent refers to the amount of solvent remaining in the final manufactured film that does not volatilize during film manufacturing.

[0061] If the content of residual solvent in the above polyamide-imide film exceeds the above range, the durability of the film may be reduced, and variations in film quality may also be affected. In particular, since it affects mechanical strength, it may have an adverse effect during post-processing of the film, and it may accelerate the hygroscopicity of the film, thereby degrading optical properties in addition to mechanical properties.

[0062] A polyamide-imide film according to an embodiment comprises a polyamide-imide polymer, and the polyamide-imide polymer can be formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound.

[0063] The above polyamide-imide polymer is a polymer comprising imide repeating units and amide repeating units.

[0064] Specifically, the polyamide-imide polymer comprises an imide repeating unit derived from the polymerization of a diamine compound and a dianhydride compound, and an amide repeating unit derived from the polymerization of the diamine compound and a dicarbonyl compound.

[0065] In one embodiment, the polyamide-imide-based polymer may be a polymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound.

[0066] The above diamine compound is a compound that forms a copolymer by bonding to the above dianhydride compound in imide and bonding to the above dicarbonyl compound in amide.

[0067] The above diamine compound is not particularly limited, but, for example, may be an aromatic diamine compound comprising an aromatic structure. For example, the above diamine compound may be a compound of the following chemical formula 1.

[0068] <Chemical Formula 1>

[0069]

[0070] In the above chemical formula 1,

[0071] E is a substituted or unsubstituted divalent C6-C 30 Aliphatic ring, substituted or unsubstituted divalent C4-C 30 Heteroaliphatic ring group, substituted or unsubstituted divalent C6-C 30 Aromatic ring, substituted or unsubstituted divalent C4-C 30Hetero-aromatic ring, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 It can be selected from alkynylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2- and -C(CH3)2-.

[0072] e is selected from integers 1 to 5, and if e is 2 or greater, E may be the same or different from each other.

[0073] (E) of the above chemical formula 1 e The may be selected from the group represented by the following chemical formulas 1-1a to 1-14a, but is not limited thereto.

[0074]

[0075] Specifically, (E) of the above chemical formula 1 e may be selected from the group represented by the following chemical formulas 1-1b to 1-13b, but is not limited thereto:

[0076]

[0077] More specifically, (E)e of the above chemical formula 1 may be a group represented by the above chemical formula 1-7b, but is not limited thereto.

[0078] In one embodiment, the diamine compound may include a compound that does not have a fluorine-containing substituent. The diamine compound may consist of a compound that does not have a fluorine-containing substituent.

[0079] In another embodiment, the diamine compound may include a compound that does not contain fluorine. The diamine compound may be composed of a compound that does not contain fluorine.

[0080] In some embodiments, the diamine compound may comprise one type of diamine compound. That is, the diamine compound may consist of a single component.

[0081] For example, the above diamine compound may include 2,2'-dimethylbenzidine (2,2'-Dimethylbenzidine, m-Tolidine) having the following structure, but is not limited thereto.

[0082]

[0083] In one embodiment, the diamine compound may be composed of 2,2'-dimethylbenzidine (m-Tolidine), but is not limited thereto.

[0084] The above dianhydride compound is a compound that can contribute to the improvement of optical properties, such as the transmittance of a film containing the above polyamide-imide polymer, because it has a low birefringence value.

[0085] The above dianhydride compound is not particularly limited, but, for example, may be an aromatic dianhydride compound comprising an aromatic structure. For example, the above aromatic dianhydride compound may be a compound of Chemical Formula 2 below.

[0086] <Chemical Formula 2>

[0087]

[0088] In the above Chemical Formula 2, G is a substituted or unsubstituted tetravalent C4-C 30 Aliphatic ring, substituted or unsubstituted tetravalent C4-C 30 Heteroaliphatic ring, substituted or unsubstituted tetravalent C6-C 30 Aromatic ring, substituted or unsubstituted tetravalent C4-C 30It is a heteroaromatic ring, wherein the aliphatic ring, the heteroaliphatic ring, the aromatic ring, or the heteroaromatic ring exists alone, is joined to form a condensed ring, or is substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 It is connected by a linker selected from alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, and -C(CH3)2-.

[0089] G in Chemical Formula 2 above is a substituted or unsubstituted tetravalent C4-C 30 It may be connected by aliphatic rings.

[0090] G of the above chemical formula 2 may be selected from the group represented by the following chemical formulas 2-1a to 2-9a, but is not limited thereto.

[0091]

[0092] For example, G in the above chemical formula 2 may be the group represented by 2-2a or the group represented by 2-8a.

[0093] In one embodiment, the dianhydride compound may include a compound that does not have a fluorine-containing substituent. The dianhydride compound may consist of a compound that does not have a fluorine-containing substituent.

[0094] In another embodiment, the dianhydride compound may include a compound that does not contain fluorine. The dianhydride compound may be composed of a compound that does not contain fluorine.

[0095] In another embodiment, the dianhydride compound may consist of one single component or two mixed components.

[0096] For example, the above dianhydride compound may include one or more selected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) having the following structure, but is not limited thereto.

[0097]

[0098]

[0099] Specifically, the dianhydride compound may include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA).

[0100] In one embodiment, the dianhydride compound may be composed of 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), but is not limited thereto.

[0101] The above diamine compound and the above dianhydride compound can polymerize to produce polyamic acid.

[0102] Subsequently, the polyamic acid can be converted into polyimide through a dehydration reaction, and the polyimide includes imide repeating units.

[0103] The above polyimide can form repeating units represented by the following chemical formula A.

[0104] <Chemical Formula A>

[0105]

[0106] In the above chemical formula A, the description of E, G, and e is as described above.

[0107] For example, the above polyimide may include repeating units represented by the following chemical formula A-1, but is not limited thereto.

[0108] <Chemical Formula A-1>

[0109]

[0110] n in the above chemical formula A-1 is an integer from 1 to 400.

[0111] The above dicarbonyl compound is not particularly limited, but may be, for example, a compound of Chemical Formula 3 below.

[0112] <Chemical Formula 3>

[0113]

[0114] In the above chemical formula 3,

[0115] J is a substituted or unsubstituted divalent C6-C 30 Aliphatic ring, substituted or unsubstituted divalent C4-C 30 Heteroaliphatic ring group, substituted or unsubstituted divalent C6-C 30 Aromatic ring, substituted or unsubstituted divalent C4-C 30 Hetero-aromatic ring, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 It can be selected from alkynylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2- and -C(CH3)2-.

[0116] j is selected from integers 1 to 5, and if j is 2 or greater, J may be the same or different.

[0117] X is a halogen atom. Specifically, X can be Cl, Br, I, etc. More specifically, X can be Cl, but is not limited thereto.

[0118] (J) of the above chemical formula 3j The may be selected from the group represented by the following chemical formulas 3-1a to 3-14a, but is not limited thereto.

[0119]

[0120] Specifically, (J) of the above chemical formula 3 j may be selected from the group represented by the following chemical formulas 3-1b to 3-8b, but is not limited thereto:

[0121]

[0122] More specifically, (J) of the above chemical formula 3 j It may be the group represented by the above chemical formula 3-1b, the group represented by the above chemical formula 3-2b, the group represented by 3-3b, or the group represented by 3-8b.

[0123] For example, (J) of the above 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.

[0124] In one embodiment, the dicarbonyl compound may be used as a single dicarbonyl compound or as a mixture of at least two different dicarbonyl compounds. When two or more dicarbonyl compounds are used, the dicarbonyl compounds are (J) in Formula 3. j Two or more types selected from the group represented by the above chemical formulas 3-1b to 3-8b may be used.

[0125] In another embodiment, the dicarbonyl compound may be an aromatic dicarbonyl compound having an aromatic structure.

[0126] In one embodiment, the dicarbonyl compound may include a compound that does not contain fluorine. The dicarbonyl compound may consist of a compound that does not contain fluorine. The dicarbonyl compound may include terephthaloyl chloride (TPC), 1,1'-biphenyl-4,4'-dicarbonyl dichloride (BPDC), isophthaloyl chloride (IPC), or a combination thereof having the following structure, but is not limited thereto.

[0127]

[0128]

[0129]

[0130] In one embodiment, the dicarbonyl compound may consist of terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC), but is not limited thereto.

[0131] The above diamine compound and the above dicarbonyl compound can polymerize to form a repeating unit represented by the following chemical formula B.

[0132] <Chemical Formula B>

[0133]

[0134] In the above chemical formula B, the description of E, J, e, and j is as described above.

[0135] For example, the above diamine compound and the above dicarbonyl compound can polymerize to form an amide repeating unit represented by the chemical formula B-1, B-2, or B-3.

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

[0137] <Chemical Formula B-1>

[0138]

[0139] x in the above chemical formula B-1 is an integer from 1 to 400.

[0140] Chemical Formula B-2

[0141]

[0142] y in the above chemical formula B-2 is an integer from 1 to 400.

[0143] <Chemical Formula B-3>

[0144]

[0145] y in the above chemical formula B-3 is an integer from 1 to 400.

[0146] According to one embodiment, the polyamide-imide polymer is a polymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound, wherein the diamine compound is represented by Chemical Formula 1, the dianhydride compound is represented by Chemical Formula 2, and the dicarbonyl compound is represented by Chemical Formula 3.

[0147] According to one embodiment, the polyamide-imide-based polymer may include a repeating unit represented by the following chemical formula A and a repeating unit represented by the following chemical formula B:

[0148] <Chemical Formula A>

[0149]

[0150] <Chemical Formula B>

[0151]

[0152] Among the above chemical formulas A and B,

[0153] E and J are independently substituted or unsubstituted divalent C6-C 30 Aliphatic ring, substituted or unsubstituted divalent C4-C 30 Heteroaliphatic ring group, substituted or unsubstituted divalent C6-C 30 Aromatic ring, substituted or unsubstituted divalent C4-C 30 Hetero-aromatic ring, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 Selected from alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2- and -C(CH3)2-, and

[0154] e and j are independently selected from integers 1 to 5, and

[0155] If e is 2 or greater, 2 or more E are identical or different from each other, and

[0156] If j is 2 or greater, J 2 or greater are identical or different from each other, and

[0157] G is a substituted or unsubstituted tetravalent C4-C 30 Aliphatic ring, substituted or unsubstituted tetravalent C4-C 30 Heteroaliphatic ring, substituted or unsubstituted tetravalent C6-C 30 Aromatic ring, substituted or unsubstituted tetravalent C4-C 30 It is a heteroaromatic ring, wherein the aliphatic ring, the heteroaliphatic ring, the aromatic ring, or the heteroaromatic ring exists alone, is joined to form a condensed ring, or is substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30It is connected by a linker selected from alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, Si(CH3)2-, and -C(CH3)2-.

[0158] In one embodiment, each of the diamine compound, dianhydride compound, and dicarbonyl compound may not contain a fluorine atom.

[0159] The above polyamide-imide polymer may contain imide repeating units and amide repeating units in a molar ratio of 2:98 to 70:30. Specifically, the molar ratio of the imide-based repeating unit and the amide-based repeating unit is 2:98 to 60:40, 2:98 to 55:45, 2:98 to 50:50, 2:98 to 45:55, 2:98 to 40:60, 2:98 to 35:65, 2:98 to 30:70, 3:97 to 70:30, 3:97 to 60:40, 3:97 to 55:45, 3:97 to 50:50, 3:97 to 45:55, 3:97 to 40:60, 3:97 to 30:70, 5:95 to 70:30, 5:95 to 60:40, 5:95 to 55:45, 5:95 to It may be 50:50, 5:95 to 40:60, 5:95 to 30:70, or 10:90 to 40:60, but is not limited thereto.

[0160] When the molar ratio of imide repeating units to amide repeating units is within the above range, combined with a characteristic process method, the quality reliability of the film is improved, and excellent optical properties, mechanical properties, and UV blocking rate can be achieved.

[0161] In the above polyamide-imide polymer, the molar ratio of the repeating unit represented by the above formula A and the repeating unit represented by the above formula B may be 2:98 to 70:30. Specifically, the molar ratio of the repeating unit represented by Chemical Formula A and the repeating unit represented by Chemical Formula B is 2:98 to 60:40, 2:98 to 55:45, 2:98 to 50:50, 2:98 to 45:55, 2:98 to 40:60, 2:98 to 35:65, 2:98 to 30:70, 3:97 to 70:30, 3:97 to 60:40, 3:97 to 55:45, 3:97 to 50:50, 3:97 to 45:55, 3:97 to 40:60, 3:97 to 30:70, 5:95 to 70:30, 5:95 to 60:40, 5:95 to 55:45, 5:95 It may be up to 50:50, 5:95 to 40:60, 5:95 to 30:70, or 10:90 to 40:60, but is not limited thereto.

[0162] In one embodiment, the polyamide-imide-based polymer may comprise one or more amide-based repeating units. Specifically, the polyamide-imide-based polymer may comprise two or more amide-based repeating units.

[0163] In one embodiment, the polyamide-imide polymer may include a first amide repeating unit and a second amide repeating unit. The first amide repeating unit may be formed by reacting a first dicarbonyl compound with the diamine compound, and the second amide repeating unit may be formed by reacting a second dicarbonyl compound with the diamine compound.

[0164] As another example, the polyamide-imide polymer may comprise a first amide repeating unit derived from a first dicarbonyl compound and a second amide repeating unit derived from a second dicarbonyl compound. Specifically, the first amide repeating unit may be derived from the first dicarbonyl compound, and the second amide repeating unit may be derived from the second dicarbonyl compound.

[0165] The first dicarbonyl compound and the second dicarbonyl compound may be different compounds from each other.

[0166] The first dicarbonyl compound and the second dicarbonyl compound may each contain two carbonyl groups. The angle between the two carbonyl groups included in the first dicarbonyl compound may be greater than the angle between the two carbonyl groups included in the second dicarbonyl compound.

[0167] In the embodiments, the first dicarbonyl compound and the second dicarbonyl compound may be structurally isomers of each other.

[0168] The first dicarbonyl compound and the second dicarbonyl compound may each be an aromatic dicarbonyl compound. In some embodiments, the first dicarbonyl compound and the second dicarbonyl compound may each have one benzene ring (phenyl group).

[0169] For example, the first dicarbonyl compound and the second dicarbonyl compound may be different aromatic dicarbonyl compounds, but are not limited thereto.

[0170] When the first dicarbonyl compound and the second dicarbonyl compound are each aromatic dicarbonyl compounds, since they contain a benzene ring, they can contribute to improving mechanical properties such as pencil hardness and tensile strength of a film containing a prepared polyamide-imide-based polymer.

[0171] For example, the angle between the two carbonyl groups included in the first dicarbonyl compound is 160 to 180 o It may be, and the angle between the two carbonyl groups included in the second dicarbonyl compound is 80 to 140 o It could be.

[0172] For example, the first dicarbonyl compound may include TPC, and the second dicarbonyl compound may include IPC, but is not limited thereto.

[0173] When TPC is appropriately combined as the first dicarbonyl compound and IPC as the second dicarbonyl compound, it contributes to improving the viscosity of the film during polymerization, allowing the film formation process to be performed appropriately, and the film containing the manufactured polyamide-imide polymer can have high light transmittance, modulus, etc., low haze and yellowness, and improved UV blocking rate.

[0174] In one embodiment, the polyamide-imide polymer comprises an imide repeating unit, a first amide repeating unit, and a second amide repeating unit, and when the sum of the imide repeating unit, the first amide repeating unit, and the second amide repeating unit is 100 mol%, the molar ratio of the first amide repeating unit may be 70 mol% or less. Specifically, when the sum of the imide repeating unit, the first amide repeating unit, and the second amide repeating unit is 100 mol%, the molar ratio of the first amide repeating unit may be 65 mol% or less, 60 mol% or less, 58 mol% or less, 55 mol% or less, 50 mol% or less, or 40 mol% or less, but is not limited thereto.

[0175] The molar ratio of the first amide-based repeating unit and the second amide-based repeating unit may be 21:79 to 79:21. Specifically, the molar ratio of the first amide-based repeating unit and the second amide-based repeating unit may be 25:75 to 79:21, 30:70 to 79:21, 35:65 to 79:21, 40:60 to 79:21, 21:79 to 75:25, 25:75 to 75:25, 30:70 to 75:25, 35:65 to 75:25, or 40:60 to 75:25.

[0176] By setting the molar ratio of the first and second amide-based repeating units to the range described above, the physical properties of the polyamide-imide-based film can be controlled to a desired range.

[0177] The polyamide-imide film according to the embodiment may further include one or more selected from the group consisting of a filler, a blue pigment, and a UVA absorber in addition to the polyamide-imide polymer.

[0178] The above filler may include, for example, oxides of metals or metalloids, carbonates, sulfur oxides, etc. For example, the above filler may include silica, calcium carbonate, barium sulfate, etc., but is not limited thereto.

[0179] The above filler may be included in particle form. Additionally, the filler may not have a special surface coating and may be evenly dispersed throughout the film.

[0180] By including the filler in the above polyamide-imide-based film, the film can secure a wide viewing angle without degrading optical properties, improve illumination and windability, and also improve the effect of improving scratch resistance during film production.

[0181] The refractive index of the above filler may be 1.55 to 1.75. Specifically, the refractive index of the above filler may be 1.60 to 1.75, 1.60 to 1.70, 1.60 to 1.68, or 1.62 to 1.65, but is not limited thereto.

[0182] By satisfying the above range for the refractive index of the filler, the birefringence values ​​related to the x-direction refractive index (nx), y-direction refractive index (ny), and z-direction refractive index (nz) of the film can be appropriately controlled, and the brightness of the film at various angles can be improved.

[0183] On the other hand, if the refractive index of the above filler falls outside the above range, the presence of the filler may be visible to the naked eye on the film, or problems may arise where haze increases due to the filler.

[0184] The content of the above filler may be 100 ppm to 15,000 ppm based on the total weight of the polyamide-imide-based polymer solids. Specifically, the content of the above filler may be 100 ppm to 14,500 ppm, 100 ppm to 14,200 ppm, 200 ppm to 14,500 ppm, 200 ppm to 14,200 ppm, 250 ppm to 14,100 ppm, or 300 ppm to 14,000 ppm based on the total weight of the polyamide-imide-based polymer solids, but is not limited thereto.

[0185] If the content of the above filler falls outside the above range, the haze of the film increases rapidly, and the fillers clump together on the film surface, causing foreign matter to be visually detected, or problems may occur during the production process, or windability may be reduced.

[0186] In some embodiments, the blue pigment may be included in an amount of 50 to 5000 ppm with respect to the total weight of the polyamide-imide polymer. Preferably, the blue pigment is present in an amount of 100 to 5000 ppm, 200 to 5000 ppm, 300 to 5000 ppm, 400 to 5000 ppm, 50 to 3000 ppm, 100 to 3000 ppm, 200 to 3000 ppm, 300 to 3000 ppm, 400 to 3000 ppm, 50 to 2000 ppm, 100 to 2000 ppm, 200 to 2000 ppm, 300 to 2000 ppm, 400 to 2000 ppm, 50 to 1000 ppm, 100 to 1000 ppm, 200 to 1000 ppm, 300 to It may be included in 1000 ppm or 400 to 1000 ppm, but is not limited thereto.

[0187] The above UVA absorber may include an absorber that absorbs electromagnetic waves with wavelengths of 10 to 400 nm used in the field. For example, the above UVA absorber may include a benzotriazole-based compound, and the above benzotriazole-based compound may include an N-phenolic benzotriazole-based compound. In some embodiments, the above N-phenolic benzotriazole-based compound may include an N-phenolic benzotriazole in which a 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 straight-chain, branched, or cyclic.

[0188] In some embodiments, the UVA absorber may be included in an amount of 0.1 to 10 weight% with respect to the total weight of the polyamide-imide-based polymer. Preferably, the UVA absorber may be included in an amount of 0.1 to 5 weight%, 0.1 to 3 weight%, 0.1 to 2 weight%, 0.5 to 10 weight%, 0.5 to 5 weight%, 0.5 to 3 weight%, 0.5 to 2 weight%, 1 to 10 weight%, 1 to 5 weight%, 1 to 3 weight%, or 1 to 2 weight% with respect to the total weight of the polyamide-imide-based polymer, but is not limited thereto.

[0189] The physical properties of the above-described polyamide-imide film are based on a thickness of 20 μm to 80 μm. For example, the physical properties of the above-described polyamide-imide film are based on a thickness of 50 μm.

[0190] The thickness of the polyamide-imide film may be 20 μm to 100 μm. Specifically, the thickness of the polyamide-imide film may be 20 μm to 80 μm, 20 μm to 60 μm, 20 μm to 50 μm, 25 μm to 100 μm, 25 μm to 80 μm, 25 μm to 60 μm, or 25 μm to 50 μm, but is not limited thereto.

[0191] The thickness of the above film can be determined by measuring the thickness at five random points on the film and taking the average value. Specifically, the thickness of the above film can be determined by using a digital micrometer 547-401 from Mitsutoyo Corporation of Japan to measure the thickness at five random points and taking the average value.

[0192] The characteristics regarding the constituent components and physical properties of the aforementioned polyamide-imide-based films can be combined with one another.

[0193] In addition, the presence and content of fluorine atoms in the polyamide-imide film and / or polyamide-imide polymer can be controlled not only by the type of monomer in the polymerization process but also by additives in the polymerization process and additives in the subsequent process.

[0194] In addition, the modulus, transmittance, haze, etc. of the polyamide-imide film can be controlled by combining the chemical and physical properties of the components constituting the polyamide-imide film and the specific process conditions of each step in the method for manufacturing the polyamide-imide film to be described later.

[0195] For example, various factors such as the composition and content of the components forming the polyamide-imide film, the content of residual solvent, and heat treatment conditions such as polymerization conditions, heat treatment steps, and cooling steps in the film manufacturing process can be combined to achieve film properties within the desired range.

[0196] Cover window for display device

[0197] A cover window for a display device according to one embodiment includes a polyamide-imide-based film and a functional layer.

[0198] The above polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and based on a film thickness of 50 μm, the modulus is 5 GPa or more.

[0199] A detailed description of the above polyamide-imide film is as described above.

[0200] The above-mentioned cover window for a display device can be usefully applied to a display device.

[0201] Display device

[0202] A display device according to one embodiment includes a display portion; and a cover window disposed on the display portion; wherein the cover window comprises a polyamide-imide-based film and a functional layer.

[0203] The above polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and based on a film thickness of 50 μm, the modulus is 5 GPa or more.

[0204] The specific description of the above-mentioned polyamide-imide film and cover window is as described above.

[0205] FIG. 1 is a schematic exploded view of a display device according to one embodiment. FIG. 2 is a schematic perspective view of a display device according to one embodiment. FIG. 3 is a schematic cross-sectional view of a display device according to one embodiment.

[0206] Specifically, FIGS. 1 to 3 illustrate a display device having a display portion (400), a polyamide-imide film (100) having a first surface (101) and a second surface (102) and a cover window (300) having a functional layer (200) disposed on the display portion (400), and an adhesive layer (500) disposed between the display portion (400) and the cover window (300).

[0207] The above display unit (400) can display an image and may have flexible characteristics.

[0208] The above display unit (400) may be a display panel for displaying images, for example, a liquid crystal display panel or an organic electroluminescent display panel. The organic electroluminescent display panel may include a front polarizer and an organic EL panel.

[0209] The front polarizer can be placed on the front surface of the organic EL panel. Specifically, the front polarizer can be adhered to the surface of the organic EL panel where an image is displayed.

[0210] The above organic EL panel can display images by self-luminescence at the pixel level. The above organic EL panel may include an organic EL substrate and a driving substrate. The above organic EL substrate may include a plurality of organic electroluminescent units corresponding to each pixel. Specifically, each may include a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and an anode. The above driving substrate may be drivenly coupled to the above organic EL substrate. That is, the above driving substrate is coupled to the above organic EL substrate so as to apply a driving signal, such as a driving current, to the above organic EL substrate, thereby applying current to each of the organic electroluminescent units to drive the above organic EL substrate.

[0211] Additionally, an adhesive layer (500) may be included between the display portion (400) and the cover window (300). The adhesive layer may be an optically transparent adhesive layer and is not particularly limited.

[0212] The cover window (300) may be placed on the display unit (400). The cover window may be located on the outer edge of the display device according to the embodiment to protect the display unit.

[0213] The above cover window (300) may include a polyamide-imide-based 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 antifouling layer, and an anti-glare layer. The functional layer may be coated on at least one surface of the polyamide-imide-based film.

[0214] In the case of the polyamide-imide-based film according to the embodiment, it is possible to provide a display device having uniform thickness, low haze, high transmittance, and transparency by simply applying it in the form of a film to the outside of a display device without changing the display driving method, color filter inside the panel, or lamination structure. Since excessive process changes or cost increases are not required, there is also an advantage of reducing production costs.

[0215] The polyamide-imide film according to the embodiment can have excellent optical properties such as high transmittance, low haze, and low yellowness, as well as mechanical properties such as modulus and flexibility, and changes (deterioration) in optical / mechanical properties can be suppressed even when exposed to ultraviolet rays.

[0216] Specifically, the polyamide-imide-based film according to the embodiment may have excellent optical properties, mechanical properties, and UV blocking rate. Accordingly, when the polyamide-imide-based film is applied to a cover window for a display device or to a display device, the quality reliability and product yield of the final product can be improved.

[0217] Method for manufacturing polyamide-imide-based films

[0218] One embodiment provides a method for manufacturing a polyamide-imide-based film.

[0219] A method for manufacturing a polyamide-imide film according to one embodiment comprises the steps of: preparing a polyamide-imide polymer solution by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent (S100); preparing a gel sheet by casting and drying the solution (S200); and heat-treating the gel sheet (S300) (see FIG. 4).

[0220] A method for manufacturing a polyamide-imide-based film according to some embodiments may further include a step of controlling the viscosity of the polyamide-imide-based polymer solution (S110), a step of aging the polyamide-imide-based polymer solution (S120), and / or a step of degassing the polyamide-imide-based polymer solution (S130).

[0221] The above polyamide-imide film is a film whose main component is a polyamide-imide polymer, wherein the polyamide-imide polymer is a polymer comprising imide repeating units and amide repeating units as structural units in a predetermined molar ratio.

[0222] In the method for manufacturing the above polyamide-imide film, the polymer solution for manufacturing the polyamide-imide polymer may be prepared by simultaneously or sequentially mixing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in a reactor and reacting the mixture (S100).

[0223] In one embodiment, the polymer solution can be prepared by simultaneously introducing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent.

[0224] In another embodiment, the step of preparing the polymer solution may include: a step of preparing a polyamic acid (PAA) solution by first mixing and reacting the diamine compound and the dianhydride compound in a solvent; and a step of forming amide bonds and imide bonds by secondarily mixing and reacting the dicarbonyl compound with the polyamic acid (PAA) solution. The polyamic acid solution is a solution containing a polymer having amic acid repeating units.

[0225] Alternatively, the step of preparing the polymer solution may include: a step of preparing a polyamic acid solution by first mixing and reacting the diamine compound and the dianhydride compound in a solvent; a step of preparing a polyimide (PI) solution by dehydrating the polyamic acid solution; and a step of secondarily 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 repeating units.

[0226] In another embodiment, the step of preparing the polymer solution may include: a step of preparing a polyamide (PA) solution by first mixing and reacting the diamine compound and the dicarbonyl compound in a solvent; and a step of secondarily mixing and reacting the dianhydride compound with the polyamide (PA) solution to additionally form an imide bond. The polyamide solution is a solution containing a polymer having amide repeating units.

[0227] The polymer solution prepared in this manner may be a solution containing a polymer selected from the group consisting of polyamic acid (PAA) repeating units, polyamide (PA) repeating units, and polyimide (PI) repeating units.

[0228] Alternatively, the polymer included in the polymer solution comprises an imide repeating unit derived from the polymerization of the diamine compound and the dianhydride compound, and an amide repeating unit derived from the polymerization of the diamine compound and the dicarbonyl compound.

[0229] The description of the above diamine compound, dianhydride compound, and dicarbonyl compound is as described above.

[0230] The content of solids contained in the polymer solution may be 10% to 30% by weight. Alternatively, the content of solids contained in the polymer solution may be 15% to 25% by weight, but is not limited thereto.

[0231] When the content of solids contained in the above polymer solution is within the above range, a polyamide-imide-based film can be effectively manufactured in the extrusion and casting processes. In addition, the manufactured polyamide-imide-based film can have excellent optical properties and UV blocking rates.

[0232] In another embodiment, the step of preparing the polymer solution may further include the step of adding a catalyst.

[0233] At this time, the catalyst may include one or more selected from the group consisting of beta-picoline, acetic anhydride, isoquinoline (IQ), and pyridine compounds, but is not limited thereto.

[0234] The above catalyst may be added in an amount of 0.01 to 0.5 molar equivalents, 0.01 to 0.4 molar equivalents, or 0.01 to 0.3 molar equivalents based on 1 mole of the polyamic acid, but is not limited thereto.

[0235] When the above catalyst is added, the reaction rate can be improved, and the chemical bonding strength between or within repeating unit structures can be enhanced.

[0236] In one embodiment, the step of preparing the polymer solution may further include the step (S110) of controlling the viscosity of the polymer solution. The viscosity of the polymer solution may be controlled to 80,000 cps to 500,000 cps, 100,000 cps to 500,000 cps, 150,000 cps to 500,000 cps, 150,000 cps to 450,000 cps, 200,000 cps to 450,000 cps, 200,000 cps to 400,000 cps, 200,000 cps to 350,000 cps, or 250,000 cps to 350,000 cps based on room temperature. In this case, thickness uniformity can be improved by enhancing the film-forming properties of the polyamide-imide-based film.

[0237] Specifically, the step of preparing the polymer solution may include: a step of preparing a first polymer solution by simultaneously or sequentially mixing and reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent; and a step of preparing a second polymer solution having a target viscosity by additionally adding the dicarbonyl compound.

[0238] In the case of the step of preparing the first polymer solution and the step of preparing the second polymer solution, the viscosity of the prepared polymer solutions is different. For example, the viscosity of the second polymer solution is higher than that of the first polymer solution.

[0239] Specifically, the viscosity of the polymer solution can be measured using the BH-II equipment of TOKI SANGYO, with the RPM set to 4 and the 4th spindle used under constant temperature conditions of 25°C.

[0240] The stirring speed when preparing the first polymer solution and the stirring speed when preparing the second polymer solution may be different. For example, the stirring speed when preparing the first polymer solution may be faster than the stirring speed when preparing the second polymer solution.

[0241] In another embodiment, 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 may be adjusted to 4 to 7, for example, to 4.5 to 7.

[0242] The pH of the polymer solution can be adjusted by adding a pH adjuster, and the pH adjuster is not particularly limited but may include, for example, amine compounds such as alkoxyamine, alkylamine, or alkanolamine.

[0243] By adjusting the pH of the polymer solution to the aforementioned range, the occurrence of defects in the film produced from the polymer solution can be prevented, and the desired optical and mechanical properties in terms of yellowness and modulus can be realized.

[0244] The above pH adjuster 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.

[0245] 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 dimethylacetamide (DMAc), but is not limited thereto.

[0246] In another embodiment, one or more selected from the group consisting of fillers, blue pigments, and UVA absorbers may be added to the polymer solution.

[0247] Specific details regarding the types, contents, etc. of the above-mentioned filler, blue pigment, and UVA absorber are as described above. The above-mentioned filler, blue pigment, and / or UVA absorber may be mixed with the polyamide-imide-based polymer within the polymer solution.

[0248] The polymer solution can 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.

[0249] When stored at the above temperature, the deterioration of the polymer solution can be prevented, and the moisture content can be reduced to prevent defects in the film manufactured therefrom.

[0250] In some embodiments, the polymer solution or the viscosity-controlled polymer solution may be aged (S120).

[0251] The above aging is performed on the polymer solution for at least 24 hours, from -10 to 10 o This can be performed by standing at a temperature of C. In this case, the polymer solution may be homogenized by, for example, completing the reaction or reaching chemical equilibrium with respect to the polyamide-imide polymer or unreacted material contained in the polymer solution, and the mechanical and optical properties of the polyamide-imide film formed therefrom may become substantially uniform over the entire surface area of ​​the film. Preferably, the aging is performed from -5 to 10 o C, -5 to 5 o C or -3 to 5 o It may be performed under C temperature conditions, but is not limited thereto.

[0252] In one embodiment, the method may further include a step (S130) of degassing the polyamide-imide-based polymer solution. By removing moisture from the polymer solution and reducing impurities through degassing, the reaction yield can be increased, and the surface appearance and mechanical properties of the final film can be achieved excellently.

[0253] The above degassing may include vacuum degassing or inert gas purging.

[0254] The above vacuum degassing can be performed for 30 minutes to 3 hours after depressurizing the reactor containing the polymer solution to 0.1 bar to 0.7 bar. By performing vacuum degassing under these conditions, bubbles inside the polymer solution can be reduced, and as a result, surface defects of the film produced therefrom can be prevented, and excellent optical properties such as haze can be achieved.

[0255] In addition, 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, moisture inside the polymer solution is removed and impurities are reduced, thereby increasing the reaction yield and enabling excellent optical properties such as haze and mechanical properties.

[0256] The above 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 above inert gas may be nitrogen.

[0257] The above vacuum degassing and the above inert gas purging can be performed as separate processes.

[0258] For example, a vacuum degassing process may be performed, followed by a purging process with an inert gas, but is not limited thereto.

[0259] By performing the above vacuum degassing and / or the above inert gas purging, the physical properties of the surface of the manufactured polyamide-imide-based film can be improved.

[0260] A gel sheet can be manufactured by casting the above polymer solution (S200).

[0261] For example, the polymer solution can be applied onto a support, extruded, and / or dried to form a gel sheet.

[0262] In addition, the casting thickness of the polymer solution may be 200 μm to 700 μm. By casting the polymer solution within the above thickness range, when it is manufactured into a final film through drying and heat treatment, appropriate thickness and thickness uniformity can be secured.

[0263] As described above, the viscosity of the polymer solution may be 100,000 cps to 500,000 cps or 150,000 cps to 500,000 cps at room temperature. By satisfying the above viscosity range, the polymer solution can be cast with a uniform thickness without defects when cast, and a polyamide-imide film of substantially uniform thickness can be formed without local / partial thickness changes during the drying process.

[0264] A gel sheet can be prepared by casting the above polymer solution and then drying it at a temperature of 60°C to 150°C, 70°C to 150°C, 80°C to 150°C, or 90°C to 150°C for a period of 5 to 60 minutes. Specifically, a gel sheet can be prepared by drying the above polymer solution at a temperature of 90°C to 140°C for a period of 15 to 40 minutes.

[0265] During the above drying process, the solvent of the polymer solution may partially or completely volatilize to produce the gel sheet.

[0266] The above dried gel sheet can be heat-treated to form a polyamide-imide film (S300).

[0267] The heat treatment of the above gel sheet can be performed, for example, through a heat curing machine.

[0268] The step of heat-treating the gel sheet includes the step of heat-treating through at least one heater.

[0269] In addition, the step of heat-treating the gel sheet may further include a step of heat-treating with hot air.

[0270] In one embodiment, the step of heat-treating the gel sheet may include a step of heat-treating by hot air; and a step of heat-treating through at least one heater.

[0271] In one embodiment, when performing the step of heat treatment by the hot air, the amount of heat can be applied evenly. If the amount of heat is not distributed evenly, satisfactory surface roughness may not be achieved or the surface quality may become non-uniform, and the surface energy may rise or fall excessively.

[0272] The heat treatment by hot air described above can be performed for 5 minutes to 200 minutes in a range of 60°C to 500°C. Specifically, the heat treatment of the gel sheet can be performed for 10 to 150 minutes while increasing the temperature at a rate of 1.5°C / min to 20°C / min in a range of 80°C to 300°C. More specifically, the heat treatment of the gel sheet can be performed in a temperature range of 140°C to 250°C.

[0273] At this time, the starting temperature of the heat treatment of the gel sheet by hot air may be 60°C or higher. Specifically, the starting temperature of the heat treatment of the gel sheet may be 80°C to 180°C. In addition, the maximum temperature during the heat treatment may be 200°C to 500°C.

[0274] In addition, the heat treatment of the gel sheet with hot air may be performed in two or more stages. Specifically, the heat treatment of the gel sheet with hot air may be performed sequentially in a first hot air treatment stage and a second hot air treatment stage, and the temperature in the second hot air treatment stage may be higher than the temperature in the first hot air treatment stage.

[0275] In one embodiment, the step of heat-treating the gel sheet may include a second heat-treatment step of heat-treating through at least one heater, specifically a step of heat-treating through a plurality of heaters.

[0276] The plurality of heaters may include a plurality of heaters spaced apart in the width direction (TD direction) of the gel sheet. The plurality of heaters may be mounted in a heater mounting portion, and two or more heater mounting portions may be arranged along the direction of travel (MD direction) of the gel sheet.

[0277] The above 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 can be varied in many ways. Specifically, the plurality of heaters may include IR heaters.

[0278] The heat treatment by the at least one heater may be performed in a temperature range of 250°C or higher. Specifically, the heat treatment by the at least one heater may be performed for 1 minute to 30 minutes, or 1 minute to 20 minutes, in a temperature range of 250°C to 400°C.

[0279] In the heat treatment by the heater described above, the temperature is the temperature within the heat treatment chamber where the gel sheet exists, and corresponds to the temperature measured by a temperature sensing sensor located in the second heat treatment section within the heat treatment chamber.

[0280] Next, after the step of heat-treating the gel sheet, a step of cooling the cured film while moving it can be performed.

[0281] The step of cooling while moving the cured film may include a first cooling step of cooling at a rate of 100℃ / min to 1000℃ / min; and a second cooling step of cooling at a rate of 40℃ / min to 400℃ / min.

[0282] At this time, specifically, the second temperature reduction step is performed after the first temperature reduction step, and the temperature reduction speed of the first temperature reduction step may be faster than the temperature reduction speed of the second temperature reduction step.

[0283] For example, the maximum speed during the first temperature reduction step is faster than the maximum speed during the second temperature reduction step. Or, the minimum speed during the first temperature reduction step is faster than the minimum speed during the second temperature reduction step.

[0284] By performing the cooling step of the cured film in multiple stages as described above, the physical properties of the cured film can be further 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.

[0285] In addition, the step of winding the cooled cured film using a winder can be performed.

[0286] At this time, 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 1:0.99 to 1:1.20, 1:0.99 to 1:1.10, or 1:1.00 to 1:1.05, but is not limited thereto.

[0287] If the ratio of the above moving speeds deviates from the above range, there is a risk that the mechanical properties of the cured film may be damaged and that the flexibility and elastic properties may be reduced.

[0288] In the method for manufacturing the above polyamide-imide film, the thickness deviation (%) according to the following general formula 1 may be 3% to 30%. Specifically, the thickness deviation (%) may be 5% to 20%, but is not limited thereto.

[0289] <General Formula 1> Thickness deviation (%) = {(M1-M2) / M1} X 100

[0290] In the above general formula 1, M1 is the thickness (μm) of the gel sheet, and M2 is the thickness (μm) of the cured film cooled during winding.

[0291] The above-described polyamide-imide film, manufactured according to the aforementioned manufacturing method, not only exhibits excellent optical and mechanical properties but also possesses an excellent UV blocking rate. Such a polyamide-imide film can be applied to various applications requiring transparency. For example, the polyamide-imide film can be applied not only to display devices but also to solar cells, semiconductor devices, sensors, etc. In particular, the polyamide-imide film according to the embodiment can be utilized in an even wider range of applications as it does not contain fluorine atoms, which may be subject to environmental regulations.

[0292] The description of the polyamide-imide film manufactured according to the above-described manufacturing method is as described above.

[0293] The above contents will be explained in more detail by the following examples. However, the following examples are merely for illustrating the present invention, and the scope of the examples is not limited to these.

[0294] <Example 1>

[0295] 516.0 g of dimethylacetamide (DMAc) was filled into a temperature-controlled double-jacketed 1L glass reactor under a nitrogen atmosphere at 20°C, and 46.7 g (0.22 mol) of 2,2'-dimethylbenzidine (m-Tolidine) was slowly added and dissolved as a diamine compound. Subsequently, 8.6 g (0.044 mol) of 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) was slowly added as a dianhydride compound and stirred for 1 hour. Then, 13.4 g (0.066 mol) of terephthaloyl chloride (TPC) was added as a dicarbonyl compound and stirred for 1 hour, and 22.33 g (0.11 mol) of isophthaloyl chloride (IPC) was added and stirred for 1 hour to prepare a polymerization solution. After applying the obtained polymerization solution to a glass plate, drying it with hot air at 80°C for 30 minutes, peeling it off from the glass plate, fixing it to a pin frame, and heating it at a rate of 2°C / min in a temperature range of 80 to 300°C to obtain a polyamide-imide film with a thickness of 50 μm.

[0296] The specific composition and molar ratio of the polyamide-imide polymer are as described in the preparation examples of Table 1 below.

[0297] <Examples 2 to 6 and Comparative Examples 1 to 6>

[0298] As described in Table 1 below, a film was prepared in the same manner as in Example 1, except that the composition and molar ratio of the polymer were different.

[0299] In the case of Comparative Example 1, during the process of adding terephthaloyl chloride (TPC) and stirring for 1 hour, a precipitate in the form of a white powder was generated in the solution, making it impossible to proceed further.

[0300] In addition, in the case of Comparative Examples 3 and 5, the viscosity for film manufacturing after polymerization was not raised to the target viscosity, so the subsequent film-making process could not be carried out.

[0301] <Preparation Example> Composition of the polymer

[0302] division Polymerization ratio of polyamide-imide-based polymers Diamine compounds (molar ratio) Dianhydride compounds (molar ratio) Dicarbonyl compounds (molar ratio) Example 1 m-Tolidine 100 CBDA 20 TPC 30IPC 50 Example 2 m-Tolidine 100 CBDA 15 TPC 30IPC 55 Example 3 m-Tolidine 100 CBDA 35 TPC 15IPC 50 Example 4 m-Tolidine 100 CBDA 13 TPC 37IPC 50 Example 5 m-Tolidine 100 CBDA 13 TPC 57IPC 30 Example 6 m-Tolidine 100 CBDA 3 TPC 69IPC 28 Comparative Example 1 m-Tolidine 100 CBDA 7 TPC 71IPC 22 Comparative Example 2 m-Tolidine 100 CBDA 100 - Comparative Example 3 m-Tolidine 100 CBDA 41 TPC 19IPC 40 Comparative Example 4 m-Tolidine 100 6FDA 100 - Comparative Example 5 TFMB 100 CBDA 100 - Comparative Example 6 TFMB 100 6FDA 10 TPC 70IPC 20

[0303] <Evaluation Example>

[0304] The physical properties of the films prepared in the examples and comparative examples were measured and evaluated as follows, and the results are shown in Table 2 below.

[0305] Evaluation Example 1: Measurement of film thickness

[0306] Using the digital micrometer 547-401 from Mitsutoyo, Japan, the thickness was measured at five points at random locations, and the average value was used to determine the thickness.

[0307] Evaluation Example 2: Transmittance and Haze Measurement

[0308] Total light transmittance and haze were measured according to the JIS K 7105 standard using the NDH-5000W haze meter from Tenshoku Kogyo Co., Ltd., Japan.

[0309] Evaluation Example 3: Yellowness Measurement

[0310] Yellow Index (YI) was measured according to ASTM-E313 standards using a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) under d65, 10° conditions.

[0311] Evaluation Example 4: Modulus Measurement

[0312] Using Instron’s universal testing machine UTM 5566A, the sample was cut to a length of 10 cm or more in a direction orthogonal to the main shrinkage direction and 10 mm in the main shrinkage direction, mounted on clips spaced 10 cm apart, and then a stress-strain curve was obtained while elongating at a speed of 10 mm / min until fracture occurred at room temperature. In the stress-strain curve, the slope of the load relative to the initial deformation was denoted as the modulus (GPa).

[0313] Evaluation Example 5: Transmittance measurement at 380 nm wavelength

[0314] Transmittance at a wavelength of 380 nm was measured using the JASCO V-670 ultraviolet / visible / near-infrared spectrophotometer.

[0315] division Evaluation example thickness Transmittance Hayes Yellowness Modulus Transmittance at 380 nm wavelength (㎛) (%) (%) (GPa) (%) Example 1 50 86.8 0.14 3.81 6.04 0.24 Example 2 50 86.7 0.14 3.84 6.33 0.27 Example 3 50 86.6 0.15 3.76 6.02 0.28 Example 4 50 86.4 0.16 4.01 6.54 0.22 Example 5 50 86.1 0.18 4.2 6.64 0.25 Example 6 50 85.8 0.23 4.42 6.81 0.19 Comparative Example 1 Crystallization occurs after TPC addition Comparative Example 2 50 76.5 25.1 13.1 4.3 0.18 Comparative Example 3 Film formation is impossible as viscosity did not rise to the target level. Comparative Example 4 50 88.6 0.1 27 4.2 0.14 Comparative Example 5 Film formation is impossible as viscosity did not rise to the target level. Comparative Example 6 50 88.1 0.18 3.2 6.1 37.6

[0316] Referring to Table 2, it was confirmed that the film according to the example has excellent optical properties such as transmittance, haze, and yellowness, and not only has an excellent modulus, but also has excellent UV blocking performance with low transmittance at a wavelength of 380 nm. Explanation of the symbols

[0317] 100 : Polyamide-imide film 101 : Page 1 102 : Page 2 200: Functional layer 300: Cover window 400 : Display part 500 : Adhesive layer

Claims

Claim 1 A polyamide-imide film comprising a polyamide-imide polymer that does not contain fluorine atoms, wherein, based on a film thickness of 50 μm, the modulus is 5 GPa or more, the polyamide-imide polymer comprises imide repeating units and amide repeating units in a molar ratio of 2:98 to 40:60, the polyamide-imide polymer is a polymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound, wherein the dianhydride compound comprises 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), and the polyamide-imide film does not contain a UV blocker. Claim 2 A polyamide-imide film according to claim 1, wherein the transmittance at a wavelength of 380 nm is 3% or less based on a film thickness of 50 μm. Claim 3 A polyamide-imide film according to claim 1, wherein, based on a film thickness of 50 μm, the total light transmittance measured in the visible light wavelength region is 80% or more, the haze is 1% or less, and the yellowness is 5 or less. Claim 4 delete Claim 5 In claim 1, the polyamide-imide film wherein the diamine compound is represented by the following Chemical Formula 1, the dianhydride compound is represented by the following Chemical Formula 2, and the dicarbonyl compound is represented by the following Chemical Formula 3: <Chemical Formula 1> <Chemical Formula 2> <Chemical Formula 3> In the above chemical formulas 1 to 3, E and J are independently substituted or unsubstituted divalent C6-C 30 Aliphatic ring, substituted or unsubstituted divalent C4-C 30 Heteroaliphatic ring group, substituted or unsubstituted divalent C6-C 30 Aromatic ring, substituted or unsubstituted divalent C4-C 30 Hetero-aromatic ring, substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 Selected from alkynylene groups, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, -Si(CH3)2-, and -C(CH3)2-; e and j are independently selected from integers 1 to 5; if e is 2 or more, 2 or more E are identical or different; if j is 2 or more, 2 or more J are identical or different; and G is a substituted or unsubstituted tetravalent C4-C 30 Aliphatic ring, substituted or unsubstituted tetravalent C4-C 30 Heteroaliphatic ring, substituted or unsubstituted tetravalent C6-C 30 Aromatic ring, substituted or unsubstituted tetravalent C4-C 30 It is a heteroaromatic ring, wherein the aliphatic ring, the heteroaliphatic ring, the aromatic ring, or the heteroaromatic ring exists alone, is joined to form a condensed ring, or is substituted or unsubstituted C1-C 30 Alkylene groups, substituted or unsubstituted C2-C 30 alkenylene group, substituted or unsubstituted C2-C 30 It is connected by a linker selected from alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O)2-, Si(CH3)2-, and -C(CH3)2-, and X is a halogen atom. Claim 6 In claim 5, the polyamide-imide film, wherein the diamine compound comprises 2,2'-dimethylbenzidine (m-Tolidine). Claim 7 delete Claim 8 A polyamide-imide film according to claim 1, wherein the polyamide-imide polymer comprises an imide repeating unit, a first amide repeating unit, and a second amide repeating unit, and when the sum of the imide repeating unit, the first amide repeating unit, and the second amide repeating unit is 100 mol%, the molar ratio of the first amide repeating unit is 70 mol% or less. Claim 9 A polyamide-imide film according to claim 8, wherein the first amide-based repeating unit is derived from a first dicarbonyl compound and the second amide-based repeating unit is derived from a second dicarbonyl compound, and the angle between two carbonyl groups in the first dicarbonyl compound is greater than the angle between two carbonyl groups in the second dicarbonyl compound. Claim 10 A polyamide-imide film according to claim 1, wherein the film has a pencil hardness of HB or higher. Claim 11 A cover window for a display device comprising a polyamide-imide film and a functional layer, wherein the polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and the modulus is 5 GPa or more based on a film thickness of 50 μm, the polyamide-imide polymer comprises imide repeating units and amide repeating units in a molar ratio of 2:98 to 40:60, the polyamide-imide polymer is a polymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound, the dianhydride compound comprises 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), and the polyamide-imide film does not contain a UV blocker. Claim 12 A display device comprising: a display portion; and a cover window disposed on the display portion; wherein the cover window comprises a polyamide-imide film and a functional layer, the polyamide-imide film comprises a polyamide-imide polymer that does not contain fluorine atoms, and based on a film thickness of 50 μm, the modulus is 5 GPa or more, the polyamide-imide polymer comprises imide repeating units and amide repeating units in a molar ratio of 2:98 to 40:60, the polyamide-imide polymer is a polymer of a diamine compound, a dianhydride compound, and a dicarbonyl compound, the dianhydride compound comprises 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), and the polyamide-imide film does not contain a UV blocker. Claim 13 A method for manufacturing a polyamide-imide film according to claim 1, comprising: a step of preparing a polyamide-imide polymer solution by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent; a step of preparing a gel sheet by casting and drying the solution; and a step of heat-treating the gel sheet. Claim 14 A method for manufacturing a polyamide-imide-based film according to claim 13, wherein the step of preparing the polymer solution comprises the step of adjusting the viscosity of the polymer solution to 100,000 cps to 500,000 cps at room temperature.

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