KR20210020395A - Polyamide-imide film, preparation method thereof, and cover window and display device comprising same - Google Patents

Abstract

An embodiment relates to a polyamide-imide film having excellent folding properties and transparency, and having improved mechanical and optical properties, a method for manufacturing the same, and a cover window and a display device including the same. The polyamide-imide film includes: a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; and metal salts, and when the polyamide-imide film is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of times of folding before fracture is 180,000 or more.

Description

Polyamide-imide film, a manufacturing method thereof, and a cover window and display device including the same TECHNICAL FIELD [0001] POLYAMIDE-IMIDE FILM, PREPARATION METHOD THEREOF, AND COVER WINDOW AND DISPLAY DEVICE COMPRISING SAME}

The embodiment relates to a polyamide-imide film having excellent folding characteristics and transparency, improved mechanical properties and optical properties, a method of manufacturing the same, and a cover window and a display device including the same.

Polyimide resins such as poly(amide-imide), PAI) have excellent friction, heat, and chemical resistance, and are primary electrical insulation materials, coatings, adhesives, extrusion resins, and heat-resistant paints. , Heat resistant plate, heat resistant adhesive, heat resistant fiber and heat resistant film.

Polyimide is used in various fields. For example, polyimide is made in powder form and used as a coating agent such as metal or magnet wire, and is mixed with other additives depending on the application. In addition, polyimide is used as a paint for decoration and corrosion prevention along with fluoropolymers, and plays a role in bonding fluoropolymers to metal substrates. In addition, polyimide is also used to coat kitchen utensils, and because of its heat resistance and chemical resistance, it is used as a membrane used for gas separation. Used.

Recently, by forming a film of polyimide, a polyimide-based film has been developed that is cheaper and has excellent optical, mechanical and thermal properties. These polyimide-based film is an organic light emitting diode (OLED; organic light-emitting diode ) or a liquid crystal display (LCD; liquid -crystal display) can be applied to the display material and the like, in the implementation phase properties antireflection film, a compensation film or a retardation Applicable to film.

When the polyimide-based film is applied to a display device, the transparent cover window included in the display device includes a hard coating layer and a base film. In the process of forming the hard coating layer, haze increases or adhesive strength decreases. A problem of deteriorating physical properties may occur. Accordingly, there is a situation in which research on the development of a film capable of solving the above problems and improving transparency, high heat resistance, and mechanical properties together is continuously required.

The embodiment is to provide a polyamide-imide film having excellent folding properties and transparency, improved mechanical properties and optical properties, a manufacturing method thereof, and a cover window and a display device including the same.

A polyamide-imide film according to an embodiment may include a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts, and when folding to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more.

A cover window for a display device according to another embodiment includes a polyamide-imide film and a functional layer, and the polyamide-imide film is a polyamide formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound. -Imide polymer; And a metal salt, wherein when the polyamide-imide film is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding times before fracture is 180,000 or more.

A display device according to another embodiment includes a display unit; And a cover window disposed on the display unit, wherein the cover window includes a polyamide-imide film and a functional layer, and the polyamide-imide film is a diamine compound, a dianhydride compound, and a dicarbohydrate. A polyamide-imide polymer formed by polymerizing a nil compound; And a metal salt, wherein when the polyamide-imide film is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding times before fracture is 180,000 or more.

A method of preparing a polyamide-imide film according to an embodiment comprises the steps of dissolving a metal salt in an organic solvent; Polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in which the metal salt is dissolved to prepare a polyamide-imide polymer solution; Injecting the polymer solution into a tank; Extruding and casting the polymer solution in the tank, followed by drying, to prepare a gel sheet; And heat-treating the gel sheet, wherein the polyamide-imide film comprises a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts, and when folding to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more.

The polyamide-imide film according to the embodiment may include a metal salt in addition to the polyamide-imide polymer, thereby improving not only transparency, but also folding characteristics according to a reduction in haze.

In addition, since the cover window for a display device according to an embodiment can implement excellent folding characteristics, it can be usefully applied to a foldable display device or a flexible display device.

1 is a cross-sectional view of a display device according to an exemplary embodiment.
2 is a schematic flowchart of a method of manufacturing a polyamide-imide film according to an embodiment.
3 schematically shows a process equipment of a polyamide-imide film according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. However, the implementation may be implemented in a variety of different forms and is not limited to the implementation described herein.

In the case where each film, window, panel, or layer, etc., is described as being formed "on" or "under" of each film, window, panel, or layer, the "top (on)" and "under" include both "directly" or "indirectly" formed. In addition, standards for the top/bottom of each component will be described based on the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation, and does not mean a size that is actually applied. In addition, the same reference numerals refer to the same elements throughout the specification.

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In the present specification, the singular expression is interpreted as meaning including the singular or plural, interpreted in context, unless otherwise specified.

In addition, all numbers and expressions representing amounts of components, reaction conditions, and the like described in the present specification are to be understood as being modified by the term "about" in all cases unless otherwise specified.

In the present specification, terms such as first and second are used to describe various components, and the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component into another component.

In addition, "substituted" in the present specification means 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 oil It means substituted with one or more substituents selected from the group consisting of a device, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group, and the substituents listed above are connected to each other Can form a ring.

Polyamide -Imide film

The embodiment provides a polyamide-imide film having excellent folding properties and transparency, and improved mechanical properties and optical properties.

A polyamide-imide film according to an embodiment may include a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts, and when folding to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more.

The number of times of folding is one that is bent and unfolded so that the radius of curvature of the film is 1 mm.

The metal of the metal salt may be at least one selected from Group 1, Group 2, Group 13, and Group 14 metals. For example, the metal of the metal salt may be a metal belonging to Group 1. As another example, the metal of the metal salt may be at least one selected from lithium (Li), sodium (Na), and potassium (K). For example, the metal salt may contain a lithium cation.

The anion of the metal salt may be at least one selected from halogen ions, carbonate ions, nitrate ions, phosphate ions and sulfate ions. In addition, the anion may be a monovalent anion or a divalent anion. Specifically, the anion is preferably a divalent anion.

The metal salt may be at least one selected from _{Li 2} CO ₃ , LiBr, LiCl, Na ₂ CO _{3 and NaCl.} For example, the metal salt may be at least one selected from _{Li 2} CO _{3, LiBr and LiCl.}

The number of metal salts contained in the polyamide-imide film may be one or two or more. For example, the number of metal salts included in the polyamide-imide film may be one.

According to an embodiment, the metal salt contained in the polyamide-imide film is preferably _{Li 2} CO _3.

Since the polyamide-imide film contains a metal salt, agglomeration caused by strong attraction between amide repeating units in the polyamide-imide polymer is prevented, and the solubility of the polymer is increased in a solvent to increase the high molecular weight. Polyamide-imide polymers can be formed.

The content of the metal salt is 0.2 to 1.5 parts by weight based on 100 parts by weight of the solid content of the polyamide-imide polymer.

Specifically, the content of the metal salt is 0.3 to 1.5 parts by weight, 0.5 to 1.5 parts by weight, 0.5 to 1 parts by weight, 0.5 to less than 1 parts by weight, 0.5 to 1.5 parts by weight, based on 100 parts by weight of the polyamide-imide polymer solid content. It may be 0.9 parts by weight or 0.5 to 0.8 parts by weight, but is not limited thereto.

When the content of the metal salt exceeds 1.5 parts by weight, the metal salt is eluted to the film surface and the aggregated particles become visually visible defects, and optically cloudy and the transparency decreases to achieve the appearance quality as an optical film. There is a problem that cannot be done.

When the polyamide-imide film according to another embodiment is folded to have a radius of curvature of 1 mm based on a thickness of 50 µm, the number of folding before fracture is 190,000 or more.

When the polyamide-imide film according to another embodiment is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding times before fracture is 200,000 or more.

The polyamide-imide film according to an embodiment includes a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound.

In one embodiment, the molar ratio of the dianhydride compound and the dicarbonyl compound is 2:98 to 15:85.

When the molar ratio of the dianhydride compound and the dicarbonyl compound is within the above range, a film having a small radius of curvature of 1 mm and a number of folding times of 180,000 or more can be implemented, as well as excellent optical properties of the film.

In another embodiment, the dianhydride compound may be composed of one type, and the dicarbonyl compound may be composed of two types.

The diamine compound is an imide bonded to the dianhydride compound and an amide bonded to the dicarbonyl compound to form a copolymer.

The diamine compound is not particularly limited, but may be, for example, an aromatic diamine compound having an aromatic structure. For example, the diamine compound may be a compound of Formula 1 below.

<Formula 1>

In Formula 1,

E is a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic cyclic group , A substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaromatic ring group, a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, It may be selected from -C(CH ₃ ) ₂ -and -C(CF ₃ ) _{2 -.}

e is selected from an integer of 1 to 5, and when e is 2 or more, E may be the same or different from each other.

(E) _e of Formula 1 may be selected from the group represented by Formulas 1-1a to 1-14a, but is not limited thereto.

Specifically, (E) _e of Formula 1 may be selected from the group represented by Formulas 1-1b to 1-13b, but is not limited thereto:

More specifically, (E)e of Formula 1 may be a group represented by Formula 1-6b or a group represented by Formula 1-9b.

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

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

In another embodiment, as the diamine compound, one type of diamine compound may be used. That is, the diamine compound may consist of a single component.

For example, the diamine compound is 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-Bis(trifluoromethyl)-4,4) having the following structure. '-diaminobiphenyl, TFDB), but is not limited thereto.

Since the dianhydride compound has a low birefringence value, the dianhydride compound is a compound capable of contributing to improvement of optical properties such as transmittance of a film containing the polyimide polymer. The polyimide-based polymer means a polymer containing an imide repeating unit.

The dianhydride compound is not particularly limited, but may be, for example, an aromatic dianhydride compound having an aromatic structure. For example, the aromatic dianhydride compound may be a compound of Formula 2 below.

<Formula 2>

In Formula 2, G is a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aromatic ring group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaromatic ring group, and the aliphatic ring group, the hetero aliphatic ring group, the aromatic ring group or the heteroaromatic ring group is present alone, or , Conjugated to each other to form a condensed ring, or a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkynylene group , -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, -C(CH ₃ ) _2- And -C(CF ₃ ) ₂ -.

G in Formula 2 may be selected from the group represented by Formulas 2-1a to 2-9a, but is not limited thereto.

For example, G in Formula 2 may be a group represented by 2-2a, a group represented by Formula 2-8a, or a group represented by 2-9a.

In one embodiment, the dianhydride compound may include a compound having a fluorine-containing substituent, a compound having a biphenyl group, or a compound having a ketone group.

The dianhydride compound may be formed of a compound having a fluorine-containing substituent. In this case, the fluorine-containing substituent may be a fluorinated hydrocarbon group, and specifically, a trifluoromethyl group, but is not limited thereto.

In another embodiment, the dianhydride compound may be composed of one single component or a mixture of two components. Specifically, the dianhydride compound may be composed of one type.

For example, the dianhydride compound is 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (2,2'-Bis- (3,4) having the following structure. -Dicarboxyphenyl)hexafluoropropane dianhydride, 6FDA) may be included, but is not limited thereto.

The diamine compound and the dianhydride compound may be polymerized to produce polyamic acid.

Subsequently, the polyamic acid may be converted to polyimide through a dehydration reaction, and the polyimide includes an imide repeating unit.

The polyimide may form a repeating unit represented by Formula A below.

<Formula A>

In Formula A, descriptions of E, G and e are as described above.

For example, the polyimide may include a repeating unit represented by Formula A-1 below, but is not limited thereto.

<Formula A-1>

In Formula A-1, n is an integer of 1 to 400.

The dicarbonyl compound is not particularly limited, but may be, for example, a compound represented by the following formula (3).

<Formula 3>

In Chemical Formula 3,

J is a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic cyclic group , A substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaromatic ring group, a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, It may be selected from -C(CH ₃ ) ₂ -and -C(CF ₃ ) _{2 -.}

j is selected from an integer of 1 to 5, and when j is 2 or more, J may be the same or different from each other.

X is a halogen atom. Specifically, X may be F, Cl, Br, I, or the like. More specifically, X may be Cl, but is not limited thereto.

(J) _j of Formula 3 may be selected from the group represented by Formulas 3-1a to 3-14a, but is not limited thereto.

Specifically, (J) _j of Formula 3 may be selected from the group represented by Formulas 3-1b to 3-8b, but is not limited thereto:

More specifically, (J) _j of Formula 3 may be a group represented by Formula 3-1b, a group represented by Formula 3-2b, a group represented by 3-3b, or a group represented by 3-8b. have.

In one embodiment, the dicarbonyl compound may be used by mixing at least two different dicarbonyl compounds. When two or more types of the dicarbonyl compounds are used, two or more types of dicarbonyl compounds selected from the group represented by _{(J) j in Chemical Formula 3 may be used.} have.

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

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

Each of the first dicarbonyl compound and the second dicarbonyl compound may be an aromatic dicarbonyl compound.

The first dicarbonyl compound and the second dicarbonyl compound may be different compounds.

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

When the first dicarbonyl compound and the second dicarbonyl compound are each an aromatic dicarbonyl compound, since it contains a benzene ring, the surface hardness and tensile strength of the film containing the prepared polyamide-imide resin It can contribute to improving mechanical properties such as.

The dicarbonyl compound is terephthaloyl chloride (TPC), 1,1'-biphenyl-4,4'-dicarbonyl dichloride (1,1'-biphenyl-4) having the following structure. , 4'-dicarbonyl dichloride, BPDC), isophthaloyl chloride (IPC), or a combination thereof, but is not limited thereto.

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

When BPDC as the first dicarbonyl compound and TPC as the second dicarbonyl compound are appropriately used in combination, a film including the prepared polyamide-imide resin may have high oxidation resistance.

Alternatively, the first dicarbonyl compound may include IPC, and the second dicarbonyl compound may include TPC, but the present invention is not limited thereto.

When using in an appropriate combination of IPC as the first dicarbonyl compound and TPC as the second dicarbonyl compound, the prepared polyamide-imide resin may have high oxidation resistance, as well as It is economical because it can reduce costs.

The diamine compound and the dicarbonyl compound may be polymerized to form a repeating unit represented by Formula B below.

<Formula B>

In Formula B, descriptions of E, J, e and j are as described above.

For example, the diamine compound and the dicarbonyl compound may be polymerized to form an amide repeating unit represented by Formulas B-1 and B-2.

Alternatively, the diamine compound and the dicarbonyl compound may be polymerized to form an amide repeating unit represented by Formulas B-2 and B-3.

<Formula B-1>

In Formula B-1, x is an integer of 1 to 400.

<Formula B-2>

Y in Formula B-2 is an integer of 1 to 400.

<Formula B-3>

Y in Formula B-3 is an integer of 1 to 400.

According to one embodiment, the polyamide-imide polymer may include a repeating unit represented by Formula A and a repeating unit represented by Formula B below:

<Formula A>

<Formula B>

In Formulas A and B,

E and J are each independently a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic ring group, substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaromatic ring group, substituted or unsubstituted C ₁ -C ₃₀ alkylene group, substituted or unsubstituted C ₂ -C ₃₀ alkenylene group , Substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si( CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) ₂ -is selected from,

e and j are each independently selected from an integer of 1 to 5,

When e is 2 or more, 2 or more E are the same or different from each other,

When j is 2 or more, 2 or more J are the same as or different from each other,

G is a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aromatic cyclic group , A substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaromatic cyclic group, and the aliphatic cyclic group, the hetero aliphatic cyclic group, the aromatic cyclic group or the heteroaromatic cyclic group is present alone or condensed with each other Or a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-,- S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) It is connected by a connector selected from _{2 -.}

The polyamide-imide polymer includes an imide repeating unit derived from polymerization of a diamine compound and a dianhydride compound, and an amide repeating unit derived from polymerization of the diamine compound and a dicarbonyl compound. .

In the polyamide-imide polymer, the molar ratio of the imide repeating unit to the amide repeating unit may be 2:98 to 15:85, but is not limited thereto. That is, the molar ratio of the repeating unit represented by Formula A and the repeating unit represented by Formula B may be 2:98 to 15:85, but is not limited thereto.

When the molar ratio between the imide repeating unit and the amide repeating unit is within the above range, the polyamide-imide film has excellent optical properties such as transmittance, haze, and mechanical properties such as folding properties, modularity, and surface hardness.

According to another embodiment, the polyamide-imide film may further include a filler.

The filler may be at least one selected from the group consisting of barium sulfate, silica, and calcium carbonate. When the polyamide-imide film includes the filler, it is possible to improve roughness and windability, as well as improve the effect of improving running scratches during film production.

In addition, the particle diameter of the filler may be 0.01㎛ or more to less than 1.0㎛. For example, the filler may have a particle diameter of 0.05 μm to 0.9 μm or 0.1 μm to 0.8 μm, but is not limited thereto.

The polyamide-imide film may contain the filler in an amount of 0.01 to 3% by weight, based on the total weight of the polyamide-imide film.

According to one embodiment, the yellow index of the polyamide-imide film may be 5 or less. For example, the yellowness may be 4 or less, 3.5 or less, or 2.8 or less.

The transmittance of the polyamide-imide film may be 80% or more. For example, the transmittance may be 85% or more, 88% or more, 80% to 99%, 80% to 99%, 85% to 99%, or 88% to 99%.

The haze of the polyamide-imide film is 1% or less. Specifically, the haze may be less than 1% or less than 0.8%, but is not limited thereto.

The polyamide-imide film has a modulus of 6.0 GPa or more. Specifically, the modulus may be more than 6.0 GPa, 6.1 GPa or more, 6.2 GPa or more, 6.3 GPa or more, 6.0 GPa to 8.0 GPa, or 6.2 GPa to 7.8 GPa, but is not limited thereto.

The compressive strength of the polyamide-imide film is 0.4 kgf/µm or more. Specifically, the compressive strength may be 0.45 kgf/µm or more, but is not limited thereto.

When perforating the polyamide-imide film in UTM compression mode at a speed of 10 mm/min using a 2.5 mm spherical tip, 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.

The polyamide-imide film has a surface hardness of HB or higher. Specifically, the surface hardness may be H or more, 2H or more, 3H or more, or 4H or more, but is not limited thereto.

The polyamide-imide film has a tensile strength of 15 kgf/mm ² or more. Specifically, the tensile strength may be 18 kgf/mm ² or more, 20 kgf/mm ² or more, 21 kgf/mm ² or more, or 22 kgf/mm ^{2 or} more, but is not limited thereto.

The polyamide-imide film has an elongation of 15% or more. Specifically, the elongation may be 16% or more, 17% or more, or 17.5% or more, but is not limited thereto.

The physical properties of the polyamide-imide film described above are based on a thickness of 40 μm to 60 μm. For example, the physical properties of the polyimide film are based on a thickness of 50 μm.

The polyamide-imide film according to an embodiment may secure excellent optical properties such as low haze, low yellowness (YI), and high transmittance as well as excellent adhesion. Further, it is possible to implement long-term stable mechanical properties for a substrate that requires flexibility in terms of folding properties, modulus, compressive strength, elongation, tensile properties, and elastic resilience.

The features of the composition and physical properties of the polyamide-imide film described above may be combined with each other.

Cover for display device window

A cover window for a display device according to an embodiment includes a polyamide-imide film and a functional layer.

The polyamide-imide film is a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts, and when folding to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more.

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

When folding the cover window for a display device according to an embodiment so that the radius of curvature is 1 mm, the number of folding times before the functional layer is broken is 180,000 or more. Specifically, the number of folding is 190,000 or more or 200,000 or more.

The cover window for a display device may be usefully applied to a display device.

In particular, since the polyamide-imide film as well as the functional layer has excellent folding characteristics, the cover window may be usefully applied to a foldable display device or a flexible display device.

Display device

A display device according to an embodiment includes a display unit; And a cover window disposed on the display unit, wherein the cover window includes a polyamide-imide film and a functional layer.

The polyamide-imide film is a polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts, and when folding to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more.

A detailed description of the polyamide-imide film and the cover window is as described above.

1 is a cross-sectional view of a display device according to an exemplary embodiment.

Specifically, FIG. 1 shows a polyamide-imide film 100 and a functional layer 200 having a first surface 101 and a second surface 102 on the display unit 400 and the display unit 400. A display device in which a cover window 300 including a is disposed and an adhesive layer 500 is disposed between the display unit 400 and the cover window 300 is illustrated.

The display unit 400 may display an image and may have a flexible characteristic.

The display unit 400 may be a display panel for displaying an image, for example, a liquid crystal display panel or an organic light emitting display panel. The organic light emitting display panel may include a front polarizing plate and an organic EL panel.

The front polarizing plate may be disposed on the front surface of the organic EL panel. Specifically, the front polarizing plate may be adhered to a surface on which an image is displayed in the organic EL panel.

The organic EL panel displays an image by self-emission in units of pixels. 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 driveably coupled to the organic EL substrate. That is, the driving substrate is coupled so as to apply a driving signal such as a driving current to the organic EL substrate, so that current is applied to each of the organic electroluminescent units to drive the organic EL substrate.

In addition, 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.

The cover window 300 is disposed on the display unit 400. The cover window may be positioned at the outermost side of the display device according to the embodiment to protect the display unit.

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

Polyamide -Method of manufacturing imide film

One embodiment provides a method of manufacturing a polyamide-imide film.

A method of manufacturing a polyamide-imide film according to an embodiment includes the steps of dissolving a metal salt in an organic solvent; Polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in which the metal salt is dissolved to prepare a polyamide-imide polymer solution; Injecting the polymer solution into a tank; Extruding and casting the polymer solution in the tank, followed by drying, to prepare a gel sheet; And heat-treating the gel sheet.

Referring to FIG. 2, a method of manufacturing a polyamide-imide film according to an embodiment includes the steps of dissolving a metal salt in an organic solvent; Simultaneously or sequentially mixing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in which a metal salt is dissolved in a polymerization facility, and reacting the mixture to prepare a polymer solution (S100); Moving the polymer solution to a tank (S200); Purging using an inert gas (S300); Casting the polymer solution in the tank on a belt and drying it to prepare a gel-sheet (S400); Manufacturing a cured film by heat treatment while moving the gel-sheet (S500); Cooling while moving the cured film (S600); And winding the cooled cured film using a winder (S700).

The polyamide-imide film is a film mainly composed of a polyamide-imide resin, and the polyamide-imide resin is a resin containing an amide repeating unit and an imide repeating unit as structural units in a predetermined molar ratio.

In the method for producing the polyamide-imide film, first, a metal salt is dissolved in an organic solvent.

Description of the type and content of the metal salt is as described above.

In the method for producing the polyamide-imide film, the polymer solution for preparing the polyamide-imide resin is a diamine compound, a dianhydride compound, and a dicarbonyl in an organic solvent in which a metal salt is dissolved in a polymerization facility. It is prepared by mixing the compounds simultaneously or sequentially, and reacting the mixture (S100).

In one embodiment, the polymer solution may be prepared by reacting a diamine compound, a dianhydride compound, and a dicarbonyl compound simultaneously in an organic solvent in which a metal salt is dissolved.

In another embodiment, the step of preparing the polymer solution may include preparing a polyamic acid (PAA) solution by first mixing and reacting the diamine compound and the dianhydride compound in a solvent; And forming an amide bond and an imide bond by secondary mixing and reacting the dicarbonyl compound with the polyamic acid (PAA) solution. The polyamic acid solution is a solution containing polyamic acid.

Alternatively, the step of preparing the polymer solution may include preparing a polyamic acid solution by first mixing and reacting the diamine compound and the dianhydride compound in a solvent; Dehydrating the polyamic acid solution to prepare a polyimide (PI) solution; And forming an amide bond by secondary mixing and reacting the dicarbonyl compound to the polyimide (PI) solution. The polyimide solution is a solution containing a polymer having an imide repeating unit.

In another embodiment, the step of preparing the polymer solution may include preparing a polyamide (PA) solution by first mixing and reacting the diamine compound and the dicarbonyl compound in a solvent; It may include a step of forming an imide bond further by secondary mixing and reacting the dianhydride compound to the polyamide (PA) solution. The polyamide solution is a solution containing a polymer having an amide repeating unit.

The polymer solution prepared as described above may be a solution containing a polymer containing at least one selected from the group consisting of polyamic acid (PAA) repeat units, polyamide (PA) repeat units, and polyimide (PI) repeat units. .

Alternatively, the polymer contained in the polymer solution is an imide repeating unit derived from polymerization of the diamine compound and the dianhydride compound, and an amide derived from polymerization of the diamine compound and the dicarbonyl compound. Includes repeating units.

The solid content contained in the polymer solution may be 10% to 30% by weight. Alternatively, the content of the solid content included in the second polymer solution may be 15% by weight to 25% by weight, but is not limited thereto.

When the content of the solid content contained in the polymer solution is within the above range, a polyamide-imide film can be effectively produced in an extrusion and casting process. In addition, the prepared polyamide-imide film may have mechanical properties such as improved modulus and optical properties such as low yellowness.

In one embodiment, preparing the polymer solution may further include introducing a catalyst.

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.

The catalyst may be added in an amount of 0.01 to 0.4 mol equivalents based on 1 mol of the polyamic acid, but is not limited thereto.

When the catalyst is added, the reaction rate may be improved, and chemical bonding between or within the repeating unit structure may be improved.

In another embodiment, preparing the polymer solution may further include adjusting the viscosity of the polymer solution.

Specifically, the step of preparing the polymer solution includes: (a) simultaneously or sequentially mixing and reacting (diamine compound and dicarbonyl compound or), diamine compound, dianhydride compound, and dicarbonyl compound in an organic solvent. Preparing a first polymer solution; (b) measuring the viscosity of the first polymer solution to evaluate whether a target viscosity is reached; And (c) preparing a second polymer solution having a target viscosity by adding the dicarbonyl compound when the viscosity of the first polymer solution does not reach the target viscosity.

The target viscosity may be 100,000 cps to 500,000 cps at room temperature. Specifically, the target viscosity may be 100,000 cps to 400,000 cps, 100,000 cps to 350,000 cps, 100,000 cps to 300,000 cps, 150,000 cps to 300,000 cps, or 150,000 to 250,000 cps at room temperature. However, it is not limited thereto.

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 solution is different. For example, the viscosity of the second polymer solution is higher than that of the first polymer solution.

The stirring speed when preparing the first polymer solution and the stirring speed when preparing the second polymer solution are different. For example, the stirring speed when preparing the first polymer solution is faster than the stirring speed when preparing the second polymer solution.

In another embodiment, the step of preparing the polymer solution may further include 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, may be adjusted to 4.5 to 7.

The pH of the polymer solution may be adjusted by adding a pH adjusting agent, and the pH adjusting agent is not particularly limited, but may include, for example, an amine-based compound such as alkoxyamine, alkylamine or alkanolamine.

By adjusting the pH of the polymer solution to the above range, it is possible to prevent damage to the equipment in the subsequent process, to prevent the occurrence of defects in the film prepared from the polymer solution, and to target optical properties in terms of yellowness and modulus. And mechanical properties.

The 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.

In another embodiment, preparing the polymer solution may further include purging using an inert gas. By removing moisture and reducing impurities through the inert gas purging step, the reaction yield can be increased, and the surface appearance and mechanical properties of the final film can be excellently implemented.

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 limited thereto. no. Specifically, the inert gas may be nitrogen.

The molar ratio of the dianhydride compound and the dicarbonyl compound used to prepare the polymer solution may be in the range of 2:98 to 15:85. By using the dianhydride compound and the dicarbonyl compound in such a molar ratio, the folding properties of the polyamide-imide film prepared from the polymer solution, mechanical properties such as modulus, and optical properties such as haze and transmittance are desired. It is advantageous to achieve at a level.

remind The description of the diamine compound, the dianhydride compound and the dicarbonyl compound is as described above.

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

Next, after the step of preparing the polymer solution, the polymer solution is moved to a tank (S200).

3 is a schematic diagram of a manufacturing process equipment for the polyamide-imide film according to an embodiment. 3, the above-described polymer solution is prepared in a polymerization facility 10, and the polymer solution thus prepared is transferred and stored in a tank 20.

In this case, after preparing the polymer solution, a step of moving the polymer solution to a tank without a separate process is performed. Specifically, the polymer solution prepared in the polymerization facility is transferred to and stored in the tank as it is without a separate precipitation and re-dissolution process for removing impurities. Conventionally, in order to remove impurities such as hydrochloric acid (HCl) generated during the preparation of the polymer solution, the prepared polymer solution was purified through a separate process to remove impurities, and a process of re-dissolving it in a solvent was performed. . However, in this case, there is a problem that the loss of the active ingredient increases in the process of removing the impurities, and as a result, the yield decreases.

Accordingly, the manufacturing method according to an embodiment minimizes the content of impurities at a source in the manufacturing process of the polymer solution, or even if predetermined impurities are present, they are appropriately controlled in a subsequent process so as not to deteriorate the physical properties of the final film. It has the advantage of producing a film without a separate precipitation or re-dissolution process.

The tank 20 is a place to store the polymer solution before filming it, and its internal temperature may be -20°C to 20°C.

Specifically, the internal temperature may be -20°C to 10°C, -20°C to 5°C, -20°C to 0°C, or 0°C to 10°C, but is not limited thereto.

By controlling the internal temperature of the tank 20 within the above range, it is possible to prevent the polymer solution from being deteriorated during storage, and to reduce the moisture content to prevent defects in the film produced therefrom.

The method of manufacturing the polyamide-imide film may further include performing vacuum defoaming on the polymer solution transferred to the tank 20.

The vacuum defoaming may be performed for 30 minutes to 3 hours after reducing the internal pressure of the tank to 0.1 bar to 0.7 bar. By performing vacuum defoaming under such conditions, air bubbles inside the polymer solution can be reduced, and as a result, surface defects of the film produced therefrom can be prevented, and optical properties such as haze can be excellently implemented.

In addition, the method of manufacturing the polyamide-imide film may further include purging the polymer solution transferred to the tank 20 using an inert gas (S300).

Specifically, the purging is performed by purging the internal pressure of the tank to 1 to 2 atmospheres using an inert gas. By performing nitrogen purging under such conditions, moisture in the polymer solution is removed and impurities are reduced, so that the reaction yield can be increased, and optical properties such as haze and mechanical properties can be excellently implemented.

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 limited thereto. no. Specifically, the inert gas may be nitrogen.

The vacuum defoaming step and the step of purging the tank using an inert gas are performed as separate processes.

For example, the vacuum degassing step may be performed, and thereafter, the step of purging the tank with an inert gas may be performed, but the present invention is not limited thereto.

By performing the step of vacuum degassing and/or the step of purging the tank using an inert gas, physical properties of the surface of the prepared polyamide-imide film may be improved.

Thereafter, it may further include storing the polymer solution in the tank 20 for 1 to 360 hours. At this time, the internal temperature of the tank may be kept at -20 ℃ to 20 ℃.

The method of manufacturing the polyamide-imide film further includes the step of preparing a gel-sheet by extruding and casting the polymer solution in the tank 20 and then drying it (S400).

The polymer solution may be cast on a casting body such as a casting roll or a casting belt.

Referring to FIG. 3, according to one embodiment, the polymer solution may be applied as a casting body on the casting belt 30 and dried while moving, and may be manufactured as a gel-like sheet.

When the polymer solution is injected onto the belt 30, the injection rate may be 300 g/min to 700 g/min. When the injection rate of the polymer solution satisfies the above range, the gel-sheet may be uniformly formed with an appropriate thickness.

In addition, the casting thickness of the polymer solution may be 200㎛ to 700㎛. When the polymer solution is cast in the above thickness range and then dried and heat treated into a final film, appropriate thickness and thickness uniformity can be ensured.

As described above, the polymer solution may be 100,000 cps to 500,000 cps at room temperature, for example, 100,000 cps to 400,000 cps, 100,000 cps to 350,000 cps, 150,000 cps to 350,000 cps, or It may be between 150,000 cps and 250,000 cps. By satisfying the viscosity range, when the polymer solution is cast on a belt, it can be cast to a uniform thickness without defects.

내지 150

의 온도로, 5분 내지 60분의 시간 동안 건조시켜 겔-시트를 제조할 수 있다. 상기 건조 중에 상기 중합체 용액의 용매가 일부 또는 전부 휘발되어 상기 겔-시트가 제조된다.60 after casting the polymer solution

To 150

At a temperature of, it is dried for a time of 5 minutes to 60 minutes to prepare a gel-sheet. During the drying, a part or all of the solvent of the polymer solution is volatilized to prepare the gel-sheet.

The moving speed of the gel-sheet on the casting body upon drying may be 0.1 m/min to 15 m/min, for example, 0.5 m/min to 10 m/min, but is not limited thereto.

The manufacturing method of the polyamide-imide film includes the step of preparing a cured film by heat treatment while moving the gel-sheet (S500).

Referring to FIG. 3, the heat treatment of the gel-sheet may be performed by passing through a thermosetting machine 40.

When passing through the thermosetting machine 40, the gel-sheet is subjected to hot air treatment.

When heat treatment by hot air is performed, the amount of heat may be evenly applied. If the amount of heat is not evenly distributed, satisfactory mechanical properties cannot be achieved. In particular, a satisfactory surface roughness cannot be achieved, and in this case, the surface tension may increase or decrease too much.

The heat treatment of the gel-sheet may be performed for 5 minutes to 40 minutes while raising the temperature at a rate of 2°C/min to 80°C/min in the range of 80°C to 500°C. Specifically, the heat treatment of the gel-sheet may be performed for 5 minutes to 30 minutes at a rate of 10°C/min to 80°C/min in a temperature range of 80°C to 470°C.

At this time, the start temperature of the heat treatment of the gel-sheet may be 80°C or higher. Specifically, it may be 80 ℃ to 180 ℃, more specifically 100 ℃ to 180 ℃.

In addition, the maximum temperature during the heat treatment may be 300 ℃ to 500 ℃. For example, the maximum temperature during the heat treatment may be 350°C to 500°C, 380°C to 500°C, 400°C to 500°C, 410°C to 480°C, 410°C to 270°C, or 410°C to 450°C.

That is, referring to FIG. 3, an inlet temperature of the thermosetting machine 40 may be a heat treatment start temperature, and a temperature of a predetermined region inside the thermosetting machine 40 may be a maximum temperature during heat treatment.

By heat treatment under such conditions, the gel-sheet can be cured to have an appropriate surface hardness and modulus, and the cured film can simultaneously secure high light transmittance and low haze.

According to one embodiment, the hot air treatment of the gel-sheet may be performed in three steps, and 1 minute to 10 minutes at a hot air temperature of 100° C. to 180° C., 10 minutes to 30 minutes at 200° C. to 300° C., 300° C. To 400 ℃ can be carried out for 5 minutes to 20 minutes.

More specifically, the hot air treatment of the gel-sheet is performed at a hot air temperature of 100°C to 170°C for 1 minute to 10 minutes, 200°C to 270°C for 10 minutes to 30 minutes, and 320°C to 370°C for 5 minutes to 15 minutes Can be.

In particular, the hot air temperature may be the starting temperature is important, the starting temperature is 100 ℃ to 170 ℃, more specifically in the range of 120 ℃ to 170 ℃, 1 minute to 4 minutes, specifically 2 minutes to 3 minutes I can.

According to another embodiment, the heat treatment may include passing through an IR heater. The heat treatment by the IR heater may be performed for 1 minute to 30 minutes at a temperature range of 300°C or higher. Specifically, the heat treatment by the IR heater may be performed for 1 minute to 20 minutes at a temperature range of 300 ℃ to 500 ℃.

The manufacturing method of the polyamide-imide film includes cooling while moving the cured film (S600).

3, the cured film is performed after passing through the thermosetting machine 40, and may be performed using a separate cooling chamber (not shown), and an appropriate temperature atmosphere without a separate cooling chamber It can also be carried out by composition.

The step of cooling while moving the cured film may include: a first temperature reduction step of reducing temperature at a rate of 100°C/min to 1000°C/min; And a second temperature reduction step of reducing temperature at a rate of 40°C/min to 400°C/min.

In this case, 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.

For example, a maximum speed during the first temperature reduction step is faster than a maximum speed during the second temperature reduction step. Alternatively, the lowest speed during the first temperature reduction step is faster than the lowest speed during the second temperature reduction step.

By performing the cooling step of the cured film in multiple steps as described above, the physical properties of the cured film can be more stabilized, and the optical properties and mechanical properties of the film established in the curing process can be more stably maintained for a long period of time.

The moving speed of the gel-sheet and the cured film is the same.

The method of manufacturing the polyamide-imide film includes the step of winding the cooled cured film using a winder (S700).

3, the winding of the cooled cured film may be performed using a roll type winder 50.

At this time, the ratio of the moving speed of the gel-sheet on the belt during drying: the moving speed of the cured film upon winding is 1:0.95 to 1:1.40. Specifically, the ratio of the moving speed may be 1:0.99 to 1:1.20, 1:0.99 to 1:1.10, or 1:1.10 to 1:1.05, but is not limited thereto.

When the ratio of the moving speed is out of the above range, there is a concern that mechanical properties of the cured film may be damaged, and flexibility and elastic properties may be deteriorated.

In the method of manufacturing the 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.

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

In 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.

The polyamide-imide film may exhibit excellent optical and mechanical properties by being manufactured according to the above-described manufacturing method. The polyamide-imide film may be applicable to a variety of applications requiring flexibility and transparency. For example, the polyamide-imide film may be applied to solar cells, displays, semiconductor devices, sensors, and the like.

The description of the polyamide-imide film prepared according to the above-described manufacturing method is as described above.

The above will be described in more detail by the following examples. However, the following examples are for illustrative purposes only, and the scope of the examples is not limited thereto.

< Example >

Example One

After filling 585.68 g of dimethylacetamide (DMAc) as an organic solvent in a 1L glass reactor with a temperature controllable double jacket under a nitrogen atmosphere at 20°C, 0.86 g of lithium carbonate metal salt (Li ₂ CO ₃ ) was slowly added and dissolved . After the metal salt was sufficiently dissolved, 64.0 g (0.2 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl (TFMB) was slowly added and dissolved. Thereafter, 4.44 g (0.01 mol) of 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) was slowly added and stirred for 1 hour. Then, 8.12 g (0.04 mol) of isophthaloyl chloride (IPC) was added and stirred for 1 hour, and 30.45 g (0.15 mol) of terephthaloyl chloride (TPC) was added and stirred for 1 hour to prepare a polymer solution. The obtained polymer solution was applied to a glass plate, dried with hot air at 80° C. for 30 minutes, peeled from the glass plate, fixed to a pin frame, and heated at a rate of 2° C./min in a temperature range of 80-300° C. A polyamide-imide film was obtained.

Example 2 to 8 and Comparative example 1 to 7

As shown in Table 1 below, a film was prepared in the same manner as in Example 1, except for different types and contents of each reactant. In addition, in the case of Comparative Examples 1 to 7, the step of introducing and dissolving a metal salt in an organic solvent was not performed.

Diamine compound Dianhydride compound Dicarbonyl compound Metal salt Metal salt content
(Compared to 100 parts by weight of polymer solid content) Example 1 TFMB 100 6-FDA 5 TPC 75 / IPC 20 Li ₂ CO ₃ 0.8 Example 2 TFMB 100 BPDA 5 TPC 75/ IPC 20 Li ₂ CO ₃ 0.8 Example 3 TFMB 100 BPTA 5 TPC 75/ IPC 20 Li ₂ CO ₃ 0.8 Example 4 TFMB 100 6-FDA 15 TPC 70 / IPC 15 Li ₂ CO ₃ 0.5 Example 5 TFMB 100 6-FDA 15 TPC 70 / BPDC 15 Li ₂ CO ₃ 0.5 Example 6 TFMB 100 6-FDA 5 TPC 75 / SD 20 Li ₂ CO ₃ 0.8 Example 7 TFMB 100 6-FDA 10 TPC 70 / BPDC 20 Li ₂ CO ₃ 0.7 Comparative Example 1 TFMB 100 6-FDA 25 TPC 55 / IPC 20 - Comparative Example 2 TFMB 100 6-FDA 20 TPC 65 / IPC 15 - Comparative Example 3 TFMB 100 6-FDA 20 TPC 65 / BPDC 15 - Comparative Example 4 TFMB 100 6-FDA 5 TPC 75 / SD 20 - Comparative Example 5 TFMB 100 BPDA 5 TPC 75/ IPC 20 - Comparative Example 6 TFMB 100 BTDA 5 TPC 75/ IPC 20 - Comparative Example 7 TFMB 100 - TPC 80/ IPC 20 -

< Evaluation example >

The following physical properties were measured and evaluated for the films prepared in Examples 1 to 8 and Comparative Examples 1 to 7, and the results are shown in Table 2 below.

Evaluation example 1: Measuring the thickness of the film

Using a digital micrometer 547-401 manufactured by Mitsutoyo, Japan, 5 points were measured in the width direction, and the thickness was measured as an average value.

Evaluation example 2: Folding Property evaluation

(One) When folding (bending and unfolding is referred to as one) so that the radius of curvature of the polyamide-imide film having a thickness of 50 μm was 1 mm, the number of folding before the film was broken was measured.

(2) When folding the cover window coated with a hard coating layer with a thickness of about 5 µm on one side of the polyamide-imide film having a thickness of 50 µm is repeated to have a radius of curvature of 1 mm (1 time to bend and unfold), the hard The number of folding before the coating layer was broken was measured.

The folding count was measured using YUASA's U-shape folding equipment.

Evaluation example 3: surface hardness measurement

The surface hardness was measured at a pencil speed of 300 mm/min while inserting a pencil for measuring pencil hardness at a 45° angle to a pencil hardness meter (CT-PC1, CORE TECH, Korea) and applying a constant load (750 g). Mitsubishi pencils were used as pencils, and pencils exhibiting strength such as H-9H, F, HB, and B-6B were used.

Evaluation example 4: transmittance and Haze Measure

The light transmittance at 550 nm was measured using a haze meter NDH-5000W manufactured by Denshoku High School in Japan.

Evaluation example 5: Yellowness measurement

Yellow Index (YI) was measured using a CIE colorimeter by a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory).

Evaluation example 6: Modulus Measure

Using Instron's universal testing machine UTM 5566A, cut at least 5 cm in the direction orthogonal to the main contraction direction of the sample and 10 mm in the main contraction direction, attach it to a clip at 5 cm intervals, and at a speed of 5 mm/min at room temperature. During stretching, a stress-strain curve was obtained until fracture occurred. In the stress-strain curve, the slope of the load against the initial deformation was taken as the modulus (GPa).

As can be seen in Tables 1 and 2, when the polyamide-imide films of Examples 1 to 8 are repeatedly folded so that the radius of curvature is 1 mm, the number of folding times before the film is broken is 200,000 times. It was confirmed that it was abnormal. In addition, when the hard coating layer was coated on one surface of the film and a folding test was performed using a cover window, the number of folding of the hard coating layer was also 200,000 or more.

In addition, it was confirmed that the polyamide-imide films of Examples 1 to 8 exhibit excellent surface hardness, transmittance, haze, yellowness, and modulus in addition to excellent folding properties.

On the other hand, the polyamide-imide films of Comparative Examples 1 to 3 were fractured without exceeding 170,000 times of folding when performing the folding test, and haze and modulus values were also decreased.

In addition, the polyamide-imide films of Comparative Examples 4 to 6 showed excellent results in terms of the number of folding when performing the folding test, but all of the haze showed a value of 1.5% or more, and the optical properties were remarkably deteriorated, and in the case of Comparative Example 7 , It gelled upon polymerization, so that the desired film was not obtained.

10: polymerization equipment
20: tank
30: belt
40: thermosetting machine
50: winder
100: polyamide-imide film
101: first page
102: second page
110: casting body
200: functional layer
300: cover window
400: display unit
500: adhesive layer

Claims (14)

A polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound; And metal salts; including,
When folding so that the radius of curvature is 1 mm based on a thickness of 50 μm, the number of folding before fracture is 180,000 or more, a polyamide-imide film.
The method of claim 1,
The metal of the metal salt is a metal belonging to Group 1, a polyamide-imide film.
The method of claim 1,
The content of the metal salt is 0.2 to 1.5 parts by weight based on 100 parts by weight of the solid content of the polyamide-imide polymer, polyamide-imide film.
The method of claim 1,
A polyamide-imide film in which the molar ratio of the dianhydride compound and the dicarbonyl compound is 2:98 to 15:85.
The method of claim 1,
The dianhydride compound consists of one kind,
The dicarbonyl compound consists of two types,
Polyamide-imide film.
The method of claim 1,
The polyamide-imide film having a folding frequency of 200,000 or more before being broken.
The method of claim 1,
The polyamide-imide polymer comprises a repeating unit represented by the following formula (A) and a repeating unit represented by the following formula (B), a polyamide-imide film:
<Formula A>

<Formula B>

E and J are each independently a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic ring group, substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaromatic ring group, substituted or unsubstituted C ₁ -C ₃₀ alkylene group, substituted or unsubstituted C ₂ -C ₃₀ alkenylene group , Substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-, -S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si( CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) ₂ -is selected from,
e and j are each independently selected from an integer of 1 to 5,
When e is 2 or more, 2 or more E are the same or different from each other,
When j is 2 or more, 2 or more J are the same as or different from each other,
G is a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic cyclic group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic cyclic group, a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aromatic cyclic group , A substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaromatic cyclic group, and the aliphatic cyclic group, the hetero aliphatic cyclic group, the aromatic cyclic group or the heteroaromatic cyclic group is present alone or condensed with each other Or a substituted or unsubstituted C ₁ -C ₃₀ alkylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkenylene group, a substituted or unsubstituted C ₂ -C ₃₀ alkynylene group, -O-,- S-, -C(=O)-, -CH(OH)-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) It is connected by a connector selected from _{2 -.}
The method of claim 7,
The molar ratio of the repeating unit represented by Formula A and the repeating unit represented by Formula B is 2:98 to 15:85, a polyamide-imide film.
The method of claim 1,
A polyamide-imide film having a haze of 1% or less.
The method of claim 1,
Polyamide-imide film with a modulus of at least 6 GPa.
Including a polyamide-imide film and a functional layer,
A polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in the polyamide-imide film; And metal salts; including,
When the polyamide-imide film is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folds before fracture is 180,000 or more.
A display unit; And
Includes; a cover window disposed on the display unit,
The cover window comprises a polyamide-imide film and a functional layer,
A polyamide-imide polymer formed by polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in the polyamide-imide film; And metal salts; including,
When the polyamide-imide film is folded to have a radius of curvature of 1 mm based on a thickness of 50 μm, the number of folding times before fracture is 180,000 or more.
Dissolving the metal salt in an organic solvent;
Polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in which the metal salt is dissolved to prepare a polyamide-imide polymer solution;
Injecting the polymer solution into a tank;
Extruding and casting the polymer solution in the tank, followed by drying, to prepare a gel sheet; And
Including; heat treatment of the gel sheet;
The method for producing the polyamide-imide film of claim 1.
The method of claim 13,
The metal of the metal salt is a metal belonging to Group 1, a method for producing a polyamide-imide film.

Images