KR102816141B1 - Polyamide-based film, process for preparing the same, and cover window and display device comprising the same - Google Patents

Abstract

The embodiments relate to a polyamide-based film having excellent loop stiffness and low haze, a method for producing the same, and a cover window and a display device including the same, wherein the polyamide-based film includes a polyamide-based polymer and a filler, and has a loop stiffness of 3 gf or more and a haze of 1% or less.

Description

Polyamide-based film, process for preparing the same, and cover window and display device comprising the same {POLYAMIDE-BASED FILM, PROCESS FOR PREPARING THE SAME, AND COVER WINDOW AND DISPLAY DEVICE COMPRISING THE SAME}

The embodiments relate to a polyamide-based film, a method for producing the same, and a cover window and a display device including the same.

Polyamide resins such as poly(amide-imide) (PAI) have excellent friction, heat, and chemical resistance and are used in primary electrical insulation materials, coatings, adhesives, extrusion resins, heat-resistant paints, heat-resistant plates, heat-resistant adhesives, heat-resistant fibers, and heat-resistant films.

Polyamide is used in various fields. For example, polyamide is made into powder form and used as a coating agent for metal or magnetic wire, and is used mixed with other additives depending on the purpose. Polyamide is also used as a paint for decoration and corrosion prevention with fluoropolymers, and plays a role in bonding fluoropolymers to metal substrates. Polyamide is also used to coat kitchen utensils, and because it has the characteristics of heat resistance and chemical resistance, it is also used as a membrane used for gas separation, and is also used in devices that filter out contaminants such as carbon dioxide, hydrogen sulfide, and impurities in natural gas wells.

Recently, polyamide films that are cheaper and have excellent optical, mechanical, and thermal properties have been developed by forming polyamide into films. These polyamide films can be applied to display materials such as organic light-emitting diodes (OLEDs) or liquid crystal displays (LCDs), and can be applied to antireflection films, compensation films, or phase-difference films when implementing phase-difference properties.

When applying these polyamide films to foldable displays, flexible displays, etc., optical properties such as transparency and colorlessness and mechanical properties such as flexibility and hardness are required. However, optical properties and mechanical properties are generally in a trade-off relationship, and when mechanical properties are improved, optical properties may deteriorate.

Therefore, there is a continuous demand for research on polyamide films with improved mechanical and optical properties.

The embodiment provides a polyamide-based film having excellent optical and mechanical properties, a cover window including the same, and a display device.

The embodiment provides a method for producing a polyamide-based film having excellent optical and mechanical properties.

A polyamide-based film according to the embodiments includes a polyamide-based polymer and a filler, has a loop stiffness of 3 gf or more, and a haze of 1% or less.

A cover window for a display device according to embodiments includes a polyamide-based film and a functional layer, wherein the polyamide-based film includes a polyamide-based polymer and a filler, and wherein the polyamide-based film has a loop stiffness of 3 gf or more and a haze of 1% or less.

A display device according to embodiments includes a display portion; and a cover window disposed on the display portion, wherein the cover window includes a polyamide-based film and a functional layer, wherein the polyamide-based film includes a polyamide-based polymer and a filler, and wherein loop stiffness of the polyamide-based film is 3 gf or more and haze is 1% or less.

A method for producing a polyamide-based film according to embodiments includes a step of polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent to produce a solution including a polyamide-based polymer; a step of casting and drying the polymer solution on a belt to produce a gel sheet; and a step of heat-treating the gel sheet.

A polyamide film according to an embodiment comprises a polyamide polymer and a filler, and has loop stiffness of 3 gf or more and haze of 1% or less, thereby minimizing film deformation that may occur at a hinge and maximizing restoring force when the film is applied to a foldable display device or a flexible display device, while having excellent optical characteristics.

FIGS. 1 to 3 are schematic perspective views, exploded views, and cross-sectional views, respectively, of a display device according to one embodiment.
Figure 4 is a schematic flow chart of a method for manufacturing a polyamide film according to one embodiment.
Figure 5 is a schematic conceptual diagram of a process facility for a polyamide film according to one embodiment.

Hereinafter, implementation examples will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. However, the implementation examples may be implemented in various different forms and are not limited to the implementation examples described in this specification.

When each film, window, panel, or layer, etc. is described as being formed "on" or "under" each film, window, panel, or layer, etc., "on" and "under" include both "directly" and "indirectly" forming each component. In addition, the reference to the above/under of each component is described based on the drawings. The size of each component in the drawings may be exaggerated for the purpose of explanation and does not mean the actual applied size. In addition, the same reference numerals indicate the same components throughout the specification.

In this specification, when a part is said to "include" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless otherwise specifically stated.

In this specification, singular expressions are interpreted to include the singular or plural as interpreted by the context, unless otherwise specified.

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.

In this specification, the terms first, second, etc. are used to describe various components, and the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

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

Polyamide film

The embodiment provides a polyamide film having excellent optical characteristics while minimizing film deformation that may occur at a hinge of a foldable display device or a flexible display device and maximizing resilience.

A polyamide-based film according to one embodiment includes a polyamide-based polymer and a filler.

The above polyamide film has a loop stiffness of 3 gf or more and a haze of 1% or less.

The above loop stiffness may be a resistance value measured when a loop-shaped collapse of a thin film material such as a film occurs. More specifically, the loop stiffness may be the central stiffness (gf) measured by cutting a film to a width of 15 mm (TD direction) and a length of 120 mm, fixing both ends to the measuring device using a measuring device (Loop Stiffness tester) from Toyoseiki, bending the film so that the gap between the two ends disappears, and then contacting a load sensor to the central portion of the bent film.

If the above loop stiffness is below the above range, a problem of the film becoming deformed after repeated folding may occur when applied to a foldable display device or the like.

The above haze may be a value measured using a haze meter NDH-5000W of Denshoku Kogyo Co., Ltd. More specifically, it may be a value measured according to the JIS K 7136 standard.

If the above haze exceeds the above range, the optical properties deteriorate and the visibility may deteriorate when the film is applied to a display.

According to implementation examples, when the loop stiffness and haze of the polyamide film satisfy the above-described ranges, when applied to a foldable display device or a flexible display device that undergoes repeated folding, no folding marks occur at the hinge portion, deformation of the film can be minimized, and optical characteristics are also excellent.

Specifically, the loop stiffness may be 3.1 gf or more, 3.2 gf or more, 3.3 gf or more, 3.4 gf or more, or 3.5 gf or more, and may be 10 gf or less, 8 gf or less, 6 gf or less, 5 gf or less, 4.5 gf or less, or 4 gf or less.

More specifically, the loop stiffness may be, but is not limited to, 3 to 10 gf, 3 to 8 gf, 3 to 6 gf, 3 to 5 gf, 3 to 4.5 gf, 3 to 4 gf, 3.3 to 10 gf, 3.3 to 8 gf, 3.3 to 6 gf, 3.3 to 5 gf, 3.3 to 4.5 gf or 3.3 to 4 gf.

Additionally, the haze may be 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, or 0.5% or less, and may be 0.1% or more, 0.2% or more, or 0.3% or more.

More specifically, the haze may be, but is not limited to, 0.1% to 1%, 0.1% to 0.9%, 0.1% to 0.8%, 0.1% to 0.7%, 0.1% to 0.6%, 0.3% to 1%, 0.3% to 0.9%, 0.3% to 0.8%, 0.3% to 0.7% or 0.3% to 0.6%.

The in-plane retardation (R _o ) of the polyamide-based film according to the embodiment may be 1,000 nm or less. Specifically, the in-plane retardation (R _o ) of the polyamide-based film may be 800 nm or less, 700 nm or less, 600 nm or less, 550 nm or less, 100 nm to 800 nm, 200 nm to 800 nm, 200 nm to 700 nm, 300 nm to 700 nm, 300 nm to 600 nm, or 300 nm to 540 nm.

Additionally, the thickness direction retardation (R _th ) of the polyamide film according to the embodiment may be 5,000 nm or less. Specifically, the thickness direction retardation (R _th ) of the polyamide-based film may be 4,800 nm or less, 4,700 nm or less, 4,650 nm or less, 1,000 nm to 5,000 nm, 1,500 nm to 5,000 nm, 2,000 nm to 5,000 nm, 2,500 nm to 5,000 nm, 3,000 nm to 5,000 nm, 3,500 nm to 5,000 nm, 4,000 nm to 5,000 nm, 3,000 nm to 4,800 nm, 3,000 nm to 4,700 nm, 4,000 nm to 4,700 nm, or 4,200 nm to 4,650 nm.

Here, the in-plane retardation (R _o ) is a parameter defined as the product of the anisotropy of the refractive index of two orthogonal axes within the plane of the film (△n _xy = ｜n _x -n _y ｜) and the film thickness (d) (△n _xy ×d), and is a measure of optical isotropy or anisotropy.

In addition, the thickness direction retardation (R _th ) is a parameter defined as the average of the retardations obtained by multiplying the two birefringences △n _xz (＝｜n _x -n _z ｜) and △n _yz (＝｜n _y -n _z ｜) when viewed from the cross-section in the film thickness direction by the film thickness (d).

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

Since the above polyamide film contains a filler, the mechanical properties of the film, such as hardness, modulus, brittleness, and flexibility, and the optical properties, such as transmittance, haze, and yellowness, can be controlled, and in particular, the loop stiffness of the film can be controlled within a predetermined range.

In some implementations, the content of the filler may be from 1 part by weight to less than 40 parts by weight based on 100 parts by weight of the polyamide-based polymer solid content.

Specifically, the content of the filler may be 1 part by weight or more, 2 parts by weight or more, 3 parts by weight or more, 4 parts by weight or more, 5 parts by weight or more, 7 parts by weight or more, 10 parts by weight or more, 13 parts by weight or more, 15 parts by weight or more, or 20 parts by weight or more, and may be less than 40 parts by weight, 37 parts by weight or less, 35 parts by weight or less, 33 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less.

More specifically, the content of the filler is 1 part by weight to 35 parts by weight, 1 part by weight to 33 parts by weight, 1 part by weight to 30 parts by weight, 1 part by weight to less than 30 parts by weight, 1 part by weight to 25 parts by weight, 3 parts by weight to 35 parts by weight, 3 parts by weight to 33 parts by weight, 3 parts by weight to 30 parts by weight, 3 parts by weight to 25 parts by weight, 5 parts by weight to 35 parts by weight, 5 parts by weight to 33 parts by weight, 5 parts by weight to 30 parts by weight, 5 parts by weight to 25 parts by weight, 10 parts by weight to 35 parts by weight, 10 parts by weight to 33 parts by weight, 10 parts by weight to 30 parts by weight, 10 parts by weight to 25 parts by weight, 15 parts by weight to 35 parts by weight, 15 parts by weight to 33 parts by weight, It may be 15 parts by weight to 30 parts by weight or 15 parts by weight to 25 parts by weight, but is not limited thereto.

According to implementation examples, by adding a filler in a high content such as the above content, a film can be manufactured that has excellent loop rigidity while maintaining a low haze and an excellent film appearance.

In one embodiment, the filler may include inorganic particles.

Specifically, the filler may include at least one selected from the group consisting of silica (SiO ₂ ), barium sulfate (BaSO ₄ ), aluminum oxide (Al ₂ O ₃ ), and zirconium oxide (ZrO ₂ ).

Preferably, the filler may include particles having a hydrophobic surface treatment.

Specifically, the filler may include particles surface-treated with a silane compound, and more specifically, particles surface-treated with a phenyl silane.

In one embodiment, the filler may include inorganic particles with a hydrophobic surface treatment.

Preferably, the filler may include at least one selected from the group consisting of hydrophobic surface-treated silica, hydrophobic surface-treated barium sulfate, hydrophobic surface-treated aluminum oxide, and hydrophobic surface-treated zirconium oxide.

More preferably, the filler may include, but is not limited to, silica surface-treated with a phenyl silane.

The above filler may contain 80% or more, 90% or more, 95% or more, 98% or more or 99% or more of silica surface-treated with a phenyl silane, and may contain 100% or less, 99.9% or less or 99.5% or less of silica.

If the content of the filler is out of the above range or the filler is a particle that has not been surface-treated, the haze of the film increases rapidly, the filler may clump together on the surface of the film, which may cause a foreign body sensation to be visually confirmed, or problems may occur in running or the windability may deteriorate in the production process. In addition, the mechanical properties of the film, such as loop stiffness, hardness, and flexibility, and the optical properties, such as transmittance and yellowness, may be comprehensively deteriorated. Specifically, even if the content of the filler is within the above range, if non-surface-treated particles are used, the haze increases significantly and particle clumping may be found on the appearance of the film surface.

For example, by controlling the type and content of the filler, the mechanical properties such as the loop stiffness and modulus and the optical properties such as haze and transmittance can be controlled to the desired range.

The filler may have a 50% cumulative mass particle size distribution diameter ( _D50 ) of 5 to 30 nm in the particle size distribution. Specifically, the 50% cumulative mass particle size distribution diameter ( _D50 ) of the filler may be, but is not limited to, 5 nm to 25 nm, 5 nm to 20 nm, 7 nm to 30 nm, 7 nm to 25 nm, 7 nm to 20 nm, 10 nm to 30 nm, 10 nm to 25 nm, or 10 nm to 20 nm.

When the filler has the above particle size, the rollability and slipperiness of the film can be improved without deteriorating the flexibility and optical properties of the film.

The refractive index of the filler may be from 1.35 to 1.55. Specifically, the refractive index of the filler may be from 1.40 to 1.55, from 1.40 to 1.50, from 1.42 to 1.49, or from 1.43 to 1.48, but is not limited thereto.

By having the refractive index of the above filler satisfy the above range, the birefringence values related to the refractive indices in each direction (n _x , n _y and n _z ) of the polyamide film can be appropriately controlled, and the brightness of the film at various angles can be improved.

On the other hand, if the refractive index of the filler is outside the above range, the presence of the film may be visually recognized on the film or the filler may cause problems such as an increase in haze.

The content of residual solvent in the polyamide film may be 1,500 ppm or less. For example, the content of the residual solvent may be 1,200 ppm or less, 1,000 ppm or less, 800 ppm or less, or 500 ppm or less, but is not limited thereto.

The above residual solvent refers to the amount of solvent that does not volatilize during film production and remains in the final film produced.

If the content of residual solvent in the polyamide film exceeds the above range, the durability of the film may deteriorate and the brightness may also be affected.

In one embodiment, the residual content of the organic solvent for polymer production in the polyamide-based film may be 1,000 ppm or less. For example, the residual content of the organic solvent for polymer production in the polyamide-based film may be 800 ppm or less, 500 ppm or less, 300 ppm or less, or 100 ppm or less, but is not limited thereto.

Specifically, the residual content of dimethylacetamide (DMAc) in the polyamide film may be 1,000 ppm or less, 800 ppm or less, 500 ppm or less, 300 ppm or less, or 100 ppm or less.

In one embodiment, the residual content of the organic solvent for dispersing the filler in the polyamide-based film may be 1,000 ppm or less. For example, the residual content of the organic solvent for dispersing the filler in the polyamide-based film may be 800 ppm or less, 500 ppm or less, 300 ppm or less, or 100 ppm or less, but is not limited thereto.

Specifically, the residual content of toluene in the polyamide film may be 1,000 ppm or less, 800 ppm or less, 500 ppm or less, 300 ppm or less, or 100 ppm or less.

According to an embodiment, when a polyamide film is folded so that a radius of curvature becomes 3 mm based on a thickness of 50 ㎛, the number of folding cycles before breaking may be 200,000 or more.

The above folding number is one cycle of bending and unfolding so that the film has a radius of curvature of 3 mm.

Since the above polyamide film satisfies the number of folding cycles described above, it can be usefully applied to a foldable display device or a flexible display device.

The surface roughness of the polyamide film according to the embodiment may be 0.01 ㎛ to 0.08 ㎛. Specifically, the surface roughness may be 0.01 ㎛ to 0.07 ㎛ or 0.01 ㎛ to 0.06 ㎛, but is not limited thereto.

Since the surface roughness of the above polyamide film satisfies the above range, it can be advantageous in implementing high brightness even when the angle from the normal direction of the surface light source increases.

In some embodiments, the polyamide-based film may have a thickness deviation of 4 ㎛ or less based on a thickness of 50 ㎛. The thickness deviation may mean a deviation between a maximum or minimum value with respect to an average of thicknesses measured at 10 points at random locations of the film. In this case, the polyamide-based film may have a uniform thickness so that optical properties and mechanical properties at each point may be uniformly exhibited.

The transmittance of the above polyamide film can be 80% or more.

Specifically, the transmittance may be 82% or more, 85% or more, 88% or more, 89% or more, 89.5% or more, or 90% or more.

More specifically, the transmittance may be, but is not limited to, 80% to 99%, 88% to 99%, 89% to 99%, 89.5% to 99%, 90% to 99%, 80% to 95%, 88% to 95%, 89% to 95%, 89.5% to 95% or 90% to 95%.

The transmittance and/or haze of the above film may be values measured in the visible light wavelength range (400 to 700 nm). Specifically, the transmittance of the film may be total light transmittance measured in the visible light wavelength range.

For example, by comprehensively controlling the monomer composition and molar ratio of the polyamide polymer, the type and content of the filler, etc., the above transmittance can be achieved even without a separate coating on the film.

The yellow index of the above polyamide film may be 5 or less. For example, the yellow index may be 4 or less, 3.5 or less, or 3 or less, but is not limited thereto.

The modulus of the above polyamide film may be 5 GPa or more. Specifically, the modulus may be 5.5 GPa or more, or 5.8 GPa or more, but is not limited thereto.

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

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

The surface hardness of the above polyamide film may be HB or higher. Specifically, the surface hardness may be H or higher, but is not limited thereto.

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

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

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

As another example, the polyamide-based film may include a polyamide-based polymer and a filler, and may have a loop stiffness of 3 gf or more, a haze of 1% or less, a transmittance of 89.5% or more, a yellowness of 5 or less, and a modulus of 5 GPa or more.

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

For example, the polyamide-based polymer can be formed by polymerizing a diamine compound and a dicarbonyl compound, and can also be formed by polymerizing a diamine compound, a dicarbonyl compound, and a dianhydride compound.

The above polyamide-based polymer is a polymer containing an amide repeating unit. In addition, the polyamide-based polymer may optionally further contain an imide repeating unit.

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

The above diamine compound is a compound that forms a copolymer by forming an imide bond with the dianhydride compound and an amide bond with the dicarbonyl compound.

The above diamine compound is not particularly limited, but may be, for example, an aromatic diamine compound containing an aromatic structure. For example, the diamine compound may be a compound represented by the following chemical formula 1.

<Chemical formula 1>

In the above chemical formula 1,

E can be selected from a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic ring group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic ring group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic ring 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 -, -C(CH ₃ ) ₂ -, and -C(CF ₃ ) ₂ -.

e is an integer from 1 to 5, and if e is 2 or greater, E may be the same or different.

(E) _e of the above chemical formula 1 may be selected from the groups represented by the following chemical formulas 1-1a to 1-14a, but is not limited thereto.

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

More specifically, (E)e of the chemical formula 1 may be a group represented by the chemical formula 1-6b or a group represented by the chemical 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 above diamine compound may be composed of a compound having a fluorine-containing substituent. At this time, the fluorine-containing substituent may be a fluorinated hydrocarbon group, and specifically, may be a trifluoromethyl group, but is not limited thereto.

In some embodiments, the diamine compound may comprise one kind of diamine compound. That is, the diamine compound may consist of a single component.

For example, the diamine compound may include, but is not limited to, 2,2'-Bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB/TFDB) having the following structure:

The above dianhydride compound is a compound that can contribute to improving optical properties, such as transmittance, of a film including the polyamide polymer because it has a low birefringence value.

The above dianhydride compound is not particularly limited, but may be, for example, an aromatic dianhydride compound including an aromatic structure. For example, the aromatic dianhydride compound may be a compound represented by the following chemical formula 2.

<Chemical Formula 2>

In the above chemical formula 2, G is a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic ring group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic ring 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 heteroaliphatic ring group, the aromatic ring group or the heteroaromatic ring group exists alone or is joined 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 - are connected by a linking group selected from among them.

G in the above chemical formula 2 may be selected from the groups represented by the following chemical formulas 2-1a to 2-9a, but is not limited thereto.

For example, G in the chemical formula 2 may be a group represented by the chemical formula 2-2a, a group represented by the chemical formula 2-8a, or a group represented by the chemical formula 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 above fluorine-containing substituent may be a fluorinated hydrocarbon group, and specifically, may be a trifluoromethyl group, but is not limited thereto.

In other embodiments, the dianhydride compound may be composed of one single component or two mixed components.

For example, the dianhydride compound may include at least one selected from the group consisting of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), which have the following structure, but are not limited thereto.

The above diamine compound and the above dianhydride compound can polymerize to produce a polyamic acid.

Next, the polyamic acid can be converted into a polyimide through a dehydration reaction, and the polyimide includes an imide repeating unit.

The above polyimide can form a repeating unit represented by the following chemical formula A.

<Chemical Formula A>

In the above chemical formula A, the descriptions of E, G, and e are as described above.

For example, the polyimide may include, but is not limited to, a repeating unit represented by the following chemical formula A-1.

<Chemical Formula A-1>

In the above chemical formula A-1, n is an integer from 1 to 400.

The above dicarbonyl compound is not particularly limited, but may be, for example, a compound of the following chemical formula 3.

<Chemical Formula 3>

In the above chemical formula 3,

J can be selected from a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic ring group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic ring group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic ring 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 -, -C(CH ₃ ) ₂ -, and -C(CF ₃ ) ₂ -.

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

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

(J) _j of the above chemical formula 3 may be selected from the groups represented by the following chemical formulas 3-1a to 3-14a, but is not limited thereto.

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

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

For example, (J) _j of the above chemical formula 3 may be a group represented by the above chemical formula 3-1b or a group represented by the above chemical formula 3-2b.

In one embodiment, the dicarbonyl compound may be used alone as one kind of dicarbonyl compound, or at least two kinds of different dicarbonyl compounds may be used as a mixture. When two or more kinds of the dicarbonyl compounds are used, the dicarbonyl compounds may be two or more kinds selected from the group represented by the chemical formulas 3-1b to 3-8b, where (J) _j in the chemical formula 3 is represented by the chemical formulas 3-1b to 3-8b.

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

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

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

<Chemical Formula B>

In the above chemical formula B, the descriptions of E, J, e and j are as described above.

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

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

<Chemical Formula B-1>

In the above chemical formula B-1, x is an integer from 1 to 400.

<Chemical Formula B-2>

In the above chemical formula B-2, y is an integer from 1 to 400.

<Chemical Formula B-3>

In the above chemical formula B-3, y is an integer from 1 to 400.

According to one embodiment, the polyamide polymer comprises a repeating unit represented by the following chemical formula B, and optionally may comprise a repeating unit represented by the following chemical formula A:

<Chemical Formula A>

<Chemical Formula B>

Among the above chemical formulas A and B,

E and J are independently selected from a substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic ring group, a substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic ring group, a substituted or unsubstituted divalent C ₆ -C ₃₀ aromatic ring 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 -, -C(CH ₃ ) ₂ - _{, and -C(CF 3 ) 2} -,

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

If e is 2 or more, two or more E are identical or different,

If j is 2 or more, two or more J are identical or different,

G is a substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic ring group, a substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic ring 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, wherein the aliphatic ring group, the heteroaliphatic ring group, the aromatic ring group or the heteroaromatic ring group exists alone or is joined 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 -, -Connected by a linker selected from -C(CH ₃ ) ₂ - and -C(CF ₃ ) ₂ -.

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

When the molar ratio of the imide repeating unit and the amide repeating unit of the above polyamide polymer is within the above range, the loop stiffness and haze characteristics of the polyamide film can be effectively controlled, and when combined with a characteristic manufacturing process, the optical characteristics and mechanical durability of the film can be improved.

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

The polyamide-based film according to the embodiment may further include at least one selected from the group consisting of a blue pigment and a UVA absorber in addition to the polyamide-based polymer.

The above blue pigment may include, but is not limited to, OP-1300A from Toyo Corporation.

In some embodiments, the blue pigment may be included in an amount of 50 to 5000 ppm based on the total weight of the polyamide-based polymer. Preferably, the blue pigment is present in an amount of 100 to 5,000 ppm, 200 to 5,000 ppm, 300 to 5,000 ppm, 400 to 5,000 ppm, 50 to 3,000 ppm, 100 to 3,000 ppm, 200 to 3,000 ppm, 300 to 3,000 ppm, 400 to 3,000 ppm, 50 to 2,000 ppm, 100 to 2,000 ppm, 200 to 2,000 ppm, 300 to 2,000 ppm, 400 to 2,000 ppm, 50 to 1,000 ppm, 100 to 1,000 ppm, 200 to 1,000 ppm, 300 to It may be included at, but is not limited to, 1000 ppm or 400 to 1000 ppm.

The UVA absorbent may include an absorbent that absorbs electromagnetic waves with a wavelength of 10 to 400 nm used in the art. For example, the UVA absorbent may include a benzotriazole-based compound, and the benzotriazole-based compound may include an N-phenolic benzotriazole-based compound. In some embodiments, the 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 atoms, and may be linear, branched, or cyclic.

In some embodiments, the UVA absorber may be present in an amount of 0.1 to 10 wt% based on the total weight of the polyamide-based polymer. Preferably, the UVA absorber may be present in an amount of, but not limited to, 0.1 to 5 wt%, 0.1 to 3 wt%, 0.1 to 2 wt%, 0.5 to 10 wt%, 0.5 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, 1 to 10 wt%, 1 to 5 wt%, 1 to 3 wt%, or 1 to 2 wt% based on the total weight of the polyamide-based polymer.

The characteristics of the composition and properties of the polyamide film described above can be combined with each other.

In addition, the aforementioned loop stiffness, haze, transmittance, modulus, yellowness, hardness, etc. of the polyamide-based film can be controlled by comprehensively combining the chemical and physical properties of the components forming the polyamide-based film with the specific process conditions of each step in the method for manufacturing the polyamide-based film described below.

For example, the composition and content of the components forming the polyamide film, the type, surface treatment and content of the filler, the polymerization conditions and heat treatment conditions in the film manufacturing process, etc., can all be integrated to implement the desired range of loop stiffness, haze, transmittance, modulus, etc.

Cover window for display device

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

The above polyamide film contains a polyamide polymer and a filler, has a loop stiffness of 3 gf or more, and a haze of 1% or less.

A specific description of the above polyamide film is as described above.

The cover window for the above display device can be usefully applied to the display device.

The above polyamide film has the above-described loop stiffness and haze, and thus, when applied to a foldable display device or a flexible display device, it minimizes film deformation that may occur at a hinge and maximizes restoring force, while also having excellent optical characteristics.

Display device

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

The above polyamide film contains a polyamide polymer and a filler, has a loop stiffness of 3 gf or more, and a haze of 1% or less.

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

FIGS. 1 to 3 are schematic perspective views, exploded views, and cross-sectional views of a display device according to one embodiment.

Specifically, FIGS. 1 to 3 illustrate a display device in which a display portion (400) and a cover window (300) including a polyamide film (100) having a first surface (101) and a second surface (102) and a functional layer (200) are disposed on the display portion (400), and an adhesive layer (500) is disposed between the display portion (400) and the cover window (300).

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

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

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

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

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.

The above cover window (300) can be placed on the display portion (400). The cover window is located at the outermost part of the display device according to the embodiment, and can protect the display portion.

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

In the case of a polyamide film according to an embodiment, a display device having uniform thickness, low haze, high light transmittance and transparency can be provided 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, laminated structure, etc., and thus there is an advantage of being able to reduce production costs because there is no need for excessive process changes or cost increases.

The polyamide film according to the embodiment may have excellent optical properties such as low haze and high transmittance along with excellent loop stiffness, as well as excellent mechanical properties such as excellent modulus and pencil hardness, and ease of handling such as slipperiness and rollability.

In addition, the polyamide film according to the embodiment can minimize optical distortion by having an in-plane phase difference and a thickness direction phase difference below a specific level, and can also reduce a light leakage phenomenon in which light leaks from the side.

In the case of a polyamide film having a loop stiffness and haze value in the above-described range, since the film has excellent optical properties and excellent resilience, even if the film is repeatedly folded, no folding marks occur at the hinge or the film is deformed, so it can be effectively applied to a rollable/flexible display device.

Method for manufacturing polyamide film

One embodiment provides a method for producing a polyamide-based film.

The properties of the polyamide film, such as loop stiffness, haze, and transmittance, may be the result of a combination of the chemical and physical properties of the components forming the polyamide film, as well as the process conditions of each step in the method for manufacturing the polyamide film, which will be described later.

For example, the composition and content of the components forming the polyamide film, the polymerization conditions and heat treatment conditions in the film manufacturing process, etc. can be comprehensively combined to implement the desired loop stiffness, haze, and transmittance characteristics.

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

A method for manufacturing a polyamide-based film according to some embodiments may further include a step of controlling the viscosity of the polyamide-based polymer solution (S110), a step of stirring the polyamide-based polymer solution by increasing its temperature (S120), and/or a step of degassing the polyamide-based polymer solution (S130).

The above polyamide-based film is a film whose main component is a polyamide-based polymer, and the polyamide-based polymer is a polymer that essentially contains an amide repeating unit as a structural unit and optionally contains an imide repeating unit.

In the method for manufacturing the above polyamide-based film, the polymer solution for manufacturing the polyamide-based polymer can be manufactured by simultaneously or sequentially mixing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent in a reactor, and reacting the mixture (S100).

In addition, the step of preparing a polyamide-based polymer solution by polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in the organic solvent may further include a step of introducing a filler dispersed in the organic solvent.

Specifically, the polyamide-based polymer solution may include a filler dispersed in an organic solvent.

In one embodiment, the polymer solution can be prepared by simultaneously introducing a diamine compound and a dicarbonyl compound into an organic solvent and reacting them.

Specifically, the step of preparing the polymer solution may include a step of preparing a polyamide solution by mixing and reacting a diamine compound and a dicarbonyl compound in an organic solvent.

In another embodiment, the polymer solution can be prepared by simultaneously introducing a diamine compound, a dianhydride compound, and a dicarbonyl compound into an organic solvent and reacting them.

For example, the step of preparing the polymer solution may include a step of first mixing and reacting the diamine compound and the dianhydride compound in a solvent to prepare a polyamic acid (PAA) solution; and a step of second mixing and reacting the dicarbonyl compound with the polyamic acid (PAA) solution to form an amide bond and an imide bond. The polyamic acid solution is a solution including polyamic acid.

Alternatively, the step of preparing the polymer solution may include a step of first mixing and reacting the diamine compound and the dianhydride compound in a solvent to prepare a polyamic acid solution; a step of dehydrating the polyamic acid solution to prepare a polyimide (PI) solution; and a step of second mixing and reacting the dicarbonyl compound with the polyimide (PI) solution to additionally form an amide bond. The polyimide solution is a solution including a polymer having an imide repeating unit.

In one embodiment, the step of preparing the polymer solution may include the steps of: first mixing and reacting the diamine compound and the dicarbonyl compound in a solvent to prepare a polyamide (PA) solution; and second mixing and reacting the dianhydride compound with the polyamide (PA) solution to additionally form an imide bond. The polyamide solution is a solution including a polymer having an amide repeating unit.

The polymer solution manufactured in this manner may be a solution containing a polymer including at least one selected from the group consisting of polyamic acid (PAA) repeating units, polyamide (PA) repeating units, and polyimide (PI) repeating units.

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

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

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

The content of the solids contained in the polymer solution may be from 10 wt% to 30 wt%. Alternatively, the content of the solids contained in the polymer solution may be from 15 wt% to 25 wt%, or from 15 wt% to 20 wt%, but is not limited thereto.

When the content of solids contained in the above polymer solution is within the above range, a polyamide film can be effectively manufactured through extrusion and casting processes.

In another embodiment, the step of preparing the polymer solution may further include the step of introducing a catalyst.

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

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

When the above catalyst is introduced, the reaction rate can be improved and the chemical bonding strength between or within the repeating unit structure can be improved.

In one embodiment, the step of preparing the polymer solution may further include a 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 200,000 cps to 300,000 cps at room temperature. In this case, by improving the film forming properties of the polyamide film, the thickness uniformity can be improved.

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 dicarbonyl compound, and optionally a dianhydride compound in an organic solvent; and a step of additionally adding the dicarbonyl compound to prepare a second polymer solution having a target viscosity.

In the step of preparing the first polymer solution and the step of preparing the second polymer solution, the viscosities of the prepared polymer solutions are 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 may be different from the stirring speed when preparing the second polymer solution. For example, the stirring speed when preparing the first polymer solution may be faster than the stirring speed when preparing the second polymer solution.

In another embodiment, the step of preparing the polymer solution may further include a 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.

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

By controlling the pH of the polymer solution within the above-mentioned range, the occurrence of defects in a film manufactured from the polymer solution can be prevented, and the desired optical and mechanical properties in terms of yellowness and modulus can be realized.

The above pH regulator can be added in an amount of 0.1 mol% to 10 mol% based on the total molar number of monomers in the polymer solution.

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

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.

Specific details of the type, content, etc. of the filler, blue pigment and UVA absorber are as described above. The filler, blue pigment and/or UVA absorber can be mixed with the polyamide-based polymer in the polymer solution.

In one embodiment, the filler may be introduced in a dispersed state in an organic solvent and may be introduced during the step of preparing a polyamide-based polymer solution.

Specifically, the method may further include a step of adding a filler dispersed in an organic solvent to a polymer solution (e.g., a second polymer solution) adjusted to a target viscosity, and then stirring the polymer solution containing the filler by heating it.

Specifically, the organic solvent may include at least one selected from the group consisting of toluene, dimethylacetamide (DMAc), and isopropyl alcohol (IPA).

More specifically, the filler can be introduced into the second polymer solution in the form of silica dispersed in a toluene solvent to form a polymer solution.

In one embodiment, the method for manufacturing the polyamide-based film may further include a step (S120) of heating and stirring the polyamide-based polymer solution. While heating and stirring the polyamide-based polymer solution, the temperature level may be maintained to heat-treat the polymer solution.

In some embodiments, the polymer solution may be heated to 35° C. to 70° C. and then heat-treated while stirring at the elevated temperature for 0.5 to 2 hours. In this case, the dispersion of the polymer solution may be improved, so that the optical properties of the film finally manufactured, such as transmittance, haze, and appearance, and/or mechanical properties, such as loop stiffness and modulus, may be improved.

Preferably, the heat treatment temperature of the polymer solution may be, but is not limited to, 40°C to 70°C, 45°C to 70°C, 50°C to 70°C, 35°C to 60°C, 40°C to 60°C, 45°C to 60°C, 50°C to 60°C, 35°C to 50°C or 40°C to 50°C.

Additionally, preferably, the heat treatment time of the polymer solution may be, but is not limited to, 0.5 to 1.5 hours, 0.5 to 1 hour or 1 to 1.5 hours.

In one embodiment, the method for manufacturing the polyamide-based film may sequentially perform the steps of: adjusting the viscosity of the polyamide-based polymer solution (S110); introducing a filler dispersed in an organic solvent; and heating and stirring the polyamide-based polymer solution (S120).

Specifically, a step (S110) of controlling the viscosity of the polyamide polymer solution may be first performed, a step of introducing a filler dispersed in an organic solvent may be performed, and a step (S120) of stirring the polymer solution containing the filler by raising its temperature may be performed.

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

The above degassing may include vacuum degassing or inert gas purging.

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

In addition, the purging can be performed by a method of purging the internal pressure of the tank to 1 to 2 atm using an inert gas. By performing the purging under these conditions, moisture inside the polymer solution can be removed, impurities can be reduced, and the reaction yield can be increased, and optical properties such as haze and mechanical properties can be excellently implemented.

The above inert gas may be at least one 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.

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

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

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

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

In one embodiment, the polymer solution may be a heat-treated polymer solution.

For example, the polymer solution may be applied, extruded, and/or dried onto a support to form a gel sheet. Specifically, the polymer solution may be cast onto a belt and dried to produce a gel sheet.

In addition, the casting thickness of the polymer solution may be 200 μm to 700 μm. When the polymer solution is cast within the above thickness range and is manufactured into a final film through drying and heat treatment, an appropriate thickness and thickness uniformity can be secured.

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

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

In some embodiments, in the step of drying the polymer solution to produce a gel sheet, the solvent evaporation amount per unit area may be controlled to 0.5 to 3.0 kg/m ² . In this case, the loop stiffness and/or haze value of the film can be effectively controlled within the target range, and accordingly, a film with improved optical properties, mechanical properties, slipperiness, and rollability can be produced. Preferably, the solvent evaporation amount per unit area is 0.5 to 2.5 kg/m ² , 0.5 to 2.0 kg/m ² , 0.5 to 1.8 kg/m ² , 0.5 to 1.6 kg/m ² , 0.5 to 1.4 kg/m ² , 0.8 to 3.0 kg/m ² , 0.8 to 2.5 kg/m ² , 0.8 to 2.0 kg/m ² , 0.8 to 1.8 kg/m ² , 0.8 to 1.6 kg/m ² , 0.8 to 1.4 kg/m ² , 1.0 to 3.0 kg/m ² , 1.0 to 2.5 kg/m ² , 1.0 to 2.0 kg/m ² , 1.0 to 1.8 kg/m ² , 1.0 to 1.6 kg/m ² , 1.0 to 1.4 kg/m ² , but is not limited thereto.

For example, the moving distance of the belt can be 40 m to 60 m. Additionally, the belt can move at a speed of 0.5 m/min to 15 m/min, specifically, 1 m/min to 10 m/min.

During the drying, part or all of the solvent of the polymer solution may be evaporated, thereby producing the gel sheet.

According to one embodiment, the content of residual solvent included in the gel sheet after drying may be 1,500 ppm or less. In this case, the loop stiffness and haze properties of the film can be effectively controlled within the target range, and accordingly, a film having improved optical properties, mechanical properties, slipperiness, and rollability can be manufactured.

The above dried gel sheet can be heat treated to form a polyamide film (S300).

For example, the dried gel sheet may be heat-treated by putting it into a thermosetting device that is heated at a temperature ranging from 80°C to 500°C at a temperature rising rate of 1°C/min to 8°C/min. Specifically, the dried gel sheet may be heat-treated by putting it into a thermosetting device that is heated at a temperature ranging from 80°C to 420°C, a temperature ranging from 80°C to 380°C, or a temperature ranging from 80°C to 350°C at a temperature rising rate of 1°C/min to 6°C/min, a temperature ranging from 1.5°C/min to 5°C/min, or a temperature ranging from 1.5°C/min to 3°C/min.

As another example, the heat treatment of the gel sheet may be performed via a heat treatment device (tenter). The heat treatment device may include at least one hot air blower and at least one heater. The heat treatment device may include only one of the at least one hot air blower or the at least one heater.

The step of heat-treating the above dried gel sheet may include a first heat-treating step of heat-treating by hot air generated from at least one hot air blower; and a second heat-treating step of heat-treating through at least one heater.

The section in which the above first heat treatment step is performed is called the first heat treatment section, and the section in which the above second heat treatment step is performed is called the second heat treatment section.

The first heat treatment step and the second heat treatment step can be performed sequentially. The second heat treatment step can be performed after the first heat treatment step is performed, and the first heat treatment step can be performed after the second heat treatment step is performed, but is not limited thereto. Specifically, the second heat treatment step can be performed after the first heat treatment step is performed.

The step of heat-treating the above gel sheet can be performed via a support that moves continuously within a heat treatment device. Specifically, the gel sheet can be positioned on the support, and the film can also be performed while moving in the longitudinal direction as the support moves in the moving direction.

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

The step of fixing both ends of the width direction of the gel sheet with fixing members and performing heat treatment while changing the width of the fixed gel sheet can be performed while the gel sheet passes through the first heat treatment section and the second heat treatment section.

In an embodiment, in the step of changing the width of the gel sheet while the gel sheet passes through the first heat treatment section in the longitudinal direction (progress direction) of the gel sheet, the width of the gel sheet can be narrowed.

In addition, in the step of changing the width of the gel sheet while the gel sheet passes through the second heat treatment section in the longitudinal direction (progress direction) of the gel sheet, the width of the gel sheet can be narrowed. Alternatively, in the step of changing the width of the gel sheet, the widening and narrowing of the gel sheet can be repeated.

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

Additionally, the width of the gel sheet at the introduction of the first heat treatment section may be greater than the width of the gel sheet at the end of the second heat treatment section, but is not limited thereto.

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

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

Additionally, the width of the gel sheet at the introduction of the first heat treatment section may be the maximum width (Wa) of the gel sheet in the first heat treatment section, and the width of the gel sheet at the end of the second heat treatment section may be the minimum width (Wc) of the gel sheet in the first heat treatment section and the second heat treatment section.

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

In an embodiment, the Wb/Wa value is from 0.955 to 0.990. For example, the Wb/Wa value may be at least 0.955, at least 0.960, at least 0.965, at least 0.968, or at least 0.969, and may be at most 0.990, at most 0.985, at most 0.980, or at most 0.975, but is not limited thereto. As another example, it may be at most 0.955 to 0.980.

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

In one embodiment, when the first heat treatment step of heat treatment is performed by hot air generated from at least one hot air blower, the amount of heat can be evenly applied. If the amount of heat is not evenly distributed, satisfactory optical/mechanical properties cannot be implemented, the surface quality may become uneven, and the surface energy may excessively increase or decrease.

The heat treatment by hot air can be performed at a temperature ranging from 100° C. to 250° C. for 5 to 100 minutes. Specifically, the heat treatment of the gel sheet by hot air can be performed at a temperature ranging from 100° C. to 250° C. for 5 to 60 minutes while increasing the temperature at a rate of 1.5° C./min to 20° C./min. More specifically, the heat treatment of the gel sheet can be performed at a temperature ranging from 140° C. to 250° C.

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

The temperature described in the heat treatment using the above hot air is the temperature inside the heat treatment device where the gel sheet exists, and corresponds to the temperature measured by the temperature detection sensor located in the first heat treatment section inside the heat treatment device.

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.

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 on heater mounting portions, and two or more of the heater mounting portions may be arranged along the progressing direction (MD direction) of the gel sheet.

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

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

The temperature described in the heat treatment by the above heater is the temperature inside the heat treatment device where the gel sheet exists, and corresponds to the temperature measured by the temperature detection sensor located in the second heat treatment section inside the heat treatment device.

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

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

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.

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.

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

Additionally, a step of winding the cooled cured film using a winder can be performed.

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 1:1.01 to 1:1.10, but is not limited thereto.

If the ratio of the above moving speeds is outside the above range, there is a concern that the mechanical properties of the cured film may be damaged, and that the flexibility and elasticity characteristics may deteriorate.

In the method for manufacturing the above polyamide 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 the above general formula 1, M1 is the thickness (㎛) of the gel sheet, and M2 is the thickness (㎛) of the cured film cooled during winding.

The above polyamide-based film, manufactured according to the above-described manufacturing method, not only exhibits excellent content resistance and excellent optical and mechanical properties, but also has excellent restoring force when the bending force is released after being in a folded state for a long time, and hardly any wrinkles are visible even after a harsh folding test. In addition, since it still implements the desired level of loop stiffness not only at room temperature but also in an extremely low-temperature environment, it can be applied to various purposes requiring flexibility and mechanical durability. For example, the above polyamide-based film can be applied not only to display devices but also to solar cells, semiconductor elements, sensors, etc.

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

The above contents are explained in more detail by the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited to these examples.

<Example 1>

Dimethylacetamide (DMAc), an organic solvent, was placed in a 1 L glass reactor with a temperature-controlled double jacket under a nitrogen atmosphere at 10°C, and 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), an aromatic diamine, was slowly added and dissolved.

Then, terephthaloyl chloride (TPC) was slowly added while stirring for 1 hour. Then, isophthaloyl chloride (IPC) (94 mol% of the total added amount) was added and stirred for 1 hour to prepare a first polymer solution. The viscosity of the prepared first polymer solution was 1,000 to 10,000 cPs.

Then, the process of adding 1 mL of an IPC solution (DMAc solvent) having a concentration of 10 wt% and stirring for 30 minutes was repeated to prepare a second polymer solution having a viscosity of 180,000 to 220,000 cPs.

At this time, the viscosity of the polymer solution was measured using BH-Ⅱ equipment from TOKI SANGYO Co., Ltd., under constant temperature conditions of 20℃, with RPM set to 4 and spindle No. 7, to confirm whether the target viscosity was achieved.

A polymer solution was prepared by adding silica (TOL-ST, solid content 40%) dispersed in a toluene solvent to the second polymer solution so that the content of filler in the film was 10 parts by weight per 100 parts by weight of the polyamide polymer solid content.

The above polymer solution was heated to 40°C and then heat-treated while stirring for 1 hour.

The above heat-treated polymer solution was cast on a belt, dried with hot air at 100°C for 30 minutes, and the dried polyamide-based gel sheet was placed in a thermosetting machine that was heated at a rate of 2°C/min in the temperature range of 80°C to 300°C, cooled, and wound to obtain a polyamide-based film having a thickness of 50 μm.

The specific composition and molar ratio of the polyamide polymer are as described in Table 1 below.

<Examples 2 to 5 and Comparative Examples 1 to 5>

For Examples 2 to 5 and Comparative Examples 1 to 5, polyamide films were obtained in the same manner as in Example 1, except that the monomer composition and molar ratio of the polyamide polymer, the content of the filler, and whether or not the surface was treated were changed according to Table 1 below.

<Evaluation example>

The physical properties of the films manufactured in the above examples and comparative examples were measured and evaluated as follows, and the results are shown in Table 1 below.

Evaluation Example 1: Film Thickness Measurement

The thickness of the film was calculated by taking the average of the thickness values measured at five random points using a digital micrometer 547-401 manufactured by Mitutoyo, Japan.

Evaluation Example 2: Transmittance and Haze Measurement

The light transmittance and haze were measured at wavelengths from 400 nm to 700 nm according to the JIS K 7136 standard using a haze meter NDH-5000W from Denshoku Kogyo Co., Ltd., Japan.

Evaluation Example 3: Yellowness Measurement

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

Evaluation Example 4: Modulus Measurement

Using a universal testing machine UTM 5566A from Instron, the sample was cut to a length of 10 cm or more in the direction perpendicular to the principal shrinkage direction and 10 mm in the principal shrinkage direction, mounted on clips at 10 cm intervals, and stretched at a rate of 12.5 mm/min until fracture occurred at room temperature to obtain a stress-strain curve. In the stress-strain curve, the slope of the load with respect to the initial deformation was taken as the modulus (GPa).

Evaluation Example 5: Measurement of loop stiffness

The film was cut to a width of 15 mm (TD direction) and a length of 120 mm, and both ends were fixed to a measuring device (Toyoseiki Loop Stiffness tester), and the film was bent so that there was no gap between the two ends. A load sensor was placed in contact with the center of the bent film to measure the stiffness (gf) of the center. The results are shown in Table 1 below.

Evaluation Example 6: Evaluation of the appearance of the film surface

The film was visually observed and evaluated according to the following criteria based on particle agglomeration and transparency of appearance.

◎: No particle agglomeration, transparent appearance

○: Some particle clumping exists, but the appearance is transparent.

△: There is particle agglomeration and the appearance is opaque.

×: White clouding occurs due to large particle agglomeration

division Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Polyamide type polymers
Polymerization ratio Diamine compound (molar ratio) TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 TFMB 100 Dianhydride
Compound (molar ratio) - - - 6FDA
7 6FDA 11
BPDA 34 - - - 6FDA
7 6FDA 11
BPDA 34 Dicarbonyl
Compound (molar ratio) TPC 60
IPC 40 TPC 60
IPC 40 TPC 60
IPC 40 TPC 71
IPC 22 TPC 55 TPC 60
IPC 40 TPC 60
IPC 40 TPC 60
IPC 40 TPC 71
IPC 22 TPC 55 Filler Content (weight parts) ¹ 10 20 30 20 20 - 40 10 - - Surface treatment Hydrophobic treatment
(Phenyl silane) Hydrophobic treatment
(Phenyl silane) Hydrophobic treatment
(Phenyl silane) Hydrophobic treatment
(Phenyl silane) Hydrophobic treatment
(Phenyl silane) - Hydrophobic treatment
(Phenyl silane) doesn't exist - - Thickness (㎛) 50 50 50 50 50 50 50 50 50 50 Transmittance (%) 89.7 90.2 90.2 90.3 90.0 89.1 90.5 90.2 89.3 88.8 Haze(%) 0.58 0.40 0.87 0.42 0.50 0.36 1.57 5.46 0.38 0.50 Yellow color 2.26 1.89 2.36 2.57 3.47 1.80 2.79 2.82 2.51 3.56 Modulus (GPa) 5.91 5.96 5.85 6.21 6.13 5.77 5.69 5.12 5.88 5.93 Loop stiffness
(Loop stiffness)
(gf) 3.03 3.47 3.50 3.64 3.55 2.61 2.93 3.15 2.88 2.92 Film surface appearance evaluation ◎ ◎ ○ ◎ ◎ ◎ ○ △ ◎ ◎

¹ The content of the above filler is expressed based on 100 parts by weight of the polyamide-based polymer solid content.

Referring to Table 1, the polyamide-based films according to Examples 1 to 5 have a loop stiffness of 3 gf or more and a haze of 1% or less, and compared to the polyamide-based films according to Comparative Examples 1 to 5, not only mechanical properties such as modulus and loop stiffness but also optical properties such as transmittance, haze, and appearance of the film surface are superior, so that when applied to a foldable display device or a flexible display device, film deformation that may occur at the hinge can be minimized and resilience can be maximized.

10: Polymerization equipment 20: Tank
30: Belt 40: Thermosetting machine
50 : Winder
100: Polyamide film
101 : Page 1 102 : Page 2
200 : Functional layer 300 : Cover window
400 : Display part 500 : Adhesive layer

Claims (10)

Containing a polyamide polymer and a filler,
The above polyamide polymer contains imide repeating units and amide repeating units in a molar ratio of 0:100 to 50:50,
The above amide repeating unit is derived from the polymerization of a diamine compound and a dicarbonyl compound.
The above diamine compound comprises a compound of the following chemical formula 1, and (E)e of the following chemical formula 1 is selected from the groups represented by the following chemical formulas 1-6b and 1-7b,
The above dicarbonyl compound comprises terephthaloyl chloride (TPC), isophthaloyl chloride (IPC) or a combination thereof,
The loop stiffness measured for a film cut to a width of 15 mm (TD direction) and a length of 120 mm based on a film thickness of 50 ㎛ is 3 to 6 gf.
Polyamide film with haze of 1% or less:
<Chemical Formula 1>


In paragraph 1,
A polyamide-based film, wherein the content of the filler is 1 part by weight to less than 40 parts by weight based on 100 parts by weight of the polyamide-based polymer solid content.
In paragraph 1,
A polyamide film, wherein the filler comprises inorganic particles having a hydrophobic surface treatment.
In paragraph 1,
A polyamide film, wherein the filler comprises silica surface-treated with a phenyl silane.
In paragraph 1,
A polyamide film having a transmittance of 89.5% or more.
In paragraph 1,
A polyamide film having a yellowness of 5 or less and a modulus of 5 GPa or more.
Containing a polyamide film and a functional layer,
The above polyamide film comprises a polyamide polymer and a filler,
The above polyamide polymer contains imide repeating units and amide repeating units in a molar ratio of 0:100 to 50:50,
The above amide repeating unit is derived from the polymerization of a diamine compound and a dicarbonyl compound.
The above diamine compound comprises a compound of the following chemical formula 1, and (E)e of the following chemical formula 1 is selected from the groups represented by the following chemical formulas 1-6b and 1-7b,
The above dicarbonyl compound comprises terephthaloyl chloride (TPC), isophthaloyl chloride (IPC) or a combination thereof,
Based on a thickness of 50 ㎛ of the above polyamide film, the loop stiffness measured for a film cut to a width of 15 mm (TD direction) and a length of 120 mm is 3 to 6 gf.
Cover window for a display device, wherein the haze of the polyamide film is 1% or less:
<Chemical Formula 1>


display section; and
A cover window disposed on the above display portion;
The above cover window comprises a polyamide film and a functional layer,
The above polyamide film comprises a polyamide polymer and a filler,
The above polyamide polymer contains imide repeating units and amide repeating units in a molar ratio of 0:100 to 50:50,
The above amide repeating unit is derived from the polymerization of a diamine compound and a dicarbonyl compound.
The above diamine compound comprises a compound of the following chemical formula 1, and (E)e of the following chemical formula 1 is selected from the groups represented by the following chemical formulas 1-6b and 1-7b,
The above dicarbonyl compound comprises terephthaloyl chloride (TPC), isophthaloyl chloride (IPC) or a combination thereof,
Based on a thickness of 50 ㎛ of the above polyamide film, the loop stiffness measured for a film cut to a width of 15 mm (TD direction) and a length of 120 mm is 3 to 6 gf.
A display device, wherein the haze of the polyamide film is 1% or less:
<Chemical Formula 1>


A step of preparing a polyamide polymer solution by polymerizing a diamine compound, a dicarbonyl compound, and optionally a dianhydride compound in an organic solvent;
A step of casting and drying the above polymer solution on a belt to produce a gel sheet; and
A step of heat treating the above gel sheet;
The above polyamide polymer solution contains a filler dispersed in an organic solvent,
The step of drying the above polymer solution is performed at a temperature of 60°C to 150°C for 5 to 60 minutes,
A method for manufacturing a polyamide film according to claim 1, wherein the step of heat-treating the gel sheet is performed by increasing the temperature at a rate of 1°C/min to 8°C/min in a temperature range of 80°C to 500°C.
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