TWI730820B - Polymer film - Google Patents

Abstract

Embodiments relate to a polymer film. The polymer film comprises a polymer resin selected from the group consisting of a polyamide-based resin and a polyimide-based resin and has a haze (HZ₀ ) before autoclave treatment of 3% or less and a ΔHZ₂₄ represented by Equation 1a of 500% or less.

Description

Polymer film

Field of invention

The embodiment relates to a polymer film that has excellent static flexural characteristics, folding characteristics, and transparency, and maintains excellent optical and mechanical properties under high temperature and high humidity.

Background of the invention

Polyimide-based resins, such as poly(amide-imide) (PAI), have excellent resistance to friction, heat and chemicals. Therefore, it is used in applications such as primary electrical insulation, coatings, adhesives, extrusion resins, heat-resistant paints, heat-resistant plates, heat-resistant adhesives, heat-resistant fibers, and heat-resistant films.

Polyimide is used in various fields. For example, polyimide is made in powder form and used as a coating for metals or magnetic wires. Polyimide is mixed with other additives, depending on its application. In addition, polyimide is used together with fluoropolymer as a paint for decoration and anti-corrosion. It also serves to bond the fluoropolymer to the metal substrate. In addition, polyimide is used to coat kitchen utensils, is used as a membrane for gas separation by virtue of its heat resistance and chemical resistance, and is used in natural gas wells to filter pollutants and impurities such as carbon dioxide and hydrogen sulfide.

In recent years, polyimide in the form of a film has been developed, which is relatively inexpensive and has excellent optical, mechanical and thermal characteristics. Such polyimide-based films can be applied to display materials for organic light-emitting diodes (OLED) or liquid crystal displays (LCD) and the like, as well as anti-reflection films, compensation films, and if To achieve retardation characteristics, it can be applied to retardation films.

Such polyimide-based films have the problem of forming barrier layers because their physical properties deteriorate under high temperature and high humidity environments. In order to solve this problem, additives that are resistant to moisture, such as clay, are introduced, in which case the optical properties or compatibility may be deteriorated.

In addition, such polyimide-based films have the problem of poor recoverability when they have been folded for a long period of time. When the recoverability is poor, there may be a problem of screen distortion when the film is applied to a foldable display and the like.

With the active development of foldable displays, flexible displays and the like in recent years, there is a continuing need for the development of features that return to the original state as much as possible when they have been folded for a long period of time and are subsequently unfolded, and features that are extremely resistant to repeated folding Films; and research on films that have excellent mechanical and optical properties while maintaining excellent physical properties under high temperature and high humidity environments.

SUMMARY The problem to be solved

The embodiment aims to provide a polymer film which has excellent static flexural characteristics, folding characteristics and transparency, and maintains excellent optical and mechanical properties under high temperature and high humidity. The solution to the problem

× 100 在等式1a中， HZ₀ 係指該薄膜在一高壓釜中處理之前的霧度， HZ₂₄ 係指該薄膜在一高壓釜中處理之後的霧度，且該高壓釜處理意謂一高壓釜填充有水且一薄膜在其中在120℃之溫度及1.2 atm之壓力下處理24小時。The polymer film according to an embodiment includes a polymer resin selected from the group consisting of: polyamide-based resin and polyimide-based resin, and the haze (HZ) before autoclave treatment ₀ ) is 3% or less, and ΔHZ ₂₄ expressed by the following equation 1a is 500% or less: [Equation 1a] ∆HZ ₂₄ (%) =

× 100 In equation 1a, HZ ₀ refers to the haze of the film before treatment in an autoclave, HZ ₂₄ refers to the haze of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours.

×100 在等式1b中， TS₀ 係指該薄膜在一高壓釜中處理之前的模數， TS₂₄ 係指該薄膜在一高壓釜中處理之後的模數，且該高壓釜處理意謂一高壓釜填充有水且一薄膜在其中在120℃之溫度及1.2 atm之壓力下處理24小時。The polymer film according to another embodiment comprises a polymer resin selected from the group consisting of: polyamide-based resin and polyimide-based resin, and the modulus before autoclave treatment ( MO ₀ ) is 5 GPa or more, and ∆TS ₂₄ expressed by the following equation 1b is 15% or less: [Equation 1b] ∆TS ₂₄ (%) =

×100 In Equation 1b, TS ₀ refers to the modulus of the film before treatment in an autoclave, TS ₂₄ refers to the modulus of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours.

The polymer film according to still another embodiment includes a polymer resin selected from the group consisting of: polyamide-based resin and polyimide-based resin; and butyric acid. Advantages of the present invention

The polymer film according to an embodiment not only has excellent static deflection characteristics, optical properties, and mechanical properties, but also maintains excellent optical properties and mechanical properties even under severe conditions of high temperature and high humidity.

In addition, the polymer film according to an embodiment has excellent recoverability when it has been folded for a long period of time and then returned to the unfolded state by releasing the force applied to the film. Therefore, when applied to foldable displays, flexible displays and the like, it can provide a uniform screen state.

In addition, the polymer film according to an embodiment has excellent folding characteristics, so that it can be advantageously applied to cover windows of display devices, foldable display devices, rollable display devices, or flexible mobile devices.

Detailed description of the preferred embodiment

Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings, so that those skilled in the art in the field to which the present invention relates can easily practice the embodiments. However, the embodiments can be implemented in many different ways and are not limited to those described herein.

Throughout this specification, when it is mentioned that each film, window, panel, layer or the like is formed "on" or "under" another film, window, panel, layer or the like, it means not only It means that one element is directly formed on or under another element, and it means that one element is formed on or under another element indirectly, and other elements (a plurality of) are interposed between these elements. In addition, the terms "up" or "down" for each element may be referred to in the drawings. For the purpose of description, the size of individual elements in the drawings may be exaggeratedly depicted, and the actual size is not indicated. In addition, throughout this specification, the same illustrated element symbols refer to the same elements.

Throughout this specification, when a part is referred to as "comprising" an element, it should be understood that, unless specifically stated otherwise, other elements may be included instead of excluding other elements.

In this specification, unless otherwise specified, the singular expression is interpreted as covering the singular or plural number interpreted in the context.

In addition, unless otherwise indicated, all numbers and expressions used herein related to the amounts of components, reaction conditions, and the like should be understood as modified by the term "about."

The terms first, second and the like are used herein to describe various elements, and the elements should not be limited by these terms. These terms are used only for the purpose of distinguishing one element from another element.

In addition, the term "substituted" as used herein means substitution with at least one substituent selected from the group consisting of deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, amine Group, formamidino group, hydrazine group, hydrazone group, ester group, keto group, substituted or unsubstituted alkyl group, substituted or unsubstituted alkenyl group, substituted or unsubstituted alkynyl group, substituted or unsubstituted alkynyl group, Substituted or unsubstituted alkoxy, substituted or unsubstituted alicyclic organic group, substituted or unsubstituted heterocyclic group, substituted or unsubstituted aryl group, and substituted or unsubstituted The heteroaryl. The substituents listed above may be connected to each other to form a ring. Polymer film

The embodiment provides a polymer film that has excellent static flexural characteristics, folding characteristics, optical characteristics, and mechanical characteristics, and maintains excellent optical characteristics and mechanical characteristics under high temperature and high humidity.

The polymer film according to an embodiment includes a polymer resin selected from the group consisting of polyamide-based resin and polyimide-based resin.

_{The haze (HZ 0} ) of the polymer film before the autoclave treatment is 3% or less.

Specifically, the haze (HZ ₀ ) of the polymer film before the autoclave treatment can be 2.5% or lower, 2.0% or lower, 1.5% or lower, 1.0% lower, 0.8% or lower or 0.6% or less, but it is not limited to this.

× 100 在等式1a中， HZ₀ 係指該薄膜在一高壓釜中處理之前的霧度， HZ₂₄ 係指該薄膜在一高壓釜中處理之後的霧度，且該高壓釜處理意謂一高壓釜填充有水且一薄膜在其中在120℃之溫度及1.2 atm之壓力下處理24小時。薄膜置於高壓釜中，該薄膜未浸沒於水中且其可經由水產生之蒸氣處理。 _{The ΔHZ 24} value of the polymer film expressed by the following equation 1a is 500% or less: [Equation 1a] ΔHZ ₂₄ (%) =

× 100 In equation 1a, HZ ₀ refers to the haze of the film before treatment in an autoclave, HZ ₂₄ refers to the haze of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the ∆HZ 24} value of the polymer film represented by the above equation 1a may be 400% or lower, 300% or lower, 250% or lower, or 200% or lower, but it is not limited to this .

_{If the haze (HZ 0} ) of the polymer film before the autoclave treatment _{and the ΔHZ 24} represented by the above equation 1a are within the above range, the film can have excellent durability, especially the optical properties hardly change, even at high temperatures And under severe conditions of high humidity. By virtue of these features, it can be advantageously applied to front panels and display devices used in displays.

The yellow index (YI ₀ ) of the polymer film before autoclave treatment is 3 or less.

Specifically, the yellow index (YI ₀ ) of the polymer film before the autoclave treatment may be 2.8 or less, or 2.7% or less, but it is not limited thereto.

The in-plane phase difference (Ro ₀ ) of the polymer film before the autoclave treatment is 180 nm or less.

Specifically, the in-plane phase difference (Ro ₀ ) of the polymer film before the autoclave treatment can be 170 nm or less, 160 nm or less, 150 nm or less, 10 nm to 160 nm, 20 nm to 160 nm, 50 nm to 160 nm, or 80 nm to 150 nm, but it is not limited thereto.

× 100 在等式2a中， YI₀ 係指該薄膜在一高壓釜中處理之前的黃色指數， YI₂₄ 係指該薄膜在一高壓釜中處理之後的黃色指數，且該高壓釜處理意謂一高壓釜填充有水且一薄膜在其中在120℃之溫度及1.2 atm之壓力下處理24小時。薄膜置於高壓釜中，該薄膜未浸沒於水中且其可經由水產生之蒸氣處理。 _{The ∆YI 24} value of the polymer film expressed by the following equation 2a is 30% or less: [Equation 2a] ∆YI ₂₄ (%) =

× 100 In Equation 2a, YI ₀ refers to the yellow index of the film before treatment in an autoclave, YI ₂₄ refers to the yellow index of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the ∆YI 24} value of the polymer film represented by the above equation 2a can be 25% or lower, 20% or lower, 15% or lower, 10% or lower or 5% or lower , But it is not limited to this.

× 100 在等式3a中， Ro₀ 係指該薄膜在一高壓釜中處理之前的平面內相位差， Ro₂₄ 係指該薄膜在一高壓釜中處理之後的平面內相位差，且該高壓釜處理意謂一高壓釜填充有水且一薄膜在其中在120℃之溫度及1.2 atm之壓力下處理24小時。薄膜置於高壓釜中，該薄膜未浸沒於水中且其可經由水產生之蒸氣處理。 _{The ∆Ro 24} value of polymer film expressed by the following equation 3a is 8% or less: [Equation 3a] ∆Ro ₂₄ (%) =

× 100 In Equation 3a, Ro ₀ refers to the in-plane phase difference of _{the film before being processed in an autoclave, Ro 24} refers to the in-plane phase difference of the film after being processed in an autoclave, and the autoclave Treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the ∆Ro 24} value of the polymer film represented by the above equation 3a may be 7% or lower, 6% or lower, 5% or lower, or 4.8% or lower, but it is not limited to this .

_{The haze (HZ 24} ) of the polymer film after being treated in an autoclave for 24 hours is 3% or less. The autoclave treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120° C. and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the haze (HZ 24} ) of the polymer film after being treated in an autoclave for 24 hours can be 2.5% or lower, 2.0% or lower, 1.8% or lower, or 1.6% or lower, but its Not limited to this.

_{The yellow index (YI 24} ) of the polymer film after being treated in the autoclave for 24 hours was 3 or less. The autoclave treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120° C. and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the yellow index (YI 24} ) of the polymer film after being processed in the autoclave for 24 hours may be 2.8 or less or 2.7 or less, but it is not limited thereto.

_{Specifically, if the yellow index (YI 24} ) of the polymer film after 24 hours of treatment in an autoclave exceeds the above range, the transparency deteriorates in a high temperature and high humidity environment, making the film unsuitable for use in front panels or display devices. In addition, since the screen is light blue and dark, it consumes more power to maintain a brighter screen to compensate for this problem.

_{The in-plane retardation (Ro 24} ) of the polymer film after being treated in an autoclave for 24 hours was 180 nm or less. The autoclave treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120° C. and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

_{Specifically, the in-plane phase difference (Ro 24} ) of the polymer film after being treated in an autoclave for 24 hours can be 160 nm or less, 150 nm or less, 145 nm or less, 20 nm to 160 nm, 40 nm to 150 nm or 60 nm to 145 nm, but it is not limited thereto.

In particular, since the polymer film according to an embodiment has a low ∆HZ ₂₄ value, a low ∆YI ₂₄ value, and a low ∆Ro ₂₄ value, it can maintain excellent optical properties under severe conditions of high temperature and high humidity. Therefore, it can be advantageously applied to a display device. Even when the display device to which the polymer film is applied is used in a high humidity or high temperature area, it is still possible to realize a transparent and clean screen.

In addition, since the polymer film according to an embodiment has HZ ₀ , YI ₀ , Ro ₀ , HZ ₂₄ , YI ₂₄ , Ro ₂₄ , ∆HZ ₂₄ , ∆YI ₂₄ and ∆Ro ₂₄ values within the above range, it is possible Not only achieves clean optical characteristics but also achieves excellent folding characteristics. Therefore, it can be advantageously applied to a foldable display device or a flexible mobile device.

The tensile strength (TS ₀ ) of the polymer film before autoclave treatment is 20 kgf/mm2 or more.

Specifically, the tensile strength (TS ₀ ) of the polymer film before the autoclave treatment is 20 kgf/mm² to 35 kgf/mm². Alternatively, the tensile strength (TS ₀ ) of the polymer film before the autoclave treatment may be 21 kgf/mm2 or more, but it is not limited thereto.

The elongation at break (EL ₀ ) of the polymer film before autoclave treatment is 15% or higher.

Specifically, the elongation at break (EL ₀ ) of the polymer film before autoclave treatment is 15% to 40%. Alternatively, the elongation at break (EL ₀ ) of the polymer film before the autoclave treatment may be 17% or higher, 18% or higher, 19% or higher, or 20% or higher, but it is not limited thereto .

_{The modulus (MO 0} ) of the polymer film before autoclave treatment is 5.0 GPa or more.

Specifically, the modulus (MO ₀ ) of the polymer film before autoclave treatment is 5 GPa to 10 GPa. Alternatively, the modulus (MO ₀ ) of the polymer film before the autoclave treatment may be 5.2 GPa or more, 5.3 GPa or more, or 5.5 GPa or more, but it is not limited thereto.

× 100The polymer film has a ΔTS ₂₄ value of 15% or less expressed by the following equation 1b. [Equation 1b] ∆TS ₂₄ (%) =

× 100

In Equation 1b, TS ₀ refers to the tensile strength of the film before treatment in an autoclave, TS ₂₄ refers to the tensile strength of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, TS ₂₄ is 20 kgf/mm2 or more.

In addition, the TS _{24 of the} polymer film may be 12% or lower, 10% or lower, or 8.5% or lower, but it is not limited thereto.

× 100The polymer film has a ΔEL ₂₄ value of 30% or less expressed by the following equation 2b. [Equation 2b] ∆EL ₂₄ (%) =

× 100

In Equation 2b, EL ₀ refers to the elongation at break of _{the film before treatment in an autoclave, EL 24} refers to the elongation at break of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, EL ₂₄ is 15% or higher. Alternatively, the EL ₂₄ may be 17% or higher or 20% or higher, but it is not limited thereto.

In addition, the EL ₂₄ value of the polymer film may be 28% or lower or 25% or lower, but it is not limited thereto.

× 100The polymer film has a ∆MO ₂₄ value of 15% or less expressed by the following equation 3b. [Equation 3b] ∆MO ₂₄ (%) =

× 100

In Equation 3b, MO ₀ refers to the modulus of the film before treatment in an autoclave, MO ₂₄ refers to the modulus of the film after treatment in an autoclave, and the autoclave treatment means an autoclave Filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, MO ₂₄ is 15% or higher. Alternatively, the MO ₂₄ may be 5 GPa or more, 5.1 GPa or more, 5.5 GPa or 6.0 GPa or more, but it is not limited thereto.

In addition, the MO ₂₄ value of the polymer film may be 12% or lower or 10% or lower, but it is not limited thereto.

The ∆SUM ₂₄ value of polymer film is 60% or lower. Here, ΔSUM ₂₄ value represents _{24, ΔEL 24} and the sum of the value of ΔTS of ΔMO _24.

Specifically, the ΔSUM ₂₄ value of the polymer film may be 50% or lower, 40% or lower, or 35% or lower, but it is not limited thereto.

Since ΔTS polymer film _{24, ΔEL 24, ΔMO 24} and ΔSUM ₂₄ value satisfies the above range, the film also has excellent durability even under high temperature and high humidity, and the physical properties hardly deformed. Therefore, it can be advantageously applied to front panels and display devices.

× 100The polymer film has a ΔTS ₇₂ value of 60% or less expressed by the following equation 4b. [Equation 4b] ∆TS ₇₂ (%) =

× 100

In Equation 4b, TS ₀ refers to the tensile strength of the film before treatment in an autoclave, TS ₇₂ refers to the tensile strength of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 72 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, the TS ₇₂ is 5 kgf/mm2 or more, 8 kgf/mm2 or more, or 9 kgf/mm2 or more.

In addition, the TS ₇₂ value of the polymer film may be 50% or lower, 40% or lower, or 30% or lower, but it is not limited thereto.

× 100 _{The ΔEL 72} value of the polymer film expressed by the following equation 5b is 50% or lower. [Equation 5b] ∆EL ₇₂ (%) =

× 100

In Equation 5b, EL ₀ refers to the elongation at break of _{the film before treatment in an autoclave, EL 72} refers to the elongation at break of the film after treatment in an autoclave, and the autoclave treatment means a The autoclave was filled with water and a film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 72 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, the EL ₇₂ value is 8% or higher, 10% or higher, or 12% or higher.

In addition, the Δ EL ₇₂ value of the polymer film can be 45% or lower or 40% or lower, but it is not limited to this.

× 100The polymer film has a ∆MO ₇₂ value of 60% or less expressed by the following equation 6b. [Equation 6b] ∆MO ₇₂ (%) =

× 100

In Equation 6b, MO ₀ refers to the modulus of the film before treatment in an autoclave, MO ₇₂ refers to the modulus of the film after treatment in an autoclave, and the autoclave treatment means an autoclave Filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 72 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

Specifically, the MO ₇₂ value is 2 GPa or more or 2.5 GPa or more.

In addition, the ΔMO ₇₂ value of the polymer film can be 50% or lower, 40% or lower, 30% or lower, or 20% or lower, but it is not limited thereto.

The ∆SUM ₇₂ value of polymer film is 160% or lower. Here, ΔSUM ₇₂ is represented, and the sum of the values of ΔEL ΔMO ₇₂ of _{72 ΔTS 72.}

Specifically, the ΔSUM ₇₂ value of the polymer film can be 150% or lower, 120% or lower, 100% or lower, or 90% or lower, but it is not limited thereto.

Since ΔTS of polymeric film _{72, ΔEL 72, ΔMO 72} and ΔSUM ₇₂ value satisfies the above range, the film also has excellent durability even under high temperature and high humidity, and the physical properties hardly deformed. Therefore, it can be advantageously applied to front panels and display devices.

When the polymer film according to an embodiment based on a thickness of 50 μm is folded to have a radius of curvature of 3 mm, the number of folds before breaking is 100,000 times or more.

When the film is folded to have a radius of curvature of 3 mm and then unfolded, the number of folds is counted as one.

Since the number of folds of the polymer film satisfies the above range, it can be advantageously applied to a foldable display device or a flexible display device.

When the polymer film according to another embodiment based on a thickness of 50 μm is folded to have a radius of curvature of 2 mm, the number of folds before breaking is 200,000 times or more.

When the film is folded to have a radius of curvature of 2 mm and then unfolded, the number of folds is counted as one.

The polymer film according to an embodiment has therein a residual solvent content of 2,500 ppm or less or 1,200 ppm or less.

For example, the residual solvent content can be 2,200 ppm or less, 2,000 ppm or less, 1,800 ppm or less, 1,500 ppm or less, 1,000 ppm or less, 800 ppm or less, 500 ppm or less , 1 ppm to 1,000 ppm, 1 ppm to 800 ppm, 1 ppm to 500 ppm, 5 ppm to 1,000 ppm, 10 ppm to 1,000 ppm, or 20 ppm to 1,000 ppm, but it is not limited thereto.

The residual solvent content refers to the amount of solvent that did not volatilize during the film production and continues to exist in the final film.

If the residual solvent content in the polymer film exceeds the above range, the durability and optical properties of the film under high temperature and high humidity conditions may be deteriorated, which may especially affect the subsequent processing of the film. Specifically, if the residual solvent content exceeds the above range, the hydrolysis of the film is accelerated, resulting in deterioration of mechanical properties or optical properties. In addition, if the residual solvent content in the polymer film exceeds the above range, the durability of the film may be deteriorated, which may affect the static flexural characteristics and folding characteristics as described above.

The IS value of the polymer film according to an embodiment is represented by the following equation 7 from 5 to 160. [Equation 7] IS = IM +

In Equation 7, IM represents the molar number of the amide repeating unit when the total molar number of the amide repeating unit and the amide repeating unit in the film is 100; and RS represents the residue in the film Solvent content (ppm).

For example, the IS value may be 5 to 150, 10 to 150, 30 to 150, 50 to 150, 5 to 80, 5 to 60, or 5 to 50, but it is not limited thereto.

If the IS value of the polymer film satisfies the above range, the film can have excellent optical properties and durability even under severe conditions of high temperature and high humidity, and have excellent folding characteristics.

In particular, if the content of imine (IM) or the content of residual solvent (RS) is high and exceeds the above range, the long-term durability of the film rapidly deteriorates. In general, if the content of imine is too high and the content of amide is thus relatively reduced, the hygroscopicity of the film will be reduced, making it likely to be vulnerable to damage under high humidity conditions.

×

在等式8中， HZ₀ 係指該薄膜在一高壓釜中處理之前的霧度，The CT value of the polymer film represented by the following equation 8 is 10 or less. [Equation 8] CT =

X

In Equation 8, HZ ₀ refers to the haze of the film before being processed in an autoclave,

HZ ₂₄ refers to the haze of the film after treatment in an autoclave, and the autoclave treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120° C. and a pressure of 1.2 atm for 24 hours. The film is placed in an autoclave, the film is not immersed in water and it can be treated with steam generated by water.

In addition, Ro ₀ refers to the in-plane phase difference of the film before being processed in an autoclave.

CT can be an index indicating heat resistance/moisture resistance, which reflects crystallinity. The higher the crystallinity of the polymer film, the _{lower the ΔHZ 24} may be. That is, the higher the crystallinity of the polymer film, the higher the heat resistance/moisture resistance of the polymer film. The higher the crystallinity of the polymer film, the higher the in-plane retardation (Ro ₀ ) of the polymer film may be and the lower the optical properties may be.

Since the polymer film is prepared with the proper composition in the proper manufacturing process, it can have enhanced optical properties and enhanced heat resistance/moisture resistance. For example, polymer films are prepared with relatively high amide content, low residual solvent content, additives such as butyric acid, and in appropriate manufacturing processes (such as drying steps and heat treatment steps). Therefore, the polymer film can reduce the ΔHZ ₂₄ and at the same time reduce the in-plane phase difference.

Therefore, the CT value can be 10 or less. CT can be 8 or less. CT can be 6 or less. CT can be 4 or less. CT can be 4 or less. CT can be 3 or less. CT can be 2 or less.

Since the polymer film has a low CT value, it can have enhanced heat resistance/humidity resistance and enhanced optical properties. Therefore, the polymer film can be advantageously used for displays. In particular, the polymer film can be advantageously applied to mobile display devices that are sensitive to harsh external conditions (such as moisture and/or heat). In particular, the polymer film can be advantageously applied to the front panel of a foldable display.

In addition to the polymer resin, the polymer film according to an embodiment contains butyric acid.

The polymer film according to an embodiment includes a polymer resin and butyric acid. The polymer resin includes polymer resins selected from the group consisting of polyamide-based resins and polyimide-based resins. The polymer film includes a polymer resin, and the polymer resin includes a plurality of imine repeating units.

Butyric acid is represented by the following formula T. [Formula T]

Specifically, butyric acid refers to the compound represented by formula T above. It does not refer to a partially substituted form of butyric acid, derivatives, salts or anhydrides of butyric acid.

The polymer film contains butyric acid, and based on the total weight of the polymer film, the butyric acid contained in the film is in an amount of 1 ppm to 1,200 ppm.

Specifically, butyric acid can be contained in the film in the following amounts: 1 ppm to 1,000 ppm, 5 ppm to 1,000 ppm, 10 ppm to 1,000 ppm, 50 ppm to 1,000 ppm, 100 ppm to 1,000 ppm, 500 ppm to 1,000 ppm, 1 ppm to 800 ppm, 1 ppm to 700 ppm, 1 ppm to 500 ppm, 1 ppm to 300 ppm, 10 ppm to 300 ppm, 30 ppm to 300 ppm, or 50 ppm to 270 ppm, but it is not limited thereto.

The content refers to the amount of solvent that did not volatilize during film production and the amount of butyric acid that continues to exist in the final film produced.

If the content of butyric acid in the polymer film exceeds the above range, there may be a problem that some substances may dissolve on the film after autoclave treatment, which quickly increases the film haze.

The butyric acid may be the residue of butyric acid added as a pH adjuster in the process of preparing the film, or may be a by-product produced by other reactions, but it is not limited thereto. That is, the butyric acid that continues to exist in the final film may be produced by various processes.

Since butyric acid continues to exist in the polymer film, the film has excellent recoverability and excellent folding characteristics when the film has been folded for a long period of time and then returned to the unfolded state by releasing the force applied to the film. Therefore, it can be advantageously applied to foldable displays, flexible displays, rollable displays and the like.

If the content of butyric acid that continues to exist in the polymer film exceeds the above range, the static flexural characteristics and folding characteristics of the film may be degraded, and optical properties such as transmittance and yellow index may also be degraded.

When the polymer film according to an embodiment based on a thickness of 50 μm is folded to have a radius of curvature of 2 mm, and then the film is allowed to stand at 25°C for 24 hours, and the force applied to the film is released, the inner angle of the film is 120° Or bigger.

Specifically, when the polymer film according to an embodiment based on a thickness of 50 μm is folded to have a radius of curvature of 2 mm, and then the film is allowed to stand at 25° C. for 24 hours, and the force applied to the film is released, the inside of the film The angle may be 125° or more, 130° or more, or 135° or more, but it is not limited thereto.

The conventional film is easily damaged by external pressure. In particular, it deforms significantly when it has been folded for a long period of time. Therefore, when applied to a display device, it does not display a uniform screen state, resulting in a problem of screen distortion. Specifically, when a conventional film based on a thickness of 50 μm is folded to have a radius of curvature of 2 mm, and then the film is allowed to stand at 25°C for 24 hours, and the force applied to the film is released, the inner angle of the film is less than 120°, Specifically, it is less than 115°, resulting in deterioration of static deflection characteristics.

In contrast, since the polymer film according to an embodiment has an internal angle of 120° or more after the above test, it ensures excellent recoverability compared to conventional films. When it undergoes subsequent manufacturing processes (for example, it is applied to a foldable display or a flexible display), the problem of screen distortion is solved.

In another embodiment, the polymer film is stretched at a stretching ratio of 1.01 to 1.15 times in the MD direction.

If the stretch ratio of the polymer film in the MD direction according to an embodiment satisfies the above range, it will hardly deform when it has been folded for a long period of time and then returns to the unfolded state by releasing the force applied to the film, and the folding characteristic is extremely Good, and excellent durability against physical shocks. Specifically, stretching causes crystallization in the film through orientation, thereby making it possible to obtain a film with excellent flex resistance.

If the stretch ratio of the polymer film in the MD direction according to an embodiment exceeds the above range, the recoverability of the film is particularly deteriorated, and it is difficult to achieve desired physical properties.

Polyamide-based resins are resins containing repeating units of amides. Polyimine-based resins are resins containing repeating units of imines.

In addition, a resin containing an amide repeating unit and an amide repeating unit may be referred to as a polyimide-based resin and may be referred to as a polyimide-based resin.

For example, the polymer resin may be a resin containing a polyimide-based resin, a resin containing a polyimide-based resin, or a polyimide-based resin and a polyimide-based resin. The main resin is the resin of both.

The polymer film according to an embodiment includes a polymer resin prepared by polymerizing a diamine compound, a dianhydride compound, and optionally a dicarbonyl compound.

As an example, the molar ratio of the dianhydride compound to the dicarbonyl compound is 2:98 to 50:50, 5:95 to 50:50, 10:90 to 50:50, 2:98 to 25:75, 2 : 98 to 15:85, 20:80 to 100:0, 25:75 to 100:0, 30:70 to 100:0, 40:60 to 100:0, or 50:50 to 100:0.

If the molar ratio of the dianhydride compound to the dicarbonyl compound is within the above range, a film with excellent optical properties and high durability in a high temperature and high humidity environment can be obtained. In addition, it is possible to obtain a transparent film having excellent recoverability and excellent folding characteristics when it has been folded for a long period of time and then returned to the unfolded state by releasing the force applied to the film.

As another example, the dianhydride compound may be composed of one, two or more types, and the dicarbonyl compound may be composed of zero, one, two or more types.

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

Here, the polymer resin may contain amide repeating units and amide repeating units in the following molar ratios: 2:98 to 50:50, 5:95 to 50:50, 10:90 to 50:50, 2: 98 to 25:75, 2:98 to 15:85, 20:80 to 100:0, 25:75 to 100:0, 30:70 to 100:0, 40:60 to 100:0 or 50:50 to 100:0, but it is not limited to this.

The diamine compound is a compound that forms an amide bond with the dianhydride compound and forms an amide bond with the dicarbonyl compound to thereby form a copolymer.

在式1中，The diamine compound is not particularly limited, but it may be, for example, an aromatic diamine compound containing an aromatic structure. For example, the diamine compound may be a compound represented by Formula 1 below. [Formula 1]

In Equation 1,

E can be selected from substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic groups, substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic groups, 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, substituted or unsubstituted C ₂ -C ₃₀ alkynylene, -O-, -S-, -C(=O)-, -CH(OH )-, -S(=O) ₂ -, -Si(CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) ₂ -.

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

_{(E) e} in Formula 1 can be selected from the groups represented by the following Formulae 1-1a to 1-14a, but it is not limited thereto.

Specifically, (E) _e in Formula 1 can be selected from the groups represented by the following Formulas 1-1b to 1-13b, but it is not limited thereto.

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

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 composed of a compound having a fluorine-containing substituent. In such cases, the fluorine-containing substituent may be a fluorinated hydrocarbon group and specifically may be a trifluoromethyl group. But it is not limited to this.

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

For example, the diamine compound may include 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) represented by the following formula, but it is not limited thereto.

Alternatively, the diamine compound may include TFMB and 4,4'-oxydiphenylamine (ODA), but it is not limited thereto.

The dianhydride compound has a low birefringence value, so that it can contribute to enhancing the optical properties of the polymer resin-containing film, such as transmittance. Polymer resin refers to a resin containing imidine repeating units.

The dianhydride compound is not particularly limited, but it may be, for example, an aromatic dianhydride compound containing an aromatic structure or an alicyclic dianhydride compound containing an alicyclic structure.

For example, the aromatic dianhydride compound may be a compound represented by Formula 2 below. [Equation 2]

In formula 2, G can be bonded by a bonding group selected from the group consisting of: substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic cyclic group, substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic ring group, substituted or unsubstituted tetravalent C ₆ -C ₃₀ aromatic ring group, substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaromatic ring group, wherein the aliphatic ring Group, heteroaliphatic ring group, aromatic ring group or heteroaromatic ring group may exist alone or may be bonded to each other to form a condensed ring, substituted or unsubstituted C ₁ -C ₃₀ alkylene, substituted or Unsubstituted C ₂ -C ₃₀ alkenylene, substituted or unsubstituted C ₂ -C ₃₀ alkynylene, -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 can be selected from the groups represented by the following Formulae 2-1a to 2-9a, but it is not limited thereto.

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

In addition, the alicyclic dianhydride compound may include a compound having a cyclobutane structure. Specifically, the alicyclic dianhydride compound may be cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), but it is not limited thereto.

In another embodiment, the dianhydride compound may include a compound having a fluorine-containing substituent, a compound having a biphenyl group, a compound having a keto group, or a compound having a cyclobutane group.

The dianhydride compound may be composed of a compound having a fluorine-containing substituent. In such cases, the fluorine-containing substituent may be a fluorinated hydrocarbon group and specifically may be a trifluoromethyl group. But it is not limited to this.

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

For example, the dianhydride compound may include 2,2'-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) represented by the following formula, but it is not limited thereto.

The diamine compound and the dianhydride compound can be polymerized to form polyamide acid.

Subsequently, the polyimide can be converted into polyimine through a dehydration reaction, and the polyimine includes an imine repeating unit.

Polyimine can form a repeating unit represented by the following formula A. [Formula A]

In formula A, E, G, and e are as described above.

For example, the polyimide may include a repeating unit represented by the following formula A-1, but it is not limited thereto. [Formula A-1]

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

在式3中，The dicarbonyl compound is not particularly limited, but it may be, for example, a compound represented by Formula 3 below. [Equation 3]

In Equation 3,

J can be selected from substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic group, substituted or unsubstituted divalent C ₄ -C ₃₀ heteroaliphatic cyclic group, 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, substituted or unsubstituted C ₂ -C ₃₀ alkynylene, -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 of 1 to 5. When j is 2 or greater, 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 it is not limited thereto.

_{(J) j} in Formula 3 can be selected from the groups represented by the following Formulae 3-1a to 3-14a, but it is not limited thereto.

Specifically, (J) _j in Formula 3 can be selected from the groups represented by the following Formulae 3-1b to 3-8b, but it is not limited thereto.

More specifically, (J) _j in Formula 3 may be a group represented by the above formula 3-1b, a group represented by the above formula 3-2b, a group represented by the above formula 3-3b, or a group represented by the above formula 3-3b or The group represented by formula 3-8b.

In one embodiment, one type of dicarbonyl compound or a mixture of at least two types of dicarbonyl compounds different from each other can be used as the dicarbonyl compound. If two or more dicarbonyl compounds are used, at least two dicarbonyl compounds in which (J) _j in the above formula 3 is selected from the groups represented by the above formulas 3-1b to 3-8b can be used as the dicarbonyl group Compound.

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

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

The first dicarbonyl compound and the second dicarbonyl compound may be aromatic dicarbonyl compounds, respectively.

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

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

If the first dicarbonyl compound and the second dicarbonyl compound are respectively aromatic dicarbonyl compounds, they include a benzene ring. Therefore, it can contribute to the improvement of the mechanical properties (such as surface hardness and tensile strength) of the resulting polyamide-imide resin-containing film.

The dicarbonyl compound may include terephthaloyl chloride (TPC), 1,1'-biphenyl-4,4'-dicarbonyl dichloride (BPDC), isophthaloyl chloride (IPC) as represented by the following formula, or Its combination. But it is not limited to this.

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

If BPDC is used as the first dicarbonyl compound and TPC is used as the second dicarbonyl compound in an appropriate combination, the resulting film containing polyamide-imide resin can have high oxidation resistance.

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

If IPC is used as the first dicarbonyl compound and TPC is used as the second dicarbonyl compound in an appropriate combination, the resulting film containing polyamide-imide resin can not only have high oxidation resistance, but also It is also economical to reduce costs.

The diamine compound and the dicarbonyl compound can be polymerized to form a repeating unit represented by the following formula B. [Formula B]

In formula B, E, J, e, and j are as described above.

For example, diamine compounds and dicarbonyl compounds can be polymerized to form amide repeating units represented by the following formulas B-1 and B-2.

Alternatively, the diamine compound and the dicarbonyl compound may be polymerized to form amide repeating units represented by the following formulas B-2 and B-3. [Formula B-1]

In formula B-1, x is an integer from 1 to 400. [Formula B-2]

In formula B-2, y is an integer from 1 to 400. [Formula B-3]

[式B]

在式A及B中， E及J各自獨立地選自經取代或未經取代之二價C₆ -C₃₀ 脂族環基、經取代或未經取代之二價C₄ -C₃₀ 雜脂族環基、經取代或未經取代之二價C₆ -C₃₀ 芳族環基、經取代或未經取代之二價C₄ -C₃₀ 雜芳族環基、經取代或未經取代之C₁ -C₃₀ 伸烷基、經取代或未經取代之C₂ -C₃₀ 伸烯基、經取代或未經取代之C₂ -C₃₀ 伸炔基、-O-、-S-、-C(=O)-、-CH(OH)-、-S(=O)₂ -、-Si(CH₃ )₂ -、-C(CH₃ )₂ -及C(CF₃ )₂ -， e及j各自獨立地選自1至5之整數， 當e為2或更大時，則二個或更多個E彼此相同或不同， 當j為2或更大時，則二個或更多個J彼此相同或不同，In formula B-3, y is an integer from 1 to 400. According to an embodiment, the polymer resin may include a repeating unit represented by the following formula A and optionally a repeating unit represented by the following formula B: [Formula A]

[Formula B]

In formulas A and B, E and J are each independently selected from substituted or unsubstituted divalent C ₆ -C ₃₀ aliphatic cyclic groups, substituted or unsubstituted divalent C ₄ -C ₃₀ heterolipids Group ring group, 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, substituted or unsubstituted C ₂ -C ₃₀ alkenylene, substituted or unsubstituted C ₂ -C ₃₀ alkynylene, -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 each independently selected from an integer of 1 to 5. When e is 2 or greater, then two or more Es are the same or different from each other, and when j is 2 or greater, then two or more J are the same or different from each other,

G can be bonded by a bonding group selected from: substituted or unsubstituted tetravalent C ₆ -C ₃₀ aliphatic ring group, substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaliphatic ring Group, substituted or unsubstituted tetravalent C ₆ -C ₃₀ aromatic ring group, substituted or unsubstituted tetravalent C ₄ -C ₃₀ heteroaromatic ring group, of which aliphatic ring group, heteroaliphatic The cyclic group, aromatic ring group or heteroaromatic ring group may exist alone or may be bonded to each other to form a fused ring, substituted or unsubstituted C ₁ -C ₃₀ alkylene, substituted or unsubstituted C ₂ -C ₃₀ alkenylene, substituted or unsubstituted C ₂ -C ₃₀ alkynylene, -O-, -S-, -C(=O)-, -CH(OH)-, -S( =O) ₂ -, -Si(CH ₃ ) ₂ -, -C(CH ₃ ) ₂ -and -C(CF ₃ ) ₂ -.

The polymer resin may comprise the repeating unit represented by the following formula A and the repeating unit represented by the following formula B in the following molar ratios: 2:98 to 50:50, 5:95 to 50:50, 10:90 to 50: 50, 2:98 to 25:75, 2:98 to 15:85, 20:80 to 100:0, 25:75 to 100:0, 30:70 to 100:0, 40:60 to 100:0 or 50:50 to 100:0, but it is not limited to this.

If the molar ratio of the repeating unit represented by the above formula A to the repeating unit represented by the above formula B is within the above range, the polymer film has excellent folding characteristics and excellent optical and mechanical properties under high temperature and high humidity.

Specifically, the CONH structure and the OH group present in the repeating unit represented by the above formula B have high affinity, thereby exhibiting excellent hygroscopicity for attracting moisture, thereby having sliding properties. Therefore, it is possible to realize a film that hardly deteriorates mechanical properties and optical properties under high temperature and high humidity.

According to another embodiment, the polymer film may further include a filler.

The filler may be at least one selected from the group consisting of barium sulfate, silicon dioxide, and calcium carbonate. Since the polymer film contains fillers, it is possible not only to enhance roughness and windability, but also to enhance the effect of improving scratches caused by sliding during film preparation.

In addition, the particle size of the filler may be 0.01 μm to 1.0 μm or 0.01 μm to less than 1.0 μm. For example, the particle size of the filler may be 0.05 μm to 0.9 μm, 0.1 μm to 0.8 μm, 0.1 μm to 0.5 μm, or 0.1 μm to 0.3 μm, but it is not limited thereto.

Based on the total weight of the polymer film, the polymer film may include a filler in an amount of 0.01 to 3.5% by weight, 0.01 to 3% by weight, or 0.01 to 2.5% by weight.

The transmittance of the polymer film can be 80% or higher. For example, the transmittance may be 85% or higher, 88% or higher, 89% or higher, 80% to 99%, 85% to 99%, or 88% to 99%.

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

The haze of the polymer film is 2% or lower, specifically, the haze can be 1.8% or lower, 1.5% or lower, 1% or lower, 0.8% or lower or 0.5% or lower , But it is not limited to this.

The modulus of the polymer film is 4.0 GPa or more, 4.2 GPa or more, 4.5 GPa or more, or 5.0 GPa or more. Specifically, the modulus may be 5.5 GPa or more, 6.0 GPa or more, 6.2 GPa or more, or 6.0 GPa to 8.0 GPa, but it is not limited thereto.

The compressive strength of the polymer film is 0.3 kgf/micron or more. Specifically, the compressive strength may be 0.4 kgf/μm or more, 0.45 kgf/μm or more, or 0.48 kgf/μm or more, but it is not limited thereto.

When the polymer film is perforated with a 2.5 mm spherical tip in the UTM compression mode at a rate of 10 mm/min, the maximum diameter (mm) of the perforation including cracks is 65 mm or less. Specifically, the maximum diameter of the perforation may be 60 mm or less, 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 it is not limited to this.

The surface hardness of the polymer film is HB or higher. Specifically, the surface hardness may be H or higher, or 2H or higher, but it is not limited thereto.

The tensile strength of the polymer film is 14 kgf/mm2 or more. Specifically, the tensile strength can be 15 kgf/mm2 or more, 16 kgf/mm2 or more, 18 kgf/mm2 or more, 20 kgf/mm2 or more, 21 Kilogram force/square millimeter or more or 22 kilogram force/square millimeter or more, but it is not limited thereto.

The elongation of the polymer film is 13% or higher. Specifically, the elongation may be 15% or higher, 16% or higher, 17% or higher, or 17.5% or higher, but it is not limited thereto.

The polymer film according to an embodiment can ensure excellent optical properties in terms of low haze and yellow index (YI), and in terms of high modulus, compressive strength, maximum perforation diameter, surface hardness, tensile strength and elongation In terms of efficiency, it has excellent mechanical properties, excellent folding characteristics, and excellent optical and mechanical properties under high temperature and high humidity. Therefore, it is possible to impart long-term stable mechanical properties and optical properties to a substrate that requires flexibility in terms of modulus, elongation, tensile characteristics, elastic restoring force, and flexural resistance.

The physical properties of the polymer film as described above are based on a thickness of 40 µm to 60 µm or a thickness of 70 µm to 90 µm. For example, the physical properties of polymer films are based on a thickness of 50 μm or a thickness of 80 μm.

The components and characteristics of the polymer film as described above can be combined with each other.

In addition, the properties of the polymer film as described above are achieved by combining the chemical and physical properties of the components constituting the polymer film with the conditions in each step of the process for preparing the polymer film as described below. the result of. For the front panel of the monitor

The front panel for a display according to an embodiment includes a polymer film and a functional layer.

The polymer film includes a polymer resin selected from the group consisting of polyamide-based resins and polyimide-based resins.

_{The haze (HZ 0} ) of the polymer film according to an embodiment before autoclave treatment is 3% or lower, and the ΔHZ ₂₄ value represented by the above equation 1a is 500% or lower.

_{The modulus (MO 0} ) of the polymer film according to another embodiment before the autoclave treatment is 5 GPa or more, and the ΔTS ₂₄ represented by the above equation 1b is 15% or less.

A polymer film according to still another embodiment includes a polymer resin and butyric acid.

The details of the polymer film are as described above.

The front panel can be advantageously applied to a display device.

The polymer film has excellent folding characteristics and can maintain excellent optical and mechanical properties even under severe conditions of high temperature and high humidity. In particular, the functional layer, not to mention the polymer film, has excellent folding characteristics, so that the front panel can be advantageously 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 front panel disposed on the display unit, wherein the front panel includes a polymer film.

In addition, the polymer film includes polymer resins selected from the group consisting of polyamide-based resins and polyimide-based resins.

_{The haze (HZ 0} ) of the polymer film according to an embodiment before autoclave treatment is 3% or lower, and the ΔHZ ₂₄ value represented by the above equation 1a is 500% or lower.

_{The modulus (MO 0} ) of the polymer film according to another embodiment before the autoclave treatment is 5 GPa or more, and the ΔTS ₂₄ represented by the above equation 1b is 15% or less.

A polymer film according to still another embodiment includes a polymer resin and butyric acid.

The details of the polymer film and the front panel are as described above.

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

Specifically, FIG. 1 shows a display device, which includes a display unit (400) and a front panel (300) disposed on the display unit (400), wherein the front panel includes a first side (101) and a second side (102). ) Polymer film (100) and functional layer (200), and an adhesive layer (500) inserted between the display unit (400) and the front panel (300).

The display unit (400) is used to display images, and it can have flexibility.

The display unit (400) can be a display panel for displaying images. For example, it can be a liquid crystal display panel or an organic electroluminescence display panel. The organic electroluminescence display panel may include a front polarizer and an organic EL panel.

The front polarizer can be placed on the front side of the organic EL panel. Specifically, the front polarizer can be attached to the side of the organic EL panel on which the image is displayed.

The organic EL panel displays images through the self-emission of the pixel unit. The organic EL panel may include an organic EL substrate and a driving substrate. The organic EL substrate may include a plurality of organic electroluminescence units, each of which corresponds to one pixel. Specifically, it may include a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and an anode. The driving substrate is operatively coupled to the organic EL substrate. That is, the driving substrate can be coupled to the organic EL substrate to apply a driving signal (such as a driving current) so that the driving substrate can drive the organic EL substrate by applying current to the respective organic electroluminescence unit.

In addition, the adhesive layer (500) can be inserted between the display unit (400) and the front panel (300). The adhesive layer may be an optically transparent adhesive layer, but it is not particularly limited.

The front panel (300) is arranged on the display unit (400). The front panel is located at the outermost position of the display device to thereby protect the display unit.

The front panel (300) may include a polymer film and a functional layer. The functional layer can be at least one selected from the group consisting of a hard coat layer, a layer that reduces reflectivity, an anti-fouling layer, and an anti-glare layer. The functional layer can be coated on at least one side of the polymer film. Process for preparing polymer film

An embodiment provides a process for preparing a polymer film.

According to an embodiment, the process for preparing a polymer film includes preparing a polymer solution containing a polymer resin selected from the group consisting of: polyamide-based resin and polyimide-based resin in an organic solvent The resin; transfer the polymer solution to the tank; extrude and cast the polymer solution in the tank and then dry it to prepare the gel sheet; and heat the gel sheet, wherein the heat treatment of the gel sheet is performed, Until the residual solvent content is 1,200 ppm or less.

According to another embodiment, the process for preparing a polymer film includes polymerizing a diamine compound, a dianhydride compound, and a dicarbonyl compound in an organic solvent in a polymerization apparatus to prepare a polymer solution containing a polymer resin; The solution is transferred to the tank; the polymer solution in the tank is extruded and cast and then dried to prepare a gel flake; and the gel flake is heat-treated, wherein the heat treatment of the gel flake is in the range of 80°C to 500°C The temperature for 5 to 180 minutes.

According to another embodiment, the process for preparing a polymer film includes preparing a polymer solution containing a polymer resin in an organic solvent; transferring the polymer solution to a tank; casting the polymer solution in the tank onto the transmission belt and then It is dried to prepare a gel sheet; and while the gel sheet is moved, it is heat-treated to prepare a cured film.

Referring to FIG. 2, the process for preparing a polymer film includes mixing a diamine compound, a dianhydride compound, and optionally a dicarbonyl compound in an organic solvent simultaneously or sequentially in a polymerization apparatus, and reacting the mixture to prepare a polymer Solution (S100); transfer the polymer solution to the tank (S200); purge with inert gas (S300); cast the polymer solution in the tank onto the transmission belt and then dry it to prepare a gel sheet (S400 ); heat the gel sheet while moving it to prepare a solidified film (S500); cool it while moving the solidified film (S600); and wind the cooled solidified film using a winder (S700).

The polymer film contains as a main component a polymer resin selected from the group consisting of polyamide-based resin and polyimide-based resin.

In the process used to prepare polymer films, the polymer solution used to prepare polymer resins is prepared by mixing diamine compounds and dicarbonyl compounds, or diamine compounds, dianhydride compounds, and dicarbonyl compounds in an organic The solvent is mixed simultaneously or sequentially, and the mixture is reacted to prepare (S100).

In one embodiment, the polymer solution can be prepared by simultaneously mixing and reacting the diamine compound, the dianhydride compound, and the dicarbonyl compound in an organic solvent.

In another embodiment, the step of preparing the polymer solution may include mixing and reacting the diamine compound and the dianhydride compound in a solvent to produce a polyamide acid solution; and subjecting the polyamide acid solution to dehydration to produce Polyimide (PI) solution.

In still another embodiment, the step of preparing the polymer solution may include first, mixing and reacting the diamine compound and the dianhydride compound in a solvent to produce a polyamide acid (PAA) solution; and second, mixing The polyamide acid (PAA) solution and the dicarbonyl compound are mixed and allowed to react to form an amide bond and an amide bond. The polyamic acid solution is a solution containing polyamic acid.

Alternatively, the step of preparing the polymer solution may include first, mixing the diamine compound and the dianhydride compound in a solvent and allowing them to react to produce a polyamide acid solution; subjecting the polyamide acid solution to dehydration to produce polyamide An imine (PI) solution; and second, the polyimine (PI) solution and the dicarbonyl compound are mixed and reacted to further form an amide bond. The polyimine solution is a solution containing a polymer having repeating units of the imine.

In still another embodiment, the step of preparing the polymer solution may include first, mixing and reacting the diamine compound and the dicarbonyl compound in a solvent to produce a polyamide (PA) solution; The amide (PA) solution and the dianhydride compound are mixed and allowed to react to further form an amide bond. The polyamide solution is a solution containing a polymer having repeating units of amide.

The polymer solution thus prepared may be a solution containing a polymer containing at least one selected from the group consisting of: polyamide acid (PAA) repeating unit, polyamide (PA) repeating unit, and polyimide (PI) Repeating unit.

For example, the polymer contained in the polymer solution may include an imine repeating unit derived from the polymerization of a diamine compound and a dianhydride compound.

Alternatively, the polymer contained in the polymer solution may include an amide repeating unit derived from the polymerization of a diamine compound and a dianhydride compound, and an amide repeating unit derived from the polymerization of a diamine compound and a dicarbonyl compound.

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

If the solid content contained in the polymer solution is within the above range, the polymer film can be effectively produced in the extrusion and casting steps. In addition, the polymer film thus prepared maintains a clean appearance and transparency, while ensuring a specific range of optical sliding index, maximum static friction coefficient and dynamic friction coefficient, resulting in excellent anti-stick properties. In addition, it can have excellent mechanical properties and optical properties (such as low yellowness) that hardly deteriorate even under high temperature and high humidity, hardly deform when a certain level of load is continuously applied for a long period of time, and has excellent folding characteristics. good.

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

Here, the catalyst may include at least one selected from the group consisting of β picoline, acetic anhydride, isoquinoline (IQ), and pyridine-based compounds, but it is not limited thereto.

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

Alternatively, the catalyst may be added in an amount of 0.01 to 0.3% by weight based on the total weight of the polymer solution. Specifically, the catalyst may be added in an amount of 0.01 to 0.2% by weight, 0.01 to 0.15% by weight, 0.01 to 0.1% by weight, or 0.02 to 0.1% by weight based on the total weight of the polymer solution, but it is not limited thereto.

Further addition of a catalyst can speed up the reaction rate and enhance the chemical bonding force between or within the repeating unit structure. In addition, it is possible to prepare a thin film with a low yellow index by using a catalyst.

In one embodiment, the step of preparing the polymer solution may further include introducing a dehydrating agent.

In such cases, the dehydrating agent may be acetic anhydride, but it is not limited thereto.

The dehydrating agent may be added in an amount of 0.01 to 10% by weight, 0.05 to 5% by weight, or 0.05 to 3% by weight based on the total weight of the polymer solution, but it is not limited thereto.

Adding a dehydrating agent produces the effect of preparing a film with low yellowness and low haze.

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

Specifically, the step of preparing the polymer solution may include (a) simultaneously or sequentially mixing and reacting the diamine compound, the dianhydride compound, and optionally the dicarbonyl compound in an organic solvent to prepare the first polymer solution ; (B) Measure the viscosity of the first polymer solution and evaluate whether it has reached the target viscosity; and (c) if the viscosity of the first polymer solution does not reach the target viscosity, further add a dianhydride compound or a dicarbonyl compound to prepare A second polymer solution with target viscosity.

The target viscosity can 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 cps to 250,000 cps, but it is not limited thereto.

In the steps of preparing the first polymer solution and the second polymer solution, the viscosity of the polymer solutions are different from each other. For example, the viscosity of the second polymer solution is higher than the viscosity of the first polymer solution.

In the steps of preparing the first polymer solution and the second polymer solution, the stirring speeds are different from each other. For example, the stirring speed when preparing the first polymer solution is faster than the stirring speed when preparing the second polymer solution.

In still 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 can be adjusted to 4 to 7, for example, 4.5 to 7, or 4.5 to less than 7, but it is not limited thereto.

The pH of the polymer solution can be adjusted by adding a pH adjuster. The pH adjuster is not particularly limited and may include, for example, amine-based compounds such as alkoxyamines, alkylamines, and alkanolamines, and carboxylic acid-based compounds such as acetic acid and butyric acid.

If the pH of the polymer solution is adjusted to the above range, it is possible to prevent damage to the equipment in the subsequent process, prevent defects in the film produced by the polymer solution, and achieve the required optics in terms of yellow index and modulus Characteristics and mechanical characteristics. In addition, recoverability and folding characteristics may be enhanced.

The pH adjuster may be added in an amount of 0.01 to 0.7% by weight, 0.01 to 0.5% by weight, or 0.02 to 0.4% by weight based on the total weight of the polymer solution, but it is not limited thereto.

Alternatively, the pH adjusting agent may be added in an amount of 0.1 mol% to 10 mol% based on the total mol of monomers in the polymer solution.

Specifically, if the catalyst is added during the preparation of the polymer solution, chemical imidization or thermal imidization using the catalyst is performed. If the catalyst is used in an appropriate amount, a transparent film with a low yellow index can be prepared. On the other hand, when a catalyst is used, by-products may be generated, or some physical properties may be deteriorated. In such cases, the pH adjuster can improve the deterioration of physical properties. For example, butyric acid can be used as a pH adjuster. A part of butyric acid continues to exist in the final film, which makes it possible to obtain a transparent film with excellent recoverability and excellent folding characteristics when it has been folded for a long period of time and then returned to the unfolded state by releasing the force applied to the film .

In many cases, chlorine end groups derived from monomers used to produce polymer resins or Cl-based by-products produced by HCl generated during the process for preparing films reduce the reactivity, thereby producing Low molecular weight polymer. However, if butyric acid is used as a pH adjuster, the reactivity of the catalyst is effectively adjusted to reduce the amount of polymers with low molecular weight and facilitate polymerization to achieve high molecular weight.

In addition, there has been a problem that the low-molecular-weight polymer remaining in the polymer dissolves after the autoclave treatment (that is, after the treatment under severe conditions of high temperature and high humidity), thereby rapidly deteriorating the optical characteristics. In addition, there has been a problem of forming barrier layers in conventional polymer films in high temperature and high humidity environments. In order to solve this problem, additives that are resistant to moisture, such as clay, are introduced, in which case the optical properties or compatibility may be deteriorated.

In contrast, as in a polymer film according to an embodiment, adding butyric acid during the polymerization process can solve the above-mentioned problems. It is possible to obtain a polymer film that hardly deteriorates in optical and mechanical properties even under severe conditions of high temperature and high humidity and has excellent folding characteristics.

In another embodiment, the step of preparing the polymer solution may further include purging with an inert gas. The step of purging with an inert gas can remove moisture, reduce impurities, increase the reaction yield, and impart excellent surface appearance and mechanical properties to the final film.

The inert gas can 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 it is not limited to this. Specifically, the inert gas may be nitrogen.

The molar ratio of the dianhydride compound to the dicarbonyl compound used to prepare the polymer solution may be 2:98 to 15:85. For example, the molar ratio can be 3:97 to 15:85, 5:95 to 15:85, 7:93 to 15:85, 2:98 to 25:75, 2:98 to 15:85, 20 : 80 to 100:0, 25:75 to 100:0, 30:70 to 100:0, 40:60 to 100:0, or 50:50 to 100:0, but it is not limited thereto.

If the dianhydride compound and the dicarbonyl compound are used in the above molar ratio, it is beneficial to realize the required mechanical and optical properties of the polymer film prepared from the polymer solution.

The details of the diamine compound, the dianhydride compound, and the dicarbonyl compound are as described above.

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

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

Fig. 3 schematically shows a process equipment for preparing a polymer film according to an embodiment. Referring to FIG. 3, the polymer solution as described above is prepared in the polymerization apparatus (10), and the polymer solution thus produced is transferred to and stored in the tank (20).

Here, once the polymer solution has been prepared, the step of transferring the polymer solution to the tank is performed without any additional steps. Specifically, the polymer solution prepared in the polymerization apparatus is transferred to and stored in the tank without any independent precipitation and redissolution steps for removing impurities. In the conventional process, in order to remove impurities generated during the preparation of the polymer solution, such as hydrochloric acid (HCl), the polymer solution thus prepared is purified through a separate step to remove the impurities, and then the purified polymer solution is redissolved In the solvent. However, in this case, there has been a problem of increased loss of active ingredients in the step of removing impurities, resulting in a decrease in yield.

Therefore, the preparation process according to an embodiment finally minimizes the amount of impurities generated in the step of preparing the polymer solution, or appropriately controls the impurities in the subsequent steps (even if there is a certain amount of impurities), so as to avoid making the final film The physical properties are degraded. Therefore, the process has advantages because the thin film is produced without a separate precipitation or re-dissolution step.

The tank (20) is a place for storing the polymer solution before forming the polymer solution into a film, and its internal temperature can 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 it is not limited thereto.

If the internal temperature of the tank (20) is controlled within the above range, it is possible to prevent the polymer solution from deteriorating during storage, and it is possible to reduce the moisture content to thereby prevent film defects caused by it.

The process for preparing the polymer film may further include vacuum degassing the polymer solution transferred to the tank (20).

Vacuum degassing can be carried out after the internal pressure of the tank is reduced to 0.1 bar to 0.7 bar for 30 minutes to 3 hours. Vacuum degassing under these conditions can reduce bubbles in the polymer solution. Therefore, it is possible to prevent surface defects of the film produced therefrom and achieve excellent optical characteristics such as haze.

In addition, the process for preparing the polymer film may further include purging the polymer solution (S300) transferred to the tank (20) with an inert gas.

Specifically, the purge is performed by purging the tank with an inert gas under an internal pressure of 1 atm to 2 atm. Nitrogen purging under these conditions can remove the moisture in the polymer solution, reduce impurities to thereby increase the reaction yield, and achieve excellent optical properties (such as haze) and mechanical properties.

The inert gas can 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 it is not limited to this. Specifically, the inert gas may be nitrogen.

The step of vacuum degassing and the step of purging the tank with inert gas are carried out in separate steps.

For example, a step of vacuum degassing can be performed, followed by a step of purging the tank with an inert gas, but it is not limited to this.

The step of vacuum degassing and/or the step of purging the groove with an inert gas can improve the physical properties of the polymer film surface produced thereby.

Thereafter, the process may further include storing the polymer solution in the tank (20) for 1 hour to 360 hours. Here, the temperature inside the tank can be maintained at -20°C to 20°C.

The process for preparing the polymer film may further include extruding and casting the polymer solution in the tank, and then drying it to prepare a gel sheet (S400).

The polymer solution can be cast onto a casting body, such as a casting roll or a casting drive belt.

3, according to an embodiment, a polymer solution can be applied to a casting belt (30) as a casting body, and it can be dried while being moved to make it into a sheet in the form of a gel .

When the polymer solution is injected onto the transmission belt (30), the injection rate can be 300 g/min to 700 g/min. If the injection rate of the polymer solution satisfies the above range, the gel sheet can be uniformly molded to an appropriate thickness.

In addition, the casting thickness of the polymer solution can be 200 µm to 700 µm. If the polymer solution is cast to a thickness within the above range, the final film produced after drying and heat treatment can have an appropriate and uniform thickness.

As described above, the viscosity of the polymer solution at room temperature may be 100,000 cps to 500,000 cps, for example, 100,000 cps to 400,000 cps, 100,000 cps to 350,000 cps, 150,000 cps to 350,000 cps, or 150,000 cps to 250,000 cps. If the viscosity meets the above range, the polymer solution can be cast on the transmission belt with a uniform thickness without defects.

The polymer solution is cast, and then dried at a temperature of 60°C to 150°C for 5 minutes to 60 minutes to prepare a gel sheet. Specifically, the drying can be performed with hot air at 60°C to 120°C for 10 minutes to 50 minutes. For example, the drying can be performed with hot air at 100°C for 30 minutes.

The solvent of the polymer solution is partially or completely volatilized during drying to prepare a gel sheet.

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

The process for preparing the polymer film includes heat-treating the gel sheet while moving it to prepare a cured film (S500).

Referring to Figure 3, the heat treatment of the gel sheet can be carried out by passing it through a thermosetting device (40).

The heat treatment of the gel sheet is performed at a temperature in the range of 80°C to 500°C for 5 minutes to 180 minutes. Specifically, the heat treatment of the gel sheet can be performed at a temperature rise rate of 2°C/min to 80°C/min at a temperature in the range of 80°C to 500°C for 5 minutes to 150 minutes. More specifically, the heat treatment of the gel sheet can be performed at a temperature rise rate of 2°C/min to 80°C/min at a temperature in the range of 80°C to 300°C.

According to another embodiment, the gel flakes may be treated with hot air.

If hot air is used for heat treatment, heat can be supplied uniformly. If heat is not supplied uniformly, satisfactory mechanical properties cannot be achieved. In particular, satisfactory surface roughness cannot be achieved, which may increase or decrease the surface tension too much.

For example, the gel sheet can be treated with hot air at a temperature in the range of 200°C to 320°C for 5 minutes to 60 minutes. More specifically, the gel sheet can be treated with hot air at a temperature in the range of 250°C to 290°C for 25 minutes to 35 minutes.

According to still another embodiment, the heat treatment of the gel sheet can be performed in two or more steps.

According to another embodiment, heat treatment may be performed until the residual solvent content contained in the gel sheet is 1,200 ppm or less or 1,000 ppm or less.

In the heat treatment, the second heat treatment step is performed after the first heat treatment step. In such cases, if the organic solvent content in the gel sheet exceeds 1,000 ppm or 1,200 ppm after the second heat treatment step, the third heat treatment step may be additionally performed.

Specifically, the heat treatment may include a first heat treatment step in the range of 60°C to 120°C for 5 to 30 minutes; and a second heat treatment step in the range of 150°C to 350°C for 30 minutes to 120 minutes.

For example, the third heat treatment step may be performed in the range of 200°C to 350°C until the residual solvent content contained in the gel sheet is 1,200 ppm or less or 1,000 ppm or less.

In addition, in the heat treatment step, the gel sheet may be stretched 1.01 times to 1.05 times in the MD direction. Between the first heat treatment step and the second heat treatment step, the gel sheet may be stretched 1.01 times to 1.05 times in the MD direction.

In the heat treatment step, the gel sheet may be stretched 1.01 times to 1.05 times in the TD direction. In the second heat treatment step, the gel sheet may be stretched 1.01 times to 1.05 times in the TD direction.

The gel sheet can be stretched 1.01 times to 1.05 times in the MD and TD directions at the same time. The gel sheet may be sequentially stretched 1.01 times to 1.05 times in the MD direction, and then stretched 1.01 times to 1.05 times in the TD direction.

Heat treatment under these conditions can cure the gel sheet to have appropriate surface hardness and modulus, and the cured film prepared therefrom may have excellent folding characteristics, excellent optical and mechanical properties under high temperature and high humidity, and has grown It has excellent recoverability when folded for a period of time and then released the force applied to the film.

The process for preparing the polymer film involves cooling the film while moving it (S600).

Referring to Figure 3, the cooling of the cured film is performed after it has passed through the thermosetting device (40). This can be done by using an independent cooling chamber (not shown) or by forming an appropriate temperature atmosphere without an independent cooling chamber.

The step of cooling while moving the solidified film may include a first cooling step of lowering the temperature at a rate of 100°C/min to 1,000°C/min, and reducing the temperature at a rate of 40°C/min to 400°C/min The second cooling step.

In such cases, specifically, the second cooling step is performed after the first cooling step. The cooling rate in the first cooling step may be faster than the cooling rate in the second cooling step.

For example, the maximum rate of the first cooling step is faster than the maximum rate of the second cooling step. Alternatively, the minimum rate of the first cooling step is faster than the minimum rate of the second cooling step.

If the step of cooling the cured film is performed in such a multi-stage manner, it is possible to further stabilize the physical properties of the cured film and maintain the optical and mechanical properties of the film realized during the curing step more stably for a long period of time.

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

The process for preparing the polymer film includes winding the cooled solidified film using a winder (S700).

Referring to Figure 3, the cooled solidified film can be wound using a roll winder (50).

In such cases, the ratio of the moving speed of the gel sheet on the drive belt during drying to the moving speed of the cured film during winding may be 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, 1:1.0 to 1:1.05, or 1:1.01 to 1:1.05, but it is not limited thereto.

If the ratio of the moving speed is outside the above range, the mechanical properties of the cured film may be impaired, and the flexibility and elastic properties may be deteriorated.

In the process for preparing the polymer film, the thickness difference (%) according to the following equation 1 can be 3% to 30%. Specifically, the thickness difference (%) may be 5% to 20%, but it is not limited thereto. [Equation 1] Thickness difference (%) = {(M1-M2)/M2} × 100

In Equation 1 above, M1 is the thickness (μm) of the gel sheet, and M2 is the thickness (μm) of the solidified film cooled during winding.

The polymer film prepared by the preparation process as described above has excellent anti-adhesion characteristics, optical characteristics and mechanical characteristics. The polymer film can be applied to various applications requiring flex resistance, flexibility, durability, and transparency. For example, polymer films can be applied to solar cells, semiconductor devices, sensors and the like, and display devices.

The details of the polymer film prepared by the process for preparing the polymer film are as described above.

Hereinafter, the above description will be described in detail by referring to examples. However, these examples are set forth to illustrate the present invention, and the scope of the present invention is not limited thereto. Examples and evaluation examples Example 1a

In a nitrogen atmosphere at 20°C, a 1 liter glass reactor equipped with a temperature-controllable double jacket was charged with dimethylacetamide (DMAc) as an organic solvent. Subsequently, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) (0.2 mol) was slowly added thereto to dissolve it. Subsequently, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) (0.1 mol) was slowly added thereto, and the mixture was stirred for 1 hour. Subsequently, terephthaloyl chloride (TPC) (0.1 mol) as a dicarbonyl compound was added, and then the mixture was stirred for 1 hour, thereby preparing a polymer solution.

Subsequently, 17 g of acetic anhydride as a dehydrating agent and 4.5 g of isoquinoline as a catalyst were added to the polymer solution, followed by stirring for 1 hour. Thereafter, butyric acid as a pH adjuster was added, followed by stirring for 2 hours to prepare a polymer solution.

The polymer solution thus obtained was coated on a glass plate and then dried with hot air at 100°C for 30 minutes. It was then detached from the glass plate and then fixed to the pin frame, and heat-treated at 270°C for 30 minutes to obtain a polymer film with a thickness of 50 μm. Examples 2a and 3a and Comparative Examples 1a and 2a

The film was prepared in the same manner as in Example 1a, except that the type and content of the respective reactants and the like were changed as shown in Table 1 below.

The films prepared in Examples 1a to 3a and Comparative Examples 1a and 2a were each measured and evaluated for the following characteristics. The results are shown in Table 1 below. Evaluation example 1a: Measurement of film thickness

A digital micrometer 547-401 manufactured by Mitutoyo Corporation was used to measure the thickness at 5 points in the lateral direction. The average value is used as the thickness. Evaluation example 2a: Measurement of residual solvent content in the film

In a thermogravimetric analyzer (DTG-50 manufactured by Shimadzu Corporation), the temperature was increased from room temperature to 300°C at a temperature increase rate of 15°C/min in a nitrogen stream, and maintained at 300°C for 30 minutes. The value obtained by dividing the sum of the weight lost during the temperature increase from 150°C to 300°C and maintaining at 300°C for 30 minutes by the initial weight of the sample is regarded as the residual solvent content in the film. Evaluation example 3a: Measurement of the content of butyric acid in the film

TD-GC MS analysis was used to measure the butyric acid content in the film. Specifically, 0.02 g of the film sample was loaded into the sample tube, and it was heated from 25°C to 300°C at a rate of 10°C/min. The gas generated as the temperature rises is adsorbed into the adsorption tube (Tenax), which is instantaneously heated (desorbed) and separated into components by gas chromatography. The separated components are detected on the mass spectrometer, and the type and content of the components in the obtained chromatogram are analyzed.

The butyric acid content is measured in ppm based on the total weight of the film. The results are shown in Table 1 below. Evaluation example 4a: Measurement of transmittance and haze

The transmittance at 550 nm is measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Kogyo. Evaluation Example 5a: Measurement of Yellow Index

The yellow index (YI) was measured with a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) using the CIE colorimetric system. Evaluation example 6a: Measurement of in-plane phase difference

The in-plane phase difference (Ro) is measured with a phase difference measuring device (Axoscan of Axometrics, measuring wavelength: 550 nm). In addition, the refractive index, which is the basic data for measuring the phase difference, was measured by Abbe refractometry (NAR-4T manufactured by Atago Co., Ltd., measurement wavelength: 589.3 nm). Evaluation example 7a: autoclave treatment

A film with a length of 10 cm, a width of 2 cm and a thickness of 50 μm was fixed in an autoclave, the autoclave was filled with 2 liters of water, and the autoclave was then closed and heated. In such cases, the temperature of the autoclave was set to 120°C and the pressure was increased to 1.2 atm for 24 hours of treatment. After the set time has elapsed, the autoclave is automatically closed. After the outlet valve is opened, the film is taken out and the physical properties are measured. The film is not immersed in water. Evaluation Example 8a: Measurement of Flexural Resistance

The number of folds is counted when a film with a thickness of 50 μm is folded to have a radius of curvature of 3 mm and then unfolded (the fold count is one after folding and unfolding). If no deformation is visually observed at the folded side after repeated folding 100,000 times, its indication is ○. If deformation is visually observed at the folded side after repeated folding 100,000 times, its indication is x. The number of times of folding is counted using YUASA U-shaped folding equipment. [Table 1] Example 1a Example 2a Example 3a Comparative example 1a Comparative example 2a composition Diamine (mole) TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 Dianhydride (mole) 6FDA 0.1 6FDA 0.02 CBDA 0.05 6FDA 0.05 6FDA 0.1 6FDA 0.02 Dicarbonyl compound (mole) TPC 0.1 IPC 0.06 TPC 0.12 TPC 0.1 TPC 0.1 IPC 0.06 TPC 0.12 Amide: Amide ratio (mole ratio) 50:50 10:90 50:50 50:50 10:90 Film thickness (µm) 50 50 50 50 50 Residual solvent content in the film (ppm) 950 850 735 1350 1520 Butyric acid content in film (ppm) 1000 1000 700 - - IS value 145 95 123.5 185 162 Transmittance % 90.1 90.3 89.5 90.1 90.2 Haze (HZ ₀ ) % 0.41 0.53 0.52 0.42 0.56 Yellow index (HZ ₀ ) - 2.3 2.5 2.7 2.3 2.5 In-plane phase difference (Ro ₀ ) nm 150 135 95 200 185 After autoclave treatment (24 hours) Haze (HZ ₂₄ ) % 1.22 1.53 1.15 3.58 4.31 ∆HZ ₂₄ % 197.56 188.68 121.15 752.38 669.64 Yellow Index (YI ₂₄ ) - 2.3 2.6 2.7 3 3.2 ∆YI ₂₄ % 0 4 0 30.43 28 In-plane phase difference (Ro ₂₄ ) nm 143 140 101 220 195 ∆Ro ₂₄ % 4.67 3.70 6.32 10 5.41 Flexural resistance 3R, 100K ○ ○ ○ X X CT value - 2.96 2.55 1.15 15.05 12.39

As can be seen from Table 1 above, the polymer films of Examples 1a to 3a have a residual solvent content of 1,200 ppm or less in the film, and a butyric acid content of 1,200 ppm or less. Therefore, it maintains excellent optical properties even after being processed under severe conditions of high temperature and high humidity.

In contrast, the polymer films of Comparative Examples 1a and 2a have no residual butyric acid in the film, and the residual solvent content exceeds 1,200 ppm. The low-molecular-weight polymer remaining in the polymer dissolves after autoclave treatment. Therefore, optical characteristics such as haze, yellowness, and in-plane phase difference are significantly deteriorated. Example 1b

In a nitrogen atmosphere at 20°C, a 1 liter glass reactor equipped with a temperature-controllable double jacket was charged with 585.68 g of dimethylacetamide (DMAc) as an organic solvent. Subsequently, 0.2 mol of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) was slowly added thereto to dissolve it. Thereafter, 0.02 mol of 3,3',4,4'-diphenyl ketone (BTDA) was slowly added, followed by stirring for 1 hour. Subsequently, 0.06 mol isophthaloyl chloride (IPC) was added, followed by stirring for 1 hour. Furthermore, 0.12 mol of terephthalochloride (TPC) was added, followed by stirring for 1 hour, thereby preparing a polymer solution. The polymer solution thus obtained was coated on a glass plate and then dried with hot air at about 80°C for 20 minutes to prepare a gel sheet. The gel sheet is detached from the glass plate and then fixed to the stitch frame. The dried gel sheet is fixed to the stitch frame while being stretched 1.03 times in the first direction and in the second direction perpendicular to the first direction. The fixed gel sheet was heat-treated at about 270°C for 30 minutes to obtain a polymer film with a thickness of 50 μm.

Regarding the contents of TFMB, BTDA, TPC and IPC, the molar numbers of dianhydride compounds and dicarbonyl compounds based on 100 molar diamine compounds are shown in Table 2. Examples 2b to 6b and Comparative Examples 1b to 3b

The film was prepared in the same manner as in Example 1b, except that the type and content of the respective reactants, the heat treatment time, and the like were changed as shown in Table 2 below.

The films prepared in Examples 1b to 6b and Comparative Examples 1b to 3b were each measured and evaluated for the following characteristics. The results are shown in Table 2 below. Evaluation example 1b: Measurement of film thickness

A digital micrometer 547-401 manufactured by Mitutoyo Corporation was used to measure the thickness at 5 points in the lateral direction. The average value is used as the thickness. Evaluation example 2b: Measurement of residual solvent in the film

A sample of 0.02 g was taken and it was purged using a Purge & Trap-GC/MSD device at 30°C for 1 hour. The degassing was collected at 300°C for 10 minutes, which was subjected to quantitative and qualitative analysis to measure the amount of residual solvent. Evaluation example 3b: Measurement of tensile strength and elongation at break

Cut the sample at least 5 cm in the direction perpendicular to the main shrinking direction of the film and 10 cm in the main shrinking direction. It is fixed in the universal testing machine Instron UTM 5566A with clips placed at intervals of 10 cm. The stress-strain curve is obtained while the sample is stretched at a rate of 12.5 mm/min at room temperature until the sample breaks. Measure the tensile strength and elongation at break from the stress-strain curve. Evaluation example 4b: Measurement of modulus

Cut the sample at least 5 cm in the direction perpendicular to the main shrinking direction of the film and 10 cm in the main shrinking direction. It is fixed in the universal testing machine Instron UTM 5566A with clips placed at intervals of 5 cm. The stress-strain curve is obtained while the sample is stretched at a rate of 5 mm/min at room temperature until the sample breaks. The slope of the load relative to the initial strain on the stress-strain curve is regarded as the modulus (GPa). Evaluation example 5b: autoclave treatment

A film with a length of 10 cm, a width of 2 cm and a thickness of 50 μm was fixed in an autoclave, the autoclave was filled with 2 liters of water, and the autoclave was then closed and heated. In such cases, the temperature of the autoclave is set to 120°C and the pressure is increased to 1.2 atm for 24 hours or 72 hours of treatment. After the set time has elapsed, the autoclave is automatically closed. After the outlet valve is opened, the film is taken out and the physical properties are measured. The film is not immersed in water. Evaluation example 6b: Measurement of transmittance

The transmittance at 550 nm is measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Kogyo. Evaluation Example 7b: Measurement of Yellow Index

The yellow index (YI) was measured with a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) using the CIE colorimetric system. Evaluation Example 8b: Measurement of Flexural Resistance

When a polymer film with a thickness of 50 μm is folded to have a radius of curvature of 3 mm and then unfolded, the number of folds is counted (the number of folds is counted as one after folding and unfolding). If it does not break after 100,000 repeated foldings, its indication is ○. If it breaks before 100,000 repeated foldings, its indication is x. The number of times of folding is counted using YUASA U-shaped folding equipment. [Table 2] Example 1b Example 2b Example 3b Example 4b Example 5b Example 6b Comparative example 1b Comparative example 2b Comparative example 3b composition Diamine TFMB 100 TFMB 80 ODA 20 TFMB 65 ODA 35 TFMB 100 TFMB 80 ODA 20 TFMB 100 TFMB 100 TFMB 80 ODA 20 TFMB 65 ODA 35 Dianhydride BTDA 10 6FDA 15 6FDA 7 BTDA 10 6FDA 15 6FDA 10 6FDA 90 6FDA 80 6FDA 60 BPDA 40 Dicarbonyl compound TPC 60 IPC 30 TPC 55 IPC 30 TPC 50 IPC 43 TPC 60 IPC 30 TPC 55 IPC 30 TPC 75 SD 15 TPC 10 TPC 20 - Amide: Amide 10:90 15:85 7:93 10:90 15:85 10:90 90:10 80:20 100:0 Residual solvent in the film (ppm) 150 340 300 100 1250 1420 80 100 750 IS value 25 49 37 20 140 152 98 90 175 Tensile strength (TS ₀ ) Kgf/square millimeter twenty one twenty four 25 twenty one twenty four 27 25 27 twenty two Elongation at break (EL ₀ ) % 20 twenty one 20 20 twenty one 18 20 30 twenty four Modulus (MO ₀ ) GPa 6.3 7.2 5.6 6.3 7.2 7.1 4.8 6.2 7.2 After autoclave treatment (24 hours) Tensile strength (TS ₂₄ ) Kgf/square millimeter 20 twenty two 20 twenty two 25 26 25 twenty two 15 ∆TS ₂₄ % 4.76 8.33 4.76 8.33 0 3.70 0 18.52 31.82 Elongation at break (EL ₂₄ ) % 25 20 25 20 18 17 20 18 16 ∆EL ₂₄ % 25 4.76 25 4.76 10 5.56 0 40 33.33 Modulus (MO ₂₄ ) GPa 6.1 6.5 6.1 6.5 5.1 6.5 4.2 5.9 6.5 ∆MO ₂₄ % 3.17 9.72 3.17 9.72 8.93 8.45 12.5 4.84 9.72 ∆SUM ₂₄ 32.94 22.82 32.94 22.82 18.93 17.71 12.5 63.36 74.87 After autoclave treatment (72 hours) Tensile strength (TS ₇₂ ) Kgf/square millimeter 16 twenty two 9 twenty two twenty four 26 19 11 8 ∆TS ₇₂ % 23.81 8.33 57.14 8.33 4 3.7 twenty four 59.26 63.64 Elongation at break (EL ₇₂ ) % 27 17 12 17 20 17 8 15 6 ∆EL ₇₂ % 35 19.05 40 19.05 0 5.56 60 50 75 Modulus (MO ₇₂ ) GPa 5.1 5.9 2.6 5 4.6 6.1 3 3.5 3.4 ∆MO ₇₂ % 19.05 18.06 58.73 30.56 17.86 14.08 37.5 43.55 52.78 ∆SUM ₇₂ 77.86 45.44 155.87 57.94 21.86 23.34 121.5 152.81 191.41 Transmittance % 89 89.2 88.7 89 89.2 90.1 89.5 90.3 88.1 YI - 3.8 2.7 3.2 3.8 5.6 3 2.6 3.5 4.2 Process 80°C (minutes) 20 15 15 10 8 15 15 15 15 270°C (minutes) 30 30 30 15 12 30 25 30 15 Flexural resistance 3R, 100K ○ ○ ○ ○ ○ ○ X X X

As can be seen from Table 2 above, when the polymer films of Examples 1b to 6b undergo repeated folding and reach a radius of curvature of 3 mm, the number of folds before breaking is 100,000 times or more.

In addition, the yellow index and transmittance of the polymer films of Examples 1b to 6b are excellent, not to mention excellent folding characteristics.

In addition, the polymer films of Examples 1b to 6b have high mechanical properties, such as tensile strength, elongation at break and modulus, and maintain excellent mechanical properties even after being treated for a certain period of time under severe conditions of high temperature and high humidity . Example 1c

In a nitrogen atmosphere at 20°C, a 1 liter glass reactor equipped with a temperature-controllable double jacket was charged with dimethylacetamide (DMAc) as an organic solvent. Subsequently, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) was slowly added thereto to dissolve it. Subsequently, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) was slowly added thereto, and the mixture was stirred for 1 hour. Subsequently, terephthalochloride (TPC) was added, followed by stirring for 2 hours.

Subsequently, pyridine as a catalyst and acetic anhydride as a dehydrating agent are added to the polymer solution. In addition, butyric acid as a pH adjuster was added, followed by stirring for 2 hours to prepare a polymer solution.

The polymer solution thus obtained was coated on a glass plate and then dried with hot air at 80°C for 30 minutes. Subsequently, the gel sheet was dried at a temperature in the range of 80°C to 300°C at a temperature increase rate of 2°C/min to obtain a polymer film with a thickness of 50 μm.

Regarding the content of diamine compound (TFMB), dianhydride compound (6FDA) and dicarbonyl compound (TPC), the molar numbers are shown in Table 3.

In addition, the content of the added catalyst (pyridine) and butyric acid is converted based on the total weight of the polymer solution, and is shown in Table 3. Examples 2c to 5c and Comparative Examples 1c to 3c

The film was prepared in the same manner as in Example 1c, except that the type and content of the respective reactants and the like were changed as shown in Table 3 below. In addition, butyric acid was not added in Comparative Examples 1c to 3c.

The films prepared in Examples 1c to 5c and Comparative Examples 1c to 3c were each measured and evaluated for the following characteristics. The results are shown in Table 3 below. Evaluation example 1c: Measurement of the content of butyric acid in the film

TD-GC MS analysis was used to measure the butyric acid content in the film. Specifically, 0.02 g of the film sample was loaded into the sample tube, and it was heated from 25°C to 300°C at a rate of 10°C/min. The gas generated as the temperature rises is adsorbed into the adsorption tube (Tenax), which is instantaneously heated (desorbed) and separated into components by gas chromatography. The separated components are detected on the mass spectrometer, and the type and content of the components in the obtained chromatogram are analyzed.

The butyric acid content is measured in ppm based on the total weight of the film. The results are shown in Table 3 below. Evaluation example 2c: Evaluation of deformation angle (static deflection test)

A polymer film with a width of 20 mm, a length of 150 mm, and a thickness of 50 μm was folded to have a radius of curvature of 2 mm, and then the film was allowed to stand at 25° C. for 24 hours, and the force applied to the film was released. Subsequently, the inner angle of the film was measured. Evaluation Example 3c: Evaluation of Folding

A film with a thickness of 50 μm is subjected to repeated folding to have a radius of curvature of 2 mm, and then unfolded (after folding and unfolding, the number of folds is counted as one). The folding speed is 60 rpm. If it does not break after repeated folding 200,000 times, it is indicated as qualified. If it breaks before repeated folding 200,000 times, it is indicated as unqualified. The number of times of folding is counted using YUASA U-shaped folding equipment. Evaluation example 4c: Measurement of transmittance

The transmittance at 550 nm is measured using a haze meter NDH-5000W manufactured by Nippon Denshoku Kogyo. Evaluation Example 5c: Measurement of Yellow Index

The yellow index (YI) was measured with a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory) using the CIE colorimetric system. Evaluation example 6c: measurement of modulus

Cut the sample at least 5 cm in the direction perpendicular to the main shrinking direction of the film and 10 cm in the main shrinking direction. It is fixed in the universal testing machine Instron UTM 5566A with clips placed at intervals of 5 cm. The stress-strain curve is obtained while the sample is stretched at a rate of 5 mm/min at room temperature until the sample breaks. The slope of the load relative to the initial strain on the stress-strain curve is regarded as the modulus (GPa). [table 3] Example 1c Example 2c Example 3c Example 4c Example 5c Comparative example 1c Comparative example 2c Comparative example 3c Diamine compound (mole) TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 TFMB 0.2 Dianhydride compound (mole) 6FDA 0.1 6FDA 0.2 6FPA 0.15 BPDA 0.05 6FDA 0.05 CBDA 0.1 6FDA 0.04 6FDA 0.1 6FDA 0.15 BPDA 0.05 6FDA 0.1 Dicarbonyl compound (mole) TPC 0.1 - - TPC 0.05 TPC 0.11 IPC 0.05 TPC 0.1 - TPC 0.05 IPC 0.05 Amide: Amide (mole ratio) 50:50 100:0 100:0 75:25 20:80 50:50 100:0 50:50 Thickness (µm) 50 50 50 50 50 50 50 50 Catalyst (wt%) Pyridine 0.04 Pyridine 0.06 Pyridine 0.06 Pyridine 0.06 Pyridine 0.06 Pyridine 0.04 Pyridine 0.04 Pyridine 0.04 Butyric acid (wt%) 0.2 0.1 0.05 0.12 0.3 - - - Butyric acid content in film (ppm) 201 97 60 130 250 - - - Transmittance(%) 89.1 89.5 88.8 88.9 89.1 89.1 88.7 88.5 YI 2.5 1 3.5 3.2 2.8 3.7 4.6 3.5 Modulus (GPa) 6 4.5 5.6 6.6 7.1 5.1 4.8 4.7 Deformation angle (24 hours, 2R) 160 165 165 135 155 110 115 110 Folding evaluation (2R) qualified qualified qualified qualified qualified Unqualified Unqualified Unqualified

As can be seen from Table 3 above, butyric acid continues to exist in the polymer films of Examples 1c to 5c. Therefore, the recoverability is excellent when it has been folded for a long period of time and then returned to the unfolded state. Specifically, the polymer films of Examples 1c to 5c had a deformation angle of 120° or greater in the static deflection test, while the polymer films of Comparative Examples 1c to 3c had a deformation angle of 115° in the static deflection test. Or smaller, showing bad results.

In addition, when the polymer films of Examples 1c to 5c were repeatedly folded and reached a radius of curvature of 2 mm, the number of folds before breaking was 200,000 times or more. Therefore, it is suitable for use in foldable displays, flexible displays, rollable displays and the like. In contrast, in the folding test, the polymer films of Comparative Examples 1c to 3c were broken before the number of folds was 200,000.

In addition, the polymer films of Examples 1c to 5c maintained excellent mechanical properties (such as static deflection characteristics, folding characteristics, and modulus) and optical properties (such as transmittance and yellow index).

10: Polymerization instrument 20: Slot 30: Transmission belt 40: thermosetting device 50: Winder 100: polymer film 101: first side 102: second side 200: functional layer 300: front panel 400: display unit 500: Adhesive layer S100: Preparation of polymer solution S200: Transfer the polymer solution to the tank S300: Purge the tank with inert gas S400: Casting a polymer solution and then drying it to prepare a gel sheet S500: Heat treatment of the gel sheet to prepare a cured film S600: Cool the solidified film S700: Use a winder to wind the cooled solidified film

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

Fig. 2 is a schematic flow chart of a process for preparing a polymer film according to an embodiment.

Fig. 3 schematically shows a process equipment for preparing a polymer film according to an embodiment.

100: polymer film

101: first side

102: second side

200: functional layer

300: front panel

400: display unit

500: Adhesive layer

Claims (9)

A polymer film comprising a polymer resin selected from the group consisting of: a polyamide-based resin and a polyimide-based resin, and it has 3% before autoclave treatment Haze (HZ ₀ ) or lower, and has a value _{of △HZ 24} represented by the following equation 1a of 500% or lower:

In Equation 1a, HZ ₀ refers to the haze of the film before treatment in an autoclave, HZ ₂₄ refers to the haze of the film after treatment in an autoclave, and the autoclave treatment means an autoclave It is filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. For example, the polymer film of claim 1, which has a value of 30% or less of △YI ₂₄ represented by the following equation 2a, and a value of 8% or less of △Ro ₂₄ represented by the following equation 3a:

In equation 2a, YI ₀ refers to the yellow index of the film before being processed in an autoclave, and YI ₂₄ refers to the yellow index of the film after being processed in an autoclave. In equation 3a, Ro ₀ is Refers to the in-plane retardation of _{the film before being processed in an autoclave, Ro 24} refers to the in-plane retardation of the film after being processed in an autoclave, and the autoclave treatment means that an autoclave is filled with water and an autoclave is filled with water. The film was treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours. Such as the polymer film of claim 1, which has an IS value of 5 to 160 expressed by the following equation 7:

In Equation 7, IM represents the molar number of the amide repeating unit when the total molar number of the amide repeating unit and the amide repeating unit in the film is 100; and RS represents the residue in the film Solvent content (ppm). Such as the polymer film of claim 1, which further contains butyric acid. A polymer film comprising a polymer resin selected from the group consisting of: a polyamide-based resin and a polyimide-based resin, and which has a polymer resin of 5.0 GPa or greater A modulus (MO ₀ ) before autoclave treatment, and a value of 15% or less of △TS ₂₄ expressed by the following equation 1b:

In Equation 1b, TS ₀ refers to the modulus of the film before treatment in an autoclave, TS ₂₄ refers to the modulus of the film after treatment in an autoclave, and the autoclave treatment means an autoclave Filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours, where the modulus is determined as follows: at least 5 cm in the direction perpendicular to the main shrinkage direction of the film and in the main Cut the sample 10cm in the shrinking direction, and then fix it in the universal testing machine Instron UTM 5566A with clips placed at intervals of 5cm; the stress-strain curve is obtained while the sample is stretched at a rate of 5 mm/min at room temperature , Until the sample breaks; and the slope of the load relative to the initial strain on the stress-strain curve is regarded as the modulus. Such as the polymer film of claim 5, which has a tensile strength (TS ₀ ) of 20 kgf/mm2 or more before the autoclave treatment, and 15% or more before the autoclave treatment The elongation at break (EL ₀ ). The polymer film of claim 5, wherein the residual solvent content in the film is 1,000 ppm or less. For example, the polymer film of claim 5, which has a △HZ _{24 value represented by the following equation 1a of 500% or less, a △YI 24} value represented by the following equation 2a of 30% or less, and 8 % Or lower is one of the values _{of △Ro 24 expressed by the following equation 3a:}

In equations 1a, 2a and 3a, HZ ₀ refers to the haze of the film before being processed in an autoclave, HZ ₂₄ refers to the haze of the film after being processed in an autoclave, and YI ₀ refers to the haze of the film The yellow index before treatment in an autoclave, YI ₂₄ refers to the yellow index of the film after treatment in an autoclave, Ro ₀ refers to the in-plane phase difference of the film before treatment in an autoclave, Ro ₂₄ Refers to the in-plane phase difference of the film after treatment in an autoclave, and the autoclave treatment means that an autoclave is filled with water and a film is treated therein at a temperature of 120°C and a pressure of 1.2 atm for 24 hours . The polymer film of claim 1, wherein when the polymer film having a thickness of 50 μm is folded to have a radius of curvature of 2 mm, the film is then allowed to stand at 25° C. for 24 hours, and release applied to the film When the force is applied, the inner angle of the film is 120° or more.

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