CN114729140A

CN114729140A - Polyimide film and method for producing same

Info

Publication number: CN114729140A
Application number: CN202080080431.7A
Authority: CN
Inventors: 元东荣; 朴势周; 金烔暎
Original assignee: Polyimide Advanced Materials Co ltd
Current assignee: Polyimide Advanced Materials Co ltd
Priority date: 2019-11-21
Filing date: 2020-10-19
Publication date: 2022-07-08
Anticipated expiration: 2040-10-19
Also published as: TWI762040B; KR20210062283A; TW202124532A; JP2023503090A; WO2021101077A1; KR102347593B1; CN114729140B

Abstract

Disclosed herein are a polyimide film derived from imidization of polyamic acid formed by reaction of dianhydride monomers and diamine monomers, wherein the dianhydride monomers include about 10 to about 90 mol% of biphenyltetracarboxylic dianhydride (BPDA) based on the total molar amount of the dianhydride monomers, the polyimide film satisfying the following formula 1, and having a modulus of about 2 to about 4.5 GPa: [ formula 1] about 21 MPa/% < A/B < 30 MPa/%, wherein A is yield strength of the polyimide film in MPa and B is yield point of the polyimide film in%.

Description

Polyimide film and method for producing same

Technical Field

The present application relates to a polyimide film and a method for producing the same. More particularly, the present application relates to a polyimide film having a high yield point at a low elastic modulus and less damage even after repeated deformation, and a method for manufacturing the same.

Background

Flexible displays, such as curved displays, bendable displays, foldable displays, rollable displays, etc., are the next generation of displays that have recently drawn attention from both academic and industrial circles. Among the various types of materials constituting flexible displays, functional film/coating materials are important polymer substrate materials constituting flexible displays, and are important for the successful implementation and development of flexible displays, and polyimide is receiving attention as such a material.

Polyimide is a polymer characterized by having a hetero imide ring in the main chain, and has excellent mechanical properties, flame retardancy, chemical resistance, low dielectric constant, and the like in addition to excellent heat resistance, and thus is widely used in the fields of coating materials, molding materials, composite materials, and the like.

The most important physical property required for polymer substrates for flexible displays is flexibility. In particular, such polymer substrates should not only be damaged during the bending, folding, curling and stretching processes of the flexible display, which repeatedly deform, but also should not lose various initial characteristics.

Disclosure of Invention

Technical problem to be solved

An object of the present invention is to provide a polyimide film having a high yield point at a low elastic modulus and less damage even after repeated deformation.

Another object of the present invention is to provide a method for producing the polyimide film.

Means for solving the problems

1. According to an aspect, there is provided a polyimide film derived from imidization of polyamic acid formed by reacting a dianhydride monomer comprising about 10 to about 90 mol% of biphenyl tetracarboxylic dianhydride (BPDA) based on the total molar amount of dianhydride monomers, satisfying the following formula 1, and having a modulus (modulus) of about 2 to about 4.5 GPa:

[ formula 1]

About 21 MPa/% < A/B < about 30 MPa/%)

In formula 1, a is yield strength (yield strength) of the polyimide film in Mpa, and B is yield point (yield point) of the polyimide film in%.

2. In the 1 st embodiment, the dianhydride monomer further comprises pyromellitic dianhydride (PMDA).

3. In the 2 nd embodiment, the pyromellitic dianhydride is included in about 10 to about 90 mol% based on the total molar amount of dianhydride monomers.

4. In any of the embodiments 1-3, the diamine monomer comprises m-toluidine (m-TD), 4 '-diaminodiphenyl ether (4,4' -oxydianiline, ODA), 1,3-bis (4-aminophenoxy) benzene (1,3-bis (4-aminophenoxy) benzene, TPE-R), 2-bis (4- [4-aminophenoxy ] -phenyl) propane (2,2-bis (4- [4-aminophenoxy ] -phenyl) propane, BAPP), or a combination thereof.

5. In the 4 th embodiment, the diamine monomer comprises m-toluidine (m-TD) and 4,4' -diaminodiphenyl ether (ODA) in a molar ratio of about 1:99 to about 20: 80.

6. In any of the 1 st to 5 th embodiments, the yield strength of the polyimide film is about 50Mpa to about 80 Mpa.

7. In any of the 1 st to 6 th embodiments, the yield point of the polyimide film is about 2.2% to about 2.9%.

8. According to another aspect, there is provided a method of manufacturing the polyimide film of any one of the 1 st to 7 th embodiments, the method may include: mixing dianhydride monomer, diamine monomer and organic solvent to react to form polyamic acid solution; mixing a dehydrating agent and an imidizing agent in the polyamic acid solution to form a polyimide precursor composition; casting the polyimide precursor composition on a support and drying to produce a gel film; and performing heat treatment on the gel film to form a polyimide film.

9. In the 8 th embodiment, the heat treatment is performed at about 100 ℃ to about 700 ℃.

Effects of the invention

The polyimide film and the method for manufacturing the same of the present invention can have the effect of providing a polyimide film having a high yield point at a low elastic modulus.

Detailed Description

In describing the present invention, if it is determined that detailed description of related well-known technologies may unnecessarily obscure the gist of the present invention, detailed description thereof will be omitted.

When "including", "having", "constituting", and the like are referred to in this specification, other parts may be added unless "only" is used. When a component is referred to as being singular, it includes plural unless explicitly stated otherwise.

In addition, when components are explained, they are to be interpreted as including an error range even if there is no individual explicit description.

In the present specification, "to" in "a to b" representing numerical ranges is defined as ≧ a and ≦ b.

According to one aspect, a polyimide film is provided. The inventors of the present invention have found that, in a polyimide film obtained by imidization of a polyamic acid formed by reacting a dianhydride monomer and a diamine monomer, when the polyimide film includes about 10 mol% to about 90 mol% of biphenyltetracarboxylic dianhydride (BPDA) as a dianhydride monomer and satisfies the following formula 1, it is possible to have a high yield point (e.g., a yield point of about 2.2% or more) at a low modulus (e.g., a modulus of about 4.5GPa or less), and as a result, the degree of damage is small even after repeated deformation is applied to the polyimide film, thereby completing the present invention.

The dianhydride monomer may comprise from about 10 mol% to about 90 mol% (e.g., 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, or 90 mol%) of biphenyltetracarboxylic dianhydride, based on the total molar amount of dianhydride monomer. Within the above range, the elastic region of the polyimide film becomes long, and a polyimide film having a high yield point at a low elastic modulus can be produced. For example, the dianhydride monomer may comprise, but is not limited to, about 15 mol% to about 80 mol%, further for example about 20 mol% to about 70 mol%, further for example about 30 mol% to about 50 mol%, of biphenyltetracarboxylic dianhydride, based on the total molar amount of the dianhydride monomer.

The polyimide film may satisfy the following formula 1.

[ formula 1]

About 21 MPa/% < A/B < about 30 MPa/%)

In the formula 1, a is the yield strength of the polyimide film in Mpa, and B is the yield point of the polyimide film in%. When the A/B is less than about 21 MPa/% there may be a problem of low tensile strength due to low yield point, and when the A/B exceeds about 30 MPa/% there may be a problem of failing to satisfy the low modulus required in the present invention, and as a result, many damages may occur when repeated deformation is applied to the polyimide film. Here, "yield strength" and "yield point" can be measured in accordance with ASTM D882 using a tensile tester with a tensile speed of 200mm/min, but are not limited thereto. According to one embodiment, the A/B value is 21 MPa/%, 22 MPa/%, 23 MPa/%, 24 MPa/%, 25 MPa/%, 26 MPa/%, 27 MPa/%, 28 MPa/%, 29 MPa/% or 30 MPa/%, according to another embodiment, about 21 MPa/% to about 29 MPa/%, according to yet another embodiment, about 22 MPa/% to about 28 MPa/%, but is not limited thereto.

The polyimide film can have a modulus of about 2GPa to about 4.5GPa (e.g., 2GPa, 2.1GPa, 2.2GPa, 2.3GPa, 2.4GPa, 2.5GPa, 2.6GPa, 2.7GPa, 2.8GPa, 2.9GPa, 3GPa, 3.1GPa, 3.2GPa, 3.3GPa, 3.4GPa, 3.5GPa, 3.6GPa, 3.7GPa, 3.8GPa, 3.9GPa, 4GPa, 4.1GPa, 4.2GPa, 4.3GPa, 4.4GPa, or 4.5 GPa). Here, "modulus" can be measured according to ASTM D882 standard using a tensile tester with a tensile speed of 200mm/min, but is not limited thereto. For example, the modulus of the polyimide film can be, but is not limited to, about 2GPa to about 4.2GPa, such as about 2.5GPa to about 4.1GPa, and such as about 2.5GPa to about 4.0 GPa.

The polyimide film may contain a dianhydride monomer in addition to the biphenyltetracarboxylic dianhydride. As for such dianhydride monomer, various dianhydride monomers may be used without limitation within the range not adversely affecting the effect of the present invention. Examples of such a dianhydride monomer include pyromellitic dianhydride (PMDA). The dianhydride monomer other than the biphenyltetracarboxylic dianhydride is contained, for example, in about 10 mol% to about 90 mol% (e.g., 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol% or 90 mol%), further for example, in about 20 mol% to about 85 mol%, further for example, in about 30 mol% to about 80 mol%, further for example, in about 50 mol% to about 70 mol%, based on the total molar amount of the dianhydride monomer, but is not limited thereto. For example, pyromellitic dianhydride is contained in an amount of, for example, about 10 to about 90 mol%, further for example about 20 to about 85 mol%, further for example about 30 to about 80 mol%, further for example about 50 to about 70 mol%, based on the total molar amount of dianhydride monomers, but is not limited thereto.

As the diamine monomer, various diamine monomers can be used without limitation within a range not adversely affecting the effect of the present invention. Examples of such diamine monomers include m-toluidine (m-TD), 4' -diaminodiphenyl ether (ODA), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 2-bis (4- [4-aminophenoxy ] -phenyl) propane (BAPP), and the like, and these monomers may be used alone or in combination of two or more.

According to one embodiment, the diamine monomer may include 4,4' -diaminodiphenyl ether, and in this case, a polyimide film having a high yield point at a low elastic modulus can be manufactured. In this case, the content of the 4,4' -diaminodiphenyl ether is, for example, more than 0 mol% to about 100 mol% (e.g., 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 95 mol%, or 100 mol%), still for example, about 50 mol% to about 100 mol%, still for example, about 70 mol% to about 100 mol%, still for example, about 75 mol% to about 100 mol%, still for example, about 80 mol% to about 100 mol%, based on the total molar amount of the diamine monomers, but is not limited thereto.

According to another embodiment, the diamine monomer may include m-toluidine, and in this case, a polyimide film having a high yield point at a low elastic modulus can be manufactured. In this case, the amount of m-toluidine is, for example, more than 0 mol% to about 100 mol% (e.g., 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 35 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, 75 mol%, 80 mol%, 85 mol%, 90 mol%, 95 mol%, or 100 mol%), further, for example, more than 0 mol% to about 50 mol%, further, for example, more than 0 mol% to about 30 mol%, further, for example, more than 0 mol% to about 25 mol%, further, for example, more than 0 mol% to about 20 mol%, based on the total molar amount of diamine monomers, but is not limited thereto.

According to another embodiment, the diamine monomer may include m-toluidine and 4,4 '-diaminodiphenyl ether, in which case the respective effects of m-toluidine and 4,4' -diaminodiphenyl ether act synergistically, enabling the production of a polyimide film having a high yield point at a low elastic modulus. In this case, the molar ratio of m-toluidine to 4,4' -diaminodiphenyl ether is about 1:99 to about 99:1 (e.g., 1:99, 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, 55:45, 60:40, 65:35, 70:30, 75:25, 80:20, 85:15, 90:10, 95:5 or 99:1), such as about 1:99 to about 50:50, such as about 1:99 to about 30:70, such as about 1:99 to about 25:75, such as about 1:99 to about 30:70, such as about 1:99 to about 20:80, such as about 5:95 to about 20:80, but not limited thereto. The total amount of m-toluidine and 4,4' -diaminodiphenyl ether is, for example, 11 mol% to about 100 mol%, for example, 50 mol% to about 100 mol%, for example, about 90 mol% to about 100 mol%, and not limited thereto, based on the number of moles of the diamine monomer.

According to one embodiment, the polyimide film can have a yield strength of about 50MPa to about 80MPa (e.g., 50MPa, 55MPa, 60MPa, 65MPa, 70MPa, 75MPa, or 80 MPa). For example, the yield strength of the polyimide film can be from about 50MPa to about 75MPa, such as from about 50MPa to about 70MPa, such as from about 60MPa to about 70MPa, but is not limited thereto.

According to one embodiment, the polyimide film has a yield point of about 2.2% to about 2.9% (e.g., 2.2%, 2.25%, 2.3%, 2.35%, 2.4%, 2.45%, 2.5%, 2.55%, 2.6%, 2.65%, 2.7%, 2.75%, 2.8%, 2.85%, or 2.9%). For example, the yield point of the polyimide film may be about 2.2% to about 2.7%, and further, for example, about 2.2% to about 2.65%, but is not limited thereto.

The thickness of the polyimide film may be appropriately selected in consideration of the use, use environment, physical properties, and the like of the polyimide film. For example, the thickness of the polyimide film may be, but is not limited to, about 10 μm to about 500 μm, and for example, about 20 μm to about 50 μm, and for example, about 40 μm to about 50 μm.

The polyimide film can be produced by various methods commonly used in the field of polyimide film production. For example, a polyimide film can be manufactured by including the steps of: mixing dianhydride monomer, diamine monomer and organic solvent to react to form polyamic acid solution; mixing a dehydrating agent and an imidizing agent in the polyamic acid solution to form a polyimide precursor composition; casting the polyimide precursor composition on a support and drying to produce a gel film; and performing heat treatment on the gel film to form a polyimide film. Since the description about the dianhydride monomer and the diamine monomer has been described above, the description thereof will be omitted.

First, a polyamic acid can be produced by reacting a dianhydride monomer and a diamine monomer. More specifically, the polyamic acid solution may be manufactured by polymerizing a dianhydride monomer and a diamine monomer in an organic solvent. At this time, all monomers may be added at once, or each monomer may be added in sequence, in which case partial polymerization may occur between the monomers.

The organic solvent is not particularly limited as long as it is a solvent capable of dissolving the polyamic acid, and may be, for example, an aprotic polar organic solvent (aprotic polar organic solvent). Non-limiting examples of the aprotic polar organic solvent include amide solvents such as N, N '-Dimethylformamide (DMF) and N, N' -dimethylacetamide (DMAc), phenolic solvents such as p-chlorophenol and o-chlorophenol, N-methylpyrrolidone (NMP), γ -butyrolactone (GBL), Diglyme (Diglyme), and the like, and these solvents may be used alone or in combination of two or more kinds. In some cases, the solubility of the polyamic acid can be adjusted by using an auxiliary solvent such as toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol, water, or the like. In one embodiment, the organic solvent may be an amide-based solvent, for example, N '-dimethylformamide or N, N' -dimethylacetamide, but is not limited thereto.

Thereafter, a polyimide precursor composition may be formed by mixing a dehydrating agent and an imidizing agent in a polyamic acid solution.

The dehydrating agent promotes the ring-closure reaction by the dehydration action of the polyamic acid, and examples thereof include aliphatic acid anhydrides, aromatic acid anhydrides, N' -dialkylcarbodiimides, low-carbon aliphatic halides (lower aliphatic halides), halogenated low-carbon fatty acid anhydrides (halogenated fatty acids anhydrides), aromatic phosphonic dihalides (aryl phosphonic dihalides), and thionyl halides (thionyl halides), and these can be used alone or in combination of two or more kinds. Among them, from the viewpoint of availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic anhydride may be used alone or in combination of two or more.

The imidizing agent is a component having an effect of promoting the ring-closure reaction of the polyamic acid, and examples thereof include aliphatic tertiary amines (aliphatic tertiary amines), aromatic tertiary amines (aromatic tertiary amines), and heterocyclic tertiary amines (heterocyclic tertiary amines). Among them, from the viewpoint of reactivity, a heterocyclic tertiary amine may be used as a catalyst. Examples thereof include quinoline (quinoline), isoquinoline (isoquinoline), β -picoline (β -picoline), pyridine (pyridine), and the like, and these may be used alone or in combination of two or more kinds thereof.

The addition amounts of the dehydrating agent and the imidizing agent are not particularly limited, and the dehydrating agent may be added in a range of about 0.5 mol to about 5mol (e.g., 0.5 mol, 1mol, 1.5 mol, 2 mol, 2.5 mol, 3 mol, 3.5 mol, 4 mol, 4.5 mol or 5 mol), for example, a ratio of about 1.0 mol to about 4 mol, per mol of the amic acid group in the polyamic acid, and the imidizing agent may be added in a range of about 0.05 mol to about 3 mol (e.g., 0.05 mol, 0.1 mol, 0.5 mol, 1mol, 1.5 mol, 2 mol, 2.5 mol or 3 mol), for example, a ratio of about 0.2 mol to about 2 mol, for example, per mol of the amic acid group in the polyamic acid, and in the above range, imidization type is sufficient and easy to form a film.

According to one embodiment, the polyamic acid can be included in an amount of about 5 wt% to about 35 wt% (e.g., 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%) based on the total weight of the polyimide precursor composition. Within the above range, the precursor composition may have a suitable molecular weight and solution viscosity to form a film. The polyamic acid may be included, for example, from about 10 wt% to about 30 wt%, and further for example, from about 15 wt% to about 20 wt%, based on the total weight of the precursor composition, but is not limited thereto.

According to one embodiment, the polyimide precursor composition may have a viscosity of about 100,000cP to about 500,000cP (e.g., 100,000cP, 150,000cP, 200,000cP, 250,000cP, 300,000cP, 350,000cP, 400,000cP, 450,000cP, or 500,000cP) at 25 ℃. Within the above range, a polyimide film can be formed with excellent processability while allowing the polyamic acid to have a predetermined weight average molecular weight. Here, "viscosity" can be measured using a Brookfield viscometer. The precursor composition can have a viscosity of, for example, from about 150,000cP to about 450,000cP, further for example from about 200,000cP to about 400,000cP, further for example from about 250,000cP to about 350,000cP, at 25 ℃, but is not limited thereto.

Thereafter, the polyimide precursor composition may be cast on a support and dried to produce a gel film.

As the support, a support commonly used in the art can be used without limitation, and examples of such a support include a glass plate, an aluminum foil, an endless (end) stainless steel belt, a stainless steel drum, and the like.

Drying may be carried out, for example, at a temperature of from about 40 ℃ to about 300 ℃, yet for example from about 80 ℃ to about 200 ℃, yet for example from about 100 ℃ to about 180 ℃, yet for example from about 100 ℃ to about 130 ℃, whereby the dehydrating agent and the imidizing agent are activated, and partial curing and/or drying may occur to form a gel film. The gel film may be self-supporting at an intermediate stage of curing from the polyamic acid to the polyimide.

In some cases, a step of stretching the gel film may be included to control the thickness and size of the finally obtained polyimide film and improve orientation, and the stretching may be performed in at least one of a Machine Direction (MD) and a Transverse Direction (TD) with respect to the machine direction.

The volatile content of the gel film is not limited thereto, but may be about 5 wt% to about 500 wt%, for example about 5 wt% to about 200 wt%, and for example about 5 wt% to about 150 wt%, and within the above range, it may have an effect of avoiding defects such as film breakage, color unevenness, and characteristic variation during the heat treatment for obtaining a polyimide film. Here, the volatile content of the gel film can be calculated using the following formula 2, where C is the weight of the gel film and D is the weight of the gel film after heating at 450 ℃ for 20 minutes in formula 2.

[ formula 2]

(C-D)*100/D

According to one embodiment, in the step of heat-treating the gel film, the gel film is subjected to a heat treatment at a variable temperature ranging from about 50 ℃ to about 700 ℃, for example, from about 150 ℃ to about 600 ℃, further for example, from about 200 ℃ to about 600 ℃ to remove a solvent and the like remaining in the gel film, and a majority of the remaining amic acid groups are imidized to obtain a polyimide film.

In some cases, the polyimide film obtained as described above may be heated at a temperature of about 400 ℃ to about 650 ℃ for about 5 seconds to about 400 seconds to further cure the polyimide film, and this may be performed under a predetermined tension in order to relax internal stress remaining in the resulting polyimide film.

The constitution and action of the present invention will be described in more detail below by way of preferred embodiments of the present invention. However, this is presented as a preferred example of the invention and should not be construed as limiting the invention in any way.

Examples

Examples 1 to 13 and comparative examples 1 to 3

3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride were mixed as dianhydride monomers and m-toluidine (m-TD) and 4,4' -diaminodiphenyl ether (ODA) were mixed as diamine monomers in Dimethylformamide (DMF) according to the molar ratios described in table 1 below, and then polymerization was performed to produce a polyamic acid solution having a solid content of 18.5 wt%. In this case, the number of moles of the dianhydride monomer and the diamine monomer is substantially equal.

In the polyamic acid solution thus produced, acetic anhydride and isoquinoline were added in a ratio of 3.5 mol and a ratio of 1.1 mol per mol of amic acid groups to obtain a composition for polyimide film production, which was cast on a SUS plate (100SA, manufactured by Sandvik corporation) using a doctor blade and dried at 90 ℃ for 4 minutes to produce a gel film. After peeling the gel film from the SUS plate, a heat treatment was performed at 250 to 380 ℃ for 14 minutes to manufacture a polyimide film having an average thickness of 50 μm.

However, in the case of comparative example 3, a polyimide film was not produced.

Evaluation example: measurement of modulus (unit: GPa), yield point (unit:%), yield strength (unit: MPa)

The produced polyimide film was cut into 15mm × 50mm to manufacture a test specimen, and the modulus, yield point and yield strength were measured at room temperature (room temp.) using a tensile tester (Instron 5564, manufactured by Instron corporation) having a tensile speed of 200mm/min according to ASTM D882, and the results thereof are shown in table 1 below.

[ Table 1]

As can be seen from table 1 above, in examples 1 to 13, the content of BPDA and the value according to formula 1 satisfy the range of the present invention, and have a high yield point with a low modulus within the range of the present invention, and as a result, it is easy to predict that the polyimide film is damaged to a small extent by repeated deformation.

On the other hand, in comparative example 1, the content of BPDA was out of the range of the present invention, and the value according to formula 1 was out of the range of the present invention, the yield point of the polyimide film was as low as 2.16%. In comparative example 2, the content of BPDA was within the range of the present invention, but the value according to formula 1 was not within the range of the present invention, and the modulus of the polyimide film was as high as 4.6 GPa. Therefore, it is predicted that the polyimide films of comparative examples 1 and 2 are damaged to a large extent when repeatedly deformed.

On the other hand, in comparative example 3, when the content of BPDA is not within the range of the present invention, a polyimide film could not be produced by applying the above-mentioned production method.

Simple modifications or changes may be readily made by those skilled in the art, and all such modifications or changes are intended to be included within the scope of the present invention.

Claims

1. A polyimide film derived from imidization of polyamic acid formed by reaction of a dianhydride monomer and a diamine monomer,

the dianhydride monomer comprises about 10 to about 90 mol% of biphenyltetracarboxylic dianhydride (BPDA), based on the total molar amount of the dianhydride monomer,

the polyimide film satisfies the following formula 1, and has a modulus of about 2GPa to about 4.5 GPa:

[ formula 1]

About 21 MPa/% < A/B < about 30 MPa/%)

In the formula 1, a is yield strength of the polyimide film in Mpa, and B is yield point of the polyimide film in%.

2. The polyimide film according to claim 1,

the dianhydride monomer also includes pyromellitic dianhydride (PMDA).

3. The polyimide film according to claim 2,

the pyromellitic dianhydride is included in an amount of about 10 to about 90 mol% based on the total molar amount of the dianhydride monomers.

4. The polyimide film according to any one of claims 1 to 3,

the diamine monomer comprises m-toluidine (m-TD), 4' -diaminodiphenyl ether (ODA), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 2-bis (4- [4-aminophenoxy ] -phenyl) propane (BAPP), or a combination thereof.

5. The polyimide film according to claim 4,

the diamine monomers comprise m-toluidine (m-TD) and 4,4' -diaminodiphenyl ether (ODA) in a molar ratio of about 1:99 to about 20: 80.

6. The polyimide film according to any one of claims 1 to 5,

the yield strength of the polyimide film is from about 50MPa to about 80 MPa.

7. The polyimide film according to any one of claims 1 to 6,

the yield point of the polyimide film is about 2.2% to about 2.9%.

8. A method for producing the polyimide film described in any one of claims 1 to 7, comprising:

mixing dianhydride monomer, diamine monomer and organic solvent to react to form polyamic acid solution;

mixing a dehydrating agent and an imidizing agent in the polyamic acid solution to form a polyimide precursor composition;

casting the polyimide precursor composition on a support and drying to produce a gel film; and

and performing heat treatment on the gel film to form a polyimide film.

9. The method for producing a polyimide film according to claim 8, wherein,

the heat treatment is performed at about 100 ℃ to about 700 ℃.