KR20210062999A - Method for preparing polyimide film and polyimide film prepared thereby - Google Patents

Abstract

The present invention relates to a method for producing a polyimide film, including the steps of: reacting a dianhydride monomer with a diamine monomer to prepare polyamic acid; preparing a polyimide precursor solution containing the polyamic acid, an imidization catalyst, a dehydrating agent, a filler and a solvent; and carrying out imidization of the polyamic acid to prepare a polyimide film, wherein the imidization catalyst is present at a molar ratio of 0.8-2.5 moles per mole of amic acid groups in the polyamic acid, the dehydrating agent is present at a molar ratio of 2.0-4.0 moles per mole of amic acid groups in the polyamic acid, the filler has an average particle diameter (D_50) of 1.6 micrometers or less, and the polyimide film has a modulus of 2.5-4.0 GPa. The present invention also relates to a polyimide film produced from the method.

Description

The manufacturing method of a polyimide film, and the polyimide film manufactured thereby

It relates to a method for producing a polyimide film and a polyimide film produced thereby. More particularly, it has a high yield point and yield strength at a low elastic modulus, and relates to a method for producing a polyimide film having a high transmittance and a low haze, and a polyimide film produced thereby.

Flexible displays, such as curved, bendable, foldable, and rollable, are the next generation displays that have recently attracted attention from both academia and industry. Among the various types of materials constituting a flexible display, functional film/coating material is an important polymer substrate material constituting a flexible display, and it can be said to be a key material essential for the successful implementation and development of a flexible display. It is attracting attention.

Polyimide is a polymer characterized by having a heteroimide ring in its main chain, and has excellent mechanical properties, flame retardancy, chemical resistance, and low dielectric constant, in addition to excellent heat resistance, and has been applied to a wide range of applications such as coating materials, molding materials, and composite materials.

The most important physical property required for a flexible display polymer substrate is flexibility. In particular, such a polymer substrate should not be damaged during the curving, bending, folding, rolling, and stretching processes in which the flexible display repeatedly deforms, and various initial physical properties should not be lost.

On the other hand, such a polymer substrate for a flexible display is required to be transparent for various purposes, and therefore, optical properties such as high light transmittance and low haze are often required.

An object of the present invention is to provide a method for producing a polyimide film having a high yield point and yield strength at a low modulus of elasticity.

Another object of the present invention is to provide a method for producing a polyimide film having high transmittance and low haze.

Another object of the present invention is to provide a polyimide film prepared by the above-described polyimide film manufacturing method.

1. According to one aspect, preparing a polyamic acid by reacting a dianhydride monomer and a diamine monomer; preparing a polyimide precursor solution including the polyamic acid, the imidization catalyst, a dehydrating agent, a filler, and a solvent; and imidizing the polyamic acid to prepare a polyimide film; wherein the imidization catalyst is in a molar ratio of 0.8 to 2.5 moles based on 1 mole of amic acid groups in the polyamic acid. The dehydrating agent is included in a molar ratio of 2.0 to 4.0 moles based on 1 mole of the amic acid group in the polyamic acid, the average particle diameter (D ₅₀ ) of the filler is 1.6 μm or less, and the modulus of the polyimide film is 2.5 to 4.0 GPa is provided.

2. In 1 above, biphenyltetracarboxylic dianhydride (BPDA) may be included in an amount of 10 to 90 mol% based on the total molar amount of the dianhydride monomer.

3. In 1 or 2 above, pyromellitic dianhydride (PMDA) may be further included in an amount of 10 to 90 mol% based on the total molar amount of the dianhydride monomer.

4. The diamine monomer according to any one of 1 to 3 above, wherein the diamine monomer is m-tolidine (m-TD), 4,4'-oxydianiline (ODA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2,2-bis(4-[4-aminophenoxy]-phenyl)propane (BAPP), or combinations thereof.

5. According to another aspect, there is provided a polyimide film manufactured by the manufacturing method of any one of 1 to 4.

6. In 5 above, the polyimide film may have a yield point of 2.3 to 2.8%.

7. In 5 or 6, the polyimide film may have a yield strength of 55 to 80 MPa.

8. In any one of 5 to 7, the polyimide film may have a transmittance of 43% or more in a visible light region.

9. In any one of 5 to 8, the polyimide film may have a haze of 7.5% or less.

The present invention may have the effect of providing a polyimide film manufacturing method having a high yield point and yield strength at a low elastic modulus, high transmittance and low haze, and a polyimide film prepared therefrom.

In describing the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

When'include','have', and'consist of' mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In addition, in interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

In "a to b" representing a numerical range in the present specification, "to" is defined as ≥a and ≤b.

When the polyimide film was prepared from polyamic acid by controlling the content of the imidization catalyst and the dehydrating agent and the average particle diameter (D ₅₀ ) of the filler, the inventor of the present invention prepared the polyimide film, even at a low modulus of 2.0 to 4.0 GPa. It has been found that it is possible to manufacture a polyimide film having a high transmittance and a low haze while having a low degree of damage even when subjected to repeated deformation by having a yield point and yield strength, and thus completed the present invention. Hereinafter, the present invention will be described in more detail.

Method for producing polyimide film

According to one aspect, a method of manufacturing a polyimide film is provided. The method for preparing the polyimide film includes preparing a polyamic acid by reacting a dianhydride monomer and a diamine monomer; preparing a polyimide precursor solution including the polyamic acid, the imidization catalyst, a dehydrating agent, a filler, and a solvent; and preparing a polyimide film by imidizing the polyamic acid, wherein the imidization catalyst is included in a molar ratio of 0.8 to 2.5 moles based on 1 mole of amic acid groups in the polyamic acid, and the dehydrating agent is the The polyamic acid may be included in a molar ratio of 2.0 to 4.0 moles with respect to 1 mole of the amic acid group, the average particle diameter (D ₅₀ ) of the filler is 1.6 μm or less, and the modulus of the polyimide film may be 2.5 to 4.0 GPa. Hereinafter, each step will be described in more detail.

First, a polyamic acid may be prepared by reacting a dianhydride monomer and a diamine monomer. More specifically, the polyamic acid solution may be prepared by polymerizing the dianhydride monomer and the diamine monomer in a solvent. In this case, all the monomers may be added at once, or each of the monomers may be added sequentially. In this case, partial polymerization between the monomers may occur.

The type of the dianhydride monomer is not particularly limited and may be variously selected within a range that does not adversely affect the effects of the present invention. For example, the dianhydride monomer may include biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), and the like, which may be used alone or in combination.

According to one embodiment, the dianhydride monomer may include biphenyltetracarboxylic dianhydride (BPDA) in an amount of 10 to 90 mol% based on the total molar amount of the dianhydride monomer. In this case, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. For example, the dianhydride monomer may be included in an amount of 15 to 85 mol%, for example 20 to 80 mol%, for another example, 30 to 70 mol%, based on the total molar amount of the dianhydride monomer, but is limited thereto it is not

According to an embodiment, the dianhydride monomer may include biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA). In this case, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. Biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) are, for example, 10:90 to 90:10, another example 20:80 to 80:20, another example 30: It may be included in a molar ratio of 70 to 70:30, but is not limited thereto. According to one embodiment, the dianhydride monomer may include biphenyltetracarboxylic dianhydride and pyromellitic dianhydride in a total molar number of greater than 10 to 100 mol% based on the total molar amount of the dianhydride monomer, but is limited thereto no.

The type of the diamine monomer is not particularly limited and may be variously selected within a range that does not adversely affect the effects of the present invention. For example, diamine monomers include m-tolidine (m-TD), 4,4'-oxydianiline (ODA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2, 2-bis(4-[4-aminophenoxy]-phenyl)propane (BAPP) and the like may be included, and these may be used alone or in combination of two or more. According to one embodiment, the diamine monomer may include m-tolidine (m-TD) or 4,4'-oxydianiline (ODA). According to another embodiment, the diamine monomer is m-tolidine (m-TD) and 4,4'-oxydianiline (ODA) 1:99 to 99:1, for example 1:99 to 50:50, For another example, 1:99 to 30:70, another example may be included in a molar ratio of 5:95 to 20:80, but is not limited thereto.

The organic solvent is not particularly limited as long as it is a solvent in which polyamic acid can be dissolved, and may be, for example, an aprotic polar organic solvent. As non-limiting examples of aprotic polar oil-borne solvents, amide solvents such as N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), p-chlorophenol, o-chloro Phenolic solvents such as phenol, N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), Diglyme, and the like, and these may be used alone or in combination of two or more. In some cases, an auxiliary solvent such as toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol, or water may be used to adjust the solubility of the polyamic acid. In one embodiment, the oil cover solvent may be an amide-based solvent, for example, N,N-dimethylformamide and N,N-dimethylacetamide, but is not limited thereto.

According to one embodiment, the polyamic acid may be included in an amount of 5 to 35 wt% based on the total weight of the polyamic acid solution. Within the above range, the polyamic acid solution may have a suitable molecular weight and solution viscosity to form a film. Based on the total weight of the polyamic acid solution, the polyamic acid may be included, for example, in an amount of 10 to 30% by weight, for example, 15 to 25% by weight, but is not limited thereto.

Then, a polyimide precursor solution including a polyamic acid, an imidization catalyst, a dehydrating agent, a filler, and a solvent may be prepared. More specifically, an imidization catalyst, a dehydrating agent, a filler, and optionally an additional solvent may be added to the polyamic acid solution to prepare a polyimide precursor solution. The additional solvent may be understood with reference to the description of the solvent used in preparing the polyamic acid solution.

The imidization catalyst may refer to a component having an effect of promoting a ring closure reaction with respect to polyamic acid, and examples thereof include a tertiary amine compound, more specifically, an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary compound. and amines. Among them, heterocyclic tertiary amines may be used from the viewpoint of reactivity as a catalyst, and examples thereof include quinoline, isoquinoline, β-picoline, pyridine, and the like, and these may be used alone or in mixture of two or more. .

The imidization catalyst is a molar ratio of 0.8 to 2.5 moles (eg, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0) with respect to 1 mole of the amic acid group in the polyamic acid. , 2.1, 2.2, 2.3, 2.4 or 2.5 mole ratio). When the content of the imidization catalyst is less than the above range, film formation is difficult, and when the content of the imidization catalyst exceeds the above range, the modulus becomes too large (for example, exceeding 4.0 GPa), and the transmittance is lowered. have. Therefore, in the above range, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. For example, the imidization catalyst may be included in a molar ratio of 0.8 to 2.4 moles based on 1 mole of the amic acid group in the polyamic acid, but is not limited thereto.

The dehydrating agent may mean promoting a ring closure reaction through dehydration action on polyamic acid, for example, aliphatic acid anhydride, aromatic acid anhydride, N,N'-dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower and fatty acid anhydrides, arylphosphonic acid dihalides, and thionyl halides, and these may be used alone or in combination of two or more. Among these, aliphatic acid anhydrides, such as acetic anhydride, propionic anhydride, and lactic anhydride, can be used individually or in mixture of 2 or more types from a viewpoint of availability and cost.

The dehydrating agent is a molar ratio of 2.0 to 4.0 moles (for example, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3 with respect to 1 mole of the amic acid group in the polyamic acid) , 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0 mole ratio). In the above range, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. For example, the dehydrating agent may be included in a molar ratio of 2.5 to 3.3 moles based on 1 mole of the amic acid group in the polyamic acid, but is not limited thereto.

According to one embodiment, the molar ratio of the imidization catalyst and the dehydrating agent (imidization catalyst: dehydrating agent) may be 1:1 to 1:10. In the above range, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. For example, the molar ratio of the imidization catalyst and the dehydrating agent may be 1:1.2 to 1:6, for example, 1:1.3 to 1:5, and for another example, 1:1.3 to 1:4, but limited thereto. it's not going to be

The filler may impart roughness to the polyimide film, and examples thereof include inorganic fillers, more specifically, dibasic calcium phosphate, barium sulfate, calcium carbonate, spherical silica, and the like, and these may be used alone or in combination of two or more. can be used for

The filler may have _{an average particle diameter (D 50} ) of 1.6 μm or less, specifically greater than 0 to 1.6 μm. In the above range, it may be possible to prepare a polyimide film having a high yield point and yield strength at a low elastic modulus, and a high transmittance and low haze. For example, the average particle diameter (D ₅₀ ) of the filler is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5 or 1.6 μm, for example It may be 0.5 to 1.6 μm, but is not limited thereto.

The content of the filler is not particularly limited, but may be included in an amount of 0.05 to 0.5% by weight, based on the total weight of the polyimide film, and in the above range, has a high yield point and yield strength at a low elastic modulus, high transmittance and low haze It may be possible to prepare a polyimide film having For example, the content of the filler may be 0.1 to 0.3% by weight, but is not limited thereto.

In one embodiment, the polyimide precursor solution may include various additives within a range that does not adversely affect the effects of the present invention. Examples of such additives include antioxidants, light stabilizers, antistatic agents, heat stabilizers, flame retardants, and the like, and these may be used alone or in combination of two or more.

Then, the polyamic acid may be imidized to prepare a polyimide film. For example, a polyimide film may be prepared by casting a polyimide precursor solution on a support and drying the solution to prepare a gel film, and imidizing the gel film by heat treatment.

According to one embodiment, in the step for forming the gel film, the polyimide precursor solution cast on a support (eg, glass plate, aluminum foil, endless stainless belt, stainless drum, etc.) is heated at 40 to 300 ° C., for example. For example, it is possible to obtain a gel film by drying at a temperature range of 80 to 200 ℃, for example 100 to 180 ℃, for another example 100 to 130 ℃. Thereby, partially curing and/or drying may take place to form a gel film. The gel film is in an intermediate stage of curing from polyamic acid to polyimide, and may have self-supporting properties.

In some cases, it may include the step of stretching the gel film to adjust the thickness and size of the finally obtained polyimide film and improve orientation, and the stretching may be performed in a machine transport direction (MD) and a transverse direction to the machine transport direction. It may be performed in at least one direction of (TD).

The volatile content of the gel film may be, but is not limited to, 5 to 500% by weight, for example, 5 to 200% by weight, and other such as 5 to 150% by weight, in the above range, then the polyimide film During the process of heat treatment to obtain a film, there may be an effect of avoiding the occurrence of defects such as breakage of the film, uneven color tone, and variation in characteristics. Here, the volatile matter content of the gel film can be calculated using Equation 2 below, in Equation 1, A is the weight of the gel film, and B is the weight after heating the gel film at 450 ° C. for 20 minutes.

<Equation 1>

(A-B)*100/B

According to one embodiment, in the step of heat-treating the gel film, the gel film remains in the gel film by heat treatment at a variable temperature in the range of 50 to 700 °C, for example 150 to 600 °C, for example 200 to 600 °C. A polyimide film can be obtained by removing the solvent and the like, and imidizing most of the remaining amic acid groups.

In some cases, the polyimide film obtained as described above may be heated and finished for 5 to 400 seconds at a temperature of 400 to 650° C. to further cure the polyimide film, and internal stress that may remain in the obtained polyimide film may be reduced. It is also possible to do this under a certain tension to relieve it.

polyimide film

According to another aspect, there is provided a polyimide film manufactured by the above-described manufacturing method. The polyimide film prepared by the above-described manufacturing method has a high yield point at a low elastic modulus, and may also have a high transmittance.

The polyimide film will have a modulus of 2.5 to 4.0 GPa (eg, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4 GPa). can According to one embodiment, the modulus of the polyimide film may be 2.7 to 3.7 GPa, but is not limited thereto.

According to one embodiment, the polyimide film may have a yield point of 2.3 to 2.8% (eg, 2.3, 2.4, 2.5, 2.6, 2.7 or 2.8%). For example, the yield point of the polyimide film may be 2.4 to 2.7%, but is not limited thereto.

According to one embodiment, the polyimide film is 55 to 80 MPa (eg, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70 , 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80 Mpa). For example, the yield strength of the polyimide film may be 55 to 75 MPa, for example 60 to 80 MPa, for another example, 60 to 75 Mpa, but is not limited thereto.

According to one embodiment, the polyimide film may have a transmittance of 43% or more (eg, 43 to 100%) in a visible light region, for example, a wavelength of 380 to 780 nm. For example, the transmittance of the polyimide film may be 43 to 90%, for example, 45 to 80%, but is not limited thereto.

According to one embodiment, the polyimide film may have a thickness of 5 to 100 μm. The thickness of the polyimide film may be, for example, 10 to 80 μm, for example 20 to 70 μm, and for another example 25 to 60 μm, but is not limited thereto.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this has been presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Example 1

In 326 g of dimethylformamide (DMF), 17 g of biphenyltetracarboxylic dianhydride (BPDA) as a dianhydride monomer and 23 g of pyromellitic dianhydride, and 4 g and 4 of m-tolidine (m-TD) as a diamine monomer 30 g of ,4'-oxydianiline (ODA) was mixed and then polymerized to prepare a polyamic acid solution having a solid content of 18.5 wt%.

To the thus-prepared polyamic acid solution, 1.0 molar ratio of isoquinoline as an imidization catalyst and 2.5 molar ratio of acetic anhydride as a dehydrating agent per 1 mole of amic acid group were added, and dibasic calcium phosphate as a filler to 0.2 wt% based on the total weight of the polyimide film ( D ₅₀ = 1.5 μm) and 57 g of DMF to prepare a polyimide precursor solution.

The polyimide precursor solution was cast on a SUS plate (100SA, Sandvik) using a doctor blade, and dried at 110° C. for 10 minutes to prepare a gel film. After separating the gel film from the SUS plate, heat treatment was performed at 400° C. for 10 minutes to prepare a polyimide film having a thickness of 50 μm.

Examples 2 to 6 and Comparative Examples 1 to 6

A polyimide film was prepared in the same manner as in Example 1, except that the contents of the imidization catalyst, the dehydrating agent, and the average particle diameter of the filler were changed as described in Table 1.

However, in Comparative Examples 4 and 5, it was impossible to form a polyimide film.

How to evaluate physical properties

(1) Modulus (unit: GPa), yield point (unit: %), yield strength (unit: Mpa): Prepare a specimen by cutting the prepared polyimide film into 15 mm x 50 mm, and according to ASTM D 882 standard However, the modulus, yield point, and yield strength were measured at room temperature using a tensile tester (Instron 5564, Instron) at a tensile speed of 200 mm/min, and the results are shown in Table 1 below.

(2) Transmittance (unit: %), haze (unit: %): Based on ASTM D1003, transmittance and haze values were measured at room temperature using a haze meter (HM-150, MURAKAMI Corporation), and the results are shown below. Table 1 shows.

Imidization catalyst content
(molar ratio) dehydrating agent
(molar ratio) filler
Average particle size (D ₅₀ )
(㎛) Modulus
(GPa) yield point
(%) Yield strength
(Mpa) permeability
(%) Haze
(%) Example 1 0.8 2.5 1.5 2.70 2.53 67.26 62 6.8 Example 2 1.0 2.5 1.5 2.80 2.52 69.09 58 6.9 Example 3 1.2 3.0 1.5 2.90 2.54 70.01 54 7.0 Example 4 1.5 3.3 1.5 3.05 2.57 70.80 52 7.0 Example 5 2.0 3.3 1.5 3.40 2.54 71.8 48 7.1 Example 6 2.4 3.3 1.5 3.70 2.53 72.4 45 7.2 Comparative Example 1 1.2 3.3 1.8 2.92 2.56 70.12 52 9.2 Comparative Example 2 1.2 3.3 2.0 2.93 2.55 69.80 50 11.0 Comparative Example 3 3.0 3.3 1.5 4.10 2.52 72.5 40 7.8 Comparative Example 4 0.5 3.3 1.5 - Comparative Example 5 0.8 1.9 1.5 - Comparative Example 6 0.8 4.5 1.5 2.71 2.53 66.90 35 7.0

As can be seen from Table 1, in Examples 1 to 6, in which the content of the imidization catalyst, the content of the dehydrating agent, and the average particle diameter of the filler are within the scope of the present invention, the polyimide film has a low modulus and a high yield point, , it can be seen that it has high transmittance and low haze.

On the other hand, in Comparative Examples 1 and 2, in which the average particle diameter of the filler was out of the range of the present invention, the haze of the polyimide film was as high as 9.2% or more. In Comparative Example 3, in which the content of the imidization catalyst exceeds the range of the present invention, the modulus of the polyimide film was as high as 4.1 GPa, and the transmittance was as low as 40% or less, and the content of the imidization catalyst did not reach the range of the present invention. In the case of Comparative Example 4, it was impossible to form a film. In Comparative Example 5, in which the content of the dehydrating agent was not within the range of the present invention, film formation was impossible, and in Comparative Example 6, in which the content of the dehydrating agent was outside the range of the present invention, the transmittance was low.

Simple modifications or changes of the present invention can be easily implemented by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (9)

preparing a polyamic acid by reacting a dianhydride monomer and a diamine monomer;
preparing a polyimide precursor solution including the polyamic acid, the imidization catalyst, a dehydrating agent, a filler, and a solvent; and
A method for producing a polyimide film comprising; imidizing the polyamic acid to prepare a polyimide film,
The imidization catalyst is included in a molar ratio of 0.8 to 2.5 moles based on 1 mole of the amic acid group in the polyamic acid,
The dehydrating agent is included in a molar ratio of 2.0 to 4.0 moles based on 1 mole of the amic acid group in the polyamic acid,
The average particle diameter (D ₅₀ ) of the filler is 1.6 μm or less,
The polyimide film has a modulus of 2.5 to 4.0 GPa.
The method of claim 1,
A method for producing a polyimide film comprising biphenyltetracarboxylic dianhydride (BPDA) in an amount of 10 to 90 mol% based on the total molar amount of the dianhydride monomer.
The method of claim 2,
A method for producing a polyimide film, wherein pyromellitic dianhydride (PMDA) is further included in an amount of 10 to 90 mol% based on the total molar amount of the dianhydride monomer.
The method of claim 1,
The diamine monomer is m-tolidine (m-TD), 4,4'-oxydianiline (ODA), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 2,2-bis A method for producing a polyimide film comprising (4-[4-aminophenoxy]-phenyl)propane (BAPP) or a combination thereof.
A polyimide film prepared by the method of any one of claims 1 to 4.
The method of claim 5,
The polyimide film is a polyimide film having a yield point of 2.3 to 2.8%.
The method of claim 5,
The polyimide film is a polyimide film having a yield strength of 55 to 80 MPa.
The method of claim 5,
The polyimide film is a polyimide film having a transmittance of 43% or more in a visible light region.
The method of claim 5,
The polyimide film is a polyimide film having a haze of 7.5% or less.