JP2023503089A - Method for producing polyimide film and polyimide film produced thereby - Google Patents

Abstract

reacting a dianhydride monomer and a diamine monomer to prepare a polyamic acid; preparing a polyimide precursor solution comprising the polyamic acid, an imidization catalyst, a dehydrating agent, a filler, and a solvent; and imidizing the polyamic acid to produce a polyimide film, wherein the imidization catalyst is about 0.8 mol per 1 mol of the amic acid group in the polyamic acid. to about 2.5 mol, the dehydrating agent is included in a molar ratio of about 2.0 mol to about 4.0 mol with respect to 1 mol of amic acid groups in the polyamic acid, and the The average particle size (D50) of the filler is about 1.6 μm or less, and the modulus of the polyimide film is about 2.5 GPa to about 4.0 GPa. Disclosed is a method for producing a polyimide film and a polyimide film produced therefrom be done. [Selection figure] None

Description

The present invention relates to a method for producing a polyimide film and a polyimide film produced thereby. More particularly, the present invention relates to a method for producing a polyimide film having a low elastic modulus, a high yield point and yield strength, a high transmittance and a low haze, and a polyimide film produced thereby.

Flexible displays such as curved, bendable, foldable, rollable, etc. are the next generation displays that have recently received interest from both academia and industry. Functional film/coating materials are important polymer substrate materials that constitute flexible displays, and are indispensable for the successful realization and development of flexible displays. Polyimide is attracting attention as a core material.

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

Flexibility is the most important physical property required for polymer substrates for flexible displays. In particular, such a polymer substrate should not be damaged during carving, bending, folding, rolling, and stretching processes that cause repeated deformation of the flexible display, and should not lose various initial physical properties.

On the other hand, such polymer substrates for flexible displays are required to be transparent for various purposes, so they often have optical properties such as high light transmittance and low haze. be requested.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a polyimide film having a low modulus and high yield point and yield strength.

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

Still another object of the present invention is to provide a polyimide film produced by the method for producing a polyimide film described above.

1. According to one aspect, reacting a dianhydride monomer and a diamine monomer to prepare a polyamic acid; and a polyimide precursor solution comprising the polyamic acid, an imidization catalyst, a dehydrating agent, a filler, and a solvent. and a step of imidizing the polyamic acid to produce a polyimide film, wherein the imidization catalyst is 1 mol of amic acid groups in the polyamic acid is contained in a molar ratio of about 0.8 mol to about 2.5 mol, and the dehydrating agent is contained in a molar ratio of about 2.0 mol to about 4.0 mol per 1 mol of the amic acid group in the polyamic acid. ratio, the average particle diameter (D ₅₀ ) of the filler is about 1.6 μm or less, and the modulus of the polyimide film is about 2.5 GPa to about 4.0 GPa. be done.

2. In the first embodiment, biphenyltetracarboxylic dianhydride (BPDA) is included in an amount of about 10 mol % to about 90 mol % based on the total molar amount of dianhydride monomers.

3. In the first or second embodiment, pyromellitic dianhydride (PMDA) is further included in an amount of about 10 mol% to about 90 mol% based on the total molar amount of dianhydride monomers.

4. In any one of the first to third embodiments, 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 according to any one of the first to fourth embodiments.

6. In the fifth embodiment, the polyimide film may have a yield point of about 2.3% to about 2.8%.

7. In the fifth or sixth embodiment, the polyimide film may have a yield strength of about 55 MPa to about 80 MPa.

8. In any one of the fifth to seventh embodiments, the polyimide film may have a transmittance of about 43% or more in the visible light region.

9. In any one of the fifth through eighth embodiments, the polyimide film may have a haze of about 7.5% or less.

Advantageous Effects of Invention The present invention provides a method for producing a polyimide film having a low elastic modulus, a high yield point and yield strength, a high transmittance and a low haze, and a polyimide film produced therefrom.

In describing the present invention, if it is determined that the specific description of such known technology may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Where "including", "having", "consisting", etc. are used as referred to herein, other parts can be added as long as "only" is not used. The singular representation of a constituent element includes the plural unless otherwise specified.

Also, in interpreting the elements, they are to be construed to include a margin of error even if there is no express description to the contrary.

In this specification, "-" in "a to b" indicating a numerical range is defined as ≧a and ≦b.

In producing a polyimide film from a polyamic acid, the inventors of the present invention found that when the polyimide film was produced by controlling the contents of the imidization catalyst and the dehydrating agent and the average particle diameter (D ₅₀ ) of the filler, the polyimide film had a polyimide film of about 2.5. It is possible to produce a polyimide film that has a high yield point and yield strength even with a low modulus of 0 GPa to about 4.0 GPa, a low degree of damage even when subjected to repeated deformation, a high transmittance and a low haze. I found it and came to complete the present invention. The present invention will be described in more detail below.

Method for Producing Polyimide Film According to one aspect, a method for producing a polyimide film is provided. The method for producing the polyimide film includes the steps of reacting a dianhydride monomer and a diamine monomer to produce a polyamic acid; and imidizing the polyamic acid to produce a polyimide film, wherein the imidization catalyst is about 0.8 mol per 1 mol of amic acid groups in the polyamic acid. to about 2.5 mol, the dehydrating agent is included in a molar ratio of about 2.0 mol to about 4.0 mol with respect to 1 mol of amic acid groups in the polyamic acid, and the The average particle size (D ₅₀ ) of the filler may be about 1.6 μm or less, and the modulus of the polyimide film may be about 2.5 GPa to about 4.0 GPa. Each step will be described in more detail below.

First, a polyamic acid can be prepared by reacting a dianhydride monomer and a diamine monomer. More specifically, a dianhydride monomer and a diamine monomer can be polymerized in a solvent to produce a polyamic acid solution. At this time, all the monomers may be added at once, or each monomer may be added sequentially, in which case partial polymerization between the monomers may occur.

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

According to one embodiment, the dianhydride monomer is from about 10 mol % to about 90 mol % (eg, 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 (BPDA). In this case, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. For example, the dianhydride monomer is from about 15 mol % to about 85 mol %, in other examples from about 20 mol % to about 80 mol %, and still other Examples include, but are not limited to, about 30 mol % to about 70 mol %.

According to one embodiment, dianhydride monomers can include biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA). In this case, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. Biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) are, for example, about 10:90 to about 90:10 (e.g., 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, or 90:10), other examples include, but are not limited to, molar ratios of from about 20:80 to about 80:20, still other examples from about 30:70 to about 70:30. . According to one embodiment, the dianhydride monomers are in excess of about 10 mol % of biphenyltetracarboxylic dianhydride and pyromellitic dianhydride, based on the total molar amount of dianhydride monomers. About 100 mol % (e.g., 11 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 %) in total moles, but are limited to not a thing

The type of diamine monomer is not particularly limited, and can be selected variously 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), which can be used alone or in combination of two or more. According to one embodiment, diamine monomers can include m-tolidine (m-TD) or 4,4'-oxydianiline (ODA). According to other embodiments, the diamine monomer is m-tolidine (m-TD) and 4,4'-oxydianiline (ODA) at 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), for example about 1:99 to about 50:50, other examples about 1 :99 to about 30:70, and as another example, from about 5:95 to about 20:80, but are not limited thereto.

The organic solvent is not particularly limited as long as it can dissolve the polyamic acid, and may be, for example, an aprotic polar organic solvent. Non-limiting examples of aprotic polar organic solvents include amide solvents such as N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), p-chlorophenol, o-chlorophenol phenolic solvents such as N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), diglyme, etc., and these can be used alone or in combination of two or more. In some cases, auxiliary solvents such as toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol, water, etc. may be used to adjust the solubility of the polyamic acid. In one embodiment, the organic solvent may be an amide solvent, such as, but not limited to, N,N-dimethylformamide or N,N-dimethylacetamide.

According to one embodiment, the polyamic acid is from about 5 wt% to about 35 wt% (e.g., 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%) based on the total weight of the polyamic acid solution. %, 30%, or 35% by weight). Within the above ranges, the polyamic acid solution can 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 includes, for example, about 10% to about 30% by weight, and other examples about 15% to about 25% by weight, but is not limited thereto. Absent.

A polyimide precursor solution can then be prepared comprising a polyamic acid, an imidization catalyst, a dehydrating agent, a filler, and a solvent. More specifically, an imidization catalyst, a dehydrating agent, a filler, and optionally an additional solvent may be added to a polyamic acid solution to prepare a polyimide precursor solution. Additional solvents can be understood with reference to the discussion of solvents used in preparing the polyamic acid solution.

The imidization catalyst can mean a component that has the effect of promoting the ring closure reaction of polyamic acid, examples of which include tertiary amine compounds, more specifically aliphatic tertiary amines, aromatic 3 Primary amines, heterocyclic tertiary amines, and the like. Among them, heterocyclic tertiary amines can be used from the viewpoint of reactivity as a catalyst, and examples thereof include quinoline, isoquinoline, β-picoline, pyridine and the like, which may be used singly or in combination of two or more. Can be mixed and used.

The imidization catalyst is used in a molar ratio of about 0.8 mol to about 2.5 mol (for example, 0.8 mol, 0.9 mol, 1.0 mol, 1 .1 mol, 1.2 mol, 1.3 mol, 1.4 mol, 1.5 mol, 1.6 mol, 1.7 mol, 1.8 mol, 1.9 mol, 2.0 mol, 2 .1 mol, 2.2 mol, 2.3 mol, 2.4 mol, or 2.5 mol). If the content of the imidization catalyst is less than the above range, film formation is difficult, and if the content of the imidization catalyst exceeds the above range, the modulus becomes excessively large (for example, exceeds about 4.0 GPa), There is a problem of low transmittance. Therefore, within the above range, it is possible to produce a polyimide film having a low elastic modulus, a high yield point and yield strength, a high transmittance and a low haze. For example, the imidization catalyst is included in a molar ratio of from about 0.8 moles to about 2.4 moles per mole of amic acid groups in the polyamic acid, but is not limited thereto.

A dehydrating agent can mean one that promotes the ring closure reaction by dehydrating the polyamic acid, such as aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimides, lower aliphatic halogen halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, thionyl halides and the like, and these can be used alone or in combination of two or more. Among them, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic acid anhydride can be used alone or in combination of two or more from the viewpoint of availability and cost.

The dehydrating agent is used in a molar ratio of about 2.0 mol to about 4.0 mol (eg, 2.0 mol, 2.1 mol, 2.2 mol, 2.0 mol, 2.2 mol, 2.0 mol, 2.0 mol, 2.2 mol, 2.0 mol, 2.0 mol, 2.2 mol, 2.0 mol, 2.0 mol, 2.2 mol, 2.0 mol, 2.0 mol, 2.2 mol, 2.0 mol) per 1 mol of amic acid groups in the polyamic acid. 3 mol, 2.4 mol, 2.5 mol, 2.6 mol, 2.7 mol, 2.8 mol, 2.9 mol, 3.0 mol, 3.1 mol, 3.2 mol, 3. 3 mol, 3.4 mol, 3.5 mol, 3.6 mol, 3.7 mol, 3.8 mol, 3.9 mol, or 4.0 mol). Within these ranges, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. For example, the dehydrating agent is included in a molar ratio of about 2.5 to about 3.3 moles per mole of amic acid groups in the polyamic acid, but is not limited thereto.

According to one embodiment, the molar ratio of imidization catalyst to dehydration agent (imidization catalyst:dehydration agent) is from about 1:1 to about 1:10 (eg, 1:1, 1:1.1, 1:1. 1:2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10). Within these ranges, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. For example, the molar ratio of imidization catalyst to dehydrating agent is from about 1:1.2 to about 1:6, in other examples from about 1:1.3 to about 1:5, still in other examples about 1:1. .3 to about 1:4, but is not limited thereto.

The filler can impart roughness to the polyimide film, examples of which include inorganic fillers, more specifically, dibasic calcium phosphate, barium sulfate, calcium carbonate, spherical silica, etc. These alone or in combination of two or more.

The filler can have an average particle size (D ₅₀ ) of about 1.6 μm or less, specifically greater than 0 μm to about 1.6 μm. Within these ranges, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. For example, the average particle size ( _D50 ) of the filler is 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm , 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, or 1.6 μm, and other examples from about 0.5 μm to about 1.6 μm, but are limited to not something.

Although the content of the filler is not particularly limited, it is about 0.05 wt% to about 0.5 wt% (e.g., 0.05 wt%, 0.1 wt%, 0.15 wt%) based on the total weight of the polyimide film. wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, or 0.5 wt%) including said In the range, it is possible to produce polyimide films with low modulus, high yield point and yield strength, high transmittance and low haze. For example, but not limited to, the filler content may be from about 0.1% to about 0.3% by weight.

In one embodiment, the polyimide precursor solution may contain various additives as long as they do 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, which can be used alone or in combination of two or more.

The polyamic acid can then be imidized to produce a polyimide film. For example, a polyimide film can be produced by casting a polyimide precursor solution on a support, drying it to produce a gel film, and heat-treating the gel film for imidization.

According to one embodiment, the step for forming the gel film includes about 40% polyimide precursor solution cast on a support (e.g., glass plate, aluminum foil, endless stainless steel belt, stainless steel drum, etc.). C. to about 300.degree. C., for example about 80.degree. C. to about 200.degree. C., for another example about 100.degree. C. to about 180.degree. Obtainable. This causes partial curing and/or drying to form a gel film. The gel film is an intermediate step in the curing of polyamic acid to polyimide and can be self-supporting.

Optionally, the step of stretching the gel film can be included to control the thickness and size of the final polyimide film and improve orientation, the stretching being in the machine direction (MD). and in at least one direction transverse to the machine transport direction (TD).

The volatile content of the gel film may be, but is not limited to, about 5 wt% to about 500 wt%, for example about 5 wt% to about 200 wt%, another example about 5 to about It may be 150% by weight, and within the above range, there is an effect of avoiding defects such as film breakage, color contamination, and characteristic fluctuation during the heat treatment process for obtaining a polyimide film later. Here, the volatile content of the gel film can be calculated using the following formula 2. In formula 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. means.

<Formula 1>
(AB) * 100/B

According to one embodiment, the step of heat-treating the gel film includes heating the gel film to a temperature in the range of about 50°C to about 700°C, such as about 150°C to about 600°C, another example of about 200°C to about 600°C. A polyimide film can be obtained by heat-treating at a variable temperature to remove the solvent remaining in the gel film and imidizing most of the remaining amic acid groups.

Optionally, the polyimide film obtained as described above may be heat finished at a temperature of about 400° C. to about 650° C. for about 5 seconds to about 400 seconds to further cure the polyimide film; This may be done under a given tension in order to relieve any internal stress that may remain in the film.

Polyimide Film According to another aspect, there is provided a polyimide film manufactured by the manufacturing method described above. The polyimide film manufactured by the manufacturing method described above has a low elastic modulus, a high yield point, and a high transmittance.

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

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

According to one embodiment, the polyimide film has a thickness of about 55 MPa to about 80 MPa (e.g. , 71 MPa, 72 MPa, 73 MPa, 74 MPa, 75 MPa, 76 MPa, 77 MPa, 78 MPa, 79 MPa, or 80 MPa). For example, but not limited to, the yield strength of the polyimide film may be from about 55 MPa to about 75 MPa, in other examples from about 60 MPa to about 80 MPa, and in still other examples from about 60 MPa to about 75 MPa. .

According to one embodiment, the polyimide film can have a transmittance of about 43% or greater (eg, about 43% to about 100%) in the visible light region, eg, wavelengths of about 380 nm to about 780 nm. For example, but not limited to, the transparency of the polyimide film may be from about 43% to about 90%, and as another example from about 45% to about 80%.

According to one embodiment, the polyimide film can have a thickness of about 5 μm to about 100 μm. The thickness of the polyimide film may be, for example, from about 10 μm to about 80 μm, another example from about 20 μm to about 70 μm, still another example from about 25 μm to about 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 is presented as a preferred example of the invention and is not to be construed as limiting the invention in any way.

Example 1
In 326 g of dimethylformamide (DMF), 17 g of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 23 g of pyromellitic dianhydride as dianhydride monomers, and a diamine monomer 4 g of m-tolidine (m-TD) and 30 g of 4,4′-oxydianiline (ODA) were mixed as a body and then polymerized to prepare a polyamic acid solution having a solid content of 18.5% by weight. .

To the polyamic acid solution thus prepared, 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 groups were added to form a polyimide film. Dibasic calcium phosphate (D ₅₀ =1.5 μm) was added as a filler so as to be 0.2% by weight, and 57 g of DMF was added 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, it was heat-treated at 400° C. for 10 minutes to prepare a polyimide film having a thickness of 50 μm.

Examples 2-6 and Comparative Examples 1-6
A polyimide film was produced using the same method as in Example 1, except that the imidization catalyst, the content of the dehydrating agent, and the average particle size of the filler were changed as shown in Table 1.

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

Physical property evaluation method (1) Modulus (unit: GPa), yield point (unit: %), yield strength (unit: Mpa): The produced polyimide film was cut to 15 mm × 50 mm to produce a test piece, and ASTM D882 standard Based on, the modulus, yield point and yield strength were measured at room temperature (room temp.) using a tensile tester (Instron 5564, Instron) with 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 standards, the transmittance and haze values were measured at room temperature using a haze meter (HM-150, MURAKAMI). are shown in Table 1 below.

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 size of the filler are within the scope of the present invention, the modulus of the polyimide film is low and , has a high yield point, high transmittance and low haze.

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

Simple variations and modifications of the present invention can be readily implemented by those of ordinary skill in the art, and all such variations and modifications are within the scope of the present invention.

Claims (9)

reacting a dianhydride monomer and a diamine monomer to produce a polyamic acid;
preparing a polyimide precursor solution comprising the polyamic acid, an imidization catalyst, a dehydrating agent, a filler, and a solvent;
imidizing the polyamic acid to produce a polyimide film, wherein
The imidization catalyst is contained in a molar ratio of about 0.8 mol to about 2.5 mol with respect to 1 mol of amic acid groups in the polyamic acid,
The dehydrating agent is contained in a molar ratio of about 2.0 mol to about 4.0 mol with respect to 1 mol of amic acid groups in the polyamic acid,
The average particle size (D ₅₀ ) of the filler is about 1.6 μm or less,
The method for producing a polyimide film, wherein the polyimide film has a modulus of about 2.5 GPa to about 4.0 GPa. 2. The process for producing a polyimide film according to claim 1, wherein biphenyltetracarboxylic dianhydride (BPDA) comprises from about 10 mol % to about 90 mol % based on the total molar amount of dianhydride monomers. 3. The process for producing a polyimide film according to claim 1 or 2, further comprising pyromellitic dianhydride (PMDA) from about 10 mol% to about 90 mol% based on the total molar amount of dianhydride monomers. . The diamine monomers include m-tolidine (m-TD), 4,4'-oxydianiline (ODA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2,2- A method for producing a polyimide film according to any one of claims 1 to 3, comprising bis(4-[4-aminophenoxy]-phenyl)propane (BAPP), or a combination thereof. A polyimide film produced by the production method according to any one of claims 1 to 4. 6. The polyimide film of claim 5, wherein the polyimide film has a yield point of about 2.3% to about 2.8%. 7. The polyimide film of claim 5 or 6, wherein the polyimide film has a yield strength of about 55 MPa to about 80 MPa. The polyimide film according to any one of claims 5 to 7, wherein the polyimide film has a transmittance of about 43% or more in the visible light region. The polyimide film of any one of claims 5-8, wherein the polyimide film has a haze of about 7.5% or less.