TWI762041B - Polyimide film and method of manufacturing the same - Google Patents

Abstract

A polyimide film and a method of manufacturing the same. The polyimide film is derived through imidization of a polyamic acid having a weight average molecular weight of about 250,000 g/mol to about 440,000 g/mol or through imidization of a polyamic acid solution containing about 14 wt% to about 20 wt% of a polyamic acid in terms of solid content. The polyimide film has a modulus of about 2 GPa to about 5 GPa.

Description

Polyimide film and method for producing the same

The present invention relates to a polyimide film and a method for producing the same. In particular, the present invention relates to a polyimide film having a high yield point at a low elastic modulus to compress damaged polyimide films even under repeated deformation and methods of making the same.

In recent years, flexible displays, such as curved displays, bendable displays, foldable displays, and rollable displays, have attracted the attention of academia and industry as next-generation displays. Among the various types of materials that make up flexible displays, functional film/coating materials are important polymer substrate materials and are considered essential materials for the successful implementation and development of flexible displays. Polyimide has attracted attention as such a material.

Polyimide is a polymer characterized by a hetero-imide ring in its main chain and its excellent properties in terms of heat resistance, mechanical properties, flame retardancy, chemical resistance, low dielectric constant, etc. It is used in a wide range of applications such as coating materials, molding materials and composite materials.

The most important physical property of polymer substrates for flexible displays is flexibility. In particular, such polymer substrates are needed to suppress damage during the bending, bending, folding, curling and stretching processes of the flexible display through repeated deformations, while maintaining its original physical properties.

An object of the present invention is to provide a high yield point at a low elastic modulus to compress damaged polyimide films even under repeated deformation.

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

1. According to one aspect of the present invention, there is provided a polyimide film derived from the imidization of a polyimide having a weight average molecular weight of about 250,000 g/mol to about 440,000 g/mol As a result, the polyimide film has a modulus of about 2 GPa to about 5 GPa.

2. According to another aspect of the present invention, there is provided a polyimide film obtained from a polyimide solution passed through a polyimide solution containing a polyamic acid having a solid content of about 14 wt % to about 20 wt %. Derived from chemistry, the polyimide membrane has a modulus of about 2 GPa to about 5 GPa.

3. In Example 1 or 2, the polyimide film may have a yield point of about 2.1% or higher.

4. In any one of Embodiments 1 to 3, the polyimide film may have a yield strength of about 47 MPa or higher.

5. In any one of embodiments 1 to 4, the polyamic acid can be formed via the reaction of a dianhydride monomer and a diamine monomer, wherein the dianhydride monomer can include pyromellitic dianhydride (pyromellitic dianhydride). dianhydride, PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride, BPDA) or combinations thereof, and diamine monomers may include 4,4'-Diaminodiphenyl ether (4,4'-oxydianiline, ODA), 2,2'-dimethyl-p-benzidine (m-tolidine, m-TD), 1,3-bis(4- Aminophenoxy)benzene (1,3-bis(4-aminophenoxy)benzene, TPE-R), 2,2-bis(4-[4-aminophenoxy)-phenyl)propane (2, 2-bis(4-[4-aminophenoxy]-phenyl)propane, BAPP) or a combination thereof.

In Example 5, the dianhydride monomer may include pyromite dianhydride (PMDA), the diamine monomer may include 4,4'-diaminodiphenyl ether (ODA), and the polyimide film may have A yield point of about 2.1% or higher.

In Example 5, the dianhydride monomers may include pyromic acid dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the diamine monomers may include 4 ,4'-diaminodiphenyl ether (ODA), and polyimide films can have yield points of about 2.35% or higher.

In Example 7, the dianhydride monomers may include pyromic acid dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxyl in a molar ratio of about 1:9 to about 9:1 acid dianhydride (BPDA).

According to yet another aspect of the present invention, there is provided a method of manufacturing the polyimide film according to any one of Embodiments 1-8. The method includes: mixing dianhydride monomers, diamine monomers and organic solvents to prepare a polyamide acid solution through a reaction therebetween; mixing a dehydrating agent and an imidizing agent with the polyamide acid solution to prepare a polyamide acid solution an imine precursor composition; casting the polyimide precursor composition on a support, then drying the polyimide precursor composition to form a gel film; and thermally treating the gel film to form a polyimide imine film.

In Example 9, the heat treatment may be performed at a temperature of about 100°C to about 700°C.

The present invention provides a polyimide film having a high yield point at a low elastic film number to be crushed even under repeated deformation and a method of making the same.

Descriptions of known functions and constructions that may unnecessarily obscure the subject matter of the present invention are omitted.

It is to be further understood that the terms "comprise, comprising" and/or "include, including" when used in this specification refer to the presence of specific recited features, integers, steps, compositions and/or groups thereof, The presence or addition of one or more other features, integers, steps, compositions and/or groups thereof is not excluded. As used herein, the singular forms "a (a, an)" and "the" are intended to include the plural forms unless the context clearly dictates otherwise.

Further, a numerical value related to a composition is to be construed in terms of compositional interpretation to include an allowable range unless clearly indicated otherwise.

The expression "a to b" as used herein to denote a specific numerical range means "≥a and ≤b".

Here, the modulus, yield point and yield strength may be measured at a tensile strength of 200 mm/min using a tensile tester according to ASTM D 882, but are not limited thereto.

The inventors of the present invention made the present invention based on the following confirmation: when having about 2 GPa to about 5 GPa (eg, 2 GPa, 2.1 GPa, 2.2 GPa, 2.3 GPa, 2.4 GPa, 2.5 GPa, 2.6 GPa, 2.7 GPa, 2.8 GPa 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, 4 GPa, 4.1 GPa, 4.2 GPa, 4.3 GPa, 4.4 GPa, 4.5 GPa, 4.6 GPa, 4.7 GPa, 4.8 GPa, 4.9 GPa, or 5 GPa) polyimide film system by adjusting the weight-average molecular weight of polyamic acid or polyamic acid in polyamic acid solution. The polyimide film has a high yield point when manufactured at a solid content.

According to one embodiment, the polyimide membrane can have a range from about 250,000 g/mol to about 440,000 g/mol (eg, 250,000 g/mol, 260,000 g/mol, 270,000 g/mol, 280,000 g/mol, 290,000 g/mol) via /mol, 300,000 g/mol, 310,000 g/mol, 320,000 g/mol, 330,000 g/mol, 340,000 g/mol, 350,000 g/mol, 360,000 g/mol, 370,000 g/mol, 380,000 g/mol, 390,000 g /mol, 400,000 g/mol, 410,000 g/mol, 420,000 g/mol, 430,000 g/mol or 440,000 g/mol) weight-average molecular weight polyamic acid imidization The imine membrane can have a modulus of about 2 GPa to about 5 GPa. As a result, the polyimide film can have a high yield point at a low elastic film count. Here, the weight-average molecular weight means the weight-average molecular weight measured by gel permeation chromatography (GPC) according to a polystyrene standard.

According to another embodiment, the polyimide film may have a solid content of from about 14 wt % to about 20 wt % (eg, 14 wt %, 14.5 wt %, 15 wt %, 15.5 wt %, 16 wt %, 16.5 wt % % by weight, 17% by weight, 17.5% by weight, 18% by weight, 18% by weight, 19% by weight, 19% by weight, 19.5% by weight, or 20% by weight) of a polyamic acid solution of polyamic acid derived from imidization is obtained and the polyimide film has a modulus of about 2 GPa to about 5 GPa. As a result, the polyimide film can have a high yield point at a low elastic film count. For example, the polyamic acid solution may include polyamic acid in a solids content of about 14 wt % to about 20 wt % and an organic solvent in an amount of about 80 wt % to about 86 wt %.

In one embodiment, the polyimide film may have a yield point of about 2.1% or higher. For example, the polyimide film can have from about 2.1% to about 2.9% (eg, 2.1%, 2.15%, 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%), as another example, from about 2.1% to about 2.8%, as a further example, from about 2.15% to about 2.7% yield point, but not limited to this.

In one embodiment, the polyimide film may have a yield strength of about 47 MPa or higher. For example, the polyimide film can have a range of about 47 MPa to about 80 MPa (eg, 47 MPa, 48 MPa, 49 MPa, 50 MPa, 51 MPa, 52 MPa, 53 MPa, 54 MPa, 55 MPa, 56 MPa, 57 MPa, 58 MPa, 59 MPa, 60 MPa, 61 MPa, 62 MPa, 63 MPa, 64 MPa, 65 MPa, 66 MPa, 67 MPa, 68 MPa, 69 MPa, 70 MPa, 71 MPa, 72 MPa, 73 MPa, 74 MPa, 75 MPa, 76 MPa, 77 MPa, 78 MPa, 79 MPa or 80 MPa), as another example, about 47 MPa to about 75 MPa, as a further example, about 47 MPa to about 75 MPa A yield strength of about 70 MPa, but not limited thereto.

In one embodiment, the polyamic acid may be formed via the reaction of dianhydride monomers with diamine monomers. The dianhydride monomer and the diamine monomer may be selected from various kinds of dianhydride monomers and diamine monomers without being limited to a specific kind. For example, dianhydride monomers may include pyrometic acid dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), or combinations thereof, and diamine monomers may include 4,4'-Diaminodiphenyl ether (ODA), 2,2'-dimethyl-p-benzidine (m-TD), 1,3-bis(4-aminophenoxy)benzene (TPE-R ), 2,2-bis(4-[4-aminophenoxy)-phenyl)propane (BAPP), or a combination thereof. In another embodiment, the dianhydride monomer may include pyrometic acid dianhydride (PMDA), the diamine monomer may include 4,4'-diaminodiphenyl ether (ODA); and the polyimide film Can have a yield point of about 2.1% or higher. In further embodiments, the dianhydride monomers may include pyromic acid dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA); the diamine monomers may include 4,4'-diaminodiphenyl ether (ODA); and the polyimide film may have a yield point of about 2.35% or higher. In this embodiment, the dianhydride monomer may comprise a molar ratio of, eg, about 1:9 to about 9:1 (eg, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 or 9:1) pyromite dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) as Another example, about 2:8 to about 8:2, as a further example, about 3:7 to about 7:3, but not limited thereto. Within this range, the polyimide film can have a high yield point at a low elastic film count.

For the polyimide film, an appropriate thickness can be selected in consideration of the applicability, use conditions and characteristics of the polyimide film. For example, the polyimide film may have a thickness of about 10 μm to about 500 μm, as another example, about 20 μm to about 50 μm, as a further example, about 40 μm to about 50 μm, but not limited thereto.

Polyimide films can be manufactured by various methods typically used in the field of manufacturing polyimide films. For example, a method of manufacturing a polyimide film includes: mixing a dianhydride monomer, a diamine monomer, and an organic solvent to prepare a polyimide solution through a reaction therebetween; mixing a dehydrating agent and an imidizing agent with the polyimide mixing acid solutions to form a polyimide precursor composition; casting the polyimide precursor composition on a support, followed by drying the precursor composition to form a gel film; and thermally treating the gel membrane. The dianhydride monomer and diamine monomer system are as described above and the details thereof will be omitted.

First, a dianhydride monomer, a diamine monomer, and an organic solvent are mixed with each other to prepare a polyamic acid solution through a reaction therebetween. Here, the monomers can be added simultaneously or sequentially. In this case, partial polymerization may occur between the monomers.

The organic solvent may include any organic solvent that can dissolve the polyamic acid, for example, an aprotic polar organic solvent. Examples of the aprotic polar organic solvent may include amide solvents such as N,N'-dimethylformamide (N,N'-dimethylformamide, DMF) and N,N'-dimethylacetamide (N,N'-dimethylformamide (N,N'-dimethylformamide) N'-dimethylacetamide, DMAc), phenolic solvents such as p-chlorophenol and o-chlorophenol, N-methyl-pyrrolidone (NMP), gamma -Butyrolactone (γ-butyrolactone, GBL) and diethylene glycol dimethyl ether (diglyme). These can be used alone or in combination. Auxiliary solvents, such as toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol or water, may be further used to adjust the solubility of the polyamic acid as required. In one embodiment, the organic solvent may be an amide solvent, for example, N,N'-dimethylformamide or N,N'-dimethylacetamide, but not limited thereto.

In one embodiment, the polyamic acid solution may have a viscosity of about 100,000 cP to about 500,000 cP (eg, 100,000 cP, 150,000 cP, 200,000 cP, 250,000 cP, 300,000 cP, 350,000 cP, 400,000 cP, 450,000 cP or 500,000 cP). Within this range, the polyimide solution can achieve good processability during polyimide film formation. Here, "viscosity" can be measured using a Brookfield viscometer. The polyamide solution may have a viscosity, eg, about 150,000 cP to about 450,000 cP, as another example, about 150,000 cP to about 350,000 cP, but not limited thereto.

Thereafter, the polyimide precursor composition can be prepared by mixing the dehydrating agent and the imidizing agent with the polyimide solution.

The dehydrating agent refers to a substance that promotes ring closure of polyamide through dehydration, and may include, for example, aliphatic acid anhydrides, aromatic acid anhydrides, N,N'-dialkylcarbodiimide (N,N'-dialkylcarbodiimide), low Lower aliphatic halides, halogenated lower fatty acid anhydrides, aryl phosphonic dihalides and thionyl halides. These can be used alone or in mixtures thereof. Among them, from the viewpoints of availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic anhydride are preferred. These can be used alone or in mixtures thereof.

The imidizing agent refers to a substance that promotes ring closure of polyamides, and can include, for example, aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines Class (heterocyclic tertiary amines). Among them, from the viewpoint of catalytic reactivity, heterocyclic tertiary amines are preferred. Examples of heterocyclic tertiary amines may include quinoline, isoquinoline, beta-picoline, and pyridine. These can be used alone or in mixtures thereof.

Although the present invention is not limited to the specific amount of dehydrating agent and imidizing agent, the dehydrating agent may be present in an amount of about 0.5 mol to about 5 mol per mol of amide group in the polyamic acid. Molar (eg, 0.5 mol, 1 mol, 1.5 mol, 2 mol, 2.5 mol, 3 mol, 3.5 mol, 4 mol, 4.5 mol, or 5 mol), eg, about 1.0 mol The imidizing agent may be present in an amount from about 0.05 moles to about 3 moles (eg, 0.05 moles, 0.1 mole, 0.5 mole, 1 mole, 1.5 mole, 2 mole, 2.5 mole, or 3 mole), for example, about 0.2 mole to about 2 mole. Within this range, the polyimide precursor composition can achieve sufficient imidization and can be easily cast into films.

Afterwards, a gel film can be formed by casting the polyimide precursor composition on a support, followed by drying.

The support body may include a support body commonly used in the art. Examples of supports may include glass sheets, aluminum foils, endless stainless steel belts, and stainless steel drums.

Drying the polyimide precursor composition can be performed at a temperature, for example, from about 40°C to about 300°C, as another example, from about 80°C to about 200°C, as a further example, from about 100°C to about 180°C, As yet another example, from about 100°C to about 130°C. Within this range, the dehydrating agent and the imidizing agent can be activated, whereby the casting precursor composition is partially cured and/or dried, resulting in the formation of a gel film. Here, the gel film refers to a self-supported film intermediate formed in the intermediate stage of the conversion of polyamide to polyimide.

As required, the method according to the present invention may further include stretching the gel film to adjust the thickness and size of the finally obtained polyimide film and to improve the orientation of the polyimide film. Here, the stretching of the gel film may be performed in at least one of a machine direction (MD) and a transverse direction (TD).

The gel film may have a volatile content of about 5 wt% to about 500 wt%, for example, about 5 wt% to about 200 wt%, as another example, about 5 wt% to about 150 wt%, but not limited thereto . Within this range, the occurrence of defects such as film cracking, uneven color tone, and variation in characteristics can be avoided during the subsequent heat treatment process for obtaining the polyimide film. Here, the volatile content of the gel film can be calculated according to Equation 1. In Equation 1, A represents the initial weight of the gel film and B represents the weight of the gel film after heating the gel film to 450°C for 20 minutes. (A-B)*100/B, ---(1)

Thermal treatment of the gel film can be performed at varying temperatures, eg, about 50°C to about 700°C, as another example, about 150°C to about 600°C, as a further example, about 200°C to about 600°C. Under these conditions, the residual solvent can be removed from the gel film, and almost all the residual imide groups can be imidized, thereby obtaining a polyimide film.

According to needs, the obtained polyimide film may be further cured by heat-finishing treatment at a temperature of about 400° C. and about 650° C. for about 5 to 400 seconds. Here, thermal processing may be performed under a predetermined tension to relieve residual stress of the obtained polyimide film.

The resulting polyimide films can have high yield points (eg, 2.1% or higher) at low elastic moduli (eg, about 2 GPa to about 5 GPa), thereby compressing to failure even with repeated deformation.

Next, the present invention will be described in more detail with reference to examples. It should be noted, however, that these examples are provided for illustration only and should not be construed as limiting the invention in any way. example

example 1 to 8 and a comparative example 1 and 2

In dimethylformamide (DMF), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was mixed as a dianhydride monomer in the molar ratio listed in Table 1 and pyromic acid dianhydride, and 4,4'-diaminodiphenyl ether (ODA) as a diamine monomer and polymerized to prepare a polyamic acid solution. The dianhydride monomer and the diamine monomer are present in substantially the same molar amount. The content of polyamide was adjusted as listed in Table 1 by adjusting the content of monomer and DMF.

3.5 mol of acetic anhydride and 1.1 mol of isoquinoline were added to the prepared polyamide solution per mol of amide acid group to prepare a composition for a polyamide film, after which a doctor blade ( doctor blade) was cast on a SUS plate (100SA, Sandvik) and dried at 90°C for 4 minutes to form a gel film. The gel film was removed from the SUS plate and heat-treated at a temperature of 250° C. to 380° C. for 14 minutes, thereby preparing a polyimide film having an average thickness of 50 μm.

Evaluation 1 : Measurement of weight average molecular weight ( unit: g/mol)

Samples for Gel Permeation Chromatography (GPC) were prepared by mixing a 2 wt% solution of polyamide with N-methylpyrrolidone (NMP) and the weight average molecular weights of the samples were according to polystyrene standards Measured by conventional methods using an HPLC apparatus (1260 Infinity 11, Agilent Technologies) at 50°C and a solvent flow rate of 0.9 ml/min.

Evaluation 2 : measure modulus ( unit: GPa ) , surrender point ( unit: %) and yield strength ( unit: MPa) :

The prepared polyimide film was cut into specimens with dimensions of 15 mm x 50 mm, and then according to ASTM D 882, using a tensile tester (Instron 5564, Instron) at room temperature and a tensile speed of 200 mm/min ( tensile speed), measure the modulus, yield point and yield strength. The results are shown in Table 1.

Table 1 BPDA (mol%) PMDA (mol%) ODA (mol%) Solid content (wt%) Weight average molecular weight (g/mol) Modulus (GPa) Yield point (%) Yield strength (MPa) Example 1 - 100 100 20 25 x 10 ⁴ 3.15 2.16 48.95 Example 2 - 100 100 17 35 x 10 ⁴ 3.05 2.22 47.04 Example 3 - 100 100 15 43 x 10 ⁴ 3.11 2.30 49.08 Example 4 35 65 100 18.5 29 x 10 ⁴ 3.26 2.36 55.16 Example 5 35 65 100 15 43 x 10 ⁴ 3.29 2.65 58.24 Example 6 35 65 100 14.0 43 x 10 ⁴ 3.30 2.58 58.25 Example 7 70 30 100 18.5 30 x 10 ⁴ 3.44 2.55 64.21 Example 8 70 30 100 15 44 x 10 ⁴ 3.45 2.62 65.0 Comparative Example 1 - 100 100 twenty three 20 x 10 ⁴ 3.15 2.05 47.35 Comparative Example 2 - 100 100 13 ^60x104 3.01 1.98 46.75

As can be seen from Table 1, Example 1 that satisfies the conditions of the weight average molecular weight or the solid content of polyimide according to the present invention is compared to the polyimide films of Comparative Examples 1 and 2 that do not satisfy the conditions according to the present invention Polyimide films to 8 have higher yield points. As a result, the polyimide films of Examples 1 to 8 can be expected to have insignificant damage even under repeated deformation.

It should be understood that those skilled in the art can make various modifications, changes, alterations and equivalent embodiments without departing from the spirit and scope of the present invention.

none.

none.

Claims (9)

A polyimide film derived from the imidization of a polyimide having a weight average molecular weight of about 250,000 g/mol to about 440,000 g/mol, the polyimide film having 2 GPa to a modulus of 5GPa, wherein the polyamic acid is formed by the reaction of a dianhydride monomer and a diamine monomer, wherein the 3,3',4 , The content of 4'-biphenyl tetracarboxylic dianhydride (BPDA) is less than or equal to 70mol%, and the content of pyrometic acid dianhydride (PMDA) is greater than or equal to 30mol%, wherein the total content of the diamine monomer is The content of 4,4'-diaminodiphenyl ether (ODA) was 100 mol % based on 100 mol %. A polyimide film derived from the imidization of a monopolyimide solution containing a polyimide having a solids content of about 14 wt % to about 20 wt %, the polyimide film The amine film has a modulus of 2GPa to 5GPa, wherein the polyamic acid is formed through the reaction of a dianhydride monomer and a diamine monomer, wherein the total content of the dianhydride monomer is 100 mol% as a benchmark, 3, The content of 3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is less than or equal to 70mol%, and the content of pyromite dianhydride (PMDA) is greater than or equal to 30mol%, wherein the diamine monomer is used The total content of 100 mol% is the basis, and the content of 4,4'-diaminodiphenyl ether (ODA) is 100 mol%. The polyimide film of claim 1 or 2, wherein the polyimide film has a yield point of 2.1% or higher. The polyimide film of claim 1 or 2, wherein the polyimide film has a yield strength of 47 MPa or higher. The polyimide film of claim 1 or 2, wherein the polyimide film has a yield point of 2.1% or higher. The polyimide film of claim 1 or 2, wherein the polyimide film has a yield point of 2.35% or higher. The polyimide film of claim 6, wherein the dianhydride monomer comprises pyromic acid dianhydride (PMDA) and 3,3',4,4' in a molar ratio of 1:9 to about 9:1 - Biphenyltetracarboxylic dianhydride (BPDA). A method for manufacturing the polyimide film of claim 1 or 2, comprising: mixing a dianhydride monomer, a diamine monomer and an organic solvent to prepare a polyimide solution through a reaction therebetween; mixing a dehydrating agent and an imidizing agent and the polyimide solution to prepare a polyimide precursor composition; casting the polyimide precursor composition on a support, and then drying the polyimide a precursor composition to form a gel film; and heat treatment of the gel film to form the polyimide film. The method of claim 8, wherein the heat treatment is carried out at a temperature of 100°C to 700°C.