TW202124533A - 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 manufacturing method thereof

The present invention relates to a polyimide film and a manufacturing method thereof. In particular, the present invention relates to a polyimide film having a low elastic modulus and a high yield point to suppress damage even in the case of repeated deformation, and a manufacturing method thereof.

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 constituting flexible displays, functional films/coating materials are important polymer substrate materials and are regarded as necessary materials for the successful implementation and development of flexible displays. Polyimide has attracted attention as such a material.

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

The most important physical property of polymer substrates used in flexible displays is flexibility. In particular, such a polymer substrate is required to suppress the damage during the bending, bending, folding, curling and stretching process of the flexible display after repeated deformation, while maintaining its original physical properties.

An object of the present invention is to provide a polyimide film that has a low elastic modulus and a high yield point to suppress damage even in the case of repeated deformation.

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

1. According to one aspect of the present invention, a polyimide film is provided, which is derived from the imidization of polyimide with 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, which is prepared from a polyimide solution containing polyimide with a solid content of about 14% to about 20% by weight. Derived by chemical reaction, the polyimide film has a modulus of about 2 GPa to about 5 GPa.

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

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

5. In any one of Examples 1 to 4, polyamide acid can be formed by the reaction of dianhydride monomer and 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 a combination 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 Embodiment 5, the dianhydride monomer may include pyromellitic 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 monomer can include pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the diamine monomer can include 4 , 4'-diaminodiphenyl ether (ODA), and polyimide films can have a yield point of about 2.35% or higher.

In Example 7, the dianhydride monomer may include pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic acid with a molar ratio of about 1:9 to about 9:1. Acid dianhydride (BPDA).

According to still another aspect of the present invention, there is provided a method of manufacturing the polyimide film according to any one of Embodiments 1 to 8. The method includes: mixing a dianhydride monomer, a diamine monomer, and an organic solvent 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 Imine precursor composition; casting the polyimine precursor composition on a support, and then drying the polyimine precursor composition to form a gel film; and heat treating the gel film to form a polyimide Imine film.

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

The present invention provides a polyimide film and a manufacturing method thereof. The polyimide film has a high yield point at a low elastic film number to suppress damage even in the case of repeated deformation.

Descriptions of known functions and structures that may unnecessarily obscure the subject of the present invention will be omitted.

It should be further understood that the terms “comprise (comprise, comprising)” and/or “include, including” when used in this specification specifically specify the existence of the described features, integers, steps, compositions and/or groups thereof, However, the existence or addition of one or more other features, integers, steps, compositions, and/or groups thereof is not excluded. As used herein, the singular forms "一 (a, an)" and "the" are intended to include the plural forms, unless the context clearly dictates.

Further, a numerical value related to a certain composition is interpreted as including an allowable range in the interpretation of the composition, unless otherwise clearly indicated.

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

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

The inventors of the present invention have completed the present invention based on the following confirmation: When having from about 2 GPa to about 5 GPa (for example, 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, 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, The polyimide film with a modulus of 4.5 GPa, 4.6 GPa, 4.7 GPa, 4.8 GPa, 4.9 GPa or 5 GPa) is adjusted by adjusting the weight average molecular weight of polyamide or the When manufactured at a solid content, the polyimide film has a high yield point.

According to one embodiment, the polyimide film can be freely passed from about 250,000 g/mol to about 440,000 g/mol (e.g., 250,000 g/mol, 260,000 g/mol, 270,000 g/mol, 280,000 g/mol, 290,000 g/mol). /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) of the weight average molecular weight of the polyamide acid imidization and derived and the polyamide The imine film may 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) based on polystyrene standards.

According to another embodiment, the polyimide film can be free from the solid content of about 14 wt% to about 20 wt% (for example, 14 wt%, 14.5 wt%, 15 wt%, 15.5 wt%, 16 wt%, 16. Weight%, 17% by weight, 17.5% by weight, 18% by weight, 18.5% by weight, 19% by weight, 19.5% by weight or 20% by weight) derived from the imidization of a polyamide solution of polyamide acid The resulting 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 having a solid content of about 14% to about 20% by weight and an organic solvent of about 80% to about 86% by weight.

In one embodiment, the polyimide film may have a yield point of about 2.1% or higher. For example, the polyimide film may have about 2.1% to about 2.9% (e.g., 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 may have about 47 MPa to about 80 MPa (e.g., 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 yield strength, as a further example, about 47 MPa to about Yield strength of about 70 MPa, but not limited to this.

In one embodiment, polyamide acid can be formed through the reaction of dianhydride monomers and diamine monomers. The dianhydride monomers and diamine monomers can be selected from various types of dianhydride monomers and diamine monomers and are not limited to specific types. For example, the dianhydride monomer may include pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) or a combination thereof, and the diamine monomer 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 pyromellitic dianhydride (PMDA), and the diamine monomer may include 4,4'-diaminodiphenyl ether (ODA); and the polyimide film It may have a yield point of about 2.1% or higher. In a further embodiment, the dianhydride monomer may include pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA); the diamine monomer 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 include a molar ratio of, for example, about 1:9 to about 9:1 (for example, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2 or 9:1) pyromellitic acid 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 number.

The polyimide film can consider the applicability, use conditions and characteristics of the polyimide film to select an appropriate thickness. 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, and as a further example, about 40 μm to about 50 μm, but is not limited thereto.

The polyimide film can be manufactured by various methods typically used in the field of manufacturing the polyimide film. For example, the method of manufacturing a polyimide film includes: mixing a dianhydride monomer, a diamine monomer, and an organic solvent to prepare a polyimide acid solution through a reaction therebetween; combining a dehydrating agent and an imidizing agent with the polyimide The acid solution is mixed to form a polyimide precursor composition; the polyimide precursor composition is cast on a support, and then the precursor composition is dried to form a gel film; and the gel is heat-treated membrane. The dianhydride monomer and diamine single system is as described above and its details will be omitted.

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

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

In one embodiment, the polyamide acid solution may have a viscosity of about 100,000 cP to about 500,000 cP at 25° C. (e.g., 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 when forming the polyimide film. Here, "viscosity" can be measured with a Brookfield viscometer. The polyamide acid solution may have a viscosity, for example, from about 150,000 cP to about 450,000 cP, as another example, from about 150,000 cP to about 350,000 cP, but is not limited thereto.

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

Dehydrating agent refers to a substance that promotes the ring closure of polyamide acid 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 a mixture thereof. Among them, from the viewpoint of availability and cost, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lactic acid anhydride are preferred. These can be used alone or in a mixture thereof.

An imidizing agent refers to a substance that promotes the ring closure of polyamide acid, and may 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, β-picoline, and pyridine. These can be used alone or in a mixture thereof.

Although the present invention has no limitation on the specific amount of dehydrating agent and imidating agent, the amount of dehydrating agent may be about 0.5 mol to about 5 mol per mol of the amide acid group in the polyamide acid. Ears (for example, 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), for example, about 1.0 mol Ears to about 4 mol, and relative to each mol of the amide acid group in the polyamide acid, the amount of the imidizing agent may be about 0.05 mol to about 3 mol (for example, 0.05 mol, 0.1 mol, 0.5 mol, 1 mol, 1.5 mol, 2 mol, 2.5 mol, or 3 mol), for example, about 0.2 mol to about 2 mol. Within this range, the polyimide precursor composition can achieve sufficient imidization and can be easily cast into a film.

After that, the gel film can be formed by casting the polyimide precursor composition on the support, and then drying.

The support may include a support commonly used in the technical field. Examples of the support may include glass plates, 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, and as a further example, from about 100°C to about 180°C, As yet another example, about 100°C to about 130°C. Within this range, the dehydrating agent and the imidizing agent can be activated, whereby the mold 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 acid to polyimide.

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

The gel film may have a volatile content of about 5% to about 500% by weight, for example, about 5% to about 200% by weight, as another example, about 5% to about 150% by weight, but not limited thereto . Within this range, during the subsequent heat treatment process for obtaining the polyimide film, defects such as film breakage, uneven color tone, and characteristic variation can be avoided. 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)

The heat treatment of the gel film may be performed at a variable temperature, for example, from about 50°C to about 700°C, as another example, from about 150°C to about 600°C, and as a further example, from 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 amide groups can be imidized, thereby obtaining a polyimide film.

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

The obtained polyimide film can have a high yield point (for example, 2.1% or higher) at a low elastic modulus (for example, about 2 GPa to about 5 GPa), thereby suppressing damage even under repeated deformation.

Next, the present invention will be explained in more detail with reference to examples. However, it should be noted that these examples are only provided for illustration and should not be construed as limiting the present invention in any way. Instance

Instance 1 to 8 And a comparative example 1 and 2

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

For each mole of amide acid groups, 3.5 mol of acetic anhydride and 1.1 mol of isoquinoline were added to the prepared polyamide acid solution to prepare a composition for polyamide film, and then a spatula was used ( Doctor blade) cast it 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 ：Measure the weight average molecular weight ( unit: g/mol)

The sample for gel permeation chromatography (GPC) was prepared by mixing 2% by weight polyamide solution and N-methylpyrrolidone (NMP), and the weight average molecular weight of the sample was based on polystyrene standards Measured by traditional method using an HPLC device (1260 Infinity ll, Agilent Technologies) at 50°C and a solvent flow rate of 0.9 ml/min.

Evaluation 2 : Measuring modulus ( unit: GPa ) , Yield point ( unit: %) And yield strength ( unit: MPa) :

The prepared polyimide film was cut into specimens with a size of 15 mm x 50 mm, and then according to ASTM D 882, a tensile tester (Instron 5564, Instron) was used at room temperature and a tension speed of 200 mm/min ( Under 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 60 x 10 ⁴ 3.01 1.98 46.75

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

It should be understood that those with ordinary knowledge in the technical field can make various modifications, changes, alterations, and equivalent embodiments without departing from the spirit and scope of the present invention.

none.

none.

none.

Claims (10)

A polyimide film derived from the imidization of polyimide with a weight average molecular weight of about 250,000 g/mol to about 440,000 g/mol, the polyimide film having 2 GPa Modulus to 5GPa. A polyimide film, which is derived from the imidization of a polyimide solution containing polyimide with a solid content of about 14% to about 20% by weight. The polyimide The amine membrane has a modulus of 2GPa to 5GPa. 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 is formed by the reaction of a dianhydride monomer and a diamine monomer, The dianhydride monomer comprises pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) or a combination thereof, The diamine monomer contains 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. The polyimide film of claim 5, wherein the dianhydride monomer comprises pyromellitic dianhydride (PMDA), and the diamine monomer comprises 4,4'-diaminodiphenyl ether (ODA), and The polyimide film has a yield point of 2.1% or higher. The polyimide film of claim 5, wherein the dianhydride monomer comprises pyromellitic acid dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), The diamine monomer includes 4,4'-diaminodiphenyl ether (ODA), and the polyimide film has a yield point of 2.35% or higher. The polyimide film of claim 7, wherein the dianhydride monomer comprises pyromellitic dianhydride (PMDA) and 3,3',4,4' with 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 dianhydride monomer, diamine monomer and an organic solvent to prepare a polyamide acid solution through the reaction therebetween; Mixing a dehydrating agent and an imidizing agent with the polyimide solution to prepare a polyimide precursor composition; Casting the polyimide precursor composition on a support, and then drying the polyimide precursor composition to form a gel film; and The gel film is heat-treated to form the polyimide film. The method of claim 9, wherein the heat treatment is performed at a temperature of 100°C to 700°C.