KR102396419B1 - Polyimide film and method for preparing the same - Google Patents

Abstract

A polyimide film induced by imidizing a polyamic acid having a weight average molecular weight of 250,000 to 440,000, or a polyimide film induced by imidizing a polyamic acid solution having a polyamic acid solid content of 14 to 20 wt%, the polyimide film A polyimide film having a modulus of silver 2 to 5 GPa, and a method for preparing the same are disclosed.

Description

Polyimide film and manufacturing method thereof

It relates to a polyimide film and a method for manufacturing the same. More specifically, it relates to a polyimide film having a high yield point at a low modulus of elasticity and thus less damaged even in repeated deformation, and a method for manufacturing the same.

Flexible displays such as curved, bendable, foldable, and rollable displays are the next-generation displays that have recently been attracting attention from both academia and industry. Among the various types of materials constituting flexible displays, functional film/coating materials are important polymer substrate materials constituting flexible displays and are essential for the successful implementation and development of flexible displays. is attracting attention.

Polyimide is a polymer characterized by having a heteroimide ring in its main chain. In addition to excellent heat resistance, it has excellent mechanical properties, flame retardancy, chemical resistance, low dielectric constant, etc.

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

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

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

1. The polyimide film according to one aspect is induced by imidization of polyamic acid having a weight average molecular weight of 250,000 to 440,000, and may have a modulus of 2 to 5 GPa.

2. The polyimide film according to another aspect is induced by imidizing a polyamic acid solution having a polyamic acid solid content of 14 to 20 wt%, and may have a modulus of 2 to 5 GPa.

3. In 1 or 2 above, the polyimide film may have a yield point of 2.1% or more.

4. In any one of 1 to 3, the polyimide film may have a yield strength of 47 Mpa or more.

5. The polyamic acid according to any one of 1 to 4, wherein the polyamic acid is formed from the reaction of a dianhydride monomer and a diamine monomer, and the dianhydride monomer is pyromellitic dianhydride (PMDA), 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) or a combination thereof, wherein the diamine monomer is 4,4'-oxydianiline (ODA), m-tolidine (m-TD), 1,3-bis( 4-aminophenoxy)benzene (TPE-R), 2,2-bis(4-[4-aminophenoxy]-phenyl)propane (BAPP), or combinations thereof.

6. In the above 5, the dianhydride monomer comprises pyromellitic dianhydride (PMDA), the diamine monomer comprises 4,4'-oxydianiline (ODA), and the polyimide film has a yield point of 2.1 % or more.

7. In the above 5, the dianhydride monomer includes pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the diamine monomer is 4,4 It contains '-oxydianiline (ODA), and the polyimide film may have a yield point of 2.35% or more.

8. In the above 7, the molar ratio of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) may be 1:9 to 9:1.

9. According to another aspect, there is provided a method for producing the polyimide film according to any one of 1 to 8 above. The method comprises mixing and reacting a dianhydride monomer, a diamine monomer and an organic solvent to form a polyamic acid solution; forming a polyimide precursor composition by mixing a dehydrating agent and an imidizing agent with the polyamic acid solution; casting the polyimide precursor composition on a support and drying to prepare a gel film; And, heat-treating the gel film to form a polyimide film; may include steps.

10. In 9 above, the heat treatment may be performed at 100 to 700 °C.

The polyimide film and the manufacturing method thereof of the present invention may have the effect of providing a polyimide film having a high yield point at a low elastic modulus and thus less damaged even after repeated deformation.

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

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, cases including the plural are included unless otherwise explicitly stated.

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

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

In the present specification, the modulus, yield point, and yield strength may be measured using a tensile tester based on ASTM D 882 standards, but with a tensile rate of 200 mm/min, but is not limited thereto.

The inventors of the present invention control the weight average molecular weight of the polyamic acid or control the content of the polyamic acid solid content in the polyamic acid solution to 2 to 5 GPa (for example, 2, 2.1, 2.2, 2.3, 2.4, 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, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5 GPa) When a polyimide film having a modulus was prepared, it was discovered that the polyimide film can have a high yield point, and the present invention was completed.

According to one embodiment, the polyimide film has a weight average molecular weight of 250,000 to 440,000 (eg, 250,000, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,000, 390,000, 400,000, 410,000, 420,000, 430,000 or 440,000) is induced by imidization of polyamic acid, and may have a modulus of 2 to 5 GPa. In this case, the polyimide film may have a high yield point at a low modulus of elasticity. Here, the 'weight average molecular weight' may mean a polystyrene equivalent weight average molecular weight measured using gel permeation chromatography (GPC).

According to another embodiment, the polyimide film has a polyamic acid solids content of 14 to 20% by weight (eg, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5 or 20). % by weight), which is induced by imidization of a polyamic acid solution, and may have a modulus of 2 to 5 GPa. In this case, the polyimide film may have a high yield point at a low modulus of elasticity. For example, the polyamic acid solution may include 14 to 20 weight percent polyamic acid solids and 80 to 86 weight percent organic solvent.

According to one embodiment, the polyimide film may have a yield point of 2.1% or more. For example, the yield point of the polyimide film is 2.1 to 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%), for example, 2.1 to 2.8%, for another example, 2.15 to 2.7%, but is not limited thereto.

According to one embodiment, the polyimide film may have a yield strength of 47 Mpa or more. For example, the yield strength of the polyimide film may be 47 to 80 Mpa, for example, 47 to 75 Mpa, for another example, 47 to 70 Mpa, but is not limited thereto.

According to one embodiment, the polyamic acid may be formed from a reaction of a dianhydride monomer and a diamine monomer. At this time, the types of the dianhydride monomer and the diamine monomer are not particularly limited, but, for example, the dianhydride monomer is pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride ( BPDA) or a combination thereof, wherein the diamine monomer is 4,4'-oxydianiline (ODA), m-tolidine (m-TD), 1,3-bis(4-aminophenoxy)benzene ( TPE-R), 2,2-bis(4-[4-aminophenoxy]-phenyl)propane (BAPP), or a combination thereof. According to one embodiment, the dianhydride monomer comprises pyromellitic dianhydride (PMDA), the diamine monomer comprises 4,4'-oxydianiline (ODA), and the polyimide film has a yield point of 2.1 % or more. According to another embodiment, the dianhydride monomer comprises pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the diamine monomer is 4,4 It contains '-oxydianiline (ODA), and the polyimide film may have a yield point of 2.35% or more. At this time, the molar ratio of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 1:9 to 9:1 (eg, 2:8 to 8) :2, for example, 3:7 to 7:3), and in the above range, the polyimide film may have a high yield point at a low elastic modulus, but is not limited thereto.

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

The above-described polyimide film may be manufactured by various methods commonly used in the field of polyimide film production. For example, the polyimide film is prepared by mixing and reacting a dianhydride monomer, a diamine monomer and an organic solvent to form a polyamic acid solution; forming a polyimide precursor composition by mixing a dehydrating agent and an imidizing agent with the polyamic acid solution; casting the polyimide precursor composition on a support and drying to prepare a gel film; And, heat-treating the gel film to form a polyimide film; It can be prepared including steps. Since the description of the dianhydride monomer and the diamine monomer has been described above, a description thereof will be omitted.

First, a dianhydride monomer, a diamine monomer, and an organic solvent may be mixed and reacted to form a polyamic acid solution. At this time, all the monomers may be added at once, or each of the monomers may be added sequentially, and in this case, partial polymerization between the monomers may occur.

The organic solvent is not particularly limited as long as it is a solvent in which the polyamic acid can be dissolved, and may be, for example, an aprotic polar organic solvent. Non-limiting examples of the aprotic polar organic solvent include amide solvents such as N,N'-dimethylformamide (DMF) and N,N'-dimethylacetamide (DMAc), p-chlorophenol, o-chloro and phenolic solvents such as phenol, N-methylpyrrolidone (NMP), gamma-butyrolactone (GBL), and Diglyme, 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, and water may be used to adjust the solubility of the polyamic acid. In an embodiment, the organic 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 solution may have a viscosity of 100,000 to 500,000 cP at 25 °C. In the above range, processability may be excellent when forming a polyimide film. Here, 'viscosity' may be measured using a Brookfield viscometer. The polyamic acid solution may have a viscosity of, for example, 150,000 to 450,000 cP, for example, 150,000 to 350,000 cP at 25° C., but is not limited thereto.

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

A dehydrating agent promotes 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 fatty acid anhydride, aryl phosphonic acid dihalide, thionyl halide, etc. may be mentioned, 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 imidizing agent means a component having an effect of promoting a ring closure reaction with respect to the polyamic acid, and for example, an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine may be used. Among them, a heterocyclic tertiary amine can be used from the viewpoint of reactivity as a catalyst. Examples thereof include quinoline, isoquinoline, β-picoline, pyridine, and the like, and these may be used alone or in combination of two or more.

The amount of the dehydrating agent and the imidizing agent is not particularly limited, but the dehydrating agent may be added in a ratio of 0.5 to 5 moles, for example, 1.0 to 4 moles, based on 1 mole of the amic acid group in the polyamic acid, and the imidizing agent is polyamic acid. It may be added in a ratio of 0.05 to 3 moles, for example, 0.2 to 2 moles, based on 1 mole of the amic acid group in the mixed acid, and imidization is sufficient in the above range, and casting into a film type may be easy.

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

As the support, a support commonly used in the art may be used without limitation, and examples of the support include a glass plate, an aluminum foil, an endless stainless belt, a stainless drum, and the like.

Drying can be carried out, for example, at a temperature of 40 to 300 °C, another for example 80 to 200 °C, another for example 100 to 180 °C, another for example 100 to 130 °C, whereby the dehydrating agent and The imidizing agent is activated, and partial curing and/or drying may take place to form a gel film. The gel film is in the intermediate stage of curing from polyamic acid to polyimide and can be self-supporting.

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

The volatile matter content of the gel film is not limited thereto, but may be 5 to 500% by weight, for example, 5 to 200% by weight, for another example, 5 to 150% by weight, in the above range, the polyimide film During the process of heat treatment to obtain it, there may be an effect of avoiding the occurrence of defects such as film breakage, color tone unevenness, and characteristic variation. Here, the volatile matter content of the gel film can be calculated by using Equation 1 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 is heat-treated at a variable temperature in the range of 50 to 700 ° C, for example 150 to 600 ° C, and another, for example 200 to 600 ° C, remaining in the gel film. 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 heat-finished at a temperature of 400 to 650 ° C. for 5 to 400 seconds to further harden the polyimide film, and internal stress that may remain in the obtained polyimide film is reduced. This may be done under a certain tension in order to relieve.

The above-described polyimide film has a high yield point (eg, 2.1% or more) at a low modulus of elasticity (eg, 2 to 5 GPa), and thus may have an effect of less damage even after repeated deformation.

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 present invention and cannot be construed as limiting the present invention in any sense.

Example

Examples 1 to 8 and Comparative Examples 1 to 2

3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) as dianhydride monomers in dimethylformamide (DMF), 4,4'-oxydihydride as diamine monomers Aniline (ODA) was mixed in the molar ratio shown in Table 1 below and then polymerized to prepare a polyamic acid solution. At this time, the number of moles of the dianhydride monomer and the diamine monomer were substantially equimolar, and the content of the monomer and DMF used was controlled to control the solid content of the polyamic acid as described in Table 1.

Acetic anhydride in a molar ratio of 3.5 and isoquinoline in a molar ratio of 1.1 per mole of the amic acid group was added to the polyamic acid solution thus prepared to obtain a composition for preparing a polyimide film, and the composition was applied on a SUS plate (100SA, Sandvik) using a doctor blade. A gel film was prepared by casting and drying at 90° C. for 4 minutes. After separating the gel film from the SUS plate, heat treatment was performed at 250 to 380° C. for 14 minutes to prepare a polyimide film having an average thickness of 50 μm.

Evaluation Example 1: Measurement of Weight Average Molecular Weight

A sample for gel permeation chromatography (GPC) was prepared by mixing a polyamic acid solution at 2 wt% in N-methylpyrrolidone (NMP) solvent, and an HPLC device (1260 Infinity ll, agilent Technologies) was used for the sample. Thus, the weight average molecular weight in terms of polystyrene was obtained under the conditions of 50 °C and 0.9 ml/min solvent flow by a conventional method.

Evaluation Example 2: Measurement of modulus (unit: GPa), yield point (unit: %), yield strength (unit: Mpa)

The prepared polyimide film was cut to 15 mm × 50 mm to prepare a specimen, and in accordance with ASTM D 882, at a tensile speed of 200 mm/min, a tensile tester (Instron 5564, Instron) was used to .) to measure the modulus, yield point and yield strength, and the results are shown in Table 1 below.

BPDA
(mole%) PMDA
(mole%) ODA
(mole%) solid content
(weight%) weight average
Molecular Weight modulus
(GPa) yield point
(%) yield strength
(MPa) Example 1 - 100 100 20 250,000 3.15 2.16 48.95 Example 2 - 100 100 17 350,000 3.05 2.22 47.04 Example 3 - 100 100 15 430,000 3.11 2.30 49.08 Example 4 35 65 100 18.5 290 thousand 3.26 2.36 55.16 Example 5 35 65 100 15 430,000 3.29 2.65 58.24 Example 6 35 65 100 14.0 430,000 3.30 2.58 58.25 Example 7 70 30 100 18.5 300,000 3.44 2.55 64.21 Example 8 70 30 100 15 440,000 3.45 2.62 65.0 Comparative Example 1 - 100 100 23 200,000 3.15 2.05 47.35 Comparative Example 2 - 100 100 13 600,000 3.01 1.98 46.75

As can be seen from Table 1 above, in the case of the polyimide films of Examples 1 to 8, in which the weight average molecular weight or the polyamic acid solid content of the polyamic acid is within the scope of the present invention, the polyimide films of Comparative Examples 1 and 2 are not. It can be easily predicted that it has a higher yield point than that of the mid film, and as a result, the degree of damage to the polyimide film from repeated deformation will be small.

Simple modifications or changes of the present invention can be easily carried out 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 (10)

It is a polyimide film induced by imidization of polyamic acid having a weight average molecular weight of 250,000 to 440,000,
The polyamic acid is formed from the reaction of a dianhydride monomer and a diamine monomer,
The content of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 70 mol% or less based on 100 mol% of the total content of the dianhydride monomer, and the content of pyromellitic dianhydride (PMDA) is The content is 30 mol% or more,
The polyimide film is a polyimide film having a modulus of 2 to 5 GPa.
It is a polyimide film induced by imidizing a polyamic acid solution having a polyamic acid solid content of 14 to 20 wt%,
The polyamic acid is formed from the reaction of a dianhydride monomer and a diamine monomer,
The content of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 70 mol% or less based on 100 mol% of the total content of the dianhydride monomer, and the content of pyromellitic dianhydride (PMDA) is The content is 30 mol% or more,
The polyimide film is a polyimide film having a modulus of 2 to 5 GPa.
3. The method of claim 1 or 2,
The polyimide film is a polyimide film with a yield point of 2.1% or more.
3. The method of claim 1 or 2,
The polyimide film is a polyimide film having a yield strength of 47 Mpa or more.
3. The method of claim 1 or 2,
The diamine monomer is 4,4'-oxydianiline (ODA), m-tolidine (m-TD), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2,2-bis A polyimide film comprising (4-[4-aminophenoxy]-phenyl)propane (BAPP) or a combination thereof.
6. The method of claim 5,
The diamine monomer includes 4,4'-oxydianiline (ODA),
The polyimide film is a polyimide film with a yield point of 2.1% or more.
6. The method of claim 5,
The diamine monomer includes 4,4'-oxydianiline (ODA),
The polyimide film is a polyimide film having a yield point of 2.35% or more.
8. The method of claim 7,
A polyimide film wherein the molar ratio of pyromellitic dianhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) is 1:9 to 9:1.
A method for producing the polyimide film of claim 1 or 2, the method comprising:
mixing and reacting a dianhydride monomer, a diamine monomer and an organic solvent to form a polyamic acid solution;
forming a polyimide precursor composition by mixing a dehydrating agent and an imidizing agent with the polyamic acid solution;
casting the polyimide precursor composition on a support and drying to prepare a gel film; And,
heat-treating the gel film to form a polyimide film;
A method for producing a polyimide film comprising the steps of.
10. The method of claim 9,
The heat treatment is performed at 100 to 700 ℃, a method for producing a polyimide film.