CN108586742B

CN108586742B - High-temperature-resistant polyimide film capable of being used as flexible OLED substrate and preparation method and application thereof

Info

Publication number: CN108586742B
Application number: CN201810397886.6A
Authority: CN
Inventors: 路庆华
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2018-04-28
Filing date: 2018-04-28
Publication date: 2020-03-06
Anticipated expiration: 2038-04-28
Also published as: CN108586742A

Abstract

The present application relates to a high temperature resistant polyimide film useful as a flexible OLED substrate made from a diamine monomer and at least 3 dianhydride monomers, wherein the diamine monomer does not include an imidazole or thiazole structure, and wherein the dianhydride monomers include at least one alkynyl containing unsaturated dianhydride monomer. The application also relates to a method for preparing the high-temperature-resistant polyimide film. The application also relates to application of the high-temperature-resistant polyimide film in preparing an OLED device. The beneficial effects of this application lie in that the diamine monomer low cost of this application can realize the volume production of polyimide film, and gained polyimide film thermal stability is good.

Description

High-temperature-resistant polyimide film capable of being used as flexible OLED substrate and preparation method and application thereof

Technical Field

The application relates to the technical field of flexible OLED materials and organic synthesis. In particular, the application relates to a high-temperature-resistant polyimide film capable of being used as a flexible OLED substrate, and a preparation method and application thereof.

Background

In recent years, with the development of flexible display technology, especially the emergence of flexible Organic Light Emitting Diodes (OLEDs), high temperature resistant polymer flexible substrates have become one of the key materials to be solved urgently. The polyimide film has excellent thermal stability, chemical stability, dielectric property, mechanical strength and other properties, and is a preferred material for the flexible substrate of the OLED. In OLED displays, the Low Temperature Polysilicon (LTPS) processing temperature is as high as 400-500 ℃, but current polyimide films cannot withstand such high temperatures.

Chinese patent application 201710220528.3 entitled "optimized preparation method of polyimide film" previously filed by the inventors discloses that a polyimide film having high thermal stability can be prepared by dissolving a diamine monomer containing a benzimidazole, benzothiazole structure and a dianhydride monomer in an aprotic polar solvent. However, diamine monomers containing benzimidazole and benzothiazole structures are expensive, which potentially limits the mass production of polyimide films.

Therefore, the development of a polyimide film which can be used as a flexible OLED substrate and has low cost and high temperature resistance and a preparation method thereof are urgently needed in the art.

Disclosure of Invention

An object of the present application is to provide a high temperature resistant polyimide film that can be used as a flexible OLED substrate, thereby solving the above-mentioned technical problems in the prior art. Specifically, the polyimide films of the present application are prepared by copolymerizing a lower cost mixture of common diamine monomers with at least 3 dianhydride monomers, wherein the dianhydride monomers include at least one alkynyl group containing unsaturated dianhydride monomer. Through the synergistic effect of the diamine monomer and at least 3 dianhydride monomers and the post-curing crosslinking effect, the cost for preparing the high-temperature-resistant polyimide film can be reduced, and the thermal stability of the obtained polyimide film can be maintained.

It is also an object of the present application to provide a method of preparing a high temperature resistant polyimide film that can be used as a flexible OLED substrate.

The application also aims to provide the application of the high-temperature-resistant polyimide film which can be used as the flexible OLED substrate in the preparation of flexible OLED devices.

In order to solve the above technical problem, the present application provides the following technical solutions:

in a first aspect, the present application provides a high temperature resistant polyimide film useful as a flexible OLED substrate, the polyimide film made from a diamine monomer and at least 3 dianhydride monomers, wherein the diamine monomer does not include an imidazole or thiazole structure, and wherein the dianhydride monomer includes at least one alkynyl group containing unsaturated dianhydride monomer.

In one embodiment of the first aspect, the at least one alkynyl containing unsaturated dianhydride monomer comprises 4, 4' - (acetylene-1, 2, -diyl) diphthalic anhydride.

In another embodiment of the first aspect, the diamine monomer comprises m-phenylenediamine, p-phenylenediamine, 4 '-diaminobiphenyl, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenyl ether, 4' -diaminobenzophenone.

In another embodiment of the first aspect, the polyimide film is made from 1 diamine monomer and 3 dianhydride monomers, wherein the diamine monomer is selected from p-phenylenediamine or 4, 4' -diaminodiphenyl ether; wherein the dianhydride monomer comprises 4,4 ' - (acetylene-1, 2, -diyl) diphthalic anhydride, pyromellitic dianhydride, and 3,3 ', 4,4 ' -biphenyltetracarboxylic dianhydride.

In another embodiment of the first aspect, the at least one alkynyl containing unsaturated dianhydride monomer comprises from greater than 0 to 30 percent of the total dianhydride monomer on a molar basis.

In another embodiment of the first aspect, the at least one alkynyl containing unsaturated dianhydride monomer comprises from 10% to 30% of the total dianhydride monomer on a molar basis.

In another embodiment of the first aspect, the 4,4 ' - (ethyne-1, 2, -diyl) diphthalic anhydride comprises from greater than 0 to 30% of the total amount of all dianhydride monomers on a molar basis, and the amount of pyromellitic dianhydride and the amount of 3,3 ', 4,4 ' -biphenyltetracarboxylic dianhydride are the same.

In a second aspect, the present application provides a method of preparing a high temperature resistant polyimide film useful as a flexible OLED substrate as described in the first aspect, the method comprising the steps of:

s1: under the condition of ice-water bath, the diamine monomer and the at least two dianhydride monomers react in a polar aprotic solvent to obtain polyamic acid low-temperature glue solution; and

s2: and uniformly coating the polyamic acid low-temperature glue solution on a substrate, removing the solvent of the polyamic acid low-temperature glue solution, and imidizing the polyamic acid glue solution to obtain the high-temperature-resistant polyimide film which can be used as the flexible OLED substrate.

In one embodiment of the second aspect, imidizing the polyamic acid paste includes thermally imidizing the polyamic acid paste in step S2.

In a third aspect, the present application provides a use of the high temperature resistant polyimide film as described in the first aspect as a flexible OLED substrate for the preparation of a flexible OLED device.

Compared with the prior art, the beneficial effects of this application lie in that the diamine monomer low cost of this application can realize the volume production of polyimide film, and gained polyimide film thermal stability is good.

Detailed Description

In the process of flexible OLED display, the formation of Low Temperature Polysilicon (LTPS) requires a processing temperature as high as 400-500 ℃, and thus the thermal stability requirement of the OLED substrate is relatively high. Polyimide films are the highest grade polymer materials with high temperature resistance, but the heat resistance of common polyimide cannot achieve such high heat resistance, and the high temperature resistant polyimide films reported in the prior patent are either high in preparation cost or easy to break. Therefore, the application provides a high-temperature-resistant polyimide film with low cost and a preparation method thereof.

Diamine monomer

In the present application, the diamine monomer may be a common diamine monomer, and does not include an imidazole or thiazole structure.

In one embodiment, the diamine monomer may be one or more of m-phenylenediamine, p-phenylenediamine, 4 '-diaminobiphenyl, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenyl ether, and 4, 4' -diaminobenzophenone.

Dianhydride monomer

In the present application, the thermal stability of the resulting polyimide film is ensured by selecting at least 3 dianhydride monomers to copolymerize with the diamine monomer. Further, the dianhydride monomer used herein includes at least one unsaturated dianhydride monomer containing an alkynyl group. After the unsaturated dianhydride monomer containing alkynyl is polymerized with diamine, the movement of a main chain can be restrained, and the steric hindrance can be increased, so that the thermal stability of the obtained polyimide film can be improved.

In one embodiment, the content of the at least one alkynyl containing unsaturated dianhydride monomer is critical to the thermal stability of the resulting polyimide film. In one embodiment, the at least one alkynyl-containing unsaturated dianhydride monomer comprises from greater than 0 to 30 percent of the total dianhydride monomer on a molar basis. In another embodiment, the at least one alkynyl-containing unsaturated dianhydride monomer comprises from 10% to 30% of the total dianhydride monomer on a molar basis.

The dianhydride monomer other than the at least one alkynyl group-containing unsaturated dianhydride monomer is not particularly limited in this application as long as it does not significantly increase the cost of the polyimide. However, in a preferred embodiment, the dianhydride monomer may include 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride and pyromellitic dianhydride. Because they can complement unsaturated dianhydride monomers in performance to generate synergistic effect, the thermal stability, mechanical property and the like of the obtained polyimide film are finally improved.

In one embodiment, the polar aprotic solvent can include one or more of N-methylpyrrolidone, N-dimethylformamide and N, N-dimethylacetamide.

Examples

The present application will now be described and illustrated in further detail with reference to the following examples. All chemical raw materials can be purchased from the market unless otherwise specified.

The structural formulae and abbreviations of the monomers used in the following examples are as follows:

P-Phenylenediamine (PDA)

4, 4' -diaminodiphenyl ether (ODA)

Pyromellitic anhydride (PMDA)

3,3 ', 4, 4' -Biphenyltetracarboxylic dianhydride (BPDA)

4, 4' - (ethyne-1, 2, -diyl) diphthalic anhydride (EBPA)

Example 1

This example relates to the synthesis of polyimide using PDA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: PDA: [ EBPA (10%) + PMDA (45%) + BPDA (45%) ] -1: 1.

The reaction process of the synthetic route comprises the following steps: first, 10mmol of PDA was added to a three-necked flask. It was dissolved well with mechanical stirring with 10ml of N, N-Dimethylacetamide (DMAC). Then, 4.5mmol PMDA, 4.5mmol BPDA and 1.0mmol EBPA were added in one portion, and reacted in an ice-water bath, during which 30ml DMAC was added in portions to adjust the viscosity of the gum solution to prevent gelation. After 24h of reaction, polyamic acid (PAA) was obtained, which was left to stand to remove air bubbles, and the glue was placed in a refrigerator for 12 h. Thereafter, the polyamic acid solution was uniformly and slowly poured onto a glass substrate of a film-laying machine at 70 ℃ and laid flat into a uniform film using a 500 μm doctor blade. Then, the film was placed in an oven and the solvent was sufficiently removed by controlling the temperature at 70 ℃/2h, 90 ℃/2h, 110 ℃/2 h. Finally, the film is placed in a high-temperature oven, and thermal imidization is carried out by programmed heating of 120 ℃/2h, 200 ℃/2h, 250 ℃/2h, 300 ℃/2h, 350 ℃/1h and 400 ℃/1 h. Finally, the polyimide is obtained. After sufficient immersion in water, the polyimide film was peeled off from the glass substrate, and dried to obtain the polyimide film according to example 1.

The resulting polyimide film was then characterized for thermal properties using DMA Q800 (model: TA Q800) and TGA (model: Pyris1TGA), the characterization results are shown in Table 1 below.

Example 2

This example relates to the synthesis of polyimide using PDA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: PDA: [ EBPA (20%) + PMDA (40%) + BPDA (40%) ] -1: 1.

The experimental procedure of this example was the same as that of example 1 except that 4.0mmol of PMDA, 4.0mmol of BPDA and 2.0mmol of EBPA were added to obtain a polyimide film according to example 2. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 1 below.

Example 3

This example relates to the synthesis of polyimide using PDA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: PDA: [ EBPA (30%) + PMDA (35%) + BPDA (35%) ] -1: 1.

The experimental procedure of this example was the same as that of example 1 except that 3.5mmol of PMDA, 3.5mmol of BPDA and 3.0mmol of EBPA were added to obtain a polyimide film according to example 3. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 1 below.

Comparative example 1

This comparative example relates to the synthesis of polyimide using PDA as the diamine monomer, where the molar ratios of the starting materials are as follows: PDA: [ EBPA (0%) + PMDA (50%) + BPDA (50%) ] -1: 1.

The experimental procedure of this example was the same as that of example 1 except that 5.0mmol of PMDA and 5.0mmol of BPDA were added to obtain a polyimide film according to comparative example 1. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 1 below.

Table 1: thermal properties of polyimide films using PDA as the diamine monomer

Tg: a glass transition temperature; td_5％: the weight loss of the material to the desired temperature of 5%.

Example 4

This example relates to the synthesis of polyimide using ODA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: ODA: [ EBPA (10%) + PMDA (40%) + BPDA (40%) ] -1: 1.

The reaction process of the synthetic route comprises the following steps: first, 10mmol of ODA was added to a three-necked flask. It was dissolved well with mechanical stirring with 10ml DMAC. Then, 4.5mmol PMDA, 4.5mmol BPDA and 1mmol EBPA were added in one portion, and reacted in an ice-water bath, during which 30ml DMAC was added in portions to adjust the viscosity of the gum solution to prevent gelation. After 24h of reaction, polyamic acid (PAA) was obtained, which was left to stand to remove air bubbles, and the glue was placed in a refrigerator for 12 h. Thereafter, the polyamic acid solution was uniformly and slowly poured onto a glass substrate of a film-laying machine at 70 ℃ and laid flat into a uniform film using a 500 μm doctor blade. Then, the film was placed in an oven and the solvent was sufficiently removed by controlling the temperature at 70 ℃/2h, 90 ℃/2h, 110 ℃/2 h. Finally, the film is placed in a high-temperature oven, and thermal imidization is carried out by programmed heating of 120 ℃/2h, 200 ℃/2h, 250 ℃/2h, 300 ℃/2h, 350 ℃/1h and 400 ℃/1 h. Finally, the polyimide is obtained. After sufficient immersion in water, the polyimide film was peeled off from the glass substrate and dried to obtain a polyimide film according to example 4.

The resulting polyimide film was then characterized for thermal properties using DMA Q800 (model: TA Q800) and TGA (model: Pyris1TGA), the characterization results are shown in Table 2 below.

Example 5

This example relates to the synthesis of polyimide using ODA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: ODA: [ EBPA (20%) + PMDA (40%) + BPDA (40%) ] -1: 1.

The experimental procedure of this example was the same as that of example 4 except that 4.0mmol of PMDA, 4.0mmol of BPDA and 2.0mmol of EBPA were added to obtain a polyimide film according to example 5. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 2 below.

Example 6

This example relates to the synthesis of polyimide using ODA as the diamine monomer, wherein the molar ratios of the raw materials are as follows: ODA: [ EBPA (30%) + PMDA (35%) + BPDA (35%) ] -1: 1.

The experimental procedure of this example was the same as that of example 4, except that 3.5mmol of PMDA, 3.5mmol of BPDA and 3.0mmol of EBPA were added, to obtain a polyimide film according to example 6. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 2 below.

Comparative example 2

This comparative example relates to the synthesis of polyimide using ODA as the diamine monomer, wherein the molar ratios of the starting materials are as follows: ODA: [ EBPA (0%) + PMDA (50%) + BPDA (50%) ] -1: 1.

The experimental procedure of this example was the same as that of example 4 except that 5.0mmol of PMDA and 5.0mmol of BPDA were added to obtain a polyimide film according to comparative example 2. Similarly, the thermal properties of the resulting polyimide film were characterized using DMA Q800 (type: TA Q800) and TGA (type: Pyris1TGA), the characterization results being shown in Table 2 below.

Table 2: thermal properties of polyimide films utilizing ODA as diamine monomer

The embodiments described above are intended to facilitate the understanding and appreciation of the application by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present application is not limited to the embodiments herein, and those skilled in the art who have the benefit of this disclosure will appreciate that many modifications and variations are possible within the scope of the present application without departing from the scope and spirit of the present application.

Claims

1. A high temperature resistant polyimide film useful as a flexible OLED substrate made from diamine monomers and at least 3 dianhydride monomers, wherein the diamine monomers do not include an imidazole or thiazole structure, and wherein the dianhydride monomers include at least one alkynyl-containing unsaturated dianhydride monomer;

the at least one alkynyl-containing unsaturated dianhydride monomer comprises 4, 4' - (acetylene-1, 2-diyl) diphthalic anhydride;

the polyimide film is made from 1 diamine monomer and 3 dianhydride monomers, wherein the diamine monomer is selected from p-phenylenediamine or 4, 4' -diaminodiphenyl ether; wherein the dianhydride monomer comprises 4,4 ' - (acetylene-1, 2-diyl) diphthalic anhydride, pyromellitic dianhydride, and 3,3 ', 4,4 ' -biphenyltetracarboxylic dianhydride;

the at least one alkynyl-containing unsaturated dianhydride monomer accounts for 10-30% of the total amount of all dianhydride monomers on a molar basis.

2. The high temperature resistant polyimide film useful as a flexible OLED substrate of claim 1 wherein the amount of pyromellitic dianhydride and the amount of 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride are the same on a molar basis.

3. A method of making the high temperature resistant polyimide film of claim 1 useful as a flexible OLED substrate, comprising the steps of:

s1: under the condition of ice-water bath, the diamine monomer and the at least 3 dianhydride monomers react in a polar aprotic solvent to obtain polyamic acid low-temperature glue solution; and

s2: and (2) uniformly coating the polyamic acid low-temperature glue solution on a substrate, removing the solvent of the polyamic acid low-temperature glue solution, and imidizing the polyamic acid glue solution to obtain the high-temperature-resistant polyimide film which can be used as the flexible OLED substrate according to claim 1.

4. The method for preparing the high temperature resistant polyimide film applicable to a flexible OLED substrate according to claim 1, wherein imidizing the polyamic acid paste comprises thermal imidizing the polyamic acid paste at step S2.

5. Use of the high temperature resistant polyimide film of claim 1 as a flexible OLED substrate in the manufacture of a flexible OLED device.