CN113773540A

CN113773540A - Polyimide film, preparation method and application thereof

Info

Publication number: CN113773540A
Application number: CN202111143436.2A
Authority: CN
Inventors: 王学文; 赵若晴; 吴昊; 黄维
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2021-12-10
Anticipated expiration: 2041-09-28
Also published as: CN113773540B

Abstract

The invention discloses a polyimide film, a preparation method and application thereof, wherein the preparation method comprises the following steps: the preparation method comprises the following steps: (1) carrying out polycondensation reaction on equimolar diamine and dianhydride monomers in a polar solvent to obtain a polyamic acid solution with the viscosity of 2-32 ten thousand cP, and spin-coating the polyamic acid solution on a substrate; the spin coating process parameters are as follows: the rotating speed of the first stage is 500rpm, the duration time is 10-30 s, the rotating speed of the second stage is 1000-9000 rpm, and the duration time is 50-120 s; (2) then the polyimide film is obtained after film formation by heat treatment and demoulding. The polyimide film obtained according to the present invention can have a thickness of 2.8 μm or less without being subjected to a stretching treatment technique, and has excellent toughness. Therefore, the polyimide film is effectively used in the fields of flexible sensor substrates, flexible solar cell bottom plates and the like, and the preparation cost of polyimide related devices is reduced.

Description

Polyimide film, preparation method and application thereof

Technical Field

The invention relates to the field of polyimide film materials, in particular to a polyimide film, a preparation method and application thereof.

Background

Polyimide film is a film material with excellent performance, and the polyimide film has good high temperature resistance, mechanical property and solvent resistance due to the specific imide ring in the polyimide structure, and is widely applied to the fields of aerospace, automobile manufacturing, electronics and the like.

At present, with the miniaturization development of the electronic device field, the microelectronic industry and the like, devices with the characteristics of flexibility, lightness, thinness and crimpability are receiving wide attention. Thus, the demand for ultra-thin polyimide films having high mechanical properties and a thickness of less than 8 μm is increasing.

For example, patent CN201911203974.9 discloses a method for preparing an ultrathin polyimide film, which realizes the preparation of an ultrathin polyamide film with a thickness of 4-8 μm, but the method has a complicated process, requires additional addition of an imidizing agent, and has a heat treatment temperature as high as 320 ℃.

For example, patent CN202110286869.7 discloses a polyimide film, which has a breakthrough in elongation at break of the film, but the thickness of the film is still above 5 μm, and the film cannot be further thinned.

Disclosure of Invention

The invention provides a polyimide film, a preparation method and application thereof.

In order to achieve the purpose, the technical scheme of the invention comprises the following steps:

a preparation method of a polyimide film comprises the following preparation steps:

(1) carrying out polycondensation reaction on equimolar diamine and dianhydride monomers in a polar solvent to obtain a polyamic acid solution with the viscosity of 2-32 ten thousand cP, and spin-coating the polyamic acid solution on a substrate;

the spin coating process parameters are as follows: the rotating speed of the first stage is 500rpm, the duration time is 10-30 s, the rotating speed of the second stage is 1000-9000 rpm, and the duration time is 50-120 s;

(2) then the polyimide film is obtained after film formation by heat treatment and demoulding.

Optionally, the polycondensation reaction process comprises:

the diamine monomer is dissolved in a polar solvent under an argon protective atmosphere, vigorously stirred, and then the dianhydride monomer is added in batches to obtain a polyamic acid solution.

Optionally, the process conditions of the vigorous stirring are as follows: stirring for 2-10 h at room temperature in a closed container under the protection of argon, wherein the stirring speed is 200-300 r/min.

Optionally, the substrate is a glass substrate;

the dianhydride is one of pyromellitic dianhydride, 3 ', 4,4' -biphenyl tetracarboxylic dianhydride and 4,4' -oxydiphthalic anhydride;

the diamine is one of 1, 4-diamino benzene, 4 '-diaminodiphenyl ether, 1, 4-bis (4-aminophenoxy) benzene and 4,4' -bis (4-aminophenoxy) biphenyl.

The polar solvent is N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone or the volume ratio of the two is 1: 1.

Optionally, the substrate is further subjected to pretreatment, and the pretreatment process conditions are as follows: and ultrasonically cleaning for 3-10 min by using ultrapure water, ethanol and acetone in sequence.

Optionally, the process parameters of the thermal treatment film formation are as follows: under the atmospheric condition, the heating rate is 2-10 ℃, the temperature is raised from room temperature to 70 ℃ for processing for 1-4 h, the temperature is 150 ℃ for processing for 2-4 h, the temperature is 200 ℃ for processing for 1-4 h, the temperature is 250 ℃ for processing for 1-24 h, and finally the mixture is slowly cooled to the room temperature.

Optionally, the demolding process conditions are as follows: and transferring the cooled sample into deionized water at the temperature of 30-70 ℃ to enable the water surface to be completely immersed in the sample.

The polyimide film is prepared by the preparation method of the polyimide film.

Optionally, the thickness of the polyimide film is 2-22 μm, the tensile strength is 120-164 MPa, the elongation at break is 28-140%, and the uniformity is 2-6%.

The polyimide film is applied to preparing a flexible sensor or a flexible solar cell.

The invention has the following beneficial effects:

the invention can obtain the ultrathin polyimide film with excellent mechanical property, and the preparation method is simple and convenient to operate and easy to carry out. The ultrathin polyimide film obtained by the invention can be used in the fields of flexible sensor substrates, solar cell substrates, semiconductor manufacturing and the like.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

FIG. 1 is a typical infrared absorption spectrum of a polyimide acid solution prepared in example 1;

FIG. 2 is a diagram showing the ultra-thin and high toughness polyimide films prepared in examples 1 to 3, wherein the films prepared in example 1, example 2 and example 3 are shown from left to right;

FIG. 3 is an optical microscope photograph of the surface of the ultra-thin high toughness polyimide film prepared in example 3;

fig. 4 is a surface scanning electron microscope picture of the ultra-thin high toughness polyimide film prepared in example 3.

Detailed Description

In order to clearly and completely describe the purpose and technical solution of the present invention, the technical solution provided by the present invention will be described below with reference to specific embodiments. It should be understood that the following detailed description is illustrative of the invention only and is not intended to limit the scope of the invention.

According to the technical scheme provided by the invention, the thickness of the ultrathin high-toughness polyimide film is 2.8-8.1 mu m, and the fracture growth rate is 29-72%.

The invention discloses a preparation method of an ultrathin high-toughness polyimide film, which comprises the following steps:

(1) preparing polyamic acid solution by performing polycondensation reaction on equimolar diamine and dianhydride monomers in a polar solvent: dissolving a diamine monomer in a polar solvent under the protection of argon, violently stirring, and then adding a dianhydride monomer in batches to obtain a polyamic acid solution;

(2) cleaning high-temperature resistant tempered glass, and blow-drying by an air gun to obtain a clean glass substrate;

(3) spin-coating the polyamic acid solution obtained in the step (1) on the glass substrate cleaned in the step (2), and placing the glass substrate in an oven for stage heat treatment to form a film;

(4) soaking in deionized water to remove the film, and obtaining the ultrathin polyimide film.

The process conditions of the violent stirring in the step (1) are as follows: and (3) vigorously stirring for 2-10 h at room temperature in a closed container under the argon atmosphere, wherein the stirring speed is 200-300 r/min.

The process conditions for cleaning the high-temperature resistant glass in the step (2) are as follows: and ultrasonically cleaning the glass substrate for 3-10 min by using ultrapure water, ethanol and acetone in sequence.

The spin coating process parameters in the step (3) are as follows: the rotating speed of the first stage is 500rpm, the duration time is 10-30 s, the rotating speed of the second stage is 1000-9000 rpm, and the duration time is 50-120 s.

The parameters of the stage heat treatment film forming process in the step (3) are as follows: the heating rate is 4-10 ℃, the temperature is increased from room temperature to 70 ℃ for processing for 1-4 h, the temperature is 150 ℃ for processing for 2-4 h, the temperature is 200 ℃ for processing for 1-4 h, the temperature is 250 ℃ for processing for 1-24 h, and the mixture is slowly cooled to room temperature. The volatilization speed of the solvent in the polyamic acid solution affects the quality of the film, and if the volatilization is fast, the polyimide film can form pores, cracks and the like.

The process conditions of soaking and demoulding in the step (4) are as follows: and transferring the cooled sample to water at the temperature of 30-70 ℃ to enable the water surface to be completely immersed in the sample.

The stripping process conditions in the step (4) are as follows: in water at room temperature or in air at room temperature after removal from water.

In the present invention, the dianhydride of the polyamic acid formed may be one of pyromellitic dianhydride, 3, 3 ', 4,4' -biphenyltetracarboxylic dianhydride, and 4,4' -oxydiphthalic anhydride, and the diamine forming the polyamic acid may be one of 1, 4-bisaminobenzene, 4,4' -diaminodiphenyl ether, 1, 4-bis (4-aminophenoxy) benzene, and 4,4' -bis (4-aminophenoxy) biphenyl.

In the present invention, the polar solvent for preparing the polyamic acid may be N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, or both of them 1: 1.

In the invention, the viscosity of the polyamic acid for film formation is 2-32 ten thousand cP.

The polyimide film prepared according to the method of the present invention has a thickness of 5 μm or less and has excellent elongation at break.

The diamine used as the starting material in the examples of the present invention was 1, 4-bis (4-aminophenoxy) benzene, the dianhydride was pyromellitic dianhydride, and the polar solvent was N, N-dimethylformamide.

Example 1:

(1) in a 50ml three-necked flask equipped with an argon inlet and mechanical stirring, 2.92g (0.01mol) of 1, 4-bis (4-aminophenoxy) benzene was added, followed by 15ml of anhydrous N, N-Dimethylformamide (DMF) and dissolved with stirring under an argon atmosphere. When the diamine was completely dissolved, 2.18g (0.01mol) of pyromellitic dianhydride (PMDA) were added in three portions with stirring, and 5ml of anhydrous DMF was added after each addition of PMDA. The solution was stirred at room temperature for 2h to obtain a polyamic acid solution having a viscosity of about 20 ten thousand cP (see FIG. 1 for an infrared spectrum).

(2) The solution obtained in part (1) was taken and diluted with anhydrous DMF to a viscosity of about 6 million cP.

(3) Cleaning high-temperature resistant tempered glass: and ultrasonically cleaning the glass substrate for 3min by using ultrapure water, ethanol and acetone in sequence, and blow-drying the glass substrate by using an air gun to obtain a clean glass substrate.

(4) The diluted polyamic acid solution in step (2) was pipetted in an ultra clean room and spin coated onto the glass substrate treated in step (3) according to the process parameters of 500rpm for 90 s.

(5) And (3) placing the spin-coated film in an oven for stage heat treatment, and forming a film by a thermal imidization method. The heat treatment process parameters are as follows: the heating rate is 4 ℃, the temperature is increased from room temperature to 70 ℃ for processing for 1h, the temperature is increased to 150 ℃ for processing for 2h, the temperature is increased to 200 ℃ for processing for 1h, the temperature is increased to 250 ℃ for processing for 1h, and the temperature is slowly cooled to room temperature.

(4) Transferring the cooled polyimide film into hot water at 70 ℃ to enable the water surface to be completely immersed in the sample; then the film is slightly peeled from the glass substrate by tweezers in room temperature air after being put in or taken out of water at room temperature, and the ultrathin high-toughness polyimide film is obtained.

A photograph of the film is shown in FIG. 2.

Example 2:

(1) in a 50ml three-necked flask equipped with an argon inlet and mechanical stirring, 2.92g (0.01mol) of 1, 4-bis (4-aminophenoxy) benzene was added, followed by 15ml of an anhydrous polar solvent, N-Dimethylformamide (DMF), and stirred to dissolve under protection of argon atmosphere. When the diamine was completely dissolved, 2.18g (0.01mol) of pyromellitic dianhydride (PMDA) were added in three portions with stirring, and 5ml of anhydrous DMF was added after each addition of PMDA. Stirring the solution at room temperature for 3 hours to obtain a polyamic acid solution with the viscosity of about 27 million cP;

(2) the solution obtained in part (1) was taken and diluted with anhydrous DMF to a viscosity of about 4 million cP.

(4) And (3) in an ultra-clean room, using a dropper to dip the diluted polyamic acid solution in the step (2) and spin-coating the diluted polyamic acid solution on the glass substrate treated in the step (3) according to the process parameters of a first-stage rotating speed of 500rpm and a duration of 30s, and a second-stage rotating speed of 4000rpm and a duration of 60 s.

A photograph of the film is shown in FIG. 2.

Example 3:

(1) in a 50ml three-necked flask equipped with an argon inlet and mechanical stirring, 2.92g (0.01mol) of 1, 4-bis (4-aminophenoxy) benzene was added, followed by 15ml of an anhydrous polar solvent, N-Dimethylformamide (DMF), and stirred to dissolve under protection of argon atmosphere. When the diamine was completely dissolved, 2.18g (0.01mol) of pyromellitic dianhydride (PMDA) were added in three portions with stirring, and 5ml of anhydrous DMF was added after each addition of PMDA. The solution was stirred at room temperature for 5 hours to obtain a polyamic acid solution having a viscosity of about 32 ten thousand cP.

(2) The solution obtained in part (1) was taken and diluted with anhydrous DMF to a viscosity of about 2 million cP.

(3) Cleaning high-temperature resistant tempered glass: and ultrasonically cleaning the glass substrate for 5min by using ultrapure water, ethanol and acetone in sequence, and blow-drying the glass substrate by using an air gun to obtain a clean glass substrate.

(4) The diluted polyamic acid solution in step (2) was spin-coated on the glass substrate treated in step (3) in an ultra-clean chamber using a pipette according to the process parameters of 500rpm for 30s in the first stage and 9000rpm for 60s in the second stage.

(4) Transferring the cooled polyimide film into hot water at 70 ℃ to enable the water surface to be completely immersed in the sample; then the film was gently peeled from the glass substrate with tweezers at room temperature in water or after being taken out from water, to obtain an ultrathin polyimide film.

The film is shown in figure 2 for a photograph, and in figures 3 and 4 for an optical microscope and a scanning electron microscope, respectively.

Test example:

the polyimide films obtained in examples 1 to 3 were subjected to the following film formation stability and surface smoothness tests in conjunction with FIGS. 2 to 4, and the results are shown in Table 1.

(1) Film forming stability: the case where no film breakage due to wrinkles or cracks occurred during film formation was marked as "o", otherwise, it was marked as "x".

(2) Surface smoothness test: visually and microscopically, the surface was smooth, had no pin holes, and had no marks, and was marked with "O" or "X".

TABLE 1

As can be seen from Table 1, the ultrathin polyimide film prepared by the invention has good film-forming stability and smooth surface.

The polyimide films obtained in examples 1 to 3 were subjected to the following tests for film thickness, uniformity and mechanical properties, and the results are shown in Table 2.

(3) Film thickness and uniformity: and uniformly selecting nine points on the film as film thickness and uniformity test points, testing the film thickness and uniformity test points by using a paint film thickness tester, and taking an average value as the film thickness.

(4) Mechanical properties: the tensile strength and elongation at break of the samples were tested at room temperature using a universal tensile tester (CMT 4103).

TABLE 2

	Example 1	Example 2	Example 3
				Film thickness (mum)	22.02	5.12	2.73
Uniformity of the film	4.75％	2.60％	5.49％
				Tensile Strength (MPa)	163.66	125.11	120.96
Elongation at Break (%)	139.81	71.65	28.66

As is clear from Table 2, the polyimide film obtained by the present invention is extremely thin, 2.8 μm or less, and has good mechanical properties. The method can be used for preparing a thin film (2.73 mu m) and a thick film (22.02 mu m) and has good mechanical properties.

The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure.

It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.

In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims

1. The preparation method of the polyimide film is characterized by comprising the following preparation steps:

2. The method for preparing a polyimide film according to claim 1, wherein the polycondensation reaction process comprises:

3. The method for preparing a polyimide film according to claim 2, wherein the process conditions of the vigorous stirring are as follows: stirring for 2-10 h at room temperature in a closed container under the protection of argon, wherein the stirring speed is 200-300 r/min.

4. The method for producing a polyimide film according to claim 1, 2 or 3, wherein the substrate is a glass substrate;

5. The method for preparing a polyimide film according to claim 1, 2 or 3, wherein the substrate is further subjected to pretreatment under the following process conditions: and ultrasonically cleaning for 3-10 min by using ultrapure water, ethanol and acetone in sequence.

6. The method for preparing a polyimide film according to claim 1, 2 or 3, wherein the process parameters of the heat treatment film formation are as follows: under the atmospheric condition, the heating rate is 2-10 ℃, the temperature is raised from room temperature to 70 ℃ for processing for 1-4 h, the temperature is 150 ℃ for processing for 2-4 h, the temperature is 200 ℃ for processing for 1-4 h, the temperature is 250 ℃ for processing for 1-24 h, and finally the mixture is slowly cooled to the room temperature.

7. The method for preparing a polyimide film according to claim 1, 2 or 3, wherein the stripping process conditions are as follows: and transferring the cooled sample into deionized water at the temperature of 30-70 ℃ to enable the water surface to be completely immersed in the sample.

8. A polyimide film obtained by the method for producing a polyimide film according to any one of claims 1 to 7.

9. The polyimide film according to claim 8, wherein the polyimide film has a thickness of 2 to 22 μm, a tensile strength of 120 to 164MPa, an elongation at break of 28 to 140%, and a uniformity of 2 to 6%.

10. Use of the polyimide film of claim 8 or 9 for the preparation of a flexible sensor or a flexible solar cell.