CN114085379A

CN114085379A - Preparation method of flexible colorless transparent polyimide film

Info

Publication number: CN114085379A
Application number: CN202111451657.6A
Authority: CN
Inventors: 王新波; 李开明; 郭逸
Original assignee: Fuyoute Shandong New Material Technology Co ltd
Current assignee: Fuyoute Shandong New Material Technology Co ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-02-25
Anticipated expiration: 2041-11-30
Also published as: CN114085379B

Abstract

The invention discloses a preparation method of a flexible colorless transparent polyimide film, belonging to the technical field of polymer films and comprising the following steps: respectively reacting excessive fluorine-containing aromatic dianhydride and aliphatic diisocyanate in a polar aprotic organic solvent to form a prepolymer solution I, reacting excessive asymmetric aromatic diamine and silicon-containing dianhydride to form a prepolymer solution II, mixing the prepolymer solution I and the prepolymer solution II, performing imidization reaction to obtain a colorless transparent polyimide solution, precipitating in low molecular alcohol, drying, dissolving in the polar aprotic organic solvent, filtering, defoaming, coating to form a film, and drying the solvent. The surface of the flexible colorless transparent polyimide film is uniform and flat, the thermal decomposition is 5 percent or more and 480 ℃ or more, and the oxygen transmission rate is less than or equal to 2 mL. T^‑1·m^‑2The water vapor transmission rate is less than or equal to 2.5gT^‑1·m^‑2The coefficient of thermal expansion is less than or equal to 30 ppm/DEG C, and the transmittance at 450nm is more than 88%.

Description

Preparation method of flexible colorless transparent polyimide film

Technical Field

The invention relates to the technical field of polymer films, in particular to a preparation method of a flexible colorless transparent polyimide film.

Background

The polyimide material is the engineering plastic with the best heat resistance at present, has the characteristics of excellent mechanical property, low temperature resistance, outstanding insulating property, solvent resistance, radiation resistance and the like, and has wide application in the fields of aerospace, electronics and microelectronics, mechanical and chemical engineering and the like. Polyimide film is one of the most demanded polyimide products, and its excellent corona resistance, radiation resistance, dielectric properties and dimensional stability make the demand for high-performance polyimide film materials continuously increasing.

The high rigidity and conjugated aromatic heterocyclic structure in the main chain of the traditional polyimide causes the polyimide to be difficult to melt and process and poor in solubility; the easy formation of charge transfer complex in the molecule leads to the appearance of yellow or brown, which severely limits the application of polyimide in the optical field.

Disclosure of Invention

In order to solve the problems of poor heat resistance, high thermal expansion coefficient and the like of the colorless transparent polyimide film prepared by the conventional preparation method, the invention provides the preparation method of the flexible colorless transparent polyimide film.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a preparation method of a flexible colorless transparent polyimide film, which comprises the following steps:

(a) reacting excessive fluorine-containing aromatic dianhydride with aliphatic diisocyanate in a polar aprotic organic solvent to form a prepolymer solution I, reacting excessive asymmetric aromatic diamine with silicon-containing dianhydride in the polar aprotic organic solvent to form a prepolymer solution II, mixing the prepolymer solution I and the prepolymer solution II at room temperature, and performing imidization reaction to obtain a colorless transparent polyimide solution;

(b) precipitating the colorless transparent polyimide solution obtained in the step (a) in low molecular alcohol, drying, dissolving in a polar aprotic organic solvent, filtering, defoaming, coating to form a film, and drying the solvent to obtain the flexible colorless transparent polyimide film.

Further, the molar ratio of the fluorine-containing aromatic dianhydride to the aliphatic diisocyanate in the prepolymer solution I is 1.3-1.1; the molar ratio of the asymmetric aromatic diamine to the silicon-containing dianhydride in the prepolymer solution II is 1.3-1.1.

Further, the polar aprotic organic solvent includes N, N-dimethylacetamide, N-dimethylformamide, or dimethylsulfoxide; the low molecular alcohol is methanol or ethanol.

Further, the reaction forming conditions of the prepolymer solution I are as follows: n is a radical of₂Reacting for 4-6 h at 140-150 ℃ in the atmosphere, and then cooling to room temperature;

the reaction forming conditions of the prepolymer solution II are as follows: n is a radical of₂Reacting for 24 hours at 0 ℃ under the atmosphere;

the reaction conditions for forming the polyimide solution after the prepolymer solution I and the prepolymer solution II are mixed at room temperature are as follows: n is a radical of₂Reacting for 24 hours at 0 ℃ in an atmosphere, then adding acetic anhydride and triethylamine, and reacting for 2-4 hours at 60-100 ℃, wherein the adding amount of the acetic anhydride is 4 times of the total mole number of the fluorine-containing aromatic dianhydride and the silicon-containing dianhydride, and the adding amount of the triethylamine is 2 times of the total mole number of the fluorine-containing aromatic dianhydride and the silicon-containing dianhydride.

Further, the fluorine-containing aromatic dianhydride comprises 2, 2-bis (3, 4-dicarboxyphenyl dianhydride) hexafluoropropane

1-phenyl-1, 1-bis (3, 4-dicarboxyphenyl dianhydride) trifluoroethane

1- (3, 5-bis-trifluoromethylphenyl) -1, 1-bis (3, 4-dicarboxyphenyl dianhydride) trifluoroethane

Or 2, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl]Hexafluoropropane dianhydride

Further, the aliphatic diisocyanate includes tetramethyl m-xylylene diisocyanate

Isophorone diisocyanate

4,4' -diisocyanate dicyclohexylmethane

Benzylidene diisocyanates

M-xylylene diisocyanate

1, 4-cyclohexane diisocyanate

Or norbornane diisocyanate

Further, the asymmetric aromatic diamine includes m-phenylenediamine

3,4' -diaminodiphenyl ether

Bis (4-amino-3, 5-dimethyl) phenylmethane

1, 3-bis (4-aminophenoxy) benzene

3, 5-bis (3-aminophenoxy) benzoic acid

Or 2,2' -bis (3-aminophenoxy) biphenyl

Further, the silicon-containing dianhydride comprises 1, 3-bis (3, 4-dicarboxyphenyl dianhydride) -1,1,3, 3-tetramethyldisiloxane

1, 3-bis (3, 4-dicarboxycyclohexane dianhydride) -1,1,3, 3-tetramethyldisiloxane

Bis (3, 4-dicarboxyphenyl dianhydride) dimethylsilane

1, 3-bis (3, 4-dicarboxynorbornane dianhydride) -1,1,3, 3-tetramethyldisiloxane

Or 1, 3-bis (3, 4-dicarboxynorbornane dianhydride) -1, 3-dimethyl-1, 3-diphenyldisiloxane

Further, the concentration of the colorless transparent polyimide solution is 5-20 wt%, and the thickness of a coating film is 50-150 μm.

The invention also provides a flexible colorless transparent polyimide film prepared by the preparation method.

The invention starts from the monomer structure and introduces strong polar groups or monomers with large side group structures. Meanwhile, on the premise of meeting the requirement of transparency, the excellent thermal property of the polyimide is kept, the thermal expansion coefficient is reduced, and the important requirement of a flexible colorless transparent polyimide film material is successfully prepared.

The invention discloses the following technical effects:

the flexible colorless transparent polyimide film prepared by the preparation method has the advantages that the surface is uniformly and flatly observed under the visual field of an optical microscope, the thermal decomposition is 5 percent or more and 480 percent, the oxygen transmission rate is less than or equal to 2 mL. T^-1·m^-2Water vapor transmission rate less than or equal to 2.5 g.T^-1·m^-2The coefficient of thermal expansion is less than or equal to 30 ppm/DEG C, and the transmittance at 450nm is more than 88%.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a reaction scheme of a prepolymer solution I in example 1;

FIG. 2 is a reaction scheme showing a prepolymer solution II in example 1;

FIG. 3 is an electron micrograph of a flexible colorless transparent polyimide film obtained in example 1;

FIG. 4 is a graph showing a thermal weight loss curve of the flexible, colorless transparent polyimide film obtained in example 1;

FIG. 5 is a reaction scheme of prepolymer solution I in example 2;

FIG. 6 is a reaction scheme showing a prepolymer solution II in example 2;

FIG. 7 is an electron micrograph of a flexible colorless transparent polyimide film obtained in example 2;

FIG. 8 is a graph showing a thermal weight loss curve of the flexible, colorless transparent polyimide film obtained in example 2;

FIG. 9 is a reaction scheme showing a prepolymer solution I in example 3;

FIG. 10 is a reaction scheme showing a prepolymer solution II in example 3;

FIG. 11 is an electron micrograph of a flexible colorless transparent polyimide film obtained in example 3;

FIG. 12 is a graph showing the weight loss on heating of the flexible, colorless transparent polyimide film obtained in example 3;

FIG. 13 is a reaction scheme showing a prepolymer solution I in example 4;

FIG. 14 is a reaction scheme showing a prepolymer solution II in example 4;

FIG. 15 is a reaction scheme showing a prepolymer solution I in example 5;

FIG. 16 is a reaction scheme showing a prepolymer solution II in example 5;

FIG. 17 is a reaction scheme showing a prepolymer solution I in example 6;

FIG. 18 is a reaction scheme showing a prepolymer solution II in example 6;

FIG. 19 is a reaction scheme showing a prepolymer solution I in example 7;

FIG. 20 is a reaction scheme showing a prepolymer solution II in example 7;

FIG. 21 is a reaction scheme showing a prepolymer solution I in example 8;

FIG. 22 is a reaction scheme showing a prepolymer solution II in example 8;

FIG. 23 is a reaction scheme showing a prepolymer solution I in example 9;

FIG. 24 is a reaction scheme showing a prepolymer solution II in example 9;

FIG. 25 is a reaction scheme showing a prepolymer solution I in example 10;

FIG. 26 is a reaction scheme showing prepolymer solution II in example 10.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1

Preparation of prepolymer solution I: 6.1g (0.025mol) of tetramethylm-xylylene diisocyanate was charged into a 250mL three-necked flask equipped with a magnetic stirrer and a condenser tube at room temperature, 20g N, N-dimethylacetamide was added thereto and dissolved by starting magnetic stirring, a solution of 12.21g (0.0275mol) of 2, 2-bis (3, 4-dicarboxyphenyl dianhydride) hexafluoropropane in 30g N, N-dimethylacetamide was added to the three-necked flask, and the mixture was poured into a flask₂The temperature is raised to 140 ℃, magnetic stirring is carried out for 4 hours, and the temperature is reduced to the room temperature. The reaction scheme for prepolymer solution I is shown in FIG. 1.

Preparation of prepolymer solution II: 6g (0.03mol) of 3,4' -diaminodiphenyl ether was placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, 25g N, N-dimethylacetamide was added, magnetic stirring was started to dissolve the mixture, and 8.8g (0.025mol) of bis (3, 4-benzenedicarboxylic acid was addedAdding the solution of anhydride) -dimethyl silane dissolved in 25g N, N-dimethyl acetamide into a three-neck flask, and introducing N₂The three-neck flask is placed in an ice-water bath and stirred magnetically for 24 hours. The reaction scheme for prepolymer solution II is shown in FIG. 2.

50g of the prepolymer solution I and 26g of the prepolymer solution II were placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, magnetic stirring was started, and N was introduced₂Placing a three-neck flask in an ice-water bath, magnetically stirring for 24h, adding 6g of acetic anhydride and 4g of triethylamine, heating to 90 ℃, stirring for 3h, cooling to room temperature, pouring into 1000mL of ethanol, filtering, collecting precipitate, washing with ethanol for 3 times, drying for 12h at 70 ℃ in a vacuum oven, dissolving in N, N-dimethylacetamide to form a solution with the concentration of 18 wt%, defoaming for 10min in vacuum, coating the solution on a dry and clean glass plate into a film with the thickness of 100 mu m by using a film coater, drying in a forced air drying oven at 80 ℃ to remove the solvent, cooling to room temperature, and separating from the glass plate to obtain the flexible colorless transparent polyimide film.

An electron micrograph of the flexible colorless transparent polyimide film obtained in this example is shown in fig. 3, and it can be seen from fig. 3 that the surface of the flexible colorless transparent polyimide film obtained in this example is uniform and flat. The light transmittance, oxygen transmittance, water vapor transmittance, thermal expansion coefficient and thermal weight loss test were carried out, and the 5% thermal decomposition temperature of the flexible colorless transparent polyimide film obtained in this example was 494 ℃ (see the thermal weight loss curve in fig. 4), and the oxygen transmittance was 1.14 mL. T^-1·m^-2The water vapor transmission rate is 2.11 g.T^-1·m^-2The coefficient of thermal expansion was 26 ppm/DEG C, and the transmittance at 450nm was 92%.

Example 2

Preparation of prepolymer solution I: 4.45g (0.025mol) of norbornane diisocyanate was charged into a 250mL three-necked flask equipped with a magnetic stirrer and condenser tube at room temperature, 30g N, N-dimethylacetamide was added thereto and dissolved by magnetic stirring, and 18.84g (0.03mol) of 2, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] acetamide was added]Adding the solution of hexafluoropropane dianhydride dissolved in 50g N, N-dimethylacetamide into a three-neck flask, and introducing N₂Heating to 140 ℃, magnetically stirring for 4h, cooling to room temperature, and preparing the prepolymer solution I as shown in the flow chart5。

Preparation of prepolymer solution II: 10.5g (0.03125mol) of 3, 5-bis (3-aminophenoxy) benzoic acid was placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, 40g N, N-dimethylacetamide was added thereto, the mixture was dissolved by magnetic stirring, 10.65g (0.025mol) of a solution of 1, 3-bis (3, 4-dicarboxybenzenedianhydride) -1,1,3, 3-tetramethyldisiloxane in 40g N, N-dimethylacetamide was added to the three-necked flask, and N-dimethylacetamide was introduced thereinto₂The three-neck flask is placed in an ice-water bath and stirred magnetically for 24 hours, and the preparation flow of the prepolymer solution II is shown in figure 6.

50g of the prepolymer solution I and 40g of the prepolymer solution II were placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, magnetic stirring was started, and N was introduced₂Placing a three-neck flask in an ice-water bath, magnetically stirring for 24h, adding 6g of acetic anhydride and 4g of triethylamine, heating to 100 ℃, stirring for 2h, cooling to room temperature, pouring into 1000mL of ethanol, filtering, collecting precipitate, washing with ethanol for 3 times, drying in a vacuum oven at 70 ℃ for 12h, dissolving in N, N-dimethylacetamide to form a solution with the concentration of 18 wt%, defoaming in vacuum for 10min, coating the solution on a dry and clean glass plate into a film with the thickness of 100 microns by using a film coater, drying in a forced air drying oven at 80 ℃ to remove the solvent, cooling to room temperature, and separating from the glass plate to obtain the flexible colorless transparent polyimide film.

An electron micrograph of the flexible colorless transparent polyimide film obtained in this example is shown in fig. 7, and it can be seen from fig. 7 that the surface of the flexible colorless transparent polyimide film obtained in this example is uniform and flat. The flexible, colorless, transparent polyimide film obtained in this example had a 5% thermal decomposition temperature of 482 ℃ (see FIG. 8 for thermogravimetric plot) and an oxygen transmission rate of 1.22 mL. T^-1·m^-2The water vapor transmission rate is 1.89 g.T^-1·m^-2The coefficient of thermal expansion was 29 ppm/DEG C, and the transmittance at 450nm was 88%.

Example 3

Preparation of prepolymer solution I: 6.55g (0.025mol) of 4,4' -diisocyanate dicyclohexylmethane was charged into a 250mL three-necked flask equipped with a magnetic stirrer and a condenser tube at room temperature, 30g N, N-dimethylacetamide was added thereto, and dissolved by activating magnetic stirring, 17.15g (0.029mol) of 1- (3,adding 5-bis (trifluoromethyl phenyl) -1, 1-bis (3, 4-dicarboxyphenyl dianhydride) trifluoroethane dissolved in 50g N, N-dimethyl acetamide solution into a three-neck flask, and introducing N₂The temperature is raised to 140 ℃, magnetic stirring is carried out for 4 hours, the temperature is reduced to room temperature, and the preparation flow of the prepolymer solution I is shown in figure 9.

Preparation of prepolymer solution II: 11.04g (0.03mol) of 2,2' -bis (3-aminophenoxy) biphenyl was placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, 35g N, N-dimethylacetamide was added thereto, the mixture was dissolved by magnetic stirring, 14.65g (0.025mol) of a solution of 1, 3-bis (3, 4-norbornanedicarboxylic anhydride) -1, 3-dimethyl-1, 3-diphenyldisiloxane in 45g N, N-dimethylacetamide was added to the three-necked flask, and the mixture was poured into a flask₂The three-neck flask is placed in an ice-water bath and stirred magnetically for 24 hours, and the preparation flow of the prepolymer solution II is shown in figure 10.

50g of the prepolymer solution I and 44g of the prepolymer solution II were placed in a 250mL three-necked flask equipped with magnetic stirring at room temperature, magnetic stirring was started, and N was introduced₂Placing a three-neck flask in an ice-water bath, magnetically stirring for 24h, adding 6g of acetic anhydride and 4g of triethylamine, heating to 80 ℃, stirring for 4h, cooling to room temperature, pouring into 1000mL of ethanol, filtering, collecting precipitate, washing with ethanol for 3 times, drying in a vacuum oven at 70 ℃ for 12h, dissolving in N, N-dimethylacetamide to form a solution with the concentration of 18 wt%, defoaming in vacuum for 10min, coating the solution on a dry and clean glass plate into a film with the thickness of 100 microns by using a film coater, drying in a forced air drying oven at 80 ℃ to remove the solvent, cooling to room temperature, and separating from the glass plate to obtain the flexible colorless transparent polyimide film.

An electron micrograph of the flexible colorless transparent polyimide film obtained in this example is shown in fig. 11, and it can be seen from fig. 11 that the surface of the flexible colorless transparent polyimide film obtained in this example is uniform and flat. The flexible, colorless, transparent polyimide film obtained in this example had a 5% thermal decomposition temperature of 502 deg.C (see FIG. 12 for thermogravimetric plot), and an oxygen transmission rate of 1.01 mL. T^-1·m^-2The water vapor transmission rate is 1.55 g.T^-1·m^-2The thermal expansion coefficient was 22 ppm/DEG C, and the transmittance at 450nm was 93%.

The reaction preparation processes of examples 4 to 10 are similar to the three examples, except that the ratio is shown in table 1, which is the ratio of the components in examples 4 to 10.

TABLE 1

Wherein, the used solvents are N, N-dimethylacetamide.

Table 2 shows the properties of the flexible colorless transparent polyimide films obtained in examples 4 to 10.

TABLE 2

Examples	Td_5％	Oxygen transmission rate	Water vapor transmission rate	Coefficient of thermal expansion	Transmittance of 450nm
						4	496℃	1.44mL·T^-1·m^-2	2.43g·T^-1·m^-2	25ppm/℃	90％
5	490℃	1.37mL·T^-1·m^-2	2.36g·T^-1·m^-2	28ppm/℃	90％
						6	492℃	1.42mL·T^-1·m^-2	2.34g·T^-1·m^-2	24ppm/℃	91％
7	498℃	1.61mL·T^-1·m^-2	2.31g·T^-1·m^-2	27ppm/℃	89％
						8	487℃	1.56mL·T^-1·m^-2	2.44g·T^-1·m^-2	29ppm/℃	92％
9	495℃	1.36mL·T^-1·m^-2	2.11g·T^-1·m^-2	26ppm/℃	92％
						10	500℃	1.32mL·T^-1·m^-2	2.09g·T^-1·m^-2	24ppm/℃	93％

FIGS. 13 to 19 are schematic diagrams of prepolymer reaction in examples 4 to 10.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. A preparation method of a flexible colorless transparent polyimide film is characterized by comprising the following steps:

2. The preparation method according to claim 1, wherein the molar ratio of the fluorine-containing aromatic dianhydride to the aliphatic diisocyanate in the prepolymer solution I is 1.3-1.1; the molar ratio of the asymmetric aromatic diamine to the silicon-containing dianhydride in the prepolymer solution II is 1.3-1.1.

3. The production method according to claim 1, wherein the polar aprotic organic solvent comprises N, N-dimethylacetamide, N-dimethylformamide, or dimethylsulfoxide; the low molecular alcohol is methanol or ethanol.

4. The method according to claim 1, wherein the prepolymer solution I is formed by the reaction under the following conditions: n is a radical of₂Reacting for 4-6 h at 140-150 ℃ in the atmosphere, and then cooling to room temperature;

5. The method according to claim 1, wherein the fluorine-containing aromatic dianhydride comprises 2, 2-bis (3, 4-dicarboxyphenyl dianhydride) hexafluoropropane, 1-phenyl-1, 1-bis (3, 4-dicarboxyphenyl dianhydride) trifluoroethane, 1- (3, 5-bis trifluoromethylphenyl) -1, 1-bis (3, 4-dicarboxyphenyl dianhydride) trifluoroethane or 2, 2-bis [4- (3, 4-dicarboxyphenoxy) phenyl ] hexafluoropropane dianhydride.

6. The method according to claim 1, wherein the aliphatic diisocyanate comprises tetramethyl m-xylylene diisocyanate, isophorone diisocyanate, 4' -diisocyanate dicyclohexylmethane, benzylidene diisocyanate, m-xylylene diisocyanate, or 1, 4-cyclohexane diisocyanate or norbornane diisocyanate.

7. The production method according to claim 1, wherein the asymmetric aromatic diamine comprises m-phenylenediamine, 3,4 '-diaminodiphenyl ether, bis (4-amino-3, 5-dimethyl) phenylmethane, 1, 3-bis (4-aminophenoxy) benzene, 3, 5-bis (3-aminophenoxy) benzoic acid or 2,2' -bis (3-aminophenoxy) biphenyl.

8. The method according to claim 1, wherein the silicon-containing dianhydride comprises 1, 3-bis (3, 4-dicarboxyphenyl dianhydride) -1,1,3, 3-tetramethyldisiloxane, 1, 3-bis (3, 4-dicarboxycyclohexane dianhydride) -1,1,3, 3-tetramethyldisiloxane, bis (3, 4-dicarboxyphenyl dianhydride) dimethylsilane, 1, 3-bis (3, 4-dicarboxynorbornane dianhydride) -1,1,3, 3-tetramethyldisiloxane, or 1, 3-bis (3, 4-dicarboxynorbornane dianhydride) -1, 3-dimethyl-1, 3-diphenyldisiloxane.

9. The method according to claim 1, wherein the colorless transparent polyimide solution has a concentration of 5 to 20 wt% and is applied to a film having a thickness of 50 to 150 μm.

10. A flexible colorless transparent polyimide film produced by the production method according to any one of claims 1 to 9.