阅读说明：本技术 一种聚酰亚胺前体、聚酰亚胺薄膜及其制备方法 (Polyimide precursor, polyimide film and preparation method thereof ) 是由 肖桂林 付华 阮敏 鲁丽平 朱双全 于 2020-12-10 设计创作，主要内容包括：本发明涉及一种聚酰亚胺前体,聚酰亚胺薄膜及其的制备方法,具体的本发明的聚酰亚胺前体由二胺A、二酐B和添加剂C在一定的反应条件下反应而形成。其中,含氟二酐或含氟二酐的质量不超过总二酐和二胺质量的5％,聚酰胺酸浆料透光率65～67％,当涂膜厚度10μm,涂布的膜厚均一性在2％以内,聚酰亚胺薄膜黄色指数21～22,在50～200℃的热膨胀系数在2～3ppm/K,400nm处波长透过率在83％～86％。(The invention relates to a polyimide precursor, a polyimide film and a preparation method thereof, and particularly relates to the polyimide precursor which is formed by reacting diamine A, dianhydride B and an additive C under certain reaction conditions. Wherein the mass of the fluorine-containing dianhydride or the fluorine-containing dianhydride is not more than 5% of the total dianhydride and diamine, the light transmittance of the polyamide acid slurry is 65-67%, when the thickness of a coating film is 10 mu m, the uniformity of the coated film is within 2%, the yellow index of the polyimide film is 21-22, the thermal expansion coefficient at 50-200 ℃ is 2-3ppm/K, and the wavelength transmittance at 400nm is 83-86%.)

1. The polyimide precursor is prepared by reacting dianhydride A, diamine B and an additive C, wherein at least one of the dianhydride A and the diamine B is fluorine-containing dianhydride or fluorine-containing diamine, the molar amount of the fluorine-containing dianhydride or the fluorine-containing dianhydride is not more than 5% of the molar amount of the total dianhydride and the diamine, and the additive C comprises one of a free radical scavenger, a hindered phenol antioxidant and a phosphite antioxidant.

2. The polyimide precursor according to claim 1, wherein: the dianhydride A is selected from one or more of 3,3',4,4' -biphenyl tetracarboxylic dianhydride (BPDA), 3,4, 4-diphenyl ketone tetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 4, 4-Oxydiphthalic Dianhydride (ODPA) and 2,2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride (6 FDA).

3. The polyimide precursor according to claim 2, wherein the dianhydride a is a combination of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA).

4. The polyimide precursor according to claim 1, wherein: the diamine B is selected from one or more of 4,4' -diaminodiphenyl ether (ODA), 2-bis [4- (4-aminophenoxy) phenyl ] propane (BAPP), p-Phenylenediamine (PDA) and 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl (TFMB).

5. The polyimide precursor according to claim 4, wherein the diamine B is a combination of 4,4' -diaminodiphenyl ether (ODA), p-Phenylenediamine (PDA) and 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl (TFMB).

6. The polyimide precursor according to claim 1, wherein: the additive C comprises one of sodium ascorbate, hydroquinone, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylene diamine or tris (2, 4-di-tert-butylphenyl) phosphite, wherein the use amount of the additive C accounts for 0.01-0.1 mol percent of the total diamine use amount.

7. The polyimide precursor according to claim 6, wherein the additive C is sodium ascorbate.

8. A polyimide film obtained by imidizing the polyimide precursor according to claim 1 to 7.

9. The polyimide film according to claim 8, wherein the polyimide film has a thermal expansion coefficient of 2 to 3ppm/K, a yellow index of 21 to 22, and a transmittance at 400nm of 83 to 86%.

10. A preparation method of a polyimide film comprises the following steps:

s1: dissolving diamine B in an organic solvent D to obtain a solution in which the diamine B is dissolved;

s2: adding an additive C into the solution dissolved with the diamine B obtained in the step S1, wherein the use amount of the additive C accounts for 0.01-0.1% of the total use amount of the diamine B;

s3: adding dianhydride A into the components of the dissolved diamine B and the additive C for multiple times, wherein the adding time is 1h, the dianhydride A needs to react at 40 ℃ for 6-10h after each time of addition until all the dianhydride A is completely added, and obtaining a polyamic acid solution after the polymerization is finished, wherein the molar ratio of the dianhydride to the diamine of the polyamic acid solution is 0.95-1.10;

s4: and (4) coating and curing the polyamic acid solution obtained in the step S3 to obtain the polyimide film.

Technical Field

The invention relates to the technical field of high polymer materials, in particular to a polyimide precursor, a polyimide film and a preparation method thereof.

Background

Polyimide is used as a special engineering plastic with a main chain containing an imide ring and a rigid chain structure, has very excellent mechanical properties, heat resistance, flame retardance, solvent resistance, radiation resistance and electrical properties, and is widely applied to a series of high and new technical fields of aerospace, photoelectricity, automobiles and the like.

With the increase of the demand of people for flexible display wearable and foldable display equipment, polyimide film materials with various advantages become key materials of people's attention, the high-temperature-resistant polyimide film is always a substrate material which is paid much attention to in the preparation process of an AMOLED panel, the high temperature resistance is that a plurality of processes in the panel manufacturing process need to be subjected to high temperature, such as laser crystallization, the general crystallization temperature reaches 450 ℃, the improvement of the transparency of the film can improve the sensitivity of fingerprint identification under the screen, the realization of the camera process under the screen can be conveniently realized, and the screen occupation ratio can be further improved, so that the real comprehensive screen is realized.

In the polyimide monomer, a large aromatic monomer containing a conjugated structure is generally used for achieving a high-temperature resistant process without deteriorating the film performance, but the monomer generally gives a film having a deep color, a yellowness index of 30 or more, and a transmittance at a wavelength of 400nm of 83% or less. Common means for improving the transparency in the prior art are: the method breaks a large conjugated structure, such as adding an aliphatic monomer into a monomer or replacing a non-fluorine-containing aromatic monomer with a fluorine-containing aromatic monomer, but both methods are based on the premise of reducing the temperature resistance of the film, and at present, although some structures can achieve the temperature resistance of about 400 ℃, the requirements of panel manufacturers cannot be met in the process of applying the structure to a panel.

Disclosure of Invention

The invention designs a novel method for preparing the polyimide precursor, the transparency of the polyimide precursor prepared by the method is improved, and the coating uniformity is improved, so that the heat resistance, the yellow index and the transparency of a polyimide film are improved simultaneously.

The first aspect of the invention provides a polyimide precursor, which is characterized in that the polyimide precursor is prepared by reacting dianhydride A, diamine B and an additive C, wherein at least one of the dianhydride A and the diamine B is fluorine-containing dianhydride or fluorine-containing diamine, the molar quantity of the fluorine-containing dianhydride or the fluorine-containing dianhydride is not more than 5% of the molar quantity of the total dianhydride and the diamine, and the additive C comprises one of a free radical trapping agent, a hindered phenol antioxidant and a phosphite antioxidant.

Further, the dianhydride A is selected from one or more of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA), 3,4, 4-diphenyl ketone tetracarboxylic dianhydride (BTDA), pyromellitic dianhydride (PMDA), 4, 4-Oxydiphthalic Dianhydride (ODPA), and 2,2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride (6 FDA).

Preferably, the dianhydride a is a combination of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA).

Further, the diamine B is selected from one or more of 4,4' -diaminodiphenyl ether (ODA), 2-bis [4- (4-aminophenoxy) phenyl ] propane (BAPP), p-Phenylenediamine (PDA) and 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl (TFMB).

Preferably, the diamine B is a combination of 4,4' -diaminodiphenyl ether (ODA), p-Phenylenediamine (PDA), and 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl (TFMB).

Further, the additive C is one of sodium ascorbate, hydroquinone, pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine or tris (2, 4-di-tert-butylphenyl) phosphite, wherein the amount of the additive C accounts for 0.01 to 0.1 mole percent of the total diamine amount.

Preferably, the additive C is sodium ascorbate.

In a second aspect of the present invention, there is provided a polyimide film obtained by imidizing the polyimide precursor.

Wherein the polyimide film has a thermal expansion coefficient of 2 to 3ppm/K, a yellow index of 21 to 22, and a transmittance at a wavelength of 400nm of 83 to 86%.

The third aspect of the present invention provides a method for preparing a polyimide film, comprising the steps of:

s1: dissolving diamine B in an organic solvent D to obtain a solution in which the diamine B is dissolved;

s2: adding an additive C into the solution dissolved with the diamine B obtained in the step S1, wherein the use amount of the additive C accounts for 0.01-0.1% of the total use amount of the diamine B;

s3: adding dianhydride A into the components of the dissolved diamine B and the additive C for multiple times, wherein the adding time is 1h, the dianhydride A needs to react at 40 ℃ for 6-10h after each time of addition until all the dianhydride A is completely added, and obtaining a polyamic acid solution after the polymerization is finished, wherein the molar ratio of the dianhydride to the diamine of the polyamic acid solution is 0.95-1.10;

s4: and (4) coating and curing the polyamic acid solution obtained in the step S3 to obtain the polyimide film. The invention has the beneficial effects that: the molar weight of the fluorine-containing dianhydride or fluorine-containing diamine is not more than 5% of the molar weight of the total dianhydride and dianhydride, and a certain amount of additive is added in the process of preparing the polyamic acid, so that the amine oxidation in the process of preparing the polyamic acid is reduced, the end group of the polyamic acid in the synthesis process can uniformly participate in the reaction, the oxidation amount is reduced due to the reduction of the oxidation amount of the amine, the transparency of the slurry is also improved, the coating uniformity is improved, the CTE of the prepared polyimide film is 2-3ppm/K, the yellow index is 21-22, and the transparency reaches 83-86%. The polyimide film obtained by curing the polyamic acid solution has excellent coating uniformity, excellent dimensional stability and high transparency, so that the polyimide film is very suitable for AMOLED substrate or cover plate materials.

Detailed Description

The polyimide precursor is prepared by reacting dianhydride A, diamine B and an additive C, at least one of the dianhydride A and the diamine B is fluorine-containing dianhydride or fluorine-containing diamine, specifically, a certain amount of diamine B is dissolved in an organic solvent D to obtain a solution in which the diamine B is dissolved, the additive C is added into the solution, then the dianhydride A is added into the components of the dissolved diamine B and the additive C for 1-5 hours in multiple times, the reaction is carried out at 40 ℃ for 6-10 hours after the dianhydride A is added each time until all the dianhydride A is completely added, and a polyamic acid solution is obtained after the polymerization is finished, so that the polyimide precursor is obtained.

In the method for synthesizing the polyamic acid solution, firstly, adding a diamine B monomer into a solvent, and then adding a dianhydride A monomer, or adding the dianhydride A monomer and then adding the diamine B monomer, or adding part of the diamine B monomer and then adding part of the dianhydride A monomer to make the amine excessive, and after adding part of the diamine B monomer for dissolving, adding the dianhydride A monomer to make the total diamine B and dianhydride A monomers approximate to an equal molar ratio; or adding part of diamine B monomer, adding part of dianhydride A monomer to make anhydride excessive, adding dianhydride A monomer after adding part of diamine B monomer to dissolve, and making the total diamine B and dianhydride A monomers approximate to equal molar ratio; the molar ratio of dianhydride A to diamine B is preferably 0.95 to 1.10.

The dianhydride A in the polyimide precursor of the present invention is selected from the group consisting of 1, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 2, 3,5, 6-pyridinetetracarboxylic dianhydride, bicyclo [3.1.1 ] hept-2-ene tetracarboxylic dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 3,4, 9, 10-perylene tetracarboxylic dianhydride, bicyclo [2.2.2 ] octane tetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, N '-bis [5, 5' -hexafluoropropane-2, 2-diyl-bis (2-hydroxyphenyl) ] bis (3, 4-dicarboxybenzamide), adamantane tetracarboxylic dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, bis (3, 4-dicarboxyphenyl) sulfone dianhydride, and, 1, 2, 3, 4-cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 1, 2, 5, 6-naphthalenetetracarboxylic dianhydride, bicyclo [2.2.1 ] heptanetetracarboxylic dianhydride, 2-bis (2, 3-dicarboxyphenyl) hexafluoropropane dianhydride, 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, bicyclo [3.3.1 ] tetracarboxylic dianhydride, 3',4,4' -biphenyltetracarboxylic dianhydride, 3,4, 4-diphenylmethanone tetracarboxylic dianhydride, pyromellitic dianhydride, 4, 4-oxydiphthalic dianhydride, 2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride, and one or more combinations of the following structural dianhydrides;

since the dianhydride a is selected from dianhydrides having an aromatic structure in terms of avoiding a decrease in the CTE value of the polyimide film after the introduction of fluorine atoms, among the dianhydrides a, one or a combination of two or more of 3,3',4,4' -biphenyltetracarboxylic dianhydride, 3,4, 4-diphenylmethanone tetracarboxylic dianhydride, pyromellitic dianhydride, 4, 4-oxydiphthalic dianhydride, and 2,2' -bis (3, 4-dicarboxylic acid) hexafluoropropane dianhydride is preferable.

Further, since the biphenyl structure and monocyclic aromatic structure molecules have high rigidity and the CTE value of the polyimide film can be further reduced, it is more preferable that the dianhydride a is a combination of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) in terms of improving the molecular rigidity.

In the polyimide precursor of the present invention, the diamine B is selected from m-phenylenediamine, 1, 5-naphthalenediamine, 2, 6-naphthalenediamine, bis (3-amino-4-hydroxyphenyl) hexafluoropropane, bis (3-amino-4-hydroxyphenyl) sulfone, bis (3-amino-4-hydroxyphenyl) propane, bis (3-amino-4-hydroxyphenyl) methane, bis (3-amino-4-hydroxyphenyl) ether, bis (3-amino-4-hydroxy) biphenyl, bis (3-amino-4-hydroxyphenyl) fluorene, 1, 4-bis (4-aminophenoxy) benzene, 2' -dimethyl-4, 4' -diaminobiphenyl, 2' -diethyl-4, 4 '-diaminobiphenyl, 3,3' -dimethyl-4, 4 '-diaminobiphenyl, 3,3' -diethyl-4, 4 '-diaminobiphenyl, 2', 3,3 '-tetramethyl-4, 4' -diaminobiphenyl, 3,3',4,4' -tetramethyl-4, 4 '-diaminobiphenyl, 2' -bis (trifluoromethyl) -5, 5 '-dihydroxybenzidine, 3, 4' -diaminodiphenyl ether, 3,4 '-diaminodiphenylmethane, 4,4' -diaminodiphenylmethane, 3,4 '-diaminodiphenylsulfone, 4,4' -diaminodiphenylsulfone, and mixtures thereof, One or more combinations of 3, 4' -diaminodiphenyl sulfide, 4,4' -diaminodiphenyl sulfide, 1, 4-bis (4-aminophenoxy) benzene, bis (4-aminophenoxyphenyl) sulfone, bis (3-aminophenoxyphenyl) sulfone, bis (4-aminophenoxy) biphenyl, bis {4- (4-aminophenoxy) phenyl } ether, 3, 5-diaminobenzoic acid, 3-carboxy-4, 4' -diaminodiphenyl ether, 2-bis [4- (4-aminophenoxy) phenyl ] propane, p-phenylenediamine, 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl, and diamines of the structure;

the diamine B is preferably a diamine having an aromatic structure from the viewpoint of higher temperature resistance of the polyimide film to be produced, and therefore the diamine B is preferably one or a combination of more of 4,4' -diaminodiphenyl ether, 2-bis [4- (4-aminophenoxy) phenyl ] propane, p-phenylenediamine, and 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl.

Since the CTE value can be effectively lowered when the diamine structure contains a single aromatic ring or two amino groups are para to each other, the diamine B is preferably a combination of 4,4' -diaminodiphenyl ether and p-phenylenediamine, and the diamine B is preferably 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl in view of improving the transparency of the film.

The dianhydride A and the diamine B of the polyimide precursor in the invention comprise at least one of the fluorine-containing dianhydride or the fluorine-containing diamine, wherein the weight of the fluorine-containing dianhydride or the fluorine-containing diamine is not more than 5% of the total dianhydride and diamine monomer, the fluorine-containing structure is preferably fluorine-containing diamine in the invention, 4 '-diamino-2, 2' -bistrifluoromethylbiphenyl is preferably selected, and the mole amount of the 4,4 '-diamino-2, 2' -bistrifluoromethylbiphenyl is preferably 1.5% of the mole amount of the total dianhydride and diamine monomer.

The additive C in the polyimide precursor comprises one of a free radical trapping agent, a hindered phenol antioxidant and a phosphite type antioxidant, and the specific additive C is selected from one of sodium ascorbate, hydroquinone, tetra [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionic acid ] pentaerythritol ester, N, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexanediamine and tris (2, 4-di-tert-butylphenyl) phosphite;

the additive C is preferably one of sodium ascorbate and N, N' -bis- (3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine, from the viewpoint of lowering the CTE value and improving the light transmittance of the slurry.

In order to further inhibit the oxidation of the diamine monomer, so that the entire polycondensation process is more uniform, the additive C is further preferably sodium ascorbate.

The mole percentage of the additive C in the total diamine B is 0.001-0.1%, preferably 0.01-0.1%, and more preferably 0.05%;

as the most preferable embodiment of the present invention, dianhydride A is further preferably 3,3,4, 4-diphenylmethanone tetracarboxylic dianhydride and pyromellitic dianhydride, diamine B is further preferably 4,4' -diaminodiphenyl ether, 4,4' -diamino-2, 2' -bistrifluoromethylbiphenyl and p-phenylenediamine, and additive C is further preferably sodium ascorbate.

In the polyimide precursor of the present invention, the organic solvent D is a mixed solvent of one or more polar solvents capable of dissolving the polyamide acid at room temperature or under heating, and in the examples of the present invention, the organic solvent D is selected from aprotic solvents, N-dimethylformamide, N-dimethylacetamide, N-diethylformamide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphoric triamide, and dimethyl sulfoxide; ether solvents such as tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, and the like; ketone solvents such as acetone, methyl ethyl ketone, diisobutyl ketone, diacetone alcohol, and cyclohexanone; one or more of organic solvents such as ethyl acetate, propylene glycol monomethyl ether acetate, and ethyl lactate.

Among them, N-methyl-2-pyrrolidone is preferable as the organic solvent D.

The embodiment of the invention also provides a preparation method of the polyimide film and the polyimide film prepared by the preparation method.

S1: dissolving diamine B in an organic solvent D to obtain a solution in which the diamine B is dissolved;

s2: adding an additive C into the solution dissolved with the diamine B obtained in the step S1, wherein the mole percentage of the additive C in the total diamine B is 0.001-0.1%, preferably 0.01-0.1%, and more preferably 0.05%;

s3: adding the dianhydride A into the components of the dissolved diamine B and the additive C for multiple times, wherein the adding time is 1-5h, preferably 1h, the dianhydride A needs to react at the temperature of 40-80 ℃ for 6-10h after being added each time until all the dianhydride A is completely added, wherein the temperature is preferably 40 ℃, and the reaction time is preferably 6h and 10h, obtaining a polyamic acid solution after the polymerization is finished, wherein the molar ratio of dianhydride to diamine of the polyamic acid solution is 0.95-1.10, and preferably the molar ratio of dianhydride to diamine is 1;

s4: and (4) coating and curing the polyamic acid solution obtained in the step S3 to obtain the polyimide film.

The step S4 is a specific implementation method, the polyamic acid is coated on a substrate, the solvent is removed by heating, and dehydration cyclization is carried out, thereby obtaining the polyimide film, the curing temperature is in the range of 60-600 ℃, the curing temperature is preferably 80-500 ℃, the curing process is generally divided into at least two stages, the first stage is heating to 150-280 ℃, then the temperature is kept for 10-60min, the second stage is heating to 400-500 ℃, the temperature is kept for 10-60min, the heating rate of the first stage is 0.5-5 ℃/min, and the heating rate of the second stage is 3-10 ℃/min. The film baking process may be performed in an air atmosphere, preferably a nitrogen atmosphere.

In the above-mentioned production method, the solid content and viscosity of the polyamic acid solution can be controlled by the ratio of the powder material and the organic solvent D, the lower limit of the solid content is preferably 8% from the viewpoint of reasonable productivity and use economy, and the upper limit of the solid content is preferably 20% from the viewpoint of good fluidity of the polyamic acid solution slurry, and the solid content is particularly preferably 13%; the viscosity is preferably 3 to 6.9 pas, more preferably 5.2 to 5.3 pas, particularly preferably 5.3 pas, from the viewpoint of coatability;

the addition of the additive C can suppress the oxidation of the diamine monomer, and the whole polycondensation process becomes more uniform, and the uniformity of the film applied to a thickness of 10 μm is preferably within 2%, and particularly preferably 1.6%.

In the above preparation method, the light transmittance of the polyamic acid solution is 62 to 71%, preferably 65 to 67%, and particularly preferably 66%, and the light transmittance of the polyamic acid solution is in the form of a 10 wt% solution in N-methyl-2-pyrrolidone, measured at a wavelength of 400nm and under a light path of 1 cm.

The polyimide film obtained by the preparation method in the embodiment of the invention has a low linear thermal expansion coefficient, and the linear thermal expansion coefficient at 50-300 ℃ is 2-9 ppm/K, preferably 2-3ppm/K, and particularly preferably 2ppm/K when measured by using a film with a thickness of 10 μm.

The polyimide film prepared by the preparation method in the embodiment of the invention has high transparency, and when the film with the thickness of 10 mu m is prepared, the yellow index is 18-26, preferably 21-22, and particularly preferably 21; the transmittance at a wavelength of 400nm is 80 to 88%, preferably 84 to 86%, particularly preferably 86%.

The characterization methods of the polyamic acid solution slurry and the polyimide film are described in detail in the examples of the present invention.

{ solid content }

Uniformly coating a polyamic acid solution slurry sample in a glass container, and weighing the mass m of the sample₁. And (3) heating the coated sample in an oven, keeping the temperature at 100 ℃ for 30min, heating to 350 ℃ at the speed of 5 ℃/min, and keeping the temperature at 350 ℃ for 30 min. Weighing the sample after the sample is cooled₂. The solid content of the sample was calculated according to the following formula:

solid content ═ m₂/m₁)×100％。

{ solution viscosity }

A sample of the polyamic acid solution slurry was measured at 25 ℃ using DHR-1 from TA at 0.314 rad/s.

{ film thickness uniformity }

D_max: coating the polyamic acid precursor with the cured dry film to a maximum thickness;

D_min: the polyamic acid precursor is coated with a dry film minimum thickness after curing.

{ slurry transparency }

The polyamic acid solution slurry was measured using a Perkinelmer model lambda 35 UV spectrophotometer at a wavelength of 400nm and a light path of 1 cm.

{ molecular weight distribution }

The polyamic acid solution slurry was subjected to gel permeation chromatography using a solvent of Waters, USA, in DMF +0.02mol/L H₃PO₄For mobile phase test, the injection concentration is 2mg/mL, and the injection volume is 100 μ L.

{ yellow index and transmittance }

The cured polyimide film is measured by a Perkinelmer model lambda 35 ultraviolet spectrophotometer, the yellow index is measured according to HG/T3862-2006 standard, and the transmittance is measured according to GB/T2410-2008 standard.

{ coefficient of linear thermal expansion and glass transition temperature }

The CTE of the cured polyimide film is measured by a thermo-mechanical analyzer of TA (temperature Advance) model Q400EM, the testing atmosphere is nitrogen, the heating rate is 10 ℃/min, the linear thermal expansion coefficients of different temperature sections are tested, and the inflection point of an expansion curve is taken as the glass transition temperature of the film material.

The following are abbreviations for the compounds used in the examples and comparative examples.

BPDA: 3,3',4,4' -biphenyltetracarboxylic dianhydride

And (3) PMDA: pyromellitic dianhydride

BTDA: 3,3,4, 4-diphenylmethanone tetracarboxylic dianhydride

ODPA: 4, 4-oxydiphthalic dianhydride

6 FDA: hexafluoro dianhydride

ODA: 4,4' -diaminodiphenyl ether

PDA: p-phenylenediamine

BAPP: 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane

TFMB: 4,4 '-diamino-2, 2' -bistrifluoromethylbiphenyl

NMP: n-methyl-2-pyrrolidone

Antioxidant 1010: tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propanoic acid ] pentaerythritol ester

Antioxidant 1098: n, N' -bis- (3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionyl) hexamethylenediamine

Antioxidant 168: tris (2, 4-di-tert-butylphenyl) phosphite

The starting materials for the above compounds are commercially available without particular limitation.

Example 1

A three-neck flask of 1L is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into the three-neck flask, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the flask and are washed by 50g of solvent, after complete dissolution, 0.0396g of sodium ascorbate and 18g of solvent are added, after 1h of reaction, 29.4215g of BPDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q1 are shown in table 1.

Curing is carried out in nitrogen atmosphere, the curing procedure is generally divided into at least two stages, the first stage is heating to 220 ℃, then heat preservation is carried out for 40min, the second stage is heating to 450 ℃, the temperature is kept for 60min, the heating rate of the first stage is 3 ℃/min, and the heating rate of the second stage is 8 ℃/min.

The test results of the cured polyimide film M1 are shown in table 2.

Example 2

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, 0.0220g of hydroquinone and 18g of solvent are added after complete dissolution, 29.4215g of BPDA is added after reaction for 1h, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, the reaction is washed by 25g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q2 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M2 are shown in table 2.

Example 3

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, 0.2355g of antioxidant 1010 and 18g of solvent are added after complete dissolution, 29.4215g of BPDA is added after reaction is carried out for 1h, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is.

The results of the performance test of the obtained polyimide precursor solution Q3 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M3 are shown in table 2.

Example 4

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, 0.1274g of antioxidant 1098 and 18g of solvent are added after complete dissolution, 29.4215g of BPDA is added after reaction is carried out for 1h, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, the reaction is carried out by 25g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization.

The results of the performance test of the obtained polyimide precursor solution Q4 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M4 are shown in table 2.

Example 5

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, 0.1294g of antioxidant 168 and 18g of solvent are added after complete dissolution, 29.4215g of BPDA is added after reaction is carried out for 1h, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is.

The results of the performance test of the obtained polyimide precursor solution Q5 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M5 are shown in table 2.

Example 6

A three-neck flask of 1L is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 600g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 41.0516g of BAPP and 20.0242g of ODA are added into the bottle and washed by 100g of solvent, 0.0396g of sodium ascorbate and 20g of solvent are added after complete dissolution, 38.6676g of BTDA is added after reaction for 1h, 50g of NMP solvent is used for washing, the temperature is controlled at 40 ℃ for reaction for 6h, 22.9556g of ODPA is added, 50g of NMP solvent is used for washing, the temperature is controlled at 40 ℃ for reaction for 8h, 2.6654g of 6FDA is added, 20g of solvent is used for washing, the temperature is controlled at 40 ℃ for reaction for 10h, and then the polymerization reaction is.

The results of the performance test of the obtained polyimide precursor solution Q6 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M6 are shown in table 2.

Example 7

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 600g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 38.5877g of BAPP, 20.0236g of ODA and 1.9214g of TFMB are added into the bottle and washed by 100g of solvent, after complete dissolution, 0.0396g of sodium ascorbate and 20g of solvent are added, after reaction for 1h, 32.2225g of BTDA are added, the bottle is washed by 50g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 31.0215g of ODPA is added, the bottle is washed by 50g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q7 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M7 are shown in table 2.

Example 8

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.0070g of ODA and 3.2023g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0396g of sodium ascorbate and 18g of solvent are added, after 1h of reaction, 29.4215g of BPDA are added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q8 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M8 are shown in table 2.

Example 9

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 200g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0396g of sodium ascorbate and 10g of solvent are added, after reaction is carried out for 1h, 26.4794g of BPDA is added, the bottle is washed by 20g of NMP solvent, the temperature is controlled to 40 ℃, reaction is carried out for 6h, 21.8120g of PMDA is added, the bottle is washed by 20g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction.

The results of the performance test of the obtained polyimide precursor solution Q9 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M9 are shown in table 2.

Example 10

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 600g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 19.4654g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0396g of sodium ascorbate and 15g of solvent are added, after reaction for 1h, 29.4215g of BPDA are added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, the reaction is carried out by 25g of NMP solvent, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q10 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M10 are shown in table 2.

Example 11

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0004g of sodium ascorbate and 18g of solvent are added, after 1h of reaction, 29.4215g of BPDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q11 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M11 are shown in table 2.

Example 12

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0021g of sodium ascorbate and 18g of solvent are added, after 1h of reaction, 29.4215g of BPDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q12 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M12 are shown in table 2.

Example 13

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, after complete dissolution, 0.0040g of sodium ascorbate and 18g of solvent are added, after 1h of reaction, 29.4215g of BPDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q13 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M13 are shown in table 2.

Example 14

A1L three-neck flask is provided with a mechanical stirrer, a spherical condenser tube and a nitrogen guide head, 400g of NMP is added into a reaction bottle, the temperature is raised to 40 ℃, 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB are added into the bottle and are washed by 50g of solvent, 0.0198g of sodium ascorbate and 18g of solvent are added after complete dissolution, 29.4215g of BPDA is added after reaction is carried out for 1h, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 6h, 21.8120g of PMDA is added, 25g of NMP solvent is used for washing, the temperature is controlled to 40 ℃, the reaction is carried out for 10h, and then the polymerization reaction is finished.

The results of the performance test of the obtained polyimide precursor solution Q14 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M14 are shown in table 2.

Comparative example 1

Comparative examples 1 to 5 the procedure was the same as in examples 1 to 5 except that additive C was not added, and the polymerization was terminated in a 1L three-necked flask equipped with a mechanical stirrer, a spherical condenser and a nitrogen head, in which 400g of NMP was charged into a reaction flask, the temperature was raised to 40 ℃ and 17.3026g of PDA, 6.8080g of ODA and 1.9214g of TFMB were charged into the flask and washed with 50g of solvent, after complete dissolution, 29.4215g of BPDA was charged, and washed with 25g of NMP solvent, the temperature was controlled at 40 ℃ for reaction for 6 hours, and 21.8120g of PMDA was charged, and washed with 25g of NMP solvent, and the reaction was carried out at 40 ℃ for 10 hours.

The results of the performance test of the obtained polyimide precursor solution Q15 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M15 are shown in table 2.

Comparative example 2

Comparative example 6 the procedure was as in example 6 except that additive C was not added, 1L three-necked flask equipped with mechanical stirring, a bulb condenser and a nitrogen head was charged into the reaction flask with 600g of NMP, the temperature was raised to 40 ℃ and 41.0516g of BAPP and 20.0242g of ODA were added to the flask and washed with 100g of solvent, after complete dissolution, 38.6676g of BTDA was added, washed with 50g of NMP solvent, the temperature was controlled at 40 ℃ for reaction for 6 hours, 22.9556g of ODPA was added, the temperature was controlled at 40 ℃ for reaction for 8 hours, 2.6654g of 6FDA was added, and the temperature was controlled at 40 ℃ for reaction for 10 hours and the polymerization was terminated.

The results of the performance test of the obtained polyimide precursor solution Q16 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M16 are shown in table 2.

Comparative example 3

Comparative example 1, 1L three-necked flask with excessive additive C, equipped with mechanical stirring, spherical condenser and nitrogen gas head, into a reaction flask 400g NMP, heated to 40 deg.C, 17.3026g PDA, 6.8080g ODA, 1.9214g TFMB, and washed with 50g solvent, after complete dissolution, 0.3960g sodium ascorbate and 18g solvent were added, after 1h of reaction, 29.4215g BPDA was added, washed with 25g NMP solvent, temperature controlled at 40 deg.C for 6h of reaction, 21.8120g PMDA was added, and washed with 25g NMP solvent, temperature controlled at 40 deg.C for 10h of reaction, and polymerization was completed.

The results of the performance test of the obtained polyimide precursor solution Q17 are shown in table 1.

The curing procedure was the same as that of example 1, and no data was shown in Table 2 for the cured polyimide film M17, which was not filmed due to blooming of M17 during curing.

Comparative example 4

Comparative example 6, the molar weight of the fluorine-containing dianhydride accounted for 5% of the molar weight of the total dianhydride and diamine, 1L three-necked flask equipped with mechanical stirring, spherical condenser and nitrogen guide, charging solvent 600g NMP into the reaction flask, heating to 40 deg.C, charging 41.0516g BAPP and 20.0242g ODA into the flask, washing with 100g solvent, after complete dissolution, charging 0.0396g sodium ascorbate and 20g solvent, after reaction for 1h, charging 38.6676g BTDA, washing with 50g NMP solvent, controlling temperature to 40 deg.C for reaction for 6h, charging 18.6126g ODPA, washing with 50g NMP solvent, controlling temperature to 40 deg.C for reaction for 8h, charging 8.8848g FDA, washing with 20g solvent, controlling temperature to 40 deg.C for reaction for 10h, and finishing polymerization reaction.

The results of the performance test of the obtained polyimide precursor solution Q18 are shown in table 1.

The curing procedure was the same as that in example 1, and the test results of the cured polyimide film M18 are shown in table 2.

TABLE 1 polyimide precursor Performance parameters

TABLE 2 polyimide film Performance parameters

As can be seen from Table 1, compared with comparative example 1 without adding additive C, examples 1 to 5 with additive C have higher slurry transparency, the sodium ascorbate and fluorine atom content are kept unchanged, diamine and dianhydride monomer components are replaced, although the slurry transparency and the transmittance after film formation are close to each other in example 7, the thermal expansion coefficient and the glass transition temperature are greatly deteriorated compared with example 1, example 8 and example 1 have the same sodium ascorbate proportion, the molar quantity of the fluorine-containing structure accounts for less than 5 mol% of the total monomers, and the slurry transparency and the film transmittance are better improved, examples 9 and 10 have different solid contents and different viscosities by adjusting the dianhydride and diamine proportion to be 0.95-1.1, so that slurries with different solid contents and different viscosities can be easily obtained to meet the use requirements of different manufacturers, examples 11 to 14 have the molar percent to be 0.001-0.1 mol%, with the increase of the addition proportion of the sodium ascorbate, the slurry transparency and the transmittance after film formation are obviously increased, and 0.01 mol% -0.1 mol% is preferably selected to obtain good slurry transparency and film transmittance, and the example 6 has higher slurry transparency than the comparative example 2 without the additive C, which shows that amino can be uniformly subjected to polycondensation with anhydride after the additive C is added, and simultaneously, the oxidation of diamine can be avoided, so that the preparation process of the polyimide precursor is ensured to be smoothly carried out, and the batch stability of the product cannot be influenced due to the occurrence of side reaction.

In addition, as can be seen from table 2, the polyimide films of examples 1 to 5 and 6, to which the additive C was added, maintained excellent properties in terms of yellow index, 400nm transmittance, thermal expansion coefficient, glass transition temperature, film thickness uniformity, etc., as compared to comparative examples 1 and 2, to which the additive C was not added.

Comparative example 3, 1 mol% of sodium ascorbate is added in the reaction process, the polyimide film after film formation has a blooming phenomenon, which shows that the introduction of excessive additive C can cause the problem of system compatibility, and comparative example 4, the fluorine-containing dianhydride monomer is increased to 5 mol% of the total monomer amount, although the transparency of the slurry and the film still keeps excellent performance, the glass transition temperature is low, and the film has a risk of failure in the high-temperature process stage.

It should be noted that, according to the disclosure and the explanation of the above description, the person skilled in the art to which the present invention pertains may make variations and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some equivalent modifications and variations of the present invention should be covered by the protection scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.