阅读说明：本技术 一种含氟和Cardo结构的无色透明聚酰亚胺薄膜及其制备方法 (Colorless transparent polyimide film containing fluorine and Cardo structure and preparation method thereof ) 是由 江艳艳 王振中 任茜 张维 于 2019-08-16 设计创作，主要内容包括：本发明提供了一种含氟取代基和Cardo结构的聚酰亚胺薄膜及其制备方法。该聚酰亚胺薄膜具有优异的耐热性、透明度和力学性能。所述透明聚酰亚胺薄膜的玻璃化转变温度(Tg)为360℃以上,热膨胀系数(CTE)为50ppm/℃以下,模量为4.0GPa以上,b*不大于5,黄度指数不大于8。该透明聚酰亚胺薄膜可用作显示基板或液晶显示器(LCD)、有机发光二极管(OLED)等领域的光学薄膜及其他领域的基材。(The invention provides a polyimide film containing a fluorine substituent and a Cardo structure and a preparation method thereof. The polyimide film has excellent heat resistance, transparency and mechanical properties. The transparent polyimide film has a glass transition temperature (Tg) of 360 ℃ or higher, a Coefficient of Thermal Expansion (CTE) of 50 ppm/DEG C or lower, a modulus of 4.0GPa or higher, b x not greater than 5, and a yellowness index of 8 or lower. The transparent polyimide film can be used as a display substrate or a base material in optical films in the fields of Liquid Crystal Displays (LCDs), Organic Light Emitting Diodes (OLEDs), and the like, and in other fields.)

1. A polyamic acid solution is characterized in that the polyamic acid is prepared by the reaction of tetracarboxylic dianhydride and diamine in an organic solvent,

wherein the molar ratio of the total amount of diamine to the total amount of tetracarboxylic dianhydride is 1: 0.98-1: 1.1;

wherein the diamine has a structure of the following chemical formula 1 or a combination of two monomers of chemical formula 1 and chemical formula 2, and the tetracarboxylic dianhydride has a structure selected from a combination of two monomers of chemical formula 3 and chemical formula 4 or a combination of three monomers of chemical formula 3, chemical formula 4 and chemical formula 5;

when the diamine is a combination of chemical formula 1 and chemical formula 2, wherein the mole percentage content of chemical formula 1 in the combination is not less than 60%;

the dianhydride comprises 10-40% of chemical formula 3, 30-80% of chemical formula 4 and 0-50% of chemical formula 5 in a molar percentage;

[ chemical formula 1]

[ chemical formula 2]

In the chemical formula 2 described above, the,

Q₁、Q₂、Q₃and Q₄Each independently selected from hydrogen, halogen atom, hydroxyl, thiol, nitro, and C_1-10Alkyl radical, C_1-4Haloalkoxy, C_1-10Haloalkyl, cyano and C_6-20An aryl group;

[ chemical formula 3]

[ chemical formula 4]

In the above chemical formula 4, Ar may be selected from any one of the following groups:

[ chemical formula 5]

In the above-described chemical formulas 4 and 5,

Q₅、Q₆and Q₇Each independently selected from the group consisting of a single bond, — O-, -S-, -SO₂- (O) -, -C (═ O) O-, -C (═ O) NH-, phenylene, and combinations thereof.

2. The polyamic acid solution of claim 1, wherein the diamine is of chemical formula 1 in a molar percentage of 60 to 95% and of chemical formula 2 in a molar percentage of 5 to 40%, and the dianhydride is of chemical formula 3 in a molar percentage of 10 to 40% and of chemical formula 4 in a molar percentage of 60 to 90%.

3. The polyamic acid solution of claim 1, wherein the diamine is of formula 1, and the dianhydride is of formula 3 in a molar percentage of 10% to 30%, of formula 4 in a molar percentage of 30% to 80%, and of formula 5 in a molar percentage of 5% to 50%.

4. The polyamic acid solution according to claim 1, wherein Q is₁、Q₂、Q₃And Q₄Is selected from hydrogen, fluorine or C_1-10Wherein the alkyl group is selected from the group consisting of methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl and naphthyl.

5. The polyamic acid solution according to claim 1, wherein said organic solvent is selected from one or more of m-cresol, dimethyl methyl imine, N-methyl-2-pyrrolidone, dimethylacetamide, dimethylsulfoxide, acetone.

6. The polyamic acid solution according to claim 1, wherein the polyamic acid solution has a solid content of 15 to 35 wt%.

7. A transparent polyimide film produced from the polyamic acid solution according to claim 1.

8. The polyimide film according to claim 7, having the following features:

the glass transition temperature (Tg) is not lower than 360 ℃, the second measurement result of the Coefficient of Thermal Expansion (CTE) in the range of 50-250 ℃ is not higher than 50 ppm/DEG C, the birefringence is not higher than 0.06, b is not higher than 5, the yellowness index is not higher than 8, and the modulus is not lower than 4.0 Gpa; the transmittance of the polyimide film at 550nm is not less than 88%, and the haze is not more than 0.5%.

9. The polyimide film according to claim 7, which is prepared by a method comprising the steps of:

adding an imidization catalyst into the polyamic acid solution of claim 1, stirring for 1-6 hours, and uniformly mixing to obtain a mixed solution;

and then coating the mixed solution on a substrate, drying and removing the solvent to obtain a film layer, and imidizing the film layer to obtain the transparent polyimide film.

10. The method for preparing a polyimide film according to claim 9, wherein the film is prepared by heating at 80 to 150 ℃ for 5 to 60 min.

11. The method for preparing a polyimide film according to claim 9, wherein the transparent polyimide film is obtained by directly subjecting the film layer to a high temperature treatment again.

12. The method for preparing a polyimide film according to claim 9, wherein the transparent polyimide film is prepared by separating the film layer from the substrate, fixing the film layer on a steel support, and then heating the film layer again at a high temperature of 300 to 400 ℃ for 10 to 60 minutes.

13. The method for preparing a polyimide film according to claim 9, wherein the imidization catalyst is one or more selected from the group consisting of tertiary amines, imidazoles, benzimidazoles, quinolones, pyridines, and isoquinolines.

14. The colorless transparent polyimide film according to claim 7 is used as a substrate for display or semiconductor applications.

Technical Field

The invention provides a polyamic acid solution and a transparent polyimide film prepared from the polyamic acid solution and capable of improving heat resistance.

Background

In the past few years, glass has been the first choice for use as a substrate for fabricating optoelectronic devices. However, the development of optoelectronic devices is tending to be flexible, which means that glass is difficult to adapt to this new trend due to its fragile nature. In this case, the polymeric material would be a good substitute for glass. It is well known that many polymeric materials can exhibit good optical properties, as well as excellent flexibility, as glass. However, flexible substrates, including OLED displays, are often subjected to high temperature processing during device fabrication, and the process temperature required to fabricate, for example, oxide TFTs and Low Temperature Polysilicon (LTPS) under high temperature conditions is typically above 350 c and sometimes even up to 500 c. Therefore, in addition to good optical properties and flexibility, some thermal and dimensional stability is required for its application.

Therefore, the development of polyimide with excellent heat resistance, optical transparency and mechanical properties is of great significance.

Polyimide has superior stability during high temperature processing compared to other polymer materials. However, the conventional polyimide film is dark brown or yellow due to the Charge Transfer Complex (CTC) interaction between aromatic rings in the main chain structure of polyimide.

In some research work, researchers have introduced linking groups, such as thione (-SO), into the backbone structure of molecules in order to minimize intermolecular or intramolecular charge transfer interactions to produce colorless, transparent polyimides₂) Hexafluoroisopropyl, ether (-O-) or bulky pendant substituents capable of imparting large free volume, or cycloaliphatic structures.

However, in most cases, the introduction of these functional groups greatly sacrifices the thermal stability of the film, and the development of transparent polyimide with high glass transition temperature plays an important role. Therefore, the invention introduces the fluorine-containing substituent and the Cardo structure into the polymer skeleton structure, and prepares the transparent polyimide film with higher thermal stability by optimizing the proportion of the groups. The transparent polyimide film has high application value as an optical film in the fields of display substrates, Liquid Crystal Displays (LCDs), Organic Light Emitting Diodes (OLEDs) and the like.

Disclosure of Invention

The invention aims to provide a polyamic acid solution which is prepared by copolymerizing tetracarboxylic dianhydride and diamine. The repeat unit structure of the polyamic acid contains at least one fluorine-containing substituent and a Cardo structure.

The polyamic acid solution is manufactured by reacting a diamine including chemical formula 1 or chemical formula 1 and chemical formula 2 with a polymerization component including tetracarboxylic dianhydride of chemical formula 3, chemical formula 4 or chemical formula 3, chemical formula 4 and chemical formula 5 in an organic solvent. Wherein the diamine includes chemical formula 1 or a combination of chemical formula 1 and chemical formula 2;

the tetracarboxylic dianhydride includes a combination of chemical formula 3, chemical formula 4 or a combination of chemical formula 3, chemical formula 4 and chemical formula 5.

[ chemical formula 1]

[ chemical formula 2]

In the chemical formula 2 described above, the,

Q₁、Q₂、Q₃and Q₄Each independently of the others, selected from hydrogen, halogen atoms, e.g. -F, — Cl, — Br, — I or hydroxy (-OH), thiol (-SH), nitro (-NO)₂)、C_1-10Alkyl radical, C_1-4Haloalkoxy, C_1-10Haloalkyl, cyano and C_6-20Aryl, preferably, Q₁、Q₂、Q₃And Q₄May be a substituent selected from the group consisting of a halogen atom, a hydroxyl group, a haloalkyl group, an alkyl group, an aryl group and a cyano group. For example, the halogen atom may be fluorine (-F), and the haloalkyl group may be a C group such as a fluoromethyl group, perfluoroethyl group, trifluoromethyl group, etc_1-10Wherein the alkyl group is selected from the group consisting of methyl, ethyl, propyl, isopropyl, tert-butyl, pentyl and naphthyl. More preferably, the substituent may be a fluoro substituent containing a fluorine atom.

[ chemical formula 3]

[ chemical formula 4]

In the above chemical formula 4, Ar may be selected from any one of the following groups:

[ chemical formula 5]

In the above-described chemical formulas 4 and 5,

Q₅、Q₆and Q₇Each independently selected from the group consisting of a single bond, — O-, -S-, -SO₂- (O) -, -C (═ O) O-, -C (═ O) NH-, phenylene, and combinations thereof.

According to one embodiment, the molar ratio of the total amount of diamine to the total amount of tetracarboxylic dianhydride is 1: 0.98-1: 1.1, preferably 1: 1-1: 1.05, and the reaction is continued for 4-48 hours in a nitrogen or argon atmosphere, and the reaction temperature is controlled at-20 ℃ to 60 ℃.

The organic solvent used in the present invention may be selected from amide solvents such as N-methyl-2-pyrrolidone (NMP), Dimethylformamide (DMF), dimethylacetamide (DMAc), and Dimethylsulfoxide (DMSO); cyclic ester solvents such as γ -valerolactone, γ -butyrolactone and α -methyl- γ -butyrolactone; phenol solvents such as m-cresol and p-cresol; one or more of sulfolane, acetophenone, dimethyl sulfoxide and other solvents having a low boiling point. The solvent used in the present invention is not limited to the above-mentioned solvents.

The solid content of the polyamic acid solution is 10 to 40 wt%, preferably 15 to 35 wt%, with respect to the total amount of the polyamic acid and the solvent.

In a preferred embodiment, in the composition of the polyamic acid solution, the diamine is a combination of chemical formula 1 and chemical formula 2 and wherein the mole percentage content of chemical formula 1 is not less than 60%;

the dianhydride comprises 10-40 mol% of chemical formula 3, 30-80 mol% of chemical formula 4 and 0-50 mol% of chemical formula 5.

In another preferred embodiment, the composition of the polyimide solution is such that the diamine is 60 to 95% by mole of formula 1 and 5 to 40% by mole of formula 2, and the dianhydride is 10 to 40% by mole of formula 3 and 60 to 90% by mole of formula 4.

According to still another preferred embodiment, the composition of the polyimide solution is such that the diamine is of formula 1 and the dianhydride is of formula 3 in a molar percentage of 10% to 30%, of formula 4 in a molar percentage of 30% to 80%, and of formula 5 in a molar percentage of 5% to 50%.

The invention also aims to provide a transparent polyimide film, which is prepared from the polyamic acid solution. The glass transition temperature (Tg) is not lower than 360 ℃, the second measurement result of the Coefficient of Thermal Expansion (CTE) in the range of 50-250 ℃ is not higher than 50 ppm/DEG C, the birefringence is not higher than 0.06, b is not higher than 5, the yellowness index is not higher than 8, and the modulus is not lower than 4.0 Gpa; the transmittance of the polyimide film at 550nm is not less than 88%, and the haze is not more than 0.5%. The transparent polyimide film has a relatively high glass transition temperature (Tg) and a relatively low Coefficient of Thermal Expansion (CTE). Has excellent heat resistance and good optical performance, and can be used as a base material in the display or semiconductor field.

The invention also aims to provide a method for preparing the polyimide film, which can be implemented by the following specific steps: mixing the polyamic acid solution with an imidization catalyst, coating the mixed solution on a substrate, heating in an oven to remove a solvent to form a pre-coated film, peeling the pre-coated film, fixing the pre-coated film on a steel support, and imidizing (dehydrating and ring closing) through heat treatment, or casting the mixed solution on a glass plate, directly removing the solvent through heat treatment and imidizing the mixed solution to obtain a polyimide film; or directly coating the polyamic acid solution on a substrate, and then obtaining a polyimide film in the same processing mode; and thirdly, or mixing the polyamic acid solution with an imidization catalyst and a dehydrating agent, and then obtaining the polyimide film in the same processing mode. The present invention is preferably (i). Wherein, the heat treatment conditions are as follows but not limited thereto: the mixture is dried at a temperature in the range of 50 ℃ to 180 ℃, preferably 80 ℃ to 150 ℃, and then further heated at a maximum temperature of 300 ℃ to 500 ℃ to complete imidization, preferably 300 ℃ to 400 ℃. The heat treatment is usually carried out in an air atmosphere or a nitrogen atmosphere, and preferably in a nitrogen atmosphere.

According to an embodiment of the present invention, the polyamic acid solution mixture solution may include an imidization catalyst, and the catalyst may be selected from imidazole compounds, benzimidazole compounds, quinolone compounds, pyridine compounds, isoquinoline compounds, and the like. Among them, the imidization catalyst may be used alone, or may be used in combination of two or more types. The amount of the imidization catalyst is preferably 0.1 to 10 wt%, and more preferably 0.9 to 7 wt%, based on the total mass of the polyamic acid polymer.

The thickness of the polyimide film is not particularly limited, but is preferably 5 to 250 μm, and more preferably 10 to 60 μm.

Detailed Description

Hereinafter, examples of the present invention will be described in more detail, but the scope of the present invention is not limited to the following examples.