阅读说明：本技术 聚酰胺酸、聚酰胺酸树脂、耐热透明聚酰亚胺及制备方法 (Polyamide acid, polyamide acid resin, heat-resistant transparent polyimide and preparation method ) 是由 江乾 刘亦武 刘杰 彭军 段瑨 胡峰 刘婷 刘含茂 王进 许双喜 于 2020-07-03 设计创作，主要内容包括：本发明公开了一种聚酰胺酸、聚酰胺酸树脂、耐热透明聚酰亚胺及制备方法,聚酰胺酸由不少于一种含氟二胺单体和不少于一种含氟二酐单体以及封端剂在非质子极性溶剂中发生聚合反应得到；其中如下结构的含氟二酐占含氟二酐总摩尔量的5～20％。<Image he="374" wi="360" file="DDA0002568906690000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>本发明制备的透明聚酰亚胺玻璃化转变温度大于370℃,热膨胀系数小于17ppm/K,500nm处透光率大于90％,适用于柔性显示领域透明基板、盖板以及触控层的制造。(The invention discloses polyamic acid, polyamic acid resin, heat-resistant transparent polyimide and a preparation method, wherein the polyamic acid is obtained by polymerization reaction of not less than one fluorine-containing diamine monomer, not less than one fluorine-containing dianhydride monomer and a capping reagent in an aprotic polar solvent; wherein the fluorine-containing dianhydride with the following structure accounts for 5-20% of the total molar amount of the fluorine-containing dianhydride. The glass transition temperature of the transparent polyimide prepared by the invention is more than 370 ℃, the thermal expansion coefficient is less than 17ppm/K, the light transmittance at 500nm is more than 90%, and the transparent polyimide is suitable for manufacturing transparent substrates, cover plates and touch layers in the field of flexible display.)

1. The polyamic acid is characterized in that the polyamic acid is obtained by carrying out polymerization reaction on not less than one fluorine-containing diamine monomer, not less than one fluorine-containing dianhydride monomer and a blocking agent in an aprotic polar solvent;

wherein the fluorine-containing dianhydride with the following structure accounts for 5-20% of the total molar weight of the fluorine-containing dianhydride;

2. the polyamic acid according to claim 1, wherein the remaining fluorine-containing dianhydride monomer is selected from one or more of the following structural monomers:

3. the polyamic acid according to claim 1 or 2, wherein the fluorine-containing diamine monomer is selected from one or more of the following structural monomers:

4. the polyamic acid according to claim 1 or 2, wherein the end-capping agent is selected from one of the following structures:

5. the polyamic acid according to claim 4, wherein the molar ratio of the end-capping agent to the fluorine-containing diamine is from 0.5: 100-1.5: 100.

6. a polyamic acid resin is characterized by comprising the following components in parts by weight: 6 to 40 parts of polyamic acid according to any one of claims 1 to 5, 0.1 to 1 part of antioxidant, 0.1 to 1 part of leveling agent, and 58 to 93 parts of aprotic polar solvent.

7. The polyamic acid resin according to claim 6, wherein the aprotic polar solvent is selected from one or more of the following: n-methylpyrrolidone, N '-dimethylformamide, N' -dimethylacetamide or gamma-butyrolactone.

8. The polyamic acid resin according to claim 6, wherein the antioxidant is selected from one or more of the following: aluminum dihydrogen phosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate or tert-butylhydroquinone; the leveling agent is selected from one or more of the following substances: polydimethylsiloxane, polyether polyester modified organosiloxane or alkyl modified organosiloxane.

9. A method for preparing the polyamic acid resin according to any one of claims 6 to 8, comprising the steps of: dissolving a fluorine-containing diamine monomer in a polar aprotic solvent, controlling the temperature at-10 ℃, protecting with inert gas, adding the fluorine-containing dianhydride monomer into the solution in batches under stirring, adding a blocking agent after full reaction, continuing the reaction, finally adding an antioxidant and a leveling agent, and uniformly stirring to obtain the polyamic acid resin.

10. A heat-resistant transparent polyimide obtained by imidizing the polyamic acid according to any one of claims 1 to 5 or the polyamic acid resin according to any one of claims 6 to 8.

Technical Field

The invention relates to polyamic acid, polyamic acid resin, heat-resistant transparent polyimide and a preparation method thereof, wherein the resin and the polyimide material can be used for manufacturing a display substrate, a cover plate and a touch layer in the field of flexible display.

Background

With the development of flexible and ultra-thin display panels, displays have new requirements for material properties, and conventional rigid glass is not suitable for the manufacture of flexible display panels. The use of transparent organic materials instead of rigid glass is a problem that the industry is demanding to solve. The substrate, the cover plate and the touch layer have high requirements on the light transmittance and the mechanical property of the material, and the high-temperature process is involved in the production process, so that the temperature resistance and the dimensional stability of the material are challenged. Transparent polyimide has excellent heat resistance, and thus is the first choice material to replace glass.

The conventional polyimide is yellow, and the transparency of the polyimide reduces the heat resistance, the dimensional stability and the mechanical property of the polyimide to a certain extent. The current commercialized transparent polyimide generally has the defects of insufficient temperature resistance and large thermal expansion coefficient, and the application of the polyimide in the manufacture of higher-level display panels is limited. How to develop the high-temperature resistant transparent polyimide is called as a difficult problem to be solved urgently.

In patent CN108586744A, a multifunctional unsaturated bond-containing additive is introduced into a transparent polyimide formula, and the prepared transparent polyimide has better thermal stability and water resistance. In this patent, the additives are added as blocking agents and a crosslinking reaction occurs at high temperatures to link the molecular chains together. But the problems of low addition amount and uncontrollable additive participating in the reaction exist, and the temperature resistance of the synthesized polyimide is improved to a limited extent.

Patent CN105694035B discloses a highly transparent polyimide film material containing tetramethyl diphenylsulfone diether structure and a preparation method thereof, which uses sulfone and ether groups to improve the molecular chain structure of polyimide, reduce the color development effect thereof, and realize the transparentization of polyimide. However, researches show that the transparent polyimide containing a sulfone structure often has the defect of high yellowness, so that the application of the transparent polyimide in the field of flexible display is limited.

Disclosure of Invention

The technical problem to be solved by the present invention is to overcome the above mentioned disadvantages and drawbacks of the background art, and to provide a polyamic acid, a polyamic acid resin, a polyimide, and a preparation method thereof, so as to improve the heat resistance and dimensional stability of the transparent polyimide.

In order to solve the technical problems, the technical scheme provided by the invention is as follows:

the polyamide acid is obtained by carrying out polymerization reaction on not less than one fluorine-containing diamine monomer, not less than one fluorine-containing dianhydride monomer and a blocking agent in an aprotic polar solvent;

wherein the fluorine-containing dianhydride with the following structure accounts for 5-20% of the total molar weight of the fluorine-containing dianhydride;

further, the rest fluorine-containing dianhydride monomer is selected from one or more of the following structural monomers:

further, the fluorine-containing diamine monomer is selected from one or more of the following structural monomers:

further, the end-capping agent is selected from one of the following structures:

further, the molar ratio of the end-capping agent to the fluorine-containing diamine is 0.5: 100-1.5: 100.

the invention provides a polyamic acid resin which comprises the following components in parts by weight: 6-40 parts of polyamide acid, 0.1-1 part of antioxidant, 0.1-1 part of flatting agent and 58-93 parts of aprotic polar solvent.

Further, the aprotic polar solvent is selected from one or more of the following substances: n-methylpyrrolidone, N '-dimethylformamide, N' -dimethylacetamide or gamma-butyrolactone.

Further, the antioxidant is selected from one or more of the following substances: aluminum dihydrogen phosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate or tert-butylhydroquinone; the leveling agent is selected from one or more of the following substances: polydimethylsiloxane, polyether polyester modified organosiloxane or alkyl modified organosiloxane.

The invention provides a preparation method of a polyamic acid resin, which comprises the following steps: dissolving a fluorine-containing diamine monomer in a polar aprotic solvent, controlling the temperature at-10 ℃, protecting with inert gas, adding the fluorine-containing dianhydride monomer into the solution in batches under stirring, adding a blocking agent after full reaction, continuing the reaction, finally adding an antioxidant and a leveling agent, and uniformly stirring to obtain the polyamic acid resin.

The invention provides heat-resistant transparent polyimide which is prepared by imidizing the polyamic acid or the polyamic acid resin.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, the fluorine-containing diamine and the fluorine-containing dianhydride monomer are polymerized to obtain the soluble transparent polyamic acid resin, the transparent polyimide is obtained through thermal imidization or chemical imidization, and the fluorine-containing dianhydride monomer containing a naphthalene structure is introduced to enhance the heat resistance and the dimensional stability of the polyimide. The glass transition temperature of the transparent polyimide prepared by the invention is more than 370 ℃, the thermal expansion coefficient is less than 17ppm/K, the light transmittance at 500nm is more than 90%, and the transparent polyimide is suitable for manufacturing transparent substrates, cover plates and touch layers in the field of flexible display.

Drawings

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

FIG. 1 is a DSC chart of example 5;

FIG. 2 is a test chart of the linear expansion coefficient of example 5;

FIG. 3 is a light transmittance test chart of example 5.

Detailed Description

In order to facilitate understanding of the invention, the invention will be described more fully and in detail with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

The polyamic acid of one embodiment of the invention is obtained by the polymerization reaction of not less than one fluorine-containing diamine monomer, not less than one fluorine-containing dianhydride monomer and a blocking agent in an aprotic polar solvent.

Wherein the fluorine-containing dianhydride (H1) with the following structure accounts for 5-20% of the total molar weight of the fluorine-containing dianhydride. H1 has a fluorinated naphthalene structure, and can obviously improve the heat resistance and the dimensional stability of the transparent PI without causing the reduction of the light transmittance of the material.

The dianhydride with naphthalene ring has stronger rigid structure, can effectively improve the temperature resistance of the polyimide material and reduce the linear expansion coefficient of the material. However, if the naphthalene ring is used in the synthesis of transparent polyimide, if no other group is on the naphthalene ring, a strong CTC effect is formed between the synthesized high molecular chains, namely, a Charge Transfer Complex (CTC) is easily formed between an electron donor (diamine) and an electron acceptor (dianhydride), the formation of the CTC is an intrinsic cause of light absorption of the material, and the stronger the CTC effect, the lower the light transmittance of the film is, and the greater the yellowness is. In the invention, the dianhydride substituted by fluorine atoms on naphthalene rings is adopted, and the fluorine atoms have high electron density, so that the electron distribution in molecules is polarized, the electron cloud is cut off, the conjugation effect is damaged, the absorption of the material to light is difficult, and the influence on the light transmittance of the film is low.

The rest fluorine-containing dianhydride monomer is selected from one or more of the following structural monomers:

the fluorine-containing diamine monomer is selected from one or more of the following structural monomers:

the adoption of the monomer containing the fluoro structure can effectively reduce the CTC effect among high molecular chains, which is an effective way for preparing the transparent polyimide. In general, the fluorine-containing group directly connected with the benzene ring has more obvious effect on reducing CTC, and also has great relation with the size of the group and the number of fluorine-containing atoms.

The blocking agent used is an anhydride-based blocking agent, the molar ratio of which to diamine is 0.5: 100-1.5: 100. the end capping agent is selected from one of the following structural monomers:

the end capping agent mainly functions to reduce free radicals at two ends of a molecular chain, and the synthesized resin is not easy to degrade and has better storage stability. The structure containing benzene rings is mainly adopted because the benzene rings have stable properties and are not easy to change in a high-temperature environment.

The polyamic acid synthesized has the following structure:

(A: fluorine-containing diamine monomer residue; H: fluorine-containing dianhydride monomer residue; C: capping agent residue)

The present invention defines polyamic acid + aprotic solvent as polyamic acid resin. In one embodiment, the transparent polyamic acid resin according to the present invention is prepared by the following method: fully dissolving a diamine monomer in a polar aprotic solvent, controlling the temperature to be-10 ℃, stirring at the speed of 50-150 r/min, and protecting with inert gas. Adding dianhydride monomers into the solution in batches, fully reacting to obtain polyamide acid resin with certain viscosity, and continuing to react for about 30min after adding an end capping agent. Then adding the antioxidant, the flatting agent and the release agent, and continuously stirring uniformly.

The polyamide acid resin comprises the following components in parts by weight: polyamic acid: 6-40 parts; antioxidant: 0.1-1 part; leveling agent: 0.1-1 part; aprotic polar solvent: 58-93 parts.

The antioxidant is selected from one of the following substances: aluminum dihydrogen phosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium pyrophosphate and tert-butyl hydroquinone.

The leveling agent is selected from one of the following substances: polydimethylsiloxane, polyether polyester modified organosiloxane and alkyl modified organosiloxane.

The aprotic polar solvent is selected from one or more of the following substances: n-methyl pyrrolidone, N '-dimethylformamide, N' -dimethylacetamide and gamma-butyrolactone.

The high-temperature resistant transparent polyimide is a polymer obtained by dehydrating and cyclizing polyamic acid by a thermal imidization method or a chemical imidization method. Chemical imidization or thermal imidization may be employed:

chemical imidization: the polyamic acid resin and the imidizing agent are fully mixed (chemical imidization reaction occurs in the step, polyamic acid is partially imidized), coated on a steel plate (or glass) substrate, and subjected to temperature programming to obtain the polyimide with complete imidization.

Thermal imidization: the polyamic acid resin is coated on a steel plate (or glass) substrate, and the polyimide which is fully imidized is obtained after temperature programming.