CN114685821B - Preparation method and application of high-performance polyimide film - Google Patents
Preparation method and application of high-performance polyimide film Download PDFInfo
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Abstract
The invention relates to a preparation method and application of a high-performance polyimide film, belongs to the technical field of polyimide, and solves the problems that the polyimide film in the prior art is poor in transparency and large in turbidity and yellowness at high temperature. The preparation method of the high-performance polyimide film provided by the invention comprises the following steps: step 1: preparing a polyamic acid solution; step 2: partially imidizing the polyamic acid solution to obtain a precursor solution; step 3: adding an end group protecting agent into the precursor solution to form a film, and carrying out imidization; step 4: and (5) post-processing to obtain the high-performance polyimide film. The preparation method of the polyimide film provided by the invention realizes effective protection of the active end group in the molecular chain, makes the aggregation state structure of the film more stable, effectively improves the optical stability of the polyimide film in a high-temperature environment, and has important application in the fields of electronics, microelectronics, optical display, optical communication and the like.
Description
Technical Field
The invention relates to the technical field of polyimide, in particular to a preparation method and application of a high-performance polyimide film.
Background
The rapid development of photoelectric technology brings urgent application demands to high-performance optical film materials, and polymer optical materials with the advantages of good transparency, light weight, toughness and the like are receiving more and more attention. Among the polymer materials, the transparent polyimide material has been the first choice of the polymer substrate material in the flexible photoelectric field because of its outstanding heat resistance and excellent mechanical properties, chemical stability, etc. In particular, in the field of novel display, display enterprises at home and abroad develop novel flexible display devices based on transparent polyimide as a cover plate and a base plate. The companies such as samsung and Huacheng also release folding mobile phones with transparent polyimide films as cover plate materials, and have great market application prospects. In addition, the transparent polyimide material has extremely wide application in other fields such as flexible electronics, microelectronics, information communication and the like.
In the fabrication of display devices, the substrate material typically needs to undergo a series of high temperature processing processes. Represented by OLED display technology, the preparation process of TFT as a key component of display drive has high temperature, high temperature treatment temperature exceeding 350 deg.C, short time activation and dehydrogenation process even up to 450-500 deg.C. Therefore, polyimide films must have both excellent optical properties and heat resistance as the most promising transparent polymeric substrate material for display applications. At present, research on transparent polyimide materials has been greatly progressed, the transmittance of the film in the visible light region can be more than 90%, the yellowness (YI value) of the film is also greatly reduced, and the glass transition temperature (T g ) And also gets a great improvement. However, the stability of optical properties of transparent polyimide films in high temperature environments is of little concern. In practical application, although the basic performance of the transparent polyimide film material can withstand high use temperature, the optical performance, namely the transparency, of the film is easy to deteriorate at high temperature, the light transmittance is reduced, the turbidity is increased, the color of the film is deepened, namely the yellowness value is increased, and the quality and the performance stability of a device are seriously affected. Therefore, how to realize that the transparent polyimide film material still keeps good transparency and low chromaticity at high temperature (more than or equal to 300 ℃), and reduces the adverse effect of high temperature on the optical performance of the film is an important technical problem to be solved.
Disclosure of Invention
In view of the above state of the art and analysis of problems, the present invention aims to provide a preparation method and application of a high performance polyimide film, so as to solve the technical challenge that the optical performance of the existing polyimide film cannot be effectively maintained at high temperature, and especially the problems that the transmittance of the transparent polyimide film is obviously reduced and the turbidity and yellowness value are increased when the service temperature is above 300 ℃.
The aim of the invention is mainly realized by the following technical scheme:
the invention provides a preparation method of a high-performance polyimide film, which comprises the following steps:
step 1: preparing a polyamic acid solution;
step 2: partially imidizing the polyamic acid solution to obtain a precursor solution;
step 3: adding a terminal group protecting agent into the precursor solution to obtain a blocked precursor solution, forming a film, and carrying out imidization;
step 4: and (5) post-processing to obtain the high-performance polyimide film.
Based on the further improvement of the preparation method, the imidization degree in the step 2 is 10-60%.
In order to obtain the preset imidization degree, polyimide systems with different structures can be used for adjusting the addition amount, the reaction temperature and the reaction time of the catalyst and the dehydrating agent in a targeted manner when a chemical imidization method is adopted; the imidization degree characterization method can be an infrared spectroscopy method, a nuclear magnetic method and a thermal decomposition method.
The higher the imidization degree of the precursor solution, the more polyamic acid is converted into polyimide, which is favorable for ordered and compact arrangement of molecular chains, and the aggregation state structure of the film tends to be more stable in combination with the subsequent high-temperature imidization process, so that the optical performance stability of the film at high temperature is better. In contrast, in the film prepared by thermal imidization of polyamide acid directly, the molecular chains are more randomly arranged, and the aggregation structure is unstable at high temperature, which is one of the reasons for the unstable optical properties of the film.
The pre-imidization degree is less than 10%, the regulation effect on the aggregation state structure is not obvious, but the pre-imidization degree is more than 60%, the solution becomes turbid or even gel due to poor solubility of the precursor, the subsequent coating film formation is not facilitated, and the quality, the optical performance and the like of the film can be influenced.
Based on a further improvement of the above preparation method, the imidization in the step 2 includes using a thermal imidization method or a chemical imidization method.
Based on the further improvement of the preparation method, the heating temperature is 40-95 ℃ and the reaction time is 0.5-24 hours when the thermal imidization method is adopted in the step 2.
The thermal imidization in step 2 is to obtain a certain degree of imidization. The invention selects the specific thermal imidization temperature (40-95 ℃) and the reaction time (0.5-24 hours) in the step 2, so that the imidization degree can be controlled to be 10-60%.
Based on the further improvement of the preparation method, the molar ratio of the catalyst to the dehydrating agent is (0.2-1.5) when the chemical imidization method is adopted in the step 2: 1.
based on a further improvement of the above preparation method, the imidization in the step 3 includes using a thermal imidization method or a chemical imidization method.
Based on the further improvement of the preparation method, the thermal imidization method adopted in the step 3 comprises the steps of first performing medium-low Wen Xianya amination and then performing high Wen Xianya amination. Preferably, the heating temperature of amination is 80-250 ℃ in middle and low Wen Xianya, the heating time is 1-2 h, the heating temperature of amination is 300-350 ℃ in high Wen Xianya, and the heating time is 0.5-2 h.
In the film drying stage after coating and film making, the film is firstly subjected to film drying at medium and low temperatures, and then is subjected to film drying at high temperature. In the middle-low temperature baking stage of the front stage, a stepped heating and heat preservation process, such as 80 ℃/2h, 120 ℃/1h, 200 ℃/1h or 250 ℃/1h is adopted, and the stage mainly comprises the step of removing the solvent and the organic auxiliary agent to complete certain imidization. And in the later stage of high-temperature baking, the film is heated for 0.5 to 2 hours at the temperature of at least 300 to 350 ℃ so as to realize the complete imidization of the film on the one hand and thoroughly remove the added organic auxiliary agent on the other hand.
In addition, chemical imidization may be used, i.e. imidizing reagent comprising catalyst and dehydrating agent is added to obtain polyimide resin or solution, and then the film is baked at medium and low temperature. The imide is completed by a chemical method, which is favorable for reducing the subsequent baking temperature and is very favorable for the optical performance of the film.
Based on the further improvement of the preparation method, the molar ratio of the catalyst to the dehydrating agent is 1 when the chemical imidization method is adopted in the step 3: (1-2.5).
Based on the further improvement of the preparation method, in the step 3, when the chemical imidization method is adopted, a terminal group protecting agent is firstly added into the precursor solution to obtain a blocked precursor solution, and then the chemical imidization is carried out to form the film.
Based on a further improvement of the above preparation method, in step 3, the step of re-imidizing is further included after adding the end group protecting agent to the precursor solution and before forming the film, so that the end-capped precursor solution is fully imidized or nearly fully imidized. The re-imidization may employ the same imidization method and process conditions as the partial imidization of the polyamic acid solution in step 2.
Based on the further improvement of the preparation method, the post-treatment in the step 4 is high-temperature heat treatment, which comprises the step of heat treating the imidized film in the step 3 at 350-450 ℃ for 5-40 minutes.
The effect of the high temperature post-treatment is two aspects, namely, the release of the thermal stress generated in the film preparation process at high temperature; and secondly, the aggregation state structure of the film is further stabilized.
The film can be laid on the fixing device and stretched in one or two directions during high temperature post treatment, which is helpful for further orientation of the molecular chains of the film, increases the ordered structure content, and improves the heat resistance, the dimensional stability and the like of the film. In addition, thermal imidization and high temperature post-treatment may be performed under vacuum, air or an oxygen-free environment, which is optimal from the viewpoint of film transparency.
Based on the further improvement of the preparation method, in the step 1, diamine and dianhydride are adopted to carry out polycondensation reaction in an organic solvent to generate polyamide acid.
In the step 1, the molar ratio of diamine to dianhydride monomer is 1: (0.90-0.99).
The diamine monomer and the dianhydride monomer can be one or more of aromatic, alicyclic, semi-aromatic, semi-alicyclic, spiro, amide-containing, ester-containing diamine and dianhydride respectively. The structure of diamine and dianhydride can be selected according to the requirements of transparency, heat resistance and the like of the polyimide film, one diamine and one diamine can be selected for homopolymerization reaction, and one diamine and multiple dianhydrides or multiple diamines and one dianhydride or multiple diamines and multiple dianhydrides can be selected for copolymerization reaction according to performance requirements.
The organic solvent used in step 1 includes one or more of N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), N '-Dimethylformamide (DMF), N' -dimethylacetamide (DMAc), N '-Diethylformamide (DEF), N' -diethylacetamide (DEAc), dimethylpropionamide (DMPA), diethylpropionamide (DEPA), dimethylsulfoxide (DMSO), cyclopentanone, and butyrolactone.
The kind of the solvent may be selected from one or more kinds of mixtures depending on the solubility of the monomer, and may be adjusted depending on the long-term storage stability of the polyamic acid, the easy removal ability of the solvent at high temperature, the solubility of the precursor after partial chemical imidization, and the like.
Based on the further improvement of the preparation method, in the step 1, when the diamine and dianhydride monomers have good activity, the reaction condition of the synthetic polyamide acid is favorable at low temperature (-10 ℃ to 20 ℃), and the low temperature is favorable for forward progress of the polyamide acid reaction because the polyamide acid synthesis reaction is an exothermic reaction; if the activity of the diamine or dianhydride monomer is low, the reaction is advantageously carried out by appropriately increasing the polycondensation reaction temperature (30 to 80 ℃) and the polymerization reaction of the monomer is not favored by excessively low reaction temperature, so that the high molecular weight polyamide acid cannot be obtained.
Based on the further improvement of the preparation method, the catalyst in the step 2 is one or more of trialkylamine, imidazole, methylimidazole, pyridine, picoline, quinoline and isoquinoline during chemical imidization; the dehydrating agent is one or more of acetic anhydride, trifluoroacetic anhydride, propionic anhydride and valerolactone; the mol ratio of the catalyst to the dehydrating agent is (0.2-1.5): 1.
the heating or the addition of the catalyst can help to improve the imidization reaction rate of the polyamic acid, and the dehydrating agent can help to remove water in the imidization reaction of the polyamic acid, so that the generated product can be removed in time in the subsequent high-temperature imidization. The dosages of the catalyst and the dehydrating agent are adjusted according to the preset imidization degree of the polyamide acid, the addition amount of the catalyst and the dehydrating agent is correspondingly improved to obtain high imidization degree, and the addition amount of the catalyst and the dehydrating agent is not excessively large to avoid the influence of auxiliary agent residue on the heat-resistant stability of the film.
Based on the further improvement of the preparation method, the molar ratio of the dehydrating agent to the diamine monomer is (3-10) when chemical imidization is adopted in the step 3: 1.
based on a further improvement of the preparation method, the end group protecting agent is a monoanhydride compound, wherein the monoanhydride compound comprises one or more of phthalic anhydride, hexahydrophthalic anhydride, methyl hexahydrophthalic anhydride, 3-fluorophthalic anhydride, 4-fluorophthalic anhydride, 3,4,5, 6-tetrafluorophthalic anhydride and naphthalene dicarboxylic anhydride; the molar ratio of the end group protecting agent to the diamine monomer is (0.02-0.24): 1.
The monoanhydride end group protecting agent is favorable for eliminating amino (-NH) reserved in the polyimide during the synthesis process 2 ) And the active amino terminal groups at the two ends of the molecular chain are exposed and deactivated, so that the yellowing of the film caused by the oxidation reaction of the active ammonia gene at high temperature is avoided.
When the addition amount of the monoanhydride end group protecting agent is too low, the yellowing resistance effect of the film is not obvious due to insufficient reaction with active amino; when the addition amount is too high, the excessive amount cannot be fully reacted into the polymer molecular chain, and the heat resistance stability of the film is potentially adversely affected.
The end group protecting agent is added after the polyamide acid has completed partial imidization reaction and reaches a certain imidization degree (10-60%). This helps to avoid the adverse effect of the monofunctional blocking agent on the polymer molecular weight increase, providing a guarantee for obtaining high molecular weight polyamic acids and polyimides. The end group protecting agent is a monofunctional compound, and the premature addition of the end group protecting agent breaks the equimolar equilibrium reaction of diamine and dianhydride, so that the viscosity of polyamide acid is too low to obtain a high molecular weight polymer.
The yellowing-resistant polyimide film provided by the method is used as a substrate material and is widely applied to the fields of electronics, microelectronics, optical display or optical communication, in particular to the flexible photoelectric field such as flexible display, flexible solar cells, flexible electronic devices and the like.
Compared with the prior art, the invention has at least one of the following beneficial effects:
(1) By introducing end group protecting group into polyimide molecular main chain, active amino group (-NH) in molecular chain can be effectively obtained 2 ) The deactivation avoids the yellowing phenomenon of the film caused by the oxidation reaction of active groups at high temperature.
(2) The preparation method of the invention adopts the preparation method that after the polyamide acid reaches a certain imidization degree through partial imidization, the end group protecting agent is added, thereby effectively avoiding the adverse effect of the monofunctional end capping agent on the molecular weight increase of the polymer and being beneficial to obtaining the high molecular weight polymer.
(3) The invention not only is beneficial to improving the final imidization degree of the film, but also is beneficial to the regular arrangement of polymer molecular chains, so that the aggregation state structure of the film tends to be more stable, thereby further improving the optical performance stability of the polyimide film in high-temperature application and avoiding adverse effects on transparency and yellowness caused by the change of the aggregation state structure.
(4) The invention adopts specific temperature (40-95 ℃) and time (0.5-24 hours) by controlling the first imidization, so that the imidization degree can be controlled to be 10-60%. (5) The preparation method of the yellowing-resistant polyimide film provided by the invention has a simple process, realizes good optical performance stability of the film at a high temperature on the basis of not changing the main structure of a molecular chain, and has an average transmittance change rate of <5% and a yellowing change rate of <10% in a visible light region after the film is resistant for 1-2 hours at a high temperature of 300-400 ℃ in an aerobic or anaerobic environment.
In the invention, the technical schemes can be mutually combined to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
FIG. 1 is a graph showing the light transmittance of the film of example 2 at room temperature (curve 1) and after being subjected to a temperature of 350℃for 1 hour under an air atmosphere (curve 2).
Fig. 2 is the light transmittance at room temperature (curve 3) of the film of comparative example 1, and the light transmittance after being resistant to 350 ℃ for 1 hour under an air atmosphere (curve 4).
Detailed Description
The invention will be further illustrated with reference to the following specific examples, but the invention is not limited to the following examples. The following examples select representative diamine, dianhydride monomer and end group protecting agent, and the preparation method provided by the invention is adopted to synthesize the yellowing-resistant polyimide film with different main chain structures, the diamine and/or dianhydride monomer and/or end group protecting agent in the examples are replaced by other diamine and/or dianhydride monomer and/or end group protecting agent described in the invention, and the prepared homo-polymerization or copolymerization polyimide film has the same effect as the example by adopting the preparation method and conditions described in the invention.
The percentage content and the percentage concentration in the invention are mass percentage content and mass percentage concentration unless specified. The starting materials are obtainable from the commercially published sources unless otherwise specified. The thickness of the polyimide film in the examples can be controlled by adjusting the type of the film coating roller and the solid content of the polyamic acid homogeneous solution.
Example 1
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 260 g of N-methylpyrrolidone were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to-10℃and 26.39 g (0.059 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride was added, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solids content of about 15% by weight and a viscosity of 26300cP.
(2) To the polyamic acid obtained in step 1, 0.56 g (0.006 mol) of picoline and 1.02 g (0.01 mol) of acetic anhydride were added, and the reaction was partially chemically imidized at room temperature for 4 hours, to obtain a precursor solution having an imidization degree of 10%.
(3) To the precursor solution obtained in step 2, 0.30 g (0.002 mol) of phthalic anhydride was added and stirred at 25℃for 6 hours to obtain a homogeneous partially imidized and blocked precursor solution.
(4) To the solution obtained in step 3, 16.76 g (0.18 mol) of picoline and 18.38 g (0.18 mol) of acetic anhydride were added and stirred at 25℃for 6 hours to obtain a blocked polyimide solution. The solution was poured into ethanol to precipitate a resin solid, which was dried under vacuum at 120℃for 12 hours.
(5) And (3) dissolving the polyimide resin obtained in the step (4) in N-methyl pyrrolidone with the solid content of 15wt%, uniformly stirring, filtering, vacuum defoaming, coating the polyimide resin on a dry glass plate with a smooth surface, placing the glass plate in an oven, and heating in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1 hour, 120 ℃/1 hour, 200 ℃/1 hour, 300 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 400 ℃/5 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-1, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Example 2
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 245 g of N-methylpyrrolidone were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to 5℃and 23.99 g (0.054 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride was added thereto, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solids content of about 15% by weight and a viscosity of 23800cP.
(2) 7.12 g (0.09 mol) of pyridine and 9.19 g (0.09 mol) of acetic anhydride were added to the polyamic acid obtained in the step 1, and the reaction was partially chemically imidized at room temperature for 12 hours to obtain a precursor solution having an imidization degree of 60%.
(3) To the precursor solution obtained in step 2, 0.31 g (0.002 mol) of hexahydrophthalic anhydride was added and stirred at 25℃for 12 hours to obtain a homogeneous partially imidized and end-capped precursor solution.
(4) To the solution obtained in step 3, 18.98 g (0.24 mol) of pyridine, 49.00 g (0.48 mol) of acetic anhydride were added and stirred at 25℃for 8 hours to obtain a blocked polyimide solution. The solution was poured into ethanol and precipitated to give a resin solid which was dried under vacuum at 120℃for 12 hours.
(5) And (3) dissolving the polyimide resin obtained in the step (4) in N-methyl pyrrolidone with the solid content of 15wt%, uniformly stirring, filtering, vacuum defoaming, coating the polyimide resin on a dry glass plate with a smooth surface, placing the glass plate in an oven, and heating in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1.5 hours, 250 ℃/1 hour, 300 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 350 ℃/40 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-2, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Example 3
(1) 19.21 g (0.06 mol) of 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl and 250 g of N, N ' -dimethylacetamide were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to 0℃and 25.32 g (0.057 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride was added, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solids content of about 15% by weight and a viscosity of 24800cP.
(2) To the polyamic acid obtained in step 1, 3.87 g (0.03 mol) of quinoline and 6.13 g (0.06 mol) of acetic anhydride were added, and the reaction was partially chemically imidized at room temperature for 8 hours, to obtain a precursor solution having an imidization degree of 40%.
(3) To the precursor solution obtained in step 2, 0.90 g (0.0054 mol) of 3-fluorophthalic anhydride was added and stirred at 25℃for 6 hours to obtain a homogeneous partially imidized and blocked precursor solution.
(4) To the solution obtained in step 3, 15.50 g (0.12 mol) of quinoline, 24.50 g (0.24 mol) of acetic anhydride were added and stirred at 25℃for 8 hours to obtain a blocked polyimide solution. The solution was poured into ethanol and precipitated to give a resin solid which was dried under vacuum at 110℃for 12 hours.
(5) And (3) dissolving the polyimide resin obtained in the step (4) in N, N' -dimethylacetamide with the solid content of 15wt%, uniformly stirring, filtering, vacuum defoaming, coating the polyimide resin on a dry glass plate with a smooth surface, placing the glass plate in an oven, and heating in a nitrogen atmosphere. The specific process is as follows: 80 ℃/2 hours, 200 ℃/1 hour, 300 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 350 ℃/20 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-3, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Example 4
(1) 19.21 g (0.06 mol) of 2,2' -bis (trifluoromethyl) -4,4' -diaminobiphenyl and 253 g of N, N ' -dimethylformamide were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to a low temperature of 10℃and 25.32 g (0.057 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride was added, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solids content of about 15% by weight and a viscosity of 24300cP.
(2) The polyamic acid obtained in the step 1 was subjected to thermal imidization at 55℃for 4 hours to obtain a precursor solution having an imidization degree of 40%.
(3) To the precursor solution obtained in step 2, 0.24 g (0.0015 mol) of 3-methylphthalic anhydride was added and stirred at 25℃for 12 hours to obtain a homogeneous partially imidized and blocked precursor solution.
(4) To the solution obtained in step 3, 16.76 g (0.18 mol) of picoline, 36.75 g (0.36 mol) of acetic anhydride were added and stirred at 25℃for 8 hours to obtain a blocked polyimide solution. The solution was poured into ethanol to precipitate a resin solid, which was dried under vacuum at 80℃for 24 hours.
(5) And (3) dissolving the polyimide resin obtained in the step (4) in N, N' -dimethylformamide with the solid content of 15wt%, uniformly stirring, filtering, vacuum defoaming, coating the polyimide resin on a dry glass plate with a flat and smooth surface, placing the glass plate in an oven, and heating in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1 hour, 150 ℃/1 hour, 250 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 375 ℃/30 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-4, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Example 5
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 210 g of N-methylpyrrolidone were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to-10℃and 17.35 g (0.059 mol) of 3,3', 4' -biphenyltetracarboxylic dianhydride was added thereto, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to obtain a homogeneous polyamic acid solution having a solid content of about 15% by weight and a viscosity of 39000cP.
(2) To the polyamic acid obtained in step 1, 3.16 g (0.04 mol) of pyridine and 6.13 g (0.06 mol) of acetic anhydride were added, and the reaction was partially chemically imidized at room temperature for 8 hours, to obtain a precursor solution having an imidization degree of 40%.
(3) To the precursor solution obtained in step 2, 0.25 g (0.0015 mol) of 3-fluorophthalic anhydride was added and stirred at 25℃for 6 hours to obtain a homogeneous partially imidized and blocked precursor solution.
(4) And (3) filtering and vacuum defoaming the precursor solution obtained in the step (3), coating the precursor solution on a dry glass plate with a flat and smooth surface, placing the dry glass plate in an oven, and heating the dry glass plate in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1 hour, 120 ℃/1 hour, 250 ℃/1 hour, 350 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 400 ℃/15 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-5, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Example 6
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 230 g of N-methylpyrrolidone were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to 5℃and 12.88 g (0.029 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride and 8.53 g (0.029 mol) of 3,3', 4' -biphenyltetracarboxylic dianhydride were added thereto, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solid content of about 15% by weight and a viscosity of 36500cP.
(2) To the polyamic acid obtained in step 1, 3.16 g (0.04 mol) of pyridine and 6.13 g (0.06 mol) of acetic anhydride were added, and the reaction was partially chemically imidized for 12 hours, to obtain a precursor solution having an imidization degree of 40%.
(3) To the precursor solution obtained in step 2, 0.33 g (0.002 mol) of hexahydrophthalic anhydride was added and stirred at 25℃for 4 hours to obtain a homogeneous partially imidized and end-capped precursor solution.
(4) And (3) filtering and vacuum defoaming the precursor solution obtained in the step (3), coating the precursor solution on a dry glass plate with a flat and smooth surface, placing the dry glass plate in an oven, and heating the dry glass plate in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1 hour, 250 ℃/2 hours, 350 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 380 ℃/20 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film PI-6, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Comparative example 1
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 310 g of N-methylpyrrolidone were introduced into a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to-5℃and 26.66 g (0.06 mol) of 4,4' - (2, 2-hexafluoroisopropyl) diphthalic anhydride was added, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to give a homogeneous polyamic acid solution having a solids content of about 15% by weight and a viscosity of 27100cP.
(2) 11.87 g (0.15 mol) of pyridine and 30.63 g (0.30 mol) of acetic anhydride are added to the polyamic acid obtained in the step 1, and the polyimide solution is obtained by chemical imidization for 12 hours. The solution was poured into ethanol and precipitated to give a resin solid which was dried under vacuum at 120℃for 12 hours.
(3) And (3) dissolving the polyimide resin obtained in the step (2) in N-methyl pyrrolidone with the solid content of 15wt%, uniformly stirring, filtering, vacuum defoaming, coating the polyimide resin on a dry glass plate with a smooth surface, placing the glass plate in an oven, and heating in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1.5 hours, 250 ℃/1 hour, 300 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 350 ℃/40 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film RPI-1, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
Comparative example 2
(1) 19.21 g (0.06 mol) of 2,2 '-bis (trifluoromethyl) -4,4' -diaminobiphenyl and 210 g of N-methylpyrrolidone were added to a three-necked flask equipped with mechanical stirring, nitrogen inlet and outlet and a thermometer under the protection of inert gas, and stirred at room temperature until completely dissolved; the system was cooled to a low temperature of 10℃and 17.65 g (0.06 mol) of 3,3', 4' -biphenyltetracarboxylic dianhydride was added thereto, and after complete dissolution, the mixture was stirred at room temperature for 24 hours to obtain a homogeneous polyamic acid solution having a solid content of about 15% by weight and a viscosity of 42200cP.
(2) And (3) filtering and vacuum defoaming the polyamic acid solution obtained in the step (1), coating the polyamic acid solution on a dry glass plate with a flat and smooth surface, placing the glass plate in an oven, and heating the glass plate in a nitrogen atmosphere. The specific process is as follows: 80 ℃/1 hour, 120 ℃/1 hour, 250 ℃/1 hour, 350 ℃/1 hour. And cooling to room temperature, soaking the substrate in deionized water, automatically peeling the film, and drying.
The obtained self-supporting film is tiled on a substrate and fixed by adopting a metal supporting frame, the self-supporting film is placed in a high-temperature oven, the temperature is gradually increased to 400 ℃/15 minutes to finish the high-temperature post-treatment of the film, the temperature is reduced to the room temperature to obtain the final polyimide film RPI-2, and the film thickness is about 30 micrometers, and the main performances are shown in Table 1.
TABLE 1 principal Properties and Properties of polyimide film
a T av : the average light transmittance of the film in the visible light area is measured by a spectrophotometer; YI: film yellowness value, measured by colorimeter
b Yellowing resistanceInvestigation: and respectively placing the films in an air or nitrogen atmosphere, and testing the change rate of the light transmittance and the yellowness after the films are tolerant for 1-2 hours at 350 ℃.
Table 1 shows the main properties of the polyimide films prepared in examples 1 to 6 described above. As shown in the table, the polyimide film prepared by the method provided by the invention has average transmittance change rate of less than 5% and yellowing change rate of less than 10% after being subjected to a test of tolerating at 350 ℃ for 1-2 hours in air or nitrogen atmosphere, which indicates that the film has good optical property stability at high temperature. In contrast, the films obtained in comparative examples 1 and 2 by the conventional preparation method have significantly deteriorated light transmittance and yellowness values after being subjected to the temperature of 350 ℃ for 1 to 2 hours, and particularly the light transmittance under an air atmosphere is greatly reduced, which indicates that the optical property stability of the films at high temperature is poor.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (7)
1. The preparation method of the high-performance polyimide film is characterized by comprising the following steps of:
step 1: preparing a polyamic acid solution;
step 2: partially imidizing the polyamic acid solution to obtain a precursor solution;
step 3: adding a terminal group protecting agent into the precursor solution to obtain a blocked precursor solution, forming a film, and carrying out imidization;
step 4: post-processing to obtain a high-performance polyimide film;
the imidization degree in the step 2 is 10% -60%;
the imidization in the step 2 comprises a thermal imidization method or a chemical imidization method;
in the step 2, the heating temperature is 40-95 ℃ and the reaction time is 0.5-24 hours when a thermal imidization method is adopted;
the post-treatment in the step 4 is high-temperature heat treatment, which comprises the steps of carrying out heat treatment on the imidized film in the step 3 at 350-450 ℃ for 5-40 minutes;
the end group protecting agent is used for inactivating active end amino groups in a molecular chain and avoiding the phenomenon of film yellowing caused by oxidation reaction of active groups at high temperature.
2. The method of claim 1, wherein the imidizing in step 2 is chemical imidizing.
3. The method according to claim 2, wherein the molar ratio of the catalyst to the dehydrating agent in the chemical imidization process used in step 2 is (0.2 to 1.5): 1.
4. the method of claim 1, wherein imidization in step 3 comprises using a thermal imidization method or a chemical imidization method.
5. The process according to claim 4, wherein the heating temperature in the step 3 is 300 to 350℃and the heating time is 0.5 to 2 hours.
6. The process according to claim 4, wherein the molar ratio of the catalyst to the dehydrating agent in the chemical imidization process used in step 3 is 1: (1-2.5).
7. The method for preparing the polyimide film, which is applied to the fields of electronics, microelectronics, optical display or optical communication, according to any one of claims 1 to 6.
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| CN111087813A (en) * | 2018-10-23 | 2020-05-01 | 中国石油化工股份有限公司 | Dimensionally stable polyimide film and method for producing same |
| CN111116950A (en) * | 2019-12-13 | 2020-05-08 | 株洲时代华鑫新材料技术有限公司 | High-performance polyimide film and preparation method thereof |
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| CN111087813A (en) * | 2018-10-23 | 2020-05-01 | 中国石油化工股份有限公司 | Dimensionally stable polyimide film and method for producing same |
| CN110204718A (en) * | 2019-06-19 | 2019-09-06 | 中山职业技术学院 | A kind of Kapton and preparation method thereof and a kind of copper-clad plate |
| CN111116950A (en) * | 2019-12-13 | 2020-05-08 | 株洲时代华鑫新材料技术有限公司 | High-performance polyimide film and preparation method thereof |
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