A low dielectric loss polyimide film and preparation method thereof

Abstract

The invention relates to the technical field of polyimide films, and in particular to a low dielectric loss polyimide film prepared based on a specific combination of fluorodianhydride and a preparation process thereof.

Description

Technical field:

[0001] The invention relates to the technical field of polyimide films, and in particular to a low dielectric loss polyimide film prepared based on a specific combination of fluorinated dianhydride and a preparation process thereof. Background technology:

[0002] As a high-performance polymer material with high temperature resistance, chemical corrosion resistance, high mechanical properties, low dielectric constant and loss, polyimide is widely used in the fields of microelectronics industry, advanced liquid crystal display technology, integrated circuits, etc. With the progress of the above-mentioned scientific and technological fields, more stringent performance requirements are put forward for polyimide. With the advent of the 5G era, the transmission of signals is required to be faster and the transmission signal strength is stronger. It requires the dielectric constant and dielectric loss of the dielectric material to be smaller under GHz working conditions; in addition, the mechanical properties, glass transition temperature and thermal expansion coefficient of the material also play a vital role in the stability of antennas and flexible circuits (Journal of Industrial and Engineering Chemistry, 2015, 28: 16-27.).

[0003] Traditional aromatic polyimide materials have difficulty meeting these performance requirements. In addition, the low solubility of aromatic polyimide in common organic solvents makes its preparation and processing difficult. Aromatic polyimide forms electron transfer complexes due to intramolecular conjugation, making the polyimide material yellow or dark brown, and the transparency cannot meet the requirements.

[0004] At present, the dielectric loss range of the commonly used low dielectric loss polyimide film in the market is (please add) ≤ 0.009. For lower loss requirements, the current low dielectric polyimide film cannot be well applied. The preparation of the commonly used low dielectric polyimide materials in the market mainly adopts a monomer structure as an alicyclic structure to destroy the charge transfer effect (CTC) between molecular chains, thereby achieving the purpose of reducing the dielectric constant. However, the polyimide film containing an alicyclic structure cannot effectively reduce the dielectric loss of the material, and is not conducive to the high dimensional stability of the material. Studies have found that the polyimide prepared from the dianhydride monomer containing a fluorine structure has good optical transparency and a low thermal expansion coefficient, and can significantly reduce the dielectric loss of the material (CN111484615), so it has received extensive attention from researchers.

[0005] At present, the research on low dielectric constant polyimide films in the existing technology is basically concentrated under kHz conditions. The development of polyimide films with low dielectric constant and low dielectric loss under GHz conditions in 5G scenarios is an unknown field. The current low dielectric polyimide films, including polyimides made from fluorine-containing dianhydride monomers, cannot be well applied. Summary of the invention:

[0006] The present invention is based on the technical problems existing in the prior art. On the basis of fluorine-containing dianhydride monomers, it is unexpectedly discovered that a fluorine-containing polyimide film with a specific combination relationship has an extremely low dielectric loss value under GHz conditions in 5G scenarios, and has high dimensional stability while maintaining good mechanical properties and good visible light transmittance.

[0007] The present invention provides a fluorinated polyimide, characterized in that the fluorinated polyimide is obtained by polymerizing a mixed fluorinated dianhydride monomer consisting of a diamine monomer and a fluorinated dianhydride monomer having any two or more structures selected from the following formulas (1) to (5) to obtain a polyimide precursor solution, followed by imidization:

[0008]

[0009] Wherein, Ar is phenyl, X is selected from O, S or NH; R 1 , R 2 , R 3 , R 4 is any one of the following formulas (6) to (11):

[0010]

[0011] Among them, 1≤n≤6;

[0012] The conditions are: R 1 -R 4 The selection should be such that each of formulae (2) to (5) has at least one fluorine-containing substituent;

[0013] The mixed fluorine-containing dianhydride monomer comprises at least one of the monomers of formula (1) and formula (5).

[0014] Preferably, the diamine monomer is selected from: one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, and 2,2'-dimethyl-4,4'-diaminobiphenyl;

[0015] Preferably, R 1 -R 4 The selection should be such that each of formulae (2) to (5) has at least 2 fluorine-containing substituents;

[0016] Preferably, the molar ratio of the mixed fluorine-containing dianhydride monomer to the diamine monomer is 1:0.85-1.15;

[0017] Preferably, the mixed fluorine-containing dianhydride monomer is selected from fluorine-containing dianhydride monomers having any two or more structures of the following formulae:

[0018]

[0019]

[0020] The present invention further provides a fluorine-containing polyimide film, which is characterized in that it is obtained by coating the polyimide precursor solution as described above and then subjecting it to imidization.

[0021] The present invention further provides a method for preparing the aforementioned fluorinated polyimide, characterized in that:

[0022] (4) preparing a polyimide precursor solution: fully dissolving a diamine monomer in an aprotic polar solvent, then adding an aprotic polar solution in which the aforementioned mixed fluorinated dianhydride monomer is dissolved, and reacting to obtain a polyimide precursor solution;

[0023] (5) High temperature imidization: under a nitrogen atmosphere, the polyimide precursor solution obtained in step (1) was dried, and then gradient heated to 360° C., with each gradient being kept for 5-90 min;

[0024] (6) Stress relief: The temperature is naturally lowered to room temperature to obtain the polyimide.

[0025] The present invention further provides a method for preparing the aforementioned fluorinated polyimide film, characterized in that:

[0026] (1) preparing a polyimide precursor solution: fully dissolving a diamine monomer in an aprotic polar solvent, then adding an aprotic polar solution in which the aforementioned mixed fluorinated dianhydride monomer is dissolved, and reacting to obtain a polyimide precursor solution;

[0027] (2) coating: coating the polyimide precursor solution obtained in step (1) on a substrate;

[0028] (3) High temperature imidization: Dry the coated substrate in a nitrogen atmosphere, and then heat it to 360°C in a gradient manner, with each gradient being kept for 5-90 minutes;

[0029] (4) Stress relief: The temperature is naturally lowered to room temperature to obtain the polyimide.

[0030] Preferably, the diamine monomer is selected from: one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl ether diphenyl sulfone, 4,4'-diaminodiphenyl ether bisphenol A, and 2,2'-dimethyl-4,4'-diaminobiphenyl;

[0031] Preferably, R 1 -R 4 The selection should be such that each of formulae (2) to (5) has at least 2 fluorine-containing substituents;

[0032] Preferably, the molar ratio of the mixed fluorine-containing dianhydride monomer to the diamine monomer is 1:0.85-1.15;

[0033] Preferably, the gradient heating step is: drying at 50-80°C for 8-24h; then heating to 100°C and keeping warm for 30-90min; then heating to 160°C and keeping warm for 30-90min; then heating to 220°C and keeping warm for 30-90min; then heating to 280°C and keeping warm for 30-90min; then heating to 320°C and keeping warm for 30-90min; finally, heating to 340-360°C and keeping warm for 40-60min.

[0034] Preferably, in the polyimide precursor solution, the total mass fraction of the fluorodianhydride monomer and the diamine monomer is 10-35wt%.

[0035] Preferably, the viscosity of the polyamic acid precursor solution is 1000-10000 cp, more preferably 2000-5000 cp.

[0036] Preferably, the aprotic polar solvent is composed of one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and diethylene glycol monomethyl ether mixed in any proportion.

[0037] Preferably, the substrate includes copper, aluminum, glass, etc.

[0038] Preferably, the coating process includes spin coating, spray coating, dipping, casting and the like.

[0039] Preferably, in step (1), the reaction temperature is 5-30°C, 0-5°C, more preferably 0-5°C, and the reaction time is 1-2h.

[0040] Preferably, in step (4), the cooling rate is 2-5°C / min, and the high temperature section 350-150°C at the beginning of the cooling is carried out under nitrogen protection.

[0041] Through the above technical solution, the fluorinated polyimide material prepared by the preparation method of the present invention obtains the following beneficial effects:

[0042] Compared with the fluorinated polyimide in the prior art, the fluorinated polyimide provided by the present invention has a comparable dielectric constant and significantly lower dielectric loss, and has not only excellent dielectric properties but also excellent mechanical properties. Specific implementation method:

[0043] Embodiment 1:

[0044] This embodiment 1 provides a polyimide film, which is mainly formed by polymerizing a mixed diamine monomer and a mixed dianhydride monomer.

[0045] The mixed diamine monomer comprises p-phenylenediamine and 4,4'-diaminodiphenyl ether in a molar ratio of 1:1.

[0046] The mixed dianhydride monomer is a 2:1:1 molar ratio Mixed.

[0047] The method for preparing the polyimide film mainly comprises the following steps:

[0048] 1. Before the reaction, the diamine monomer was vacuum dried at 40-50°C for 12 h, and the fluorodianhydride monomer was vacuum dried at 100-110°C for 24 h.

[0049] 2. Dissolve the purified p-phenylenediamine and 4,4'-diaminodiphenyl ether in N,N-dimethylacetamide. After they are completely dissolved, control the temperature to 10°C, slowly drip the mixed dianhydride monomer dissolved in N,N-dimethylacetamide, and after the dripping is completed, continue the reaction for 2 hours to terminate the reaction, and finally obtain a viscous polyamic acid solution with a solid content of 8-30wt% and a viscosity of 1000-10000cp. The solution is colorless or light yellow, clear and transparent.

[0050] 3. After degassing the generated polyamic acid, a coating machine was used to obtain a polyamic acid solution film with uniform thickness. Most of the DMAC solvent was dried at a low temperature of 60°C to obtain a polyamic acid gel film. The temperature was programmed to rise at different gradients of 100°C, 160°C, 220°C, 280°C, 320°C, and 350°C, and the film was cooled to room temperature. The polyimide film was peeled off from the substrate and annealed at 80°C to obtain a polyimide film with a smooth surface and uniform thickness.

[0051] Embodiment 2:

[0052] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is composed of a 1:1 molar ratio of Mixed.

[0053] Embodiment 3:

[0054] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is composed of a 1:1 molar ratio of Mixed.

[0055] Embodiment 4:

[0056] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is composed of a molar ratio of 3:2:1 Mixed.

[0057] Embodiment 5:

[0058] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is composed of a molar ratio of 3:2:1 Mixed.

[0059] Embodiment 6:

[0060] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is composed of a molar ratio of 3:2:1 Mixed.

[0061] Comparative Example 1:

[0062] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is only composed of Become.

[0063] Comparative Example 2:

[0064] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is only composed of Become.

[0065] Comparative Example 3:

[0066] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is only composed of Become.

[0067] Comparative Example 4:

[0068] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is only composed of Become.

[0069] Comparative Example 5:

[0070] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is only composed of Become.

[0071] Comparative Example 6:

[0072] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is 1:1 Mixed.

[0073] Comparative Example 7:

[0074] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is 1:1 Mixed.

[0075] Comparative Example 8:

[0076] The specific implementation is consistent with Example 1, except that the mixed dianhydride monomer is 1:1 Mixed.

[0077] Example 7 Dielectric constant and dielectric loss performance test results of Examples 1-6 and Comparative Examples 1-8 (10 GHz)

[0078] The dielectric constant and dielectric loss of the polyimide films of Examples 1-6 and Comparative Examples 1-8 were tested at 25°C and 10 GHz using a N5224B PNA microwave network analyzer. The measurement results are shown in the following table:

[0079] Schedule 1

[0080]

[0081]

[0082] From the above results, it can be seen that compared with the fluorinated dianhydride of the single component, when the mixed fluorinated dianhydride contains When the above two components are not contained, the dielectric loss value of the prepared polyimide is significantly reduced. When multiple fluorinated dianhydrides are mixed, the dielectric loss value of the prepared polyimide does not change significantly.

[0083] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A fluorinated polyimide, characterized in that: The fluorinated polyimide is obtained by polymerizing a mixed fluorinated dianhydride monomer consisting of a diamine monomer and a fluorinated dianhydride monomer selected from any two or more of the following structures to obtain a polyimide precursor solution, and then imidizing the solution: The mixed fluorine-containing dianhydride monomer comprises at least A type of monomer; The diamine monomer is selected from one or more of 1,4-diaminobenzene, 4,4'-diaminobiphenyl, 4,4-diaminodiphenyl ether, and 2,2'-dimethyl-4,4'-diaminobiphenyl.

2. The fluorinated polyimide according to claim 1, characterized in that: The molar ratio of the mixed fluorine-containing dianhydride monomer to the diamine monomer is 1:0.85-1.

15.

3. A fluorinated polyimide film, characterized in that: The polyimide precursor solution according to any one of claims 1 to 2 is coated and then imidized to obtain the polyimide precursor solution.

4. A method for preparing a fluorinated polyimide according to any one of claims 1 to 2, characterized in that: (1) preparing a polyimide precursor solution: fully dissolving a diamine monomer in an aprotic polar solvent, then adding an aprotic polar solution in which the aforementioned mixed fluorinated dianhydride monomer is dissolved, and reacting to obtain a polyimide precursor solution; (2) High temperature imidization: under a nitrogen atmosphere, the polyimide precursor solution obtained in step (1) was dried, and then gradient heated to 360° C., with each gradient being kept for 5-90 min; (3) Stress relief: The temperature is naturally lowered to room temperature to obtain the polyimide.

5. The method for preparing the fluorinated polyimide according to claim 4, characterized in that: The polyimide precursor solution is coated and then imidized.

6. The method for preparing a fluorinated polyimide according to any one of claims 4 to 5, characterized in that: The gradient heating steps are: drying at 50-80°C for 8-24h; then heating to 100°C and keeping warm for 30-90min; then heating to 160°C and keeping warm for 30-90min; then heating to 220°C and keeping warm for 30-90min; then heating to 280°C and keeping warm for 30-90min; then heating to 320°C and keeping warm for 30-90min; finally, heating to 340-360°C and keeping warm for 40-60min.

7. The method for preparing a fluorinated polyimide according to any one of claims 4 to 5, characterized in that: In the polyimide precursor solution, the total mass fraction of the fluorodianhydride monomer and the diamine monomer is 10-35wt%.

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