Intrinsic black polyimide film with good mechanical and thermal stability and preparation method thereof

Abstract

The invention belongs to the technical field of polymer films, and particularly relates to an intrinsic black polyimide film with good mechanical and thermal stability and a preparation method thereof, and the preparation method comprises the following steps: (1) sequentially adding a diamine monomer, a dianhydride monomer and a filler into a solvent, and carrying out condensation polymerization to obtain polyamide acid resin; (2) carrying out casting and stretching on the polyamide acid resin through a thermal imidization or chemical imidization process to obtain an original PI film; (3) annealing and cutting the original PI film to obtain a commercial PI film; dihydrophenazine diamine (DPA) molecules are introduced into a PI molecular chain, compared with commonly used 4, 4 '-diaminodiphenylamine (NDA), each DPA molecule contains two imino groups (-NH-), the promotion on a charge transfer CT effect is more obvious, and meanwhile, the annular structure of phenazine has relatively strong rigidity and has an enhancement effect on mechanical and thermal properties of a PI film.

Description

Technical Field

[0001] The invention relates to the technical field of polymer films, in particular to an intrinsic black polyimide film with good mechanical and thermal stability and a preparation method thereof. Background Art

[0002] As electronic devices continue to develop towards high density, miniaturization and flexibility, flexible copper clad laminate (FCCL), as a key component, has higher and higher performance requirements. FCCL is mainly composed of polyimide (PI) film and copper foil. In recent years, terminal companies represented by Apple have put forward new requirements for FCCL, namely black FCCL. Black FCCL is for aesthetic considerations on the one hand, and can effectively protect the internal circuit design from being copied on the other hand. Compared with conventional FCCL, black FCCL requires the use of black PI film as a substrate. At present, the preparation of black PI film is mainly achieved by adding carbon black or organic black dye to conventional PI film, or coating the surface of conventional PI film with black coating. However, the above methods all have shortcomings. The conductive properties of carbon black will reduce the insulation properties of PI film, and if unevenly added, the mechanical properties of the film will be significantly reduced; organic black dyes have poor heat resistance and poor tinting strength, and cannot fully meet the performance requirements of PI film in electrical and optical applications.

[0003] The use of intrinsic black PI film is an effective way to solve the above problems. Through molecular design, chromophores can be introduced into the PI molecular chain segments to promote the occurrence of charge transfer (CT) between PI molecular chains and molecules, so that the PI film has significant absorption in the visible light region. A common method is to introduce an aromatic diamine monomer containing an imine chromophore—4, 4′-diaminodiphenylamine (NDA)—into the PI formula. On the one hand, the lone pair of electrons on the imine N atom in the NDA molecular structure can promote the occurrence of CT; on the other hand, the imine group (-NH-) undergoes high-temperature oxidation during the preparation of the PI film, which can directly generate black substances. For example, patents CN118702941, CN113072700, and CN109180936 all add NDA to the formula. However, as described in patent CN113072700, if too little NDA is added, black performance cannot be achieved. If too much NDA is added, the number average molecular weight of the polyamic acid solution (PAA) will be reduced, thereby reducing the physical and chemical properties of the PI film. Summary of the invention

[0004] The purpose of the present invention is to provide an intrinsic black polyimide film with good mechanical and thermal stability and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology. The present invention introduces dihydrophenazine diamine (DPA) into the PI molecular chain. Compared with NDA, each DPA molecule contains two imine groups (-NH-), which promotes the charge transfer CT effect more significantly. At the same time, the ring structure of phenazine has strong rigidity, which has an enhancing effect on the mechanical and thermal properties of the PI film. The structural formulas of DPA and NDA are shown below.

[0005] (NDA); (DPA).

[0006] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a method for preparing an intrinsic black polyimide film with good mechanical and thermal stability, comprising the following steps: (1) preparing PAA resin, adding diamine monomer, dianhydride monomer and filler in a solvent in sequence, and obtaining PAA resin after polycondensation reaction; (2) PAA resin is subjected to thermal imidization or chemical imidization process, and then cast and stretched to obtain the original PI film; (3) The original PI film is annealed at 350-380°C and cut to obtain a commercial PI film.

[0007] Furthermore, in step (1), the mass fraction of the PAA resin is 20-30%, and the viscosity is 200,000-300,000 cp; the molar ratio of diamine to dianhydride is 1:(0.8-1.2), preferably 1:1; and the mass ratio of the filler to the total amount of the diamine monomer and the dianhydride monomer is 0.05-2:100.

[0008] Furthermore, the diamine monomer is an aromatic diamine, and the diamine monomer includes dihydrophenazine diamine and other diamine monomers, and the other diamine monomers are one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, and 3,4'-diaminodiphenyl ether.

[0009] Furthermore, the molar ratio of dihydrophenazine diamine to the total amount of diamine monomers is 0.15-0.50:1.

[0010] Preferably, the molar ratio of dihydrophenazine diamine to the total amount of diamine monomers is 0.20-0.40:1.

[0011] Furthermore, the dianhydride monomer is an aromatic dianhydride, and the aromatic dianhydride is one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

[0012] Furthermore, the filler is one or more of oxides, nitrides and carbides.

[0013] Preferably, the filler is silicon dioxide or calcium hydrogen phosphate.

[0014] Furthermore, the solvent is one or more of N,N'-dimethylformamide, N,N'-dimethylacetamide, and N-methylpyrrolidone.

[0015] The present invention also provides an intrinsic black polyimide film with good mechanical and thermal stability prepared by the preparation method as described above.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces dihydrophenazine diamine (DPA) into the PI molecular chain. Compared with NDA, each DPA molecule contains two imine groups (-NH-), which promotes the charge transfer CT effect more significantly. When the same amount is added, the black effect is better. At the same time, the ring structure of phenazine has strong rigidity. The addition of DPA improves the mechanical and thermal properties of the PI film. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0018] (1) preparing polyamic acid (PAA) resin, adding diamine monomer, pyromellitic dianhydride (PMDA) and calcium hydrogen phosphate to N,N'-dimethylformamide in sequence, and obtaining PAA resin after polycondensation reaction; (2) PAA resin is subjected to thermal imidization or chemical imidization process, followed by casting and stretching to obtain the original PI film; (3) The original PI film was annealed at 350°C and cut to obtain a commercial PI film.

[0019] Among them, the viscosity of PAA resin is 230,000 cp; the molar ratio of diamine to dianhydride is 1:1; the diamine is DPA and 4,4'-diaminodiphenyl ether (ODA), and the molar ratio of DPA to ODA is 15:85; the ratio of the added amount of calcium hydrogen phosphate to the total mass of dianhydride and diamine is 2:100.

[0020] Specifically, the mass of PMDA was 12.98 kg, ODA was 10.2 kg, DPA was 1.91 kg, calcium hydrogen phosphate was 0.5 kg, and solvent was 75 kg. The polycondensation reaction was carried out at 30° C. for 5 hours.

[0021] Both the thermal imidization process and the chemical imidization process are conventional processes for preparing polyimide films, and the process conditions are well known. Example 2

[0022] The rest is the same as Example 1, except that the molar ratio of DPA to ODA is 20:80, the filler is calcium hydrogen phosphate, and the ratio of the added amount to the total mass of dianhydride and diamine in the PAA resin is 1:100. Example 3

[0023] The other parts are the same as Example 1, except that the molar ratio of DPA to ODA is 30:70. The filler is calcium hydrogen phosphate, and the ratio of the added amount to the total mass of dianhydride and diamine in the PAA resin is 0.5:100. Example 4

[0024] The rest is the same as Example 1, except that the molar ratio of DPA to ODA is 40:60, the filler is calcium hydrogen phosphate, and the ratio of the added amount to the total mass of dianhydride and diamine in the PAA resin is 0.2:100. Example 5

[0025] The rest is the same as Example 1, except that the molar ratio of DPA to ODA is 50:50, the filler is calcium hydrogen phosphate, and the ratio of the added amount to the total mass of dianhydride and diamine in the PAA resin is 0.1:100. Comparative Example 1

[0026] The rest is the same as in Example 1, except that DPA is not added. Comparative Example 2

[0027] The other parts are the same as in Example 1, except that the molar ratio of DPA to ODA is 60:40. Comparative Example 3

[0028] The other aspects are the same as in Example 1, except that the molar ratio of DPA to ODA is 5:95.

[0029] The PI films prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to the following performance tests: tensile strength (ASTM D882), elongation (ASTM D882), modulus (ASTM D882), coefficient of thermal expansion CTE (ASTM D696), glass transition temperature Tg (tested using DMA), breakdown strength (ASTM D149), cutoff wavelength λcut and transmittance T at 500 nm. 500 (Using UV spectrophotometer to test, the test wavelength range is 190-800nm), the test results are shown in Table 1.

[0030] Table 1 Performance list

[0031] As shown in Table 1, as the DPA content increases, the tensile strength and modulus of the film increase significantly, and the mechanical properties are enhanced; the thermal expansion coefficient decreases, and the Tg increases, that is, the thermal stability is enhanced; at the same time, the original breakdown strength is maintained. In terms of optical properties, the cutoff wavelength increases, T 500 The transmittance decreased significantly.

[0032] However, if the proportion of DPA is too low (Comparative Examples 1 and 2), the intrinsic black color is poor; if the molar ratio of DPA to the diamine monomer reaches 60% (Comparative Example 3), the film is too rigid to be used.

[0033] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0034] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an intrinsic black polyimide film having good mechanical and thermal stability, characterized in that: The following steps are involved: (1) adding a diamine monomer, a dianhydride monomer and a filler to a solvent in sequence, and obtaining a polyamic acid resin after polycondensation reaction; the diamine monomer comprises dihydrophenazine diamine; (2) The polyamic acid resin is subjected to thermal imidization or chemical imidization process, and then cast and stretched to obtain the original polyimide film; (3) The original polyimide film is annealed at 350-380°C and cut to obtain the finished polyimide film.

2. The method for preparing an intrinsic black polyimide film having good mechanical and thermal stability according to claim 1, characterized in that: In step (1), the molar ratio of diamine to dianhydride is 1:0.8-1.2; and the mass ratio of the filler to the total amount of diamine monomer and dianhydride monomer is 0.05-2:

100.

3. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 1, characterized in that: In step (1), the diamine monomer further comprises other diamine monomers, and the other diamine monomers are one or more of p-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, and 3,4'-diaminodiphenyl ether.

4. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 3, characterized in that: The molar ratio of dihydrophenazine diamine to the total amount of diamine monomers is 0.15-0.50:

1.

5. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 4, characterized in that: The molar ratio of dihydrophenazine diamine to the total amount of diamine monomers is 0.20-0.40:

1.

6. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 2, characterized in that: The dianhydride monomer is an aromatic dianhydride, and the aromatic dianhydride is one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride, and 3,3',4,4'-benzophenone tetracarboxylic dianhydride.

7. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 2, characterized in that: The filler is one or more of oxides, nitrides and carbides.

8. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 7, characterized in that: The filler is silicon dioxide or calcium hydrogen phosphate.

9. The method for preparing an intrinsic black polyimide film with good mechanical and thermal stability according to claim 1, characterized in that: The solvent is one or more of N,N'-dimethylformamide, N,N'-dimethylacetamide and N-methylpyrrolidone.

10. An intrinsic black polyimide film having good mechanical and thermal stability prepared by the preparation method according to any one of claims 1 to 9.

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