A polyimide film and its preparation method, production device and application

Abstract

The present invention belongs to the technical field of polymer materials, and provides a polyimide film and a preparation method, a production device and an application thereof, the method comprising the following steps: sequentially including mixed chemical imidization of glue solution, film casting, heating and curing, peeling, at least one infiltration chemical imidization, solvent elution, biaxial stretching and high temperature treatment to obtain the polyimide film. The preparation method of the polyimide film provided by the present invention has the technical effects of simple method, easy industrialization, and the glue film is not easy to be damaged and easy to be peeled during the manufacturing process, and is not easy to tear during high temperature stretching, and can manufacture a polyimide film with a thickness of 3.5μm~12.5μm and a linear thermal expansion coefficient of 2ppm / ℃~20ppm / ℃.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a polyimide film and a preparation method, a production device and an application thereof. Background Art

[0002] Polyimide (PI) film is a kind of organic polymer film material with excellent comprehensive performance. Since the industrialization of Kapton-type PI film by DuPont in the United States in the 1960s, PI film has been widely used in high-tech fields such as aviation, aerospace, electronics, and electrical engineering. It has developed into a key basic material for modern industry and plays an irreplaceable role that other materials cannot replace. Especially in the microelectronics industry, PI film, as the substrate of flexible copper clad laminate (FCCL), has promoted the rapid progress and large-scale application of flexible circuit board (FPCB) technology, and has also been affecting the update and iteration of microelectronic packaging technology. In recent years, with the emergence of emerging technologies such as 5G, Internet of Things, artificial intelligence, and new displays, electronic devices are developing towards thinness, miniaturization, and diversified design, driving the market for ultra-thin flexible circuit boards to continue to expand. The demand for high-performance ultra-thin PI films with a thickness of less than 12.5μm has surged, and it is expected to become the mainstream substrate for the next generation of FPCB.

[0003] At present, the industrialized PI film manufacturing technology mainly adopts a two-step method. First, a polyamic acid (PAA) solution with a certain viscosity is prepared by condensation polymerization of aromatic dianhydride and aromatic diamine in a solvent. Then, a film containing a certain amount of solvent is prepared by casting the PAA solution onto an endless steel belt, or PAA is mixed with a dehydrating agent, a catalyst, etc. and cast onto an endless steel belt to prepare a film containing a certain amount of solvent. The film is then stretched and treated at high temperature to obtain a PI film. However, there are the following technical bottlenecks when using this technology to manufacture PI films with a thickness of 12.5μm and below: First, compared with the casting process of PI films with a thickness of more than 12.5μm, the amount of PAA solution extruded from the die head per unit time is reduced exponentially, and the "curtain flow" formed by the casting is both light and thin. During the production process, it is very easy to be disturbed by the surrounding air, resulting in wrinkles or damage on the surface of the film formed on the annular steel belt, affecting product quality. In severe cases, production cannot even be achieved; secondly, the cast film is heated and devolatilized on the annular steel belt. After the organic volatiles evaporate, the "thin" film containing a small amount of solvent is firmly bonded to the smooth and flat steel belt and is difficult to peel off, and the process stability cannot be guaranteed; finally, when the peeled "thin" film is stretched and treated at high temperature under the fixation of the clamp, due to the low tensile strength and poor toughness of the "thin" film, it is very easy to tear when stretched at high temperature, often resulting in production interruptions and poor production continuity.

[0004] In order to solve the above technical problems, Japanese invention patent JP2009226632A discloses a method for preparing an ultra-thin PI film, by adding a release agent to the precursor PAA solution and coating it on the surface of the substrate to form a film, the formed gel film is not subjected to peeling and stretching treatment, but is directly heated and cured on the surface of the substrate, and then peeled to obtain an ultra-thin PI film. Chinese invention patent CN110343275B discloses a method for preparing an ultra-thin PI film, by adding a certain amount of plasticizer to the PAA solution to improve the elongation at break and toughness of the film, and has the effect of reducing the glass transition temperature of the film, and then the film is subjected to high-temperature longitudinal stretching at a large ratio and low-temperature transverse stretching, so as to manufacture a PI film with a thickness of 5μm. The proposals of the above two invention patents are both based on the improved methods of the mature two-step manufacturing technology in industry. Although Japanese invention patent JP2009226632A can manufacture PI films with a thickness of less than 10μm, this method will affect the roughness of the surface of the PI film, and there is also the problem of low production efficiency. The method of Chinese invention patent CN110343275B has extremely high requirements on the precision of film-making equipment. When stretched at a large ratio, uneven stretching force will cause wrinkles and deformation in local areas of the produced PI film or uneven thickness to produce color difference, affecting product performance and appearance quality. In addition, phthalate plasticizers have been identified as carcinogenic, teratogenic and biomutagenic, which have a great impact on human health and have been banned in many plastic product processing industries. Therefore, this method has limitations in industrial promotion. In addition, Chinese invention patents CN104059551A, CN105131320B, and CN116238220A all disclose technical solutions for manufacturing ultra-thin PI films by coating, which can provide PI films with a thickness of 1μm~6μm. Specifically, PAA solution is coated on the surface of a substrate with a release agent or adhesive, and then high-temperature imidization is performed to obtain a composite film containing an ultra-thin PI film layer. The composite film can be used directly or after the base layer is peeled off. However, the thickness uniformity of the ultra-thin PI film manufactured by this method is poor and the mechanical strength is low, and it is impossible to directly produce ultra-thin PI films in a roll-to-roll manner with high efficiency. Chinese invention patents CN113372591B and CN108409994B disclose a technical solution for manufacturing ultra-thin PI films in one step. First, a soluble PI solution is manufactured, and then the soluble PI solution is coated on the surface of the substrate to form a film, and then the ultra-thin PI film is obtained by heating and drying the solvent and peeling it off. This solution does not require imidization and high-temperature stretching treatment, and the operation is simple and efficient. However, this solution requires soluble PI as a coating precursor solution, which not only limits the molecular structure of PI, but also faces the problem of monomers being difficult to obtain and high raw material costs. The mechanical properties of ultra-thin PI films are often insufficient.

[0005] From the above content, it can be seen that developing a method for preparing ultra-thin polyimide films with a simple, stable process and easy industrialization has become a research direction in this field. Summary of the invention

[0006] The invention provides a method for preparing a polyimide film, which achieves the technical effects that the film is not easily damaged and can be easily peeled off during the manufacturing process and is not easily torn when stretched at high temperature.

[0007] The invention provides a polyimide film, which has the characteristics of a thickness of 3.5 μm to 12.5 μm and a linear thermal expansion coefficient of 2 ppm / °C to 20 ppm / °C.

[0008] The present invention provides a polyimide film production device, which achieves the technical effects that the film is not easily damaged and easy to peel off during the manufacturing process and is not easily torn after high-temperature stretching. The polyimide film with a thickness of 3.5μm~12.5μm and a linear thermal expansion coefficient of 2ppm / ℃~20ppm / ℃ can be manufactured.

[0009] The present invention provides a method for preparing a polyimide film, which comprises the following steps:

[0010] The glue solution is sequentially subjected to mixed chemical imidization treatment, cast film forming treatment, stripping treatment, heat curing treatment, at least one infiltration chemical imidization treatment, solvent elution treatment, biaxial stretching treatment and high temperature treatment to obtain the polyimide film;

[0011] The glue solution is a mixed solution of a first polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a polyimide-polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a first polyamic acid solution, a polyimide-polyamic acid solution, and a chemical imidization agent solution;

[0012] The treatment temperature of the heating and curing treatment is 60°C-120°C, and the treatment time is 15s-20s;

[0013] The solid content of the first polyamic acid solution and the polyimide-polyamic acid solution is 8%-12%;

[0014] The first polyamic acid solution is prepared by a polycondensation reaction of a first aromatic dianhydride and a first aromatic diamine in a solvent in which a nanofiller is dispersed;

[0015] The first aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-diphenyltrimethylol dianhydride, 1,5,6,10-tetrahydro-methylene-oxazo[4,5-D]oxepane-2,4,7,9-tetraone, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride;

[0016] The first aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenylenediamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;

[0017] The nanofiller is selected from at least one of silicon dioxide, calcium hydrogen phosphate, calcium pyrophosphate, calcium oxide, aluminum oxide, titanium dioxide, and zirconium dioxide;

[0018] The polyimide-polyamic acid solution is a mixed solution of a second polyamic acid solution and polyimide or a polyamic acid-polyimide copolymer solution, wherein the second polyamic acid solution is prepared by a polycondensation reaction of a second aromatic dianhydride and a second aromatic diamine in a solvent dispersed with a nanofiller;

[0019] The second aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-triphenylene dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride;

[0020] The second aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,4-diaminotoluene, 1,3-bis(aminopropyl)tetramethyldisiloxane, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenyl diamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;

[0021] The polyimide is a thermoplastic polyimide; the thermoplastic polyimide is obtained by reacting a second polyamic acid solution with a tertiary amine compound under heating conditions; or,

[0022] The thermoplastic polyimide is a solution comprising commercial thermoplastic polyimide;

[0023] The tertiary amine compound is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole;

[0024] The polyimide-polyamic acid copolymer solution is prepared by reacting the second polyamic acid solution with a tertiary amine compound under heating conditions.

[0025] The method for preparing the polyimide film as described above, wherein the chemical imidization agent comprises a dehydrating agent, a catalyst, a solvent, and an auxiliary agent;

[0026] The dehydrating agent is selected from at least one of acetic anhydride, trifluoroacetic anhydride, benzoic anhydride, acetyl chloride and thionyl chloride;

[0027] The catalyst is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole;

[0028] The solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone;

[0029] The auxiliary agent is selected from at least one of tricresyl phosphate, triphenyl phosphate, toluene diphenyl phosphate and trioctyl trimellitate.

[0030] The method for preparing the polyimide film as described above, wherein the impregnation chemical imidization treatment comprises a first impregnation chemical imidization treatment and a second impregnation chemical imidization treatment sequentially performed on the product obtained by the heat curing treatment;

[0031] The treatment temperature of the first wet chemical imidization treatment is 45° C.-100° C., and the treatment time is 5s-40s; and / or,

[0032] The treatment temperature of the second wet chemical imidization treatment is 80° C.-150° C., and the treatment time is 5s-40s; and / or,

[0033] The treatment temperature of the solvent elution treatment is 10° C.-30° C., and the treatment time is 5 s-20 s.

[0034] The method for preparing the polyimide film as described above, wherein in the glue solution, the mass ratio of the first polyamic acid solution, the polyimide-polyamic acid solution and the imidization agent is (10:1) to (1:1); and / or,

[0035] The viscosity of the first polyamic acid solution and / or the polyimide-polyamic acid solution is 5000-20000 cP.

[0036] The method for preparing a polyimide film as described above, wherein the polyimide included in the polyimide-polyamic acid solution is obtained by reacting a second polyamic acid solution with a tertiary amine compound under heating conditions, and the amount of the tertiary amine compound added is 5% to 50% of the total molar amount of the second aromatic dianhydride or the second aromatic diamine in the second polyamic acid solution; the heating time is 5 min to 50 min; and the heating temperature is 20°C to 120°C.

[0037] The present invention also provides a polyimide film, wherein the polyimide film is manufactured using any of the above-mentioned methods for preparing the polyimide film.

[0038] The polyimide film as described above, wherein the thickness of the polyimide film is 3.5 μm to 12.5 μm; and / or,

[0039] The linear thermal expansion coefficient of the polyimide film is 2 ppm / °C-20 ppm / °C.

[0040] The present invention also provides application of a polyimide film prepared by any one of the above-mentioned polyimide film preparation methods on a circuit board.

[0041] The present invention also provides a polyimide film production device for executing any of the above-mentioned polyimide film preparation methods, comprising a mixer, an extrusion die head, a heating drive roller, a first chemical imidization reaction container, a second chemical imidization reaction container, and a solvent elution container;

[0042] The mixer is connected to the extrusion die; the extrusion die is arranged opposite to the heating drive roller, so that the adhesive liquid extruded by the extrusion die can contact the heating drive roller to perform the heating and curing treatment to obtain an initial adhesive film;

[0043] The first chemical imidization reaction container is used to perform the first infiltration chemical imidization process;

[0044] The second chemical imidization reaction container is used to perform the second infiltration chemical imidization process;

[0045] The solvent elution container is used to perform the solvent elution process.

[0046] The polyimide film production device as described above, wherein the first chemical imidization reaction container, the second chemical imidization reaction container and the solvent elution container are each provided with at least two guide rollers, so that the initial adhesive film can sequentially contact with the solvent in the first chemical imidization reaction container, the second chemical imidization reaction container and the solvent elution container; and / or,

[0047] The width of the glue liquid extruded by the extrusion die head is 200mm-2000mm.

[0048] The method for preparing a polyimide film provided by the present invention regulates the solvent content of the film by reducing the solid content of the adhesive solution in combination with controlling the temperature and time of the heating and curing treatment; improves the tensile strength of the film by mixed chemical imidization of the adhesive solution; further improves the tensile strength of the film by at least one infiltration chemical imidization in which the film is in contact with a chemical imine reagent; and further regulates the solvent content of the film by contact elution between the film and a solvent. The method has the technical effects of being simple in preparation method and easy to industrialize, and the film is not easy to be damaged and peeled off during the manufacturing process, and is not easy to tear after high-temperature stretching, and can manufacture a polyimide film with a thickness of 3.5μm-12.5μm and a linear thermal expansion coefficient of 2ppm / ℃-20ppm / ℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a structural diagram of the polyimide film production device provided by the present invention.

[0050] Description of reference numerals:

[0051] 101-Mixer;

[0052] 102-extrusion die head;

[0053] 103-heating driving roller;

[0054] 104-first guide roller;

[0055] 105- second guide roller;

[0056] 106- third guide roller;

[0057] 107- fourth guide roller;

[0058] 108-fifth guide roller;

[0059] 109-sixth guide roller;

[0060] 110-seventh guide roller;

[0061] 111-eighth guide roller;

[0062] 112- ninth guide roller;

[0063] 113- tenth guide roller;

[0064] 201-first chemical imidization reaction vessel;

[0065] 202-second chemical imidization reaction vessel;

[0066] 203-Solvent elution vessel. DETAILED DESCRIPTION

[0067] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0068] The polyimide film preparation method provided by the present invention can be used to manufacture polyimide films. Polyimide films have been widely used in high-tech fields such as aviation, aerospace, electronics, and electrical engineering, and have developed into a key basic material for modern industry. In the prior art, the manufacture of ultra-thin polyimide films has bottlenecks such as the "curtain flow" formed by the glue casting is easily disturbed by air, resulting in wrinkles and damage on the surface of the film, the film is difficult to peel off, and it is easy to tear during high-temperature stretching. The reasons may be: first, the amount of glue extruded from the die head per unit time during the production process of ultra-thin polyimide films is small, and the curtain flow formed by the casting is thin and light; secondly, the "thin" film formed by the glue casting has a small amount of solvent content, which is very easy to over-evaporate in the existing heating devolatilization device; thirdly, the method for controlling the solvent content of the film is single; finally, the film has low tensile strength and poor toughness. Therefore, in the prior art, the preparation process of ultra-thin polyimide films has the above-mentioned defects.

[0069] In view of the defects of the above-mentioned prior art, the present invention solves them by the following means: first, by reducing the solid content of the glue solution, increasing the thickness and weight of the "curtain flow" formed by glue casting, and increasing the solvent content inside the cast film; second, designing and preparing a polyimide-polyamic acid solution with specific composition and solid content, so as to improve the tensile strength of the film formed by casting; third, by combining the chemical imidization treatment of glue mixing with the chemical imidization treatment of the film infiltration, the tensile strength of the film is improved in two steps; further, using low-temperature heating combined with solvent elution treatment to achieve effective and precise control of the solvent content in the film; finally, designing and providing a production device for polyimide film. The above-mentioned means are used to solve the above-mentioned problems.

[0070] Based on this, the first aspect of the present invention provides a method for preparing an imide film, comprising the following steps:

[0071] A method for preparing a polyimide film comprises the following steps:

[0072] The glue solution is sequentially subjected to mixed chemical imidization treatment, cast film forming treatment, stripping treatment, heat curing treatment, at least one infiltration chemical imidization treatment, solvent elution treatment, biaxial stretching treatment and high temperature treatment to obtain a polyimide film;

[0073] The glue solution is a mixed solution of a first polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a polyimide-polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a first polyamic acid solution, a polyimide-polyamic acid solution, and a chemical imidization agent solution;

[0074] The treatment temperature of the heating curing treatment is 60℃-120℃, and the treatment time is 15s-20s;

[0075] The solid content of the first polyamic acid solution and the polyimide-polyamic acid solution is 8%-12%;

[0076] The first polyamic acid solution is prepared by polycondensation reaction of a first aromatic dianhydride and a first aromatic diamine in a solvent in which a nanofiller is dispersed;

[0077] The first aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-diphenyltrimethylol dianhydride, 1,5,6,10-tetrahydro-methylene-oxazo[4,5-D]oxepane-2,4,7,9-tetraone, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride;

[0078] The first aromatic diamine is at least one selected from 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenylenediamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;

[0079] The nanofiller is selected from at least one of silicon dioxide, calcium hydrogen phosphate, calcium pyrophosphate, calcium oxide, aluminum oxide, titanium dioxide, and zirconium dioxide;

[0080] The polyimide-polyamic acid solution is a mixed solution of a second polyamic acid solution and polyimide or a polyamic acid-polyimide copolymer solution, wherein the second polyamic acid solution is prepared by a polycondensation reaction of a second aromatic dianhydride and a second aromatic diamine in a solvent dispersed with a nanofiller;

[0081] The second aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-triphenylene dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride;

[0082] The second aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,4-diaminotoluene, 1,3-bis(aminopropyl)tetramethyldisiloxane, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenyl diamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;

[0083] The polyimide is a thermoplastic polyimide; the thermoplastic polyimide is obtained by reacting the second polyamic acid solution with a tertiary amine compound under heating conditions; or,

[0084] The thermoplastic polyimide is a solution including commercial thermoplastic polyimide;

[0085] The tertiary amine compound is at least one selected from quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole;

[0086] The polyimide-polyamic acid copolymer solution is prepared by reacting the second polyamic acid solution with a tertiary amine compound under heating conditions.

[0087] Specifically, the preparation method of the polyimide film provided by the present invention sequentially performs mixed chemical imidization, cast film forming treatment, heat curing treatment, and stripping treatment on the adhesive solution to obtain an initial adhesive film (HGF), the initial adhesive film is subjected to at least one infiltration chemical imidization treatment and solvent elution treatment to obtain an intermediate adhesive film (SGF), and the intermediate adhesive film is subjected to biaxial stretching and high temperature treatment to obtain a polyimide film. Among them, the initial adhesive film (HGF) has the characteristics of a tensile strength of 10MPa~100MPa; the intermediate adhesive film (SGF) has the characteristics of a tensile strength of 30MPa~120MPa and a solvent content of 30%~180%.

[0088] In the preparation method of the polyimide film provided by the present invention, the glue used includes an imidization agent solution, and also includes at least one of a first polyamic acid solution and a polyimide-polyamic acid solution. That is, the glue is a mixed solution of the first polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a polyimide-polyamic acid solution and a chemical imidization agent solution, or a mixed solution of the first polyamic acid solution, a polyimide-polyamic acid solution, and a chemical imidization agent solution.

[0089] The first polyamic acid solution is prepared by a polycondensation reaction of a first aromatic dianhydride and a first aromatic diamine in a solvent in which a nanofiller is dispersed. The present invention does not limit the specific conditions of the polycondensation reaction, and the reaction conditions commonly used in the art can be used. For example, in one embodiment, under nitrogen protection, the nanofiller is first dispersed in a solvent, and then the first aromatic dianhydride and the first aromatic diamine are added respectively, so that the first aromatic dianhydride and the first aromatic diamine undergo a polycondensation reaction to prepare the first polyamic acid solution.

[0090] In the method provided by the present invention, the first aromatic dianhydride can be selected from pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (a-BPDA), 4,4'-biphenyl ether dianhydride (ODPA), 3,4,3',4'-triphenyl diether dianhydride (HQDPA), biphenyl diether dianhydride (BzDPA), 4,4'-( At least one of hexafluoroisopropyl) diphthalic anhydride (6FDA), 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride (PDPA), p-phenylene-diphthalic acid dianhydride (TAHQ), 1,5,6,10-tetrahydro-methylene-oxazo[4,5-D]oxacycloheptane-2,4,7,9-tetraone (DTOPT), 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione (TPDA), and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF).

[0091] In the method provided by the present invention, the first aromatic diamine can be selected from at least one of 4,4'-diaminodiphenyl ether (4,4'-ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 1,4-phenylenediamine (PDA), 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB), 9,9-bis(4-aminophenyl)fluorene (BAPF), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-biphenylenediamine (Bz), 2,6-diamino-9H-fluorene-9-one (DAFT), and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (HFBAPP).

[0092] The present invention does not limit the molar ratio of the first aromatic diamine to the first aromatic dianhydride. In one embodiment, the molar ratio of the first aromatic diamine to the first aromatic dianhydride is 1:0.995 to 1:1.02.

[0093] More specifically, the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetone, butanone, toluene, ethyl acetate, tetrahydrofuran, and chloroform, and the nanofiller is selected from at least one of silicon dioxide, calcium hydrogen phosphate, calcium pyrophosphate, calcium oxide, aluminum oxide, titanium dioxide, and zirconium dioxide. The filler is used to improve the opening performance of the polyimide film and can achieve the technical effects of antistatic and anti-adhesion. The added amount is 0.05% to 5% of the sum of the mass of the aromatic diamine and the aromatic dianhydride.

[0094] The polyimide-polyamic acid solution is a mixed solution of the second polyamic acid solution and polyimide, or a copolymer solution of polyimide-polyamic acid, wherein the second polyamic acid solution is prepared by a polycondensation reaction of a second aromatic dianhydride and a second aromatic diamine in a solvent in which a nanofiller is dispersed. The present invention also does not limit the specific conditions of the polycondensation reaction, and reference may be made to the preparation method of the first polyamic acid solution.

[0095] In the method provided by the present invention, the second aromatic dianhydride can be selected from at least one of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (a-BPDA), 4,4'-biphenyl ether dianhydride (ODPA), 3,4,3',4'-triphenyl diether dianhydride (HQDPA), biphenyl diether dianhydride (BzDPA), 4,4'-(hexafluoroisopropylene) diphthalic anhydride (6FDA), 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride (PDPA), p-phenylene-triphenylene dianhydride (TAHQ), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA).

[0096] In the method provided by the present invention, the second aromatic diamine can be selected from 4,4'-diaminodiphenyl ether (4,4'-ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-diaminodiphenylmethane (MDA), 2,2-bis(4-aminophenyl)propane (IDPA), 1,3-bis(3-aminophenoxy)benzene (1,3,3-APB), 1,4-bis(4-aminophenoxy)benzene (1,4,4-APB), 2,4 di At least one of aminotoluene (DAT), 1,3-bis(aminopropyl)tetramethyldisiloxane (GAPDS), 9,9-bis(4-aminophenyl)fluorene (BAPF), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-biphenyl diamine (Bz), 2,6-diamino-9H-fluorene-9-one (DAFT), and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (HFBAPP).

[0097] The polyimide may be selected from any of the following sources: In one embodiment, the polyimide is a thermoplastic polyimide (externally purchased TPI powder); In another embodiment, the polyimide is prepared by reacting a second polyamic acid solution with a tertiary amine compound under heating conditions. Under heating conditions, the second polyamic acid solution undergoes a cyclodehydration reaction under the catalytic action of the tertiary amine compound to generate a polyimide. The tertiary amine compound is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole.

[0098] The copolymer solution of imide-polyamic acid is prepared by reacting the second polyamic acid solution with a tertiary amine compound under heating conditions. Under heating conditions, the second polyamic acid solution undergoes a partial cyclization dehydration reaction under the catalytic action of the tertiary amine compound to generate polyimide. The tertiary amine compound is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole.

[0099] In the method provided by the present invention, the solid content of the first polyamic acid solution and the polyimide-polyamic acid solution is 8%-12%. Wherein, the solid content refers to the ratio of the sum of the mass of aromatic diamine and aromatic dianhydride in the first polyamic acid solution and the polyimide-polyamic acid solution to the total mass of the glue. Specifically, when the glue contains only the first polyamic acid solution in addition to the chemical imidization agent, the solid content of the first polyamic acid solution is 8%-12%. When the glue contains the first polyamic acid solution and the polyimide-polyamic acid solution in addition to the chemical imidization agent, the solid content of the first polyamic acid solution and the polyimide-polyamic acid solution is 8%-12%. The mixing ratio of the first polyamic acid solution and the polyimide-polyamic acid solution is an arbitrary mass ratio.

[0100] For the first polyamic acid solution, a solid content of 8%-12% can be achieved by the following two methods:

[0101] Method 1: Directly prepare a first polyamic acid solution with a solid content of 8% to 12% by polycondensing the first aromatic dianhydride and the first aromatic diamine in a solvent dispersed with nanofillers. The viscosity of the solution prepared by the above method is 5000 cP to 200000 cP.

[0102] Method 2: Use method 1 to prepare a high viscosity solution with a solid content of 15%-30% and a viscosity of 100000 cP~1000000 cP, and add a solvent to dilute it to a first polyamic acid solution with a solid content of 8%-12% and a viscosity of 5000 cP~200000 cP.

[0103] For polyimide-polyamic acid solution, solid content of 8%-12% can be achieved by the following two methods:

[0104] Method 1: First, the second aromatic dianhydride and the second aromatic diamine are subjected to a condensation reaction in a solvent dispersed with a nanofiller to prepare a second polyamic acid solution with a solid content of 8% to 12%, and then a tertiary amine compound is added and heated to react so that part of the polyamic acid is converted into polyimide to obtain a PAA-PI solution with a solid content of 8% to 12%.

[0105] Method 2: Mix the second polyamic acid solution with a solid content of 8% to 12% with polyimide. The source of polyimide can be selected from any of the following: The first method: dissolve commercial TPI powder in a solvent to prepare a soluble polyimide solution with a solid content of 8% to 12%. The solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetone, butanone, tetrahydrofuran, chlorobenzene, and meta-cresol. The second method is to add a tertiary amine compound to the second polyamic acid solution with a solid content of 8% to 12%, and heat to completely convert the polyamic acid in the second polyamic acid solution into polyimide to obtain a polyimide solution with a solid content of 8% to 12% and a viscosity of 5000 cP to 200000 cP. The solution is mixed with the second polyamic acid solution with a solid content of 8% to 12%, and a polyimide-polyamic acid solution with a solid content of 8% to 12% is obtained.

[0106] The imidization agent is used to react the polyamic acid contained in the glue to generate polyimide. The present invention does not limit the composition of the chemical imidization agent, and conventional chemical imidization agents in the art can be used.

[0107] It is worth noting that the chemical imidization reagent contained in the glue solution (i.e., the chemical imidization reagent used to perform the mixed chemical imidization of the glue solution) and the chemical imidization reagent used to perform the infiltration chemical imidization treatment may be the same or different. For the convenience of distinction, the chemical imidization reagent contained in the glue solution (i.e., the chemical imidization reagent used to perform the mixed chemical imidization of the glue solution) is called the first chemical imidization reagent, and the chemical imidization reagent used to perform the infiltration chemical imidization treatment is called the second chemical imidization reagent.

[0108] The adhesive liquid is sequentially subjected to mixed chemical imidization treatment, cast film treatment (extruded from the extrusion die head onto the surface of the support), and then subjected to heat curing treatment. During the heat curing process, the initial adhesive film formed by the adhesive liquid casting is heated, and part of the solvent contained therein is volatilized to obtain the initial adhesive film (HGF). The initial adhesive film is peeled off from the support, and after at least one infiltration chemical imidization treatment and solvent elution treatment, an intermediate adhesive film (SGF) can be obtained. The intermediate adhesive film is then subjected to biaxial stretching and high temperature treatment to obtain a polyimide film.

[0109] Among them, during the whole manufacturing process, the chemical imidization treatment can be carried out twice or more, including mixed imidization of the first polyamic acid solution and the first chemical imidization agent solution, or mixed imidization of the polyimide-polyamic acid solution and the first chemical imidization agent solution, or mixed imidization of the first polyamic acid solution, the polyimide-polyamic acid solution and the first chemical imidization agent solution, and at least one infiltration imidization of the initial adhesive film with the second chemical imidization agent solution.

[0110] The solvent elution treatment includes contacting the film treated with chemical imidization with a solvent to obtain an intermediate film. The present invention does not limit the specific number and specific conditions of the chemical imidization treatment, nor does it limit the treatment time and treatment temperature of the solvent elution treatment, as long as the above requirements are met.

[0111] The biaxial stretching high temperature treatment may also use the common conditions in the art, for example, the film is longitudinally stretched at room temperature, and transversely stretched at 150° C. to 600° C., and cooled to obtain a polyimide film.

[0112] In the process of manufacturing the polyimide film using the above method, the film (including the initial film and the intermediate film) has the characteristics of not being easy to be damaged, easy to peel off, and not easy to tear after high-temperature stretching. According to the above phenomenon, the reasons are as follows: first, the solid content of the cast adhesive is low, and the "curtain flow" formed by the cast adhesive will not be affected by the surrounding airflow, avoiding the problems of "wrinkles" and "holes"; secondly, the adhesive with a high solvent content combined with the reasonably designed heating and curing treatment time and heating temperature can effectively control the film to have a high solvent content, thereby reducing the bonding strength between the film and the substrate surface, solving the problem of difficult peeling; thirdly, the design of polyimide-polyamic acid in the adhesive and the rapid chemical imidization of polyamic acid or the rapid chemical imidization of polyimide-polyamic acid Imidization obtains polyimide-polyamic acid with a high proportion of imide rings, thereby increasing the tensile strength of the initial film; then, the initial film is further improved in tensile strength by infiltration chemical imidization; finally, the film treated with infiltration chemical imidization is further treated with solvent elution to effectively regulate the solvent content in the film at a reasonable level; in summary, the intermediate film obtained has both strength and toughness, which solves the problem of tearing and breaking of the film during biaxial stretching and high-temperature treatment, helps to accurately control the condensed structure of the molecules in the film, and manufactures a polyimide film with high dimensional stability. Therefore, the preparation method of the polyimide film provided by the present invention can achieve the technical effect that the film is not easy to be damaged, easy to peel, and not easy to tear during high-temperature stretching during the manufacturing process.

[0113] In order to further improve the tensile strength of the polyimide film, in one embodiment, the chemical imidization agent includes a dehydrating agent, a catalyst, a solvent, and an auxiliary agent. Among them, the dehydrating agent is selected from at least one of acetic anhydride, trifluoroacetic anhydride, benzoic anhydride, acetyl chloride, and thionyl chloride; the catalyst is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole; the solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; the auxiliary agent is selected from at least one of tricresyl phosphate, triphenyl phosphate, diphenyl phosphate, and trioctyl trimellitate. The above-mentioned imidization agent can further increase the proportion of imide rings in the film, thereby improving the tensile strength of the film.

[0114] More specifically, in order to further increase the tensile strength of the polyimide film, in one embodiment, the infiltration chemical imidization treatment includes sequentially performing a first infiltration chemical imidization treatment and a second infiltration chemical imidization treatment on the product obtained by the heat curing treatment; the treatment temperature of the first infiltration chemical imidization treatment is 45°C-100°C, and the treatment time is 5s-40s; the treatment temperature of the second infiltration chemical imidization treatment is 80°C-150°C, and the treatment time is 5s-40s. The above treatment temperature and treatment time can further increase the proportion of imide rings in the adhesive film, thereby increasing the tensile strength of the obtained polyimide film.

[0115] It is worth noting that, as mentioned above, the chemical imidization reagent contained in the glue solution and the chemical imidization reagent used to perform the infiltration chemical imidization treatment may be the same or different. When the infiltration chemical imidization treatment includes a first infiltration chemical imidization treatment and a second infiltration chemical imidization treatment performed sequentially, the chemical imidization reagent used in the first infiltration chemical imidization treatment and the second infiltration chemical imidization treatment may also be the same or different. For the convenience of distinction, the chemical imidization reagent contained in the glue solution is referred to as the first chemical imidization reagent, the chemical imidization reagent used to perform the first infiltration chemical imidization treatment is referred to as the second chemical imidization reagent, and the chemical imidization reagent used to perform the second infiltration chemical imidization treatment is referred to as the third chemical imidization reagent. Among them, the third chemical imidization reagent and the second chemical imidization reagent may be the same or different. When the two are the same, it is considered that the infiltration chemical imidization treatment uses the second chemical imidization reagent.

[0116] In order to further solve the problem that the film is easy to tear and break during biaxial stretching and high temperature treatment and facilitate the manufacture of polyimide film with high dimensional stability, an intermediate film with controllable solvent content is manufactured, and the treatment temperature of the solvent elution treatment is 10℃-30℃ and the treatment time is 5s-20s. The above treatment conditions can effectively control the solvent content in the film, so that the film has both strength and toughness, so that it is not easy to tear and break during biaxial stretching and high temperature treatment, and a polyimide film with high dimensional stability is obtained.

[0117] Furthermore, the mass ratio of the sum of the mass of the first polyamic acid solution and the polyimide-polyamic acid solution to the imidization agent in the glue solution is controlled to be (10:1) to (1:1). Specifically, when the glue solution only includes the first polyamic acid solution, the mass ratio of the first polyamic acid solution to the imidization agent is (10:1) to (1:1); when the glue solution only includes the polyimide-polyamic acid solution, the mass ratio of the polyimide-polyamic acid solution to the imidization agent is (10:1) to (1:1); when the glue solution includes the first polyamic acid solution and the polyimide-polyamic acid solution at the same time, the mass ratio of the sum of the mass of the first polyamic acid solution and the polyimide-polyamic acid solution to the imidization agent is (10:1) to (1:1). The above mass ratio can make the obtained polyimide film have higher tensile strength.

[0118] As shown above, the polyimide included in the polyimide-polyamic acid solution can be prepared by reacting the second polyamic acid solution with a tertiary amine compound under heating conditions. At this time, the amount of the tertiary amine compound added can be controlled to be 10% to 150% of the total molar amount of the second aromatic dianhydride or the second aromatic diamine in the second polyamic acid solution; the heating time is 180 min to 360 min; the heating temperature is 80°C to 200°C. The above reaction conditions can make the polyamic acid included in the second polyamic acid solution have a higher polyimide conversion rate. It is worth noting that although the second aromatic dianhydride or the second aromatic diamine forms the second polyamic acid solution through a condensation reaction, the above content still uses the second aromatic dianhydride or the second aromatic diamine required to form the second polyamic acid solution as a benchmark to determine the amount of tertiary amine compound added.

[0119] The second aspect of the present invention provides a polyimide film, which is prepared using any of the above-mentioned methods for preparing polyimide films, and has the technical effect that the film is easy to peel and is not easy to tear during high-temperature stretching. Since the polyimide film is not easy to tear during high-temperature stretching, the polyimide film can be processed into a lower thickness. Specifically, in one embodiment, the thickness of the polyimide film is 3.5μm~12.5μm.

[0120] The third aspect of the present invention provides the use of a polyimide film prepared by any one of the above-mentioned methods for preparing a polyimide film on a circuit board.

[0121] A fourth aspect of the present invention provides a polyimide film production device, which is used to execute the polyimide film production method provided by the first aspect of the present invention. Figure 1 is a device diagram of a polyimide film production device provided by the present invention, such as Figure 1As shown, the device includes 101-mixer, 102-extrusion die head, cylindrical 103-heating drive roller, 201-first chemical imidization reaction container, 202-second chemical imidization reaction container, 203-solvent elution container. The above three containers can use rectangular stainless steel containers. Figure 1 It can be seen that the 101-mixer mixes the first polyamic acid solution, the chemical imidization solution, and the polyimide-polyamic acid solution (if any) and then pumps them into the 102-extrusion die. The 102-extrusion die is arranged opposite to the cylindrical 103-heating drive roller, so that the glue extruded by the 102-extrusion die can contact the 103-heating drive roller when falling under the action of gravity. The 103-heating drive roller can rotate counterclockwise in contact, and during the rotation process, it receives the glue extruded from the 102-extrusion die, and at the same time, the received glue is heated and cured. By controlling the heating temperature and rotation speed of the 103-heating drive roller, the treatment temperature of the heating and curing treatment can be controlled to be 60℃-180℃, and the treatment temperature is 15s-20s. When the adhesive film runs to the peeling point, the heating drum is peeled off, and the peeling method is manual traction peeling. After the adhesive is heated and cured, the initial adhesive film (HGF) is obtained. After HGF is peeled off from the surface of the heated driving roller 103, it enters 201-the first chemical imidization reaction container, 202-the second chemical imidization reaction container, and 203-the solvent elution container in sequence. Among them, 201-the first chemical imidization reaction container and 202-the second chemical imidization reaction container contain the same or different chemical imidization reagents, 203-the solvent elution container contains the solvent for solvent elution treatment, and the above three containers are equipped with heating devices. HGF is immersed in the contents of 201-the first chemical imidization reaction container for the first infiltration chemical imidization treatment, immersed in the contents of 202-the second chemical imidization reaction container for the second infiltration chemical imidization treatment, immersed in the contents of 203-the solvent elution container for the solvent elution treatment, and the intermediate film (SGF) is obtained. Controlling the running speed of HGF and the temperature of the contents of the above three containers can control the processing time and processing temperature of the first infiltration chemical imidization treatment, the second infiltration chemical imidization treatment and the solvent elution treatment. The intermediate film is further subjected to biaxial stretching high temperature treatment (the corresponding treatment equipment is common in the art, Figure 1 Not shown), to obtain a polyimide film.

[0122] The polyimide film production device provided by the present invention uses a single heated drive roller design to replace the traditional endless steel belt design, which can reduce the complexity of equipment design and manufacturing cost, shorten the distance and time of film drying and devolatilization, reduce production energy consumption and improve production efficiency, and achieve the technical effect that the film is not easy to be damaged and easy to peel off during the manufacturing process and is not easy to be torn when stretched at high temperature.

[0123] Furthermore, in order to prolong the residence time of HGF in 201-the first chemical imidization reaction container, 202-the second chemical imidization reaction container, and 203-the solvent elution container, in one embodiment, at least two guide rollers are respectively provided in 201-the first chemical imidization reaction container, 202-the second chemical imidization reaction container, and 203-the solvent elution container, so that the initial adhesive film can contact the contents in 201-the first chemical imidization reaction container, 202-the second chemical imidization reaction container, and 203-the solvent elution container in sequence.

[0124] Specifically, if Figure 1 As shown, Figure 1 It also includes 104-first guide roller, 105-second guide roller, 106-third guide roller, 107-fourth guide roller, 108-fifth guide roller, 109-sixth guide roller, 110-seventh guide roller, 111-eighth guide roller, 112-ninth guide roller, and 113-tenth guide roller. Among them, 105-second guide roller and 106-third guide roller are arranged in 201-first chemical imidization reaction container, 108-fifth guide roller and 109-sixth guide roller are arranged in 202-second chemical imidization reaction container, 111-eighth guide roller and 112-ninth guide roller are arranged in 203-solvent elution container, for example, they can be stainless steel guide rollers arranged at the bottom of the container. The above-mentioned setting positions allow the initial adhesive film to be immersed in the above-mentioned three containers and contact with the contents in the containers for corresponding treatment. 107-the fourth guide roller, 110-the seventh guide roller, and 113-the tenth guide roller are arranged outside the container to transfer the initial film to different containers. The present invention does not limit the driving and driven relationship of the first to tenth guide rollers, and they can be arranged as needed. For example, in one embodiment, 107-the fourth guide roller, 110-the seventh guide roller, and 113-the tenth guide roller are driving guide rollers.

[0125] More specifically, in one embodiment, the width of the adhesive liquid extruded by the extrusion die head 102 can be controlled to be 200 mm-2000 mm. The adhesive liquid with the above width can be more evenly distributed on the surface of the heated driving roller 03, so that the initial adhesive film has a more uniform texture.

[0126] The present invention also proposes a tensile strength standard of HGF as shown in Table 1, which shows the relationship between the specification of HGF and the tensile strength of the polyimide film finally produced.

[0127] The tensile strength is measured using an Instron 68SC-05 universal tensile testing machine.

[0128]

[0129] The present invention also provides the solvent content of SGF and the tensile strength standard of SGF as shown in Table 2:

[0130]

[0131] Among them, the solvent content of SGF = [(total weight of SGF before high temperature treatment - weight of SGF after high temperature treatment) / weight of SGF after high temperature treatment] × 100%; the weight of SGF after high temperature treatment is the weight of SGF after heating at 450℃ for 2h; the tensile strength of SGF is tested by Instron 68SC-05 universal tensile testing machine. For example, to obtain a polyimide film with a specification of 12.5μm, the solvent content of SGF needs to be controlled at 40%-70%, and the tensile strength needs to be controlled at 70MPa-100MPa.

[0132] The present invention is further described below through specific embodiments.

[0133] Example 1

[0134] 1) Under nitrogen protection, add 11220.7g NMP to a 20L reactor and start stirring; weigh 26g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 373.2g ODA and 201.5g PDA and add them to the reactor and stir at room temperature for 30min; weigh 405.1g PMDA and 545.9g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 12% and a viscosity of 1595P; freeze and store at -10°C after degassing for later use. The PAA solution is the first polyamic acid solution.

[0135] 2) Under nitrogen protection, 1025 g NMP, 2217 g acetic anhydride, 858 g pyridine and 275 g triphenyl phosphate were added to a 5 L reactor in sequence and stirred for 180 min to obtain a first chemical imidization reagent solution, which was frozen and stored at -10°C for future use.

[0136] 3) Under nitrogen protection, 8750 g of NMP, 24050 g of acetic anhydride and 11000 g of 3-methylpyridine were added to a 50 L reactor in sequence and stirred for 180 min to obtain a second chemical imidization reagent solution.

[0137] According to this method, 40000 g of the second chemical imidization reagent solution is respectively prepared, and the second chemical imidization reagent solution is respectively transferred to the first imidization reaction container and the second imidization reaction container, and stored at room temperature for standby use.

[0138] 4) Add 40,000 g of n-hexane into the solvent elution container and store at room temperature for future use.

[0139] 5) Set the pump speed of the first polyamic acid solution output pump to 50g / min, the pump speed of the first chemical imidization agent solution output pump to 15g / min, the stirring speed of the mixer to 300rpm, the vertical distance between the extrusion die and the heating drive roller to 10㎜, the heating temperature of the heating drive roller to 80°C (i.e., the processing temperature of the heating and curing treatment), the temperature of the imidization agent in the first imidization reaction container and the second imidization reaction container to 60°C (i.e., the processing temperature of the first and second infiltration chemical imidization treatments), and the temperature of the solvent in the solvent elution container to 25°C (i.e., the processing temperature of the solvent elution treatment); turn on the equipment, control the rotation rate of the heating drive roller, so that the processing time of the heating and curing treatment is 45s, the processing time of the first and second infiltration chemical imidization treatments is 30s respectively, and the processing time of the solvent elution treatment is 30s. The first polyamic acid solution and the chemical imidization agent solution are pumped into the mixer at the same time for mixing, and the mixed solution then enters the extrusion die. The mixed solution extruded from the extrusion die forms a yellow transparent "curtain flow" and falls onto the surface of the heated driving roller to form a film. The film is heated by the heated driving roller to remove part of the solvent and is peeled off at the peeling point to obtain an initial film (HGF-1); the initial film (HGF-1) is pulled by a guide roller and immersed in the first imidization reaction container and the second imidization reaction container and the solvent elution container in turn to obtain an intermediate film (SGF-1). The intermediate film (SGF-1) is then subjected to biaxial stretching and high-temperature treatment to obtain a high-performance ultra-thin PI film UHPI-1 with a thickness of 7.5 μm.

[0140] Example 2

[0141] 1) Under nitrogen protection, add 10456.7g NMP to a 25L reactor and start stirring; weigh 36g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 559.8g ODA and 302.3g PDA and add them to the reactor and stir at room temperature for 30min; weigh 610.2g PMDA and 822.9g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 8935P; slowly add 6375g NMP to the reactor and continue stirring for 120min to obtain a PAA solution with a solid content of 12% and a viscosity of 1250P, and freeze and store at -10°C after degassing for standby use. The PAA solution is the first polyamic acid solution.

[0142] 2) The first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as those in Example 1.

[0143] 3) HGF-2 and SGF-2 were manufactured according to the method of Example 1, and SGF-2 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-2 with a thickness of 7.5 μm.

[0144] Example 3

[0145] 1) Under nitrogen protection, add 15990g NMP to a 35L reactor and start stirring; weigh 52g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 578g ODA and 1186.3g BAPP and add them to the reactor and stir at room temperature for 30min; weigh 895.9g ODPA and 849.7g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 9330P; slowly add 9750g NMP to the reactor and continue stirring for 180min to obtain a PAA solution with a solid content of 12% and a viscosity of 1071P, then add 373g isoquinoline, stir for 10min, then heat to 120℃, continue stirring and react for 30min, stop heating, degas the mixed solution and freeze it at -10℃ for standby use. This solution is a polyimide-polyamic acid solution.

[0146] 2) Under nitrogen protection, 5520 g NMP, 3381.6 g acetic anhydride, 2138.4 g isoquinoline, and 555 g triphenyl phosphate were added to a 15 L reactor in sequence and stirred for 180 min to obtain a first chemical imidization reagent solution, which was frozen and stored at -10°C for future use.

[0147] 3) The second chemical imidization reagent solution and the solvent in the film solvent elution tank are the same as those in Example 1.

[0148] 4) HGF-3 and SGF-3 were manufactured according to the method of Example 1, and SGF-3 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-3 with a thickness of 7.5 μm.

[0149] Example 4

[0150] 1) PAA solution, first chemical imidization reagent solution, second chemical imidization reagent solution, and solvent in the solvent elution container are the same as those in Example 1;

[0151] 2) The mixed solution extrusion amount per unit time of the die head was increased proportionally, and the remaining methods were the same as in Example 1 to produce HGF-4 and SGF-4. The SGF-4 was then subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-4 with a thickness of 10 μm.

[0152] Example 5

[0153] 1) PAA solution, first chemical imidization reagent solution, second chemical imidization reagent solution, and solvent in the solvent elution container are the same as those in Example 1;

[0154] 2) The mixed solution extrusion amount per unit time of the die head was increased proportionally, and the rest of the method was the same as in Example 1 to produce HGF-5 and SGF-5. The SGF-5 was then subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-5 with a thickness of 12.5 μm.

[0155] Example 6

[0156] 1) Under nitrogen protection, add 15033.3g NMP to a 35L reactor and start stirring; weigh 50g calcium hydrogen phosphate and add it, stir and disperse for 30min; weigh 345.2g ODA and 745.6g PDA and add them to the reactor and stir at room temperature for 30min; weigh 940.6g PMDA and 1268.6g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 12679P; slowly add 14466.7g NMP to the reactor and continue stirring for 120min to obtain a PAA solution with a solid content of 10% and a viscosity of 995P, and freeze and store at -10°C after degassing for standby use. The PAA solution is the first polyamic acid solution.

[0157] The first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as those in Example 1.

[0158] 2) HGF-6 and SGF-6 were manufactured according to the method of Example 1, and SGF-6 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-6 with a thickness of 5 μm.

[0159] Example 7

[0160] 1) Under nitrogen protection, add 13666.7g NMP to a 40L reactor and start stirring; weigh 50g calcium hydrogen phosphate and add it, stir and disperse for 30min; weigh 307.7g ODA and 664.6g PDA and add them to the reactor and stir at room temperature for 30min; weigh 670.8g PMDA and 1356.9g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 18130P; slowly add 20833.3g NMP to the reactor and continue stirring for 120min to obtain a PAA solution with a solid content of 8% and a viscosity of 632P, and freeze and store at -10°C after degassing for standby use. The PAA solution is the first polyamic acid solution.

[0161] The first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the film solvent elution tank are the same as those in Example 1.

[0162] 2) HGF-7 and SGF-7 were manufactured according to the method of Example 1, and SGF-7 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-7 with a thickness of 3.5 μm.

[0163] Example 8

[0164] 1) The PAA solution, the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as those in Example 1.

[0165] 2) HGF-8 and SGF-8 were manufactured according to the method of Example 1, except that HGF-8 was only subjected to the first imidization reaction vessel, that is, only the first imidization treatment was performed to obtain SGF-8. SGF-8 was then subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-8 with a thickness of 7.5 μm.

[0166] Example 9

[0167] 1) Under nitrogen protection, add 15944.4g NMP to a 30L reactor and start stirring; weigh 52g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 1255.1g ODA and 290.5g PDA and add them to the reactor and stir at room temperature for 30min; weigh 1954.4g PMDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 10431P; slowly add 9722.2g NMP to the reactor and continue stirring for 120min to obtain a PAA solution with a solid content of 12% and a viscosity of 763P, and freeze and store at -10°C after degassing for standby use. The PAA solution is the first polyamic acid solution.

[0168] The first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as those in Example 1.

[0169] 2) HGF-9 and SGF-9 were manufactured according to the method of Example 1, and SGF-9 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-9 with a thickness of 7.5 μm.

[0170] Example 10

[0171] 1) Under nitrogen protection, add 10456.7g NMP to a 25L reactor and start stirring; weigh 36g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 559.8g ODA and 302.3g PDA and add them to the reactor and stir at room temperature for 30min; weigh 608.2g PMDA and 820.3g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 1926P, and freeze and store at -10°C after degassing for standby use. The PAA solution is the first polyamic acid solution.

[0172] The first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as those in Example 1.

[0173] 2) HGF-10 and SGF-10 were manufactured according to the method of Example 1, and SGF-10 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-10 with a thickness of 25 μm.

[0174] Embodiment 11

[0175] 1) The preparation of the PAA solution is the same as in Example 10, and the solvents in the solvent elution containers of the first chemical imidization reagent solution and the second chemical imidization reagent solution are the same as in Example 1.

[0176] 2) HGF-11 and SGF-11 were manufactured according to the method of Example 1, and SGF-11 was further subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-11 with a thickness of 50 μm.

[0177] Example 12

[0178] 1) The preparation of the PAA solution is the same as in Example 10, and the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as in Example 1.

[0179] 2) The temperature of the heating cylinder is designed to be 100°C. The cast rubber solution is heated and solidified after forming a film on the surface of the heating cylinder, and HGF-12 is obtained by peeling. SGF-12 is manufactured according to the method of Example 1. SGF-12 is then subjected to biaxial stretching and high-temperature treatment to obtain a high-performance ultra-thin PI film UHPI-12 with a thickness of 7.5 μm.

[0180] Example 13

[0181] 1) The preparation of the PAA solution is the same as in Example 10, and the solvents in the solvent elution containers of the first chemical imidization reagent solution and the second chemical imidization reagent solution are the same as in Example 1.

[0182] 2) The temperature of the heating cylinder is designed to be 120°C. The cast rubber solution is heated and solidified after forming a film on the surface of the heating cylinder, and HGF-13 is obtained by peeling. SGF-13 is manufactured according to the method of Example 1. SGF-13 is then subjected to biaxial stretching and high-temperature treatment to obtain a high-performance ultra-thin PI film UHPI-13 with a thickness of 7.5 μm.

[0183] Embodiment 14

[0184] 1) The preparation of the PAA solution is the same as in Example 10, and the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as in Example 1.

[0185] 2) The temperatures of the first chemical imidization reaction vessel and the second chemical imidization reaction vessel are both set to 100°C; HGF-14 and SGF-14 are manufactured according to the method of Example 1, and SGF-14 is then subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-14 with a thickness of 7.5 μm.

[0186] Embodiment 15

[0187] 3) The preparation of PAA solution is the same as in Example 10, and the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the solvent elution container are the same as in Example 1.

[0188] 4) The temperatures of the first chemical imidization reaction vessel and the second chemical imidization reaction vessel are set to 100° C. and 120° C., respectively; HGF-15 and SGF-15 are manufactured according to the method of Example 1, and SGF-15 is then subjected to biaxial stretching and high temperature treatment to obtain a high-performance ultra-thin PI film UHPI-15 with a thickness of 7.5 μm.

[0189] Comparative Example 1

[0190] 1) Under nitrogen protection, add 10456.7g NMP to a 25L reactor and start stirring; weigh 50g calcium hydrogen phosphate and add it, stir and disperse for 20min; weigh 559.8g ODA and 302.3g PDA and add them to the reactor and stir at room temperature for 30min; weigh 607.2g PMDA and 819.3g s-BPDA and slowly add them to the reactor in sequence; stir for 300min to obtain a PAA solution with a solid content of 18% and a viscosity of 1356P. The solvents in the solvent elution containers of the first chemical imidization reagent solution and the second chemical imidization reagent solution are the same as those in Example 1.

[0191] 2) HGF-12 was manufactured according to the method of Example 1, but wrinkles and holes existed on the surface of HGF-12, and HGF-12 could not be completely peeled off from the surface of the heating roller, and could not be stably manufactured.

[0192] Comparative Example 2

[0193] 1) The solvents in the solvent elution containers of the PAA solution, the first chemical imidization reagent solution, and the second chemical imidization reagent solution are the same as those in Example 1.

[0194] 2) HGF-13 and SGF-13 were manufactured according to the method of Example 1, but HGF did not pass through the first imidization reaction vessel and the second imidization reaction vessel, that is, the first imidization treatment and the second imidization treatment were not performed. SGF-13 was torn during biaxial stretching and high temperature treatment after being fixed by a clamp, and could not be produced continuously.

[0195] Comparative Example 3

[0196] 1) The solvents in the solvent elution containers of the PAA solution, the first chemical imidization reagent solution, and the second chemical imidization reagent solution are the same as those in Example 1.

[0197] 2) HGF-14 and SGF-14 were manufactured according to the method of Example 1, but HGF was not passed through the solvent elution tank. SGF-14 was torn during biaxial stretching and high temperature treatment after being fixed by a clamp, and could not be produced continuously.

[0198] Comparative Example 4

[0199] This comparative example does not use the equipment provided by the second aspect of the present invention, but uses an endless steel belt to make the "curtain flow" formed by the glue fall onto the surface of the endless steel belt to form a film and dry. The drying temperature is 150°C and the drying time is 45s.

[0200] 1) The PAA solution, the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the film solvent elution tank are the same as those in Example 1.

[0201] 2) The “curtain flow” falls onto the surface of the endless steel belt to form a film and dry to obtain HGF-15, but it cannot be completely peeled off from the surface of the steel belt.

[0202] Comparative Example 5

[0203] 1) The PAA solution, the first chemical imidization reagent solution, the second chemical imidization reagent solution, and the solvent in the film solvent elution tank are the same as those in Example 1.

[0204] 2) The temperature of the heating roller is set to 150°C, and the "curtain flow" falls onto the surface of the heating roller to form a film and dry to obtain HGF-16, but it cannot be completely peeled off from the surface of the steel strip.

[0205] The properties of the samples prepared in each embodiment and comparative example were measured, and the results are shown in Table 3.

[0206] Thickness measurement method: using CHY-CA mechanical contact thickness gauge produced by China Saicheng Instruments;

[0207] Tensile strength / elongation measurement method: measured using Instron 68SC-05 universal tensile testing machine;

[0208] CTE measurement method: measured using TMA450 static thermomechanical analyzer from TA Company, USA, with a heating rate of 3°C / min.

[0209]

[0210] Note: ×——It is impossible to produce film / thin film for testing.

[0211] It can be seen from Table 3 that, compared with the comparative examples, the polyimide films with higher tensile strength and elongation can be prepared in the embodiments. At the same time, the polyimide films prepared in the embodiments have lower linear thermal expansion coefficients.

[0212] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a polyimide film, characterized in that: The steps include: The glue solution is sequentially subjected to mixed chemical imidization treatment, cast film forming treatment, heat curing treatment, and peeling treatment to obtain an initial glue film, the initial glue film is subjected to at least one infiltration chemical imidization treatment and solvent elution treatment to obtain an intermediate glue film, and the intermediate glue film is subjected to biaxial stretching treatment and high temperature treatment to obtain the polyimide film; The tensile strength of the initial film is 10MPa~100MPa; The solvent content of the intermediate film is 30% to 180%, and the tensile strength is 30MPa to 120MPa; The thickness of the polyimide film is 3.5 μm to 12.5 μm; and / or, The linear thermal expansion coefficient of the polyimide film is 2ppm / °C-20ppm / °C; The glue solution is a mixed solution of a first polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a polyimide-polyamic acid solution and a chemical imidization agent solution, or a mixed solution of a first polyamic acid solution, a polyimide-polyamic acid solution, and a chemical imidization agent solution; The treatment temperature of the heating and curing treatment is 60°C-120°C, and the treatment time is 15s-20s; The solid content of the first polyamic acid solution and the polyimide-polyamic acid solution is 8%-12%; The first polyamic acid solution is prepared by a polycondensation reaction of a first aromatic dianhydride and a first aromatic diamine in a solvent in which a nanofiller is dispersed; The first aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-diphenyltrimethylol dianhydride, 1,5,6,10-tetrahydro-methylene-oxazo[4,5-D]oxepane-2,4,7,9-tetraone, 5-[4-(1,3-dioxo-2-benzofuran-5-yl)phenyl]-2-benzofuran-1,3-dione, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride; The first aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,4-phenylenediamine, 1,4-bis(4-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenylenediamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane; The nanofiller is selected from at least one of silicon dioxide, calcium hydrogen phosphate, calcium pyrophosphate, calcium oxide, aluminum oxide, titanium dioxide, and zirconium dioxide; The polyimide-polyamic acid solution is a mixed solution of a second polyamic acid solution and polyimide or a polyamic acid-polyimide copolymer solution, wherein the second polyamic acid solution is prepared by a polycondensation reaction of a second aromatic dianhydride and a second aromatic diamine in a solvent dispersed with a nanofiller; The second aromatic dianhydride is selected from at least one of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-biphenyl ether dianhydride, 3,4,3',4'-triphenyl diether dianhydride, biphenyl diether dianhydride, 4,4'-(hexafluoroisopropylene) diphthalic anhydride, 2,2-diphenylpropane-3,4,3',4'-tetracarboxylic dianhydride, p-phenylene-triphenylene dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride; The second aromatic diamine is selected from at least one of 4,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,4-diaminotoluene, 1,3-bis(aminopropyl)tetramethyldisiloxane, 9,9-bis(4-aminophenyl)fluorene, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-biphenyl diamine, 2,6-diamino-9H-fluorene-9-one, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane; The polyimide is a thermoplastic polyimide; the thermoplastic polyimide is obtained by reacting a second polyamic acid solution with an organic amine compound under heating conditions; or, The thermoplastic polyimide is a solution comprising commercial thermoplastic polyimide; The organic amine compound is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole; The polyimide-polyamic acid copolymer solution is prepared by reacting the second polyamic acid solution with an organic amine compound under heating conditions; The infiltration chemical imidization treatment includes a first infiltration chemical imidization treatment and a second infiltration chemical imidization treatment sequentially performed on the product obtained by the heat curing treatment; The treatment temperature of the first wet chemical imidization treatment is 45° C.-100° C., and the treatment time is 5s-40s; and / or, The treatment temperature of the second wet chemical imidization treatment is 80° C.-150° C., and the treatment time is 5s-40s; and / or, The treatment temperature of the solvent elution treatment is 10° C.-30° C., and the treatment time is 5 s-20 s.

2. The method for preparing a polyimide film according to claim 1, characterized in that: The chemical imidization reagent includes a dehydrating agent, a catalyst, a solvent, and an auxiliary agent; The dehydrating agent is selected from at least one of acetic anhydride, trifluoroacetic anhydride, benzoic anhydride, acetyl chloride and thionyl chloride; The catalyst is selected from at least one of quinoline, isoquinoline, pyridine, 3-methylpyridine, triethylamine, and N-methylimidazole; The solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; The auxiliary agent is selected from at least one of tricresyl phosphate, triphenyl phosphate, toluene diphenyl phosphate and trioctyl trimellitate.

3. The method for preparing a polyimide film according to claim 1, characterized in that: In the glue solution, the mass ratio of the first polyamic acid solution, the polyimide-polyamic acid solution and the imidization agent is (10:1) to (1:1); and / or, The viscosity of the first polyamic acid solution and / or the polyimide-polyamic acid solution is 5000 cP-20000 cP; Among them, when the glue solution is a mixed solution of a first polyamic acid solution and a chemical imidization agent solution, the mass ratio of the first polyamic acid solution to the imidization agent is (10:1) to (1:1); when the glue solution is a mixed solution of a polyimide-polyamic acid solution and a chemical imidization agent solution, the mass ratio of the polyimide-polyamic acid solution to the imidization agent is (10:1) to (1:1); when the glue solution is a mixed solution of a first polyamic acid solution, a polyimide-polyamic acid solution, and a chemical imidization agent solution, the mass ratio of the sum of the masses of the first polyamic acid solution and the polyimide-polyamic acid solution to the imidization agent is (10:1) to (1:1).

4. The method for preparing a polyimide film according to claim 3, characterized in that: The polyimide included in the polyimide-polyamic acid solution is prepared by reacting a second polyamic acid solution with an organic amine compound under heating conditions, wherein the amount of the organic amine compound added is 5% to 50% of the total molar amount of the second aromatic dianhydride or the second aromatic diamine in the second polyamic acid solution; the heating time is 5 min to 50 min; and the heating temperature is 20° C. to 120° C.

5. A polyimide film, characterized in that: The polyimide film is manufactured using the method for preparing the polyimide film according to any one of claims 1 to 4.

6. The polyimide film according to claim 5, characterized in that The thickness of the polyimide film is 3.5 μm to 12.5 μm; and / or, The linear thermal expansion coefficient of the polyimide film is 2 ppm / °C-20 ppm / °C.

7. Use of a polyimide film obtained by the method for preparing a polyimide film according to any one of claims 1 to 4 on a circuit board.

8. A polyimide film production device for executing the method for preparing a polyimide film according to any one of claims 1 to 4, characterized in that: It includes a mixer, an extrusion die, a heating drive roller, a first chemical imidization reaction container, a second chemical imidization reaction container, and a solvent elution container; The mixer is connected to the extrusion die; the extrusion die is arranged opposite to the heating drive roller, so that the adhesive liquid extruded by the extrusion die can contact the heating drive roller to perform the heating curing treatment to obtain an initial adhesive film; The first chemical imidization reaction container is used to perform a first immersion chemical imidization process; The second chemical imidization reaction container is used to perform a second immersion chemical imidization process; The solvent elution container is used to perform the solvent elution process.

9. The polyimide film production device according to claim 8, characterized in that: The first chemical imidization reaction container, the second chemical imidization reaction container and the solvent elution container are each provided with at least two guide rollers, so that the initial adhesive film can contact with the solvent in the first chemical imidization reaction container, the second chemical imidization reaction container and the solvent elution container in sequence; and / or, The width of the glue liquid extruded by the extrusion die head is 200mm-2000mm.

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