CN119036971B

CN119036971B - A polyimide composite film, preparation method and application thereof

Info

Publication number: CN119036971B
Application number: CN202411523348.9A
Authority: CN
Inventors: 金弘盛; 庞冲; 史恩台; 孙善卫; 潘成; 方超
Original assignee: Anhui Guofeng New Material Technology Co ltd; Anhui Guofeng New Material Co ltd
Current assignee: Anhui Guofeng New Material Technology Co ltd; Anhui Guofeng New Material Co ltd
Priority date: 2024-10-30
Filing date: 2024-10-30
Publication date: 2025-03-18
Anticipated expiration: 2044-10-30
Also published as: CN119036971A

Abstract

The invention discloses a polyimide composite film, a preparation method and application thereof, and belongs to the technical field of polyimide film preparation. The polyimide composite film comprises two identical thermoplastic polyimide layers and a thermosetting polyimide layer, wherein the thermosetting polyimide layer is arranged between the two thermoplastic polyimide layers; the preparation method of the thermoplastic polyimide layer comprises: dissolving a diamine monomer in N,N-dimethylacetamide, stirring; then adding a dianhydride monomer, stirring, dissolving; then adding a dianhydride monomer, stirring, then extruding, casting, drying, widening and imidizing; the preparation method of the thermosetting polyimide layer comprises: dissolving p-phenylenediamine in N,N-dimethylacetamide, stirring, dissolving; adding a dianhydride monomer, stirring, then extruding, casting, drying, widening and imidizing; the invention improves the production stability and yield rate of the polyimide composite film.

Description

Polyimide composite film, preparation method and application thereof

Technical Field

The invention belongs to the technical field of polyimide film preparation, and particularly relates to a polyimide composite film, a preparation method and application thereof.

Background

Flexible copper clad laminates FCCL have received a great deal of attention as an indispensable material for flexible printed circuits FPCs, supporting the rapid development of microelectronic applications in recent years. Polyimide PIs are good candidates for FCCL base film materials because of their excellent thermal, mechanical and electrical properties. There are typically three and two layers of FCCL. Wherein the three-layer FCCL is composed of copper, an organic adhesion promoter (such as epoxy) and a PI-based film. However, three-layer FCCL has a significant disadvantage in terms of thermal stability due to the weak heat resistance of the organic binder and the relatively low dimensional stability. Recently, to solve these problems, a double-layer FCCL without any adhesive has been developed. However, the PI performance requirements for two-layer FCCL applications are quite stringent. These requirements include excellent heat resistance, mechanical, dimensional stability and good adhesion properties.

The conventional method for producing a laminate for a two-layer FCCL mainly includes a casting method of casting a polyimide precursor polyamide acid onto a metal foil and then imidizing the polyimide precursor polyamide acid, a plating metal method of directly forming a metal layer on a polyimide film by sputtering or plating, and a lamination method of bonding a polyimide film and a metal foil by a thermoplastic polyimide. Of these methods, lamination is advantageous in that the thickness range of the metal foil which is satisfactory for the lamination method is wider than that for the casting method, and the cost of the apparatus is lower than that for the metallization method.

In the lamination method, a composite film composed of a thermoplastic imide layer having high peel strength on both upper and lower surfaces of a thermosetting polyimide layer having high heat resistance is generally laminated with a copper foil.

The traditional method for producing the TPI/PI/TPI composite film mainly comprises two types of extrusion method and coating method. The extrusion method is TPI, PI, TPI three-layer coextrusion, one-step molding, and a representative enterprise is brillouin chemistry, and the difficulty is to maintain the characteristics of each layer, the uniformity of the thickness between layers, the stability of the catalyst and long-time production. The coating method is to uniformly coat TPI resin on a thermosetting PI film by a coater with a high-precision coating head, and then perform high-temperature heat treatment and imidization to prepare a three-layer composite film. In the preparation method of the coating method, the intermediate layer thermosetting PI film needs to be subjected to secondary imidization, so that certain loss can be generated on the performance of the film, and the composite film is easy to generate layering phenomenon.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a polyimide composite film, a preparation method and application thereof.

A polyimide composite film comprises two identical thermoplastic polyimide layers and a thermosetting polyimide layer, wherein the thermosetting polyimide layer is arranged in the middle of the two thermoplastic polyimide layers, the preparation method of the thermoplastic polyimide layer comprises the steps of dissolving diamine monomers in N, N-dimethylacetamide, stirring, adding dianhydride monomers, stirring, dissolving to obtain a reaction solution A, adding dianhydride monomers into the reaction solution A, stirring to obtain a thermoplastic polyamic acid solution, extruding the thermoplastic polyamic acid solution, casting, drying, expanding and imidizing the thermoplastic polyamic acid solution to obtain the thermoplastic polyimide layer, the preparation method of the thermosetting polyimide layer comprises the steps of dissolving p-phenylenediamine in N, N-dimethylacetamide, stirring, dissolving to obtain a reaction solution B, adding dianhydride monomers into the reaction solution B, stirring to obtain a thermosetting polyamic acid solution, extruding the thermosetting polyamic acid solution, casting, drying, expanding and imidizing the thermosetting polyimide layer.

A preparation method of a polyimide composite film comprises the following steps:

(1) Preparing a thermoplastic polyamic acid solution, dissolving diamine monomer in N, N-dimethylacetamide, stirring, adding dianhydride monomer, stirring, dissolving to obtain a reaction solution A, adding dianhydride monomer into the reaction solution A, and stirring to obtain a thermoplastic polyamic acid solution;

(2) Preparing thermosetting polyamide acid solution, dissolving p-phenylenediamine in N, N-dimethylacetamide, stirring and dissolving to obtain reaction solution B;

(3) Extruding the prepared thermoplastic polyamic acid solution and thermosetting polyamic acid solution, and carrying out tape casting, drying, expanding and imidization to obtain the polyimide composite film with a thermosetting polyimide layer and two thermoplastic polyimide layers, wherein the thermosetting polyimide layer is arranged between the two thermoplastic polyimide layers.

Preferably, the stirring time in the step (1) and the step (2) is 1h.

Preferably, the viscosity of the thermosetting polyamic acid solution and the thermoplastic polyamic acid solution is 30000 to 150000 mPa.s.

Preferably, the solid content of the thermosetting polyamic acid solution and the thermoplastic polyamic acid solution is 10-30wt%.

Preferably, the drying temperature is 120-180 ℃.

Preferably, the diamine monomer comprises

One or more of the following.

Preferably, the dianhydride monomer comprises

One or more of the following.

Preferably, the thickness ratio of any one of the thermoplastic polyimide layers to the thermosetting polyimide layer is 1:1 to 1:5.

The polyimide composite film prepared by the preparation method or the application of the polyimide composite film in the production of flexible copper-clad laminates.

The invention has the beneficial effects that:

the polyimide composite film prepared by the method greatly improves the problem of A/B surface caused by different solvent volatilization rates on the upper and lower surfaces of the thermoplastic-thermosetting-thermoplastic polyimide composite film and the problem of uneven thickness among polyimide layers when the ultrathin polyimide composite film is prepared, and improves the production and manufacturing stability and yield of the polyimide composite film.

Drawings

In order to more clearly illustrate the embodiments of the present disclosure or the prior art, the drawings that are required for the description of the embodiments or the prior art will be briefly described, and it will be apparent to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic flow chart of a method for producing a polyimide composite film according to the present invention.

FIG. 2 is an electron microscope image of a polyimide composite film prepared according to the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the present invention, an extrusion-casting coating method is used. The extrusion-casting coating method is a method for producing a film comprising the steps of extruding a polyamic acid solution from a single-channel die onto a self-supporting body, casting, drying, and then transferring the solution into a high-temperature oven for thermal imidization. As the casting apparatus, a known apparatus can be used. Examples of the casting apparatus include, but are not limited to, a rotating roll, a rotating belt, a moving plate, and the like. From the viewpoint of easiness in introducing the drying step after casting, a rotary belt is preferably used. As the material of the rotating roller, the rotating belt, and the moving plate, metal, cloth, resin, glass, magnetic devices, and the like can be used. From the viewpoint of structural stability of the film, metals are preferable, and from the viewpoint of easiness of peeling the film and corrosion resistance, stainless steel is most preferable. Further, in order to further improve the peeling property and corrosion resistance of the film, chromium-based, nickel-based, tin-based, or the like plating may be performed on the surfaces of the rotating rolls, rotating belts, and moving plates made of metal.

The liquid film formed by casting is dried in a drying oven and then formed into a gel-like film. In the present invention, a known drying oven can be used as the drying oven. Examples of the drying furnace include, but are not limited to, a hot air drying furnace, an infrared drying furnace, and the like. From the viewpoint of effectively drying the solvent, a hot air drying furnace is preferable. If the drying temperature is too low, the film cannot be sufficiently dried, and if it is too high, the solvent contained therein boils, which may prevent formation of a smooth film. In particular, fine defects tend to occur in a thin surface layer such as a thermoplastic polyimide layer, which becomes an adhesive layer. Thus, the drying temperature is preferably less than +50℃. Specifically, a multilayer film having self-supporting properties can be obtained by volatilizing at least a part of the solvent, preferably at 80 to 200 ℃, more preferably at 120 to 180 ℃.

The film dried in the above-mentioned drying furnace remains a solvent and the imidization reaction does not proceed sufficiently, so that the film is further dried in the firing furnace to complete the imidization reaction. As the firing furnace, a known firing furnace can be used. Examples of the firing furnace include, but are not limited to, a hot air firing furnace, an infrared firing furnace, and the like. These firing furnaces are preferably used in combination according to the degree of firing. Preferably, the heating is performed by a hot air firing furnace at 100-500 ℃ and then by an infrared firing furnace at 300-600 ℃. The imidization time is not particularly limited, and may be appropriately set in a range of about 10 to 1800 seconds as long as the imidization and drying are substantially completed for a sufficient time.

The multilayer film introduced into the firing furnace may be held on or peeled off from the support, and in order to improve the melt flowability into the thermoplastic layer, the imidization ratio may be intentionally reduced or the solvent may be left. This improves adhesion to a conductor such as a copper foil.

The thermoplastic layer-thermosetting layer-thermoplastic layer polyimide composite film prepared by the preparation method has the thickness of the thermoplastic polyimide layer of 2-10 mu m, the thickness of the thermosetting polyimide layer of 4-40 mu m, and as shown in figure 2, the three polyimide composite films directly contact the polyimide layer of the support body and the polyimide layer at the opposite side of the polyimide layer without generating characteristic difference, the peel strength difference of the A/B surface is less than 0.5N/cm, and the polyimide composite film with the total thickness of-4% of the deviation of the film thickness composition rate in the film width direction can be prepared, so that the current requirement on the performance of the base film of the two-layer flexible copper-clad plate can be met.

The technical scheme of the present invention will be further described in detail with reference to the following specific examples, which are to be construed as merely illustrative, and not limitative of the remainder of the disclosure.

First, some synthesis examples of the thermoplastic polyamic acid solution and the thermosetting polyamic acid solution used in the following examples are given:

synthesis of thermoplastic polyamic acid solution:

Synthesis example 1:

2.05 kg of 2,2 '-bis [4- (4-aminophenoxyphenyl) ] propane (BAPP) and 1.00 kg of 4,4' -diaminodiphenyl ether (ODA) were dissolved in 25.56kg of N, N-dimethylacetamide (DMAc) and stirred for 1 hour to dissolve them. 1.47 kg biphenyl tetracarboxylic dianhydride (s-BPDA) was added thereto and stirred for 1 hour to dissolve. 1.09 kg pyromellitic dianhydride (PMDA) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 35000 mPa. Multidot.s. Stirring was performed for 1 hour to obtain a polyamic acid solution (hereinafter referred to as PAA-1) having a solid content of 18% by weight and a rotational viscosity of 35000 mPa.s at 23 ℃.

Synthesis example 2:

1.46kg of 1, 3-bis (4 ' -aminophenoxy) benzene (TPE-R), 1.00 kg of 4,4' -diaminodiphenyl ether (ODA) were dissolved in 25.24 kg's N, N-dimethylacetamide (DMAc) and stirred for 1 hour to dissolve. 1.47 kg biphenyl tetracarboxylic dianhydride (s-BPDA) was added thereto and stirred for 1 hour to dissolve. 1.61 kg of 3,3', 4' -Benzophenone Tetracarboxylic Dianhydride (BTDA) was slowly added to the reaction mixture, and the addition was stopped when the viscosity reached about 35000 mPa. Multidot.s. Stirring was performed for 1 hour to obtain a polyamic acid solution (hereinafter referred to as PAA-2) having a solid content of 18% by weight and a rotational viscosity of 35000 mPa.s at 23 ℃.

Synthesis of thermosetting polyamic acid solution:

synthesis example 3:

2.70 of p-Phenylenediamine (PDA) kg was dissolved in 45.78 kg of N, N-dimethylacetamide (DMAc) and stirred for 1 hour to dissolve. To this reaction solution, 7.35 kg diphenyl tetracarboxylic dianhydride (s-BPDA) was slowly added, and the addition was stopped when the viscosity reached about 40000 mPa. Multidot.s. Stirring was performed for 1 hour to obtain a polyamic acid solution (hereinafter referred to as PAA-3) having a solid content of 18% by weight and a rotational viscosity of 40000 mPa. Multidot.s at 23 ℃.

Synthesis example 4:

2.05 kg of 2,2 '-bis [4- (4-aminophenoxyphenyl) ] propane (BAPP) and 1.00 kg of 4,4' -diaminodiphenyl ether (ODA) were dissolved in 25.56kg of N, N-dimethylacetamide (DMAc) and stirred for 1 hour to dissolve them. 1.47 kg biphenyl tetracarboxylic dianhydride (s-BPDA) was added thereto and stirred for 1 hour to dissolve. 1.09 kg pyromellitic dianhydride (PMDA) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 120000 mPa. Multidot.s. Stirring was performed for 1 hour to obtain a polyamic acid solution (hereinafter referred to as PAA-4) having a solid content of 18% by weight and a rotational viscosity of 120000 mPa. Multidot.s at 23 ℃.

Synthesis example 5:

2.70 of p-Phenylenediamine (PDA) kg was dissolved in 45.78 kg of N, N-dimethylacetamide (DMAc) and stirred for 1 hour to dissolve. To this reaction solution, 7.35 kg diphenyl tetracarboxylic dianhydride (s-BPDA) was slowly added, and the addition was stopped when the viscosity reached about 130000 mPa. Multidot.s. Stirring was performed for 1 hour to obtain a polyamic acid solution (hereinafter referred to as PAA-5) having a solid content of 18% by weight and a rotational viscosity of 130000 mPa. Multidot.s at 23 ℃.

Example 1

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 1 and Synthesis example 3 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, followed by heating the thermoplastic-thermosetting-thermoplastic three-layer composite film at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, and fixing the 3-layer self-supporting film to a metal frame, expanding, and then drying at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 2.0 μm/8.5 μm/2.0 μm of thermoplastic polyimide layer/thermosetting polyimide, as shown in FIG. 1.

Example 2

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 2 and Synthesis example 3 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, followed by heating the thermoplastic-thermosetting-thermoplastic three-layer composite film at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, fixing the 3-layer self-supporting film to a metal frame, expanding the width, and then drying at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 2.0 μm/8.5 μm/2.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Example 3

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 1 and Synthesis example 3 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, followed by heating the thermoplastic-thermosetting-thermoplastic three-layer composite film at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, fixing the 3-layer self-supporting film to a metal frame, expanding, and then drying at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 5.0 μm/15 μm/5.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Example 4

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 2 and Synthesis example 3 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, followed by heating the thermoplastic-thermosetting-thermoplastic three-layer composite film at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, fixing the 3-layer self-supporting film to a metal frame, expanding, and then drying at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 5.0 μm/15 μm/5.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Example 5

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 4 and Synthesis example 5 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, and then the thermoplastic-thermosetting-thermoplastic three-layer composite film was heated at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, and the 3-layer self-supporting film was fixed to a metal frame, subjected to tentering, and then dried at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 5.0 μm/5.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Example 6

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 4 and Synthesis example 5 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, followed by heating the thermoplastic-thermosetting-thermoplastic three-layer composite film at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, fixing the 3-layer self-supporting film to a metal frame, expanding the width, and then drying at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 5.0 μm/15 μm/5.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Example 7

The thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained in Synthesis example 4 and Synthesis example 5 were sequentially extruded on a casting roll by using a single-pass die having a die lip width of 200mm, and then the thermoplastic-thermosetting-thermoplastic three-layer composite film was heated at 150℃for 300 seconds to obtain a three-layer self-supporting film having self-supporting properties, and the 3-layer self-supporting film was fixed to a metal frame, subjected to tentering, and then dried at 400℃for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 2.0 μm/10.0 μm/2.0 μm of thermoplastic polyimide layer/thermosetting polyimide.

Comparative example 1

The thermoplastic polyamic acid solution obtained in Synthesis example 1, the thermosetting polyamic acid solution obtained in Synthesis example 3 were sequentially cast on a casting roll in a three-layer structure using a 3-layer coextrusion three-layer die having a die lip amplitude of 200mm, wherein the thermoplastic polyamic acid solution was brought into contact with the casting roll, and the thermosetting polyamic acid solution was on the upper surface thereof. Next, the three-layer film was heated at 150 ℃ for 300 seconds to obtain a 3-layer self-supporting film, and the 3-layer self-supporting film was fixed to a metal frame, subjected to tentering, and then dried at 400 ℃ for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of 5.0 μm/15.0 μm/5.0 μm of thermoplastic polyimide layer/thermosetting polyimide layer/thermoplastic polyimide.

Comparative example 2

The thermoplastic polyamic acid solution obtained in Synthesis example 1 was double-coated on the upper and lower surfaces of a base film (15 μm) using a double-sided coating apparatus with the polyimide film prepared from the thermosetting polyamic acid solution obtained in Synthesis example 3. Next, the three-layer film was heated at 150 ℃ for 300 seconds to obtain a 3-layer composite film having a thermosetting polyimide film as an intermediate layer and thermoplastic polyamic acid gel films as upper and lower layers, and the 3-layer composite film was fixed to a metal frame, subjected to tentering, and then dried at 400 ℃ for 600 seconds, thereby performing thermal imidization, to obtain a three-layer polyimide composite film having a thickness of thermoplastic polyimide layer/thermosetting polyimide layer/thermoplastic polyimide of 5.0 μm/15.0 μm/5.0 μm.

Performance testing

1. Static thermo-mechanical analysis experimental method

Static thermo-mechanical analysis (TMA) A instrument TMA Q400EM static thermo-mechanical analyzer (room temperature to 400 ℃ C., 5 ℃ C./min) was used in the United states.

2. Mechanical property test experiment method

INSTRON 5567 universal strength tester, 5mm/min tensile rate, test temperature at room temperature (about 23 ℃) with an initial clamp span of about 20mm, sample dimensions of about 0.025mm thick, 15mm wide and 100mm long.

3. Test method for peel strength

INSTRON 5567 universal strength tester, stretching rate 5mm/min, testing temperature at room temperature (about 23 ℃), after hot pressing film and copper foil, 180 ° peel and stretch test, data processing is as follows:

L _M =minimum load

W _S = measured width of peel strip

The properties of the products obtained in Synthesis examples 1 to 5 were measured, and the results are shown in Table 1.

TABLE 1 comparison of Properties of the products obtained in Synthesis examples 1 to 5

The properties of the products obtained in examples 1 to 7 and comparative examples 1 to 2 were measured, and the results are shown in Table 2.

Table 2 comparison of properties of the products obtained in examples 1 to 7 comparative examples 1 to 2

From examples 1 and 2 in Table 2, it is understood that the glass transition temperature of the thermoplastic layer is lowered and the peel strength is improved as the ratio of the flexible monomer is increased. In comparative examples 1 and 2, examples 3 and 4, the film thickness was increased as a whole, but the peel strength was decreased, which may be related to the inability of heat to be transferred in time to melt the entire thermoplastic layer during hot pressing. The same comparative examples 5, 7 show that the composite films with different thickness ratios also maintain the above trend, and the overall tensile strength of the film is obviously improved with the increase of the thickness ratio of the middle thermosetting layer. Comparative examples 3 and 6 the overall tensile strength of the composite film was significantly improved as the viscosity of the PAA solution increased. The data of comparative example 1 show that although the TPI composite film prepared by three-layer coextrusion maintains good mechanical properties, the peeling strength has the phenomenon of overlarge A/B surface difference, and the thickness composition rate deviation is also overlarge. Whereas comparative example 2 prepared a TPI composite film by a double-sided coating method, the overall decrease in peel strength and tensile strength was significant. Therefore, in general, the polyimide composite films prepared in examples 1to 7 were uniform and controllable in thickness, and ultrathin TPI composite films could be prepared, with a deviation of film thickness composition rate in the film width direction of-4% to 4%, and a peel strength difference of the A/B plane of < 0.5N/cm. Meets the current requirements on the performance of the base film of the two layers of flexible copper-clad plates.

In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims.

Claims

1. A method for preparing a polyimide composite film, characterized in that the polyimide composite film comprises two identical thermoplastic polyimide layers and a thermosetting polyimide layer, wherein the thermosetting polyimide layer is arranged between the two thermoplastic polyimide layers; the method for preparing the thermoplastic polyimide layer comprises: dissolving a diamine monomer in N,N-dimethylacetamide, stirring; then adding a dianhydride monomer, stirring, dissolving, and obtaining a reaction solution A; adding the dianhydride monomer to the reaction solution A, stirring, and obtaining a thermoplastic The preparation method of the thermosetting polyimide layer comprises: dissolving p-phenylenediamine in N,N-dimethylacetamide, stirring, dissolving, and obtaining a reaction solution B; adding a dianhydride monomer to the reaction solution B, stirring, and obtaining a thermosetting polyamic acid solution; extruding the thermosetting polyamic acid solution through a single-channel die head, casting, drying, expanding, and imidizing, and obtaining a thermosetting polyimide layer;

The viscosity of the thermosetting polyamic acid solution and the thermoplastic polyamic acid solution are both 30000-150000 mPa·s, and the thickness ratio of the thermoplastic polyimide layer to the thermosetting polyimide layer is 1:1-1:5;

The preparation method of the polyimide composite film comprises the following steps:

(1) preparing a thermoplastic polyamic acid solution, dissolving a diamine monomer in N,N-dimethylacetamide and stirring; then adding a dianhydride monomer, stirring, and dissolving to obtain a reaction solution A; adding the dianhydride monomer to the reaction solution A and stirring to obtain a thermoplastic polyamic acid solution;

(2) preparing a thermosetting polyamic acid solution, dissolving p-phenylenediamine in N,N-dimethylacetamide, stirring and dissolving to obtain a reaction solution B; adding a dianhydride monomer to the reaction solution B, stirring and obtaining a thermosetting polyamic acid solution;

(3) using a single-channel die head for extrusion, the thermoplastic polyamic acid solution and the thermosetting polyamic acid solution obtained above are sequentially extruded onto a casting roller for casting, drying, widening and imidization to obtain a polyimide composite film having a thermosetting polyimide layer and two thermoplastic polyimide layers; the thermosetting polyimide layer is arranged between the two thermoplastic polyimide layers.

2. The method for preparing a polyimide composite film according to claim 1, characterized in that the stirring time in step (1) and step (2) is 1 hour.

3 . The method for preparing a polyimide composite film according to claim 1 , wherein the viscosity of the thermosetting polyamic acid solution and the thermoplastic polyamic acid solution are both 30,000 to 150,000 mPa·s.

4 . The method for preparing a polyimide composite film according to claim 1 , wherein the solid content of the thermosetting polyamic acid solution and the thermoplastic polyamic acid solution is 10 to 30 wt %.

5 . The method for preparing a polyimide composite film according to claim 1 , wherein the drying temperature is 120° C. to 180° C.

6. The method for preparing a polyimide composite film according to claim 1, wherein the diamine monomer comprises

One or more of .

7. The method for preparing a polyimide composite film according to claim 1, wherein the dianhydride monomer comprises

One or more of .

8 . The method for preparing a polyimide composite film according to claim 1 , wherein a thickness ratio of any one of the thermoplastic polyimide layer and the thermosetting polyimide layer is 1:1-1:5.

9. Use of the polyimide composite film obtained by the preparation method according to any one of claims 1 to 8 or the polyimide composite film according to claim 1 in the production of flexible copper-clad laminates.