High-adhesion polyimide composite film used in flexible copper-clad laminates and method for manufacturing the same

Abstract

This invention provides a highly adhesive polyimide composite film for use in flexible copper-clad laminates and a method for manufacturing the same. [Solution] The polyimide composite film of the present invention is composed of a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer provided on at least one surface of the thermosetting polyimide support layer. An interface layer formed by the reaction of terminal amino group superbranched polyamide grafted silica particles and thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer, and the terminal groups of the thermoplastic polyimide contain imidazole rings that can form complexes with copper. In the present invention, by embedding terminal amino group superbranched polyamide grafted silica particles at the interface between the thermosetting layer and the thermoplastic layer, the contact area between the support layer and the adhesive layer is increased, and at the same time, the complex formation effect between the imidazole ring and copper produces a polyimide composite film with high adhesion, high dimensional stability, high heat resistance and a low glass transition temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyimide films, and particularly relates to a high-adhesion polyimide composite film for use in flexible copper-clad laminates and a method for producing the same. Background Art

[0002] Flexible printed circuit boards (FPCs) feature light weight, thin profile, and free bendability, and are widely used in the fields of electronic products, home appliances, medical treatment, automobiles, aerospace and military. Flexible copper-clad laminates (FCCLs) are important base materials for FPCs. Conventional three-layer FCCLs are composed of copper foil, thermoset polyimide film, and epoxy or organosilica adhesive; whereas two-layer FCCLs employ a thermoplastic polyimide layer instead of epoxy or organosilica adhesive, which gives copper-clad laminates the advantages of being lighter and thinner and having excellent heat resistance, and has gradually become the mainstream in the industry.

[0003] Chinese patent application document CN103739842A proposes a thermoplastic polyimide film for two-layer FCCLs. In order to guarantee certain dimensional stability, diamine containing aromatic heterocycles such as benzoxazole and benzimidazole is introduced to reduce the thermoplasticity of the entire molecular chain, whereby the adhesion force thereof is only 1.1 to 1.2 N / mm, which brings potential risks to subsequent applications.

[0004] Chinese patent application document CN115746351A proposes a method for producing a thermoplastic polyimide film with a low coefficient of thermal expansion. The method reduces the coefficient of thermal expansion of the film by introducing double bonds into polyimide molecular chains and achieving photocrosslinking through the action of a crosslinking agent and a photoinitiator. However, the crosslinked structure restricts the movement of molecular chains, so that the glass transition temperature thereof is close to 300°C, which is disadvantageous to hot press processing and makes it difficult to realize commercialization.

[0005] Chinese patent application document CN1957051A proposes an adhesive film and a method for manufacturing the same, using a co-extrusion-casting coating method to obtain a composite film that can be bonded by heating by compounding a thermoplastic polyimide adhesive layer on one or both sides of a thermosetting polyimide core layer. In both the thermosetting and thermoplastic polyamic acid precursors, polycondensation with diamine or dianhydride is used. When the terminal group is an amino group, it is thermally oxidized, reducing the heat resistance of the film, especially the adhesion after heat exposure. However, when the terminal group is an anhydride group, it is prone to ring-opening hydrolysis, resulting in a non-uniform molecular weight distribution of polyimide, which further affects the uniformity of performance.

[0006] From the above, it is clear that in order to meet the performance requirements of 2-layer FCCL for film substrates, such as high adhesion, high dimensional stability, high heat resistance, and low glass transition temperature, it is necessary to improve conventional technology to meet increasingly stringent application requirements. [Overview of the project] [Problems that the invention aims to solve]

[0007] To overcome the problems of conventional technology, the present invention provides a highly adhesive polyimide composite film for use in flexible copper-clad laminates and a method for producing the same, thereby enabling the production of a polyimide composite film having high adhesion, high dimensional stability, high heat resistance, and a low glass transition temperature. [Means for solving the problem]

[0008] To solve the above technical problems, the technical solution proposed by the present invention is as follows.

[0009] The present invention provides a highly adhesive polyimide composite film for flexible copper-clad laminates, the polyimide composite film comprising a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer provided on at least one surface of the thermosetting polyimide support layer, wherein an interface layer formed by the reaction of terminal amino group superbranched polyamide grafted silica particles and thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer.

[0010] In this invention, terminal amino group hyperbranched polyamide grafted silica particles are embedded at the interface between the thermosetting layer and the thermoplastic layer, thereby increasing the contact area between the support layer and the adhesive layer, improving the peel strength of the composite film, and increasing its adhesiveness.

[0011] As a selective embodiment, in the polyimide composite film according to the present invention, the method for forming the interface layer includes dispersing the terminal amino group superbranched polyamide grafted silica particles in a chemical casting reagent, mixing them with a thermosetting polyamic acid resin, and obtaining the layer by a polymerization reaction.

[0012] As a selective embodiment, in the polyimide composite film according to the present invention, the thermosetting polyimide support layer is obtained by reacting a flexible aromatic diamine with a rigid aromatic diamine and an aromatic dianhydride, and the molar ratio of the flexible aromatic diamine to the rigid aromatic diamine is 5-35:65-95.

[0013] In this invention, the precursor polyamic acid resin is obtained by polycondensation reaction of a flexible aromatic diamine, a rigid aromatic diamine, and an aromatic dianhydride. By using a rigid aromatic diamine monomer, the coefficient of linear expansion can be reduced, and at the same time, the water absorption rate can be controlled by tight molecular packing, thereby reducing the risk of delamination and rupture of copper-clad laminates due to moisture absorption of the film. However, excessive rigid aromatic diamine further reduces the flexibility of the film, making it impossible to meet application demands. Therefore, in this invention, a flexible aromatic diamine monomer is also introduced to improve the elongation rate and enhance application performance.

[0014] As a selective embodiment, in the polyimide composite film according to the present invention, the terminal groups of the thermoplastic polyimide adhesive layer contain imidazole rings that can form complexes with copper.

[0015] Based on the same technical concept, the present invention further provides a method for manufacturing a highly adhesive polyimide composite film for the above-mentioned flexible copper-clad laminate. Step S1 involves a polycondensation reaction between a flexible aromatic diamine, a rigid aromatic diamine, and an aromatic dianhydride to produce a polyamic acid resin A. In step S2, surface-amination silica is subjected to an addition reaction with acrylate or its analogue, and then reacted with an aliphatic diamine or its analogue to produce terminal amino group hyperbranched polyamide grafted silica particles. Finally, this is dispersed in a chemical casting reagent and rapidly mixed with the polyamic acid resin A produced in step S1 to obtain a mixed solution. The mass ratio of the surface-amination silica, acrylate or its analogue and the aliphatic diamine or its analogue is 1:1 to 3:0.7 to 4. Step S3 involves a polycondensation reaction of a diamine, a dianhydride, and a monoamine to produce a polyamic acid resin B, Step S4 includes a step in which a polyimide composite film is manufactured by a film formation process, using the mixed solution from step S2 as a thermosetting polyimide support layer and the polyamic acid resin B manufactured in step S3 as a thermoplastic polyimide adhesive layer.

[0016] In this invention, the degree of branching of terminal amino group superbranched polyamide grafted silica particles is controlled by controlling the amount of acrylate or its homologues and aliphatic diamine or its homologues used. If the degree of branching is too low, the number of amino groups is small, and the improvement in compatibility with the resin is not significant. If the degree of branching is too high, polymer crosslinking occurs, affecting the film performance. When terminal amino group superbranched polyamide grafted silica particles are dispersed in a chemical casting reagent and mixed with a thermosetting polyamic acid resin, the liquid chemical casting reagent can significantly reduce the resin viscosity and help in the uniform dispersion of terminal amino group superbranched polyamide grafted silica particles. By using the chemical casting reagent, the gelation of the resin within a short time is promoted, the distribution of terminal amino group superbranched polyamide grafted silica particles in the film is fixed, avoiding sedimentation and secondary aggregation of terminal amino group superbranched polyamide grafted silica particles due to excessively long storage or reaction time. The unique superbranched molecular structure of the silica surface, low chain entanglement, and relatively high number of amino groups can enhance the compatibility between silica inorganic particles and organic systems. During high-speed mixing and casting film formation, the thermosetting polyamic acid reacts with the terminal anhydride groups of the molecular chains, removing residual active groups and forming a cross-linked network structure, thereby improving the dimensional stability and heat resistance of the film. In the field of chemistry, a congener is an organic compound that has a similar structure but differs in molecular composition by only one or more "CH2" atomic groups.

[0017] As a selective embodiment, in the manufacturing method according to the present invention, in step S2, the amount of terminal amino group hyperbranched polyamide grafted silica particles added is 0.05 to 1% of the mass of the thermosetting polyimide support layer, and the particle size of the terminal amino group hyperbranched polyamide grafted silica particles is 0.1 to 10 μm.

[0018] Furthermore, it is preferable that the particle size of the terminal amino group hyperbranched polyamide grafted silica particles is 0.2 to 6 μm.

[0019] In this invention, the amount of terminal amino group hyperbranched polyamide grafted silica particles added is calculated based on the total amount of input powder. By controlling the particle size and amount of terminal amino group hyperbranched polyamide grafted silica particles, the terminal amino group hyperbranched polyamide grafted silica particles are embedded in the interface between the thermosetting layer and the thermoplastic layer, thereby increasing the contact area between the support layer and the adhesive layer, improving the peel strength of the composite film, and without affecting other performance aspects.

[0020] As a selective embodiment, in the production method according to the present invention, in step S2, the chemical casting reagent consists of a catalyst, a dehydrating agent, and an organic solvent, the catalyst is one or more selected from the group consisting of pyridine and derivatives, quinoline, isoquinoline, and triethylamine, the amount of the catalyst used is 1 to 5% of the mass of polyamic acid resin A, and the dehydrating agent is one or more selected from the group consisting of acetic anhydride, propionic anhydride, and benzoic anhydride, the amount of the dehydrating agent used is 15 to 35% of the mass of polyamic acid resin A. In the field of chemistry, a derivative is a more complex product derived by substituting an atom or group of atoms in a compound molecule with another atom or group of atoms, and may be a new substance converted and produced from the original substance by a chemical reaction.

[0021] As a selective embodiment, in the manufacturing method according to the present invention, the film formation process in step S4 includes a step in which the mixed solution from step S2 is used as a support layer, the polyamic acid resin B produced in step S3 is used as an adhesive layer, and high-temperature treatment is performed through two or three co-extrusion dies to obtain a polyimide composite film.

[0022] As a selective embodiment, in the manufacturing method according to the present invention, the film formation process in step S4 further includes the step of producing a thermosetting polyimide support layer by a chemical casting method, then applying polyamic acid resin B to one or both sides, and producing a polyimide composite film by high-temperature imidization.

[0023] In an alternative embodiment, in the production method according to the present invention, in step S1, the molar ratio of the sum of the used molar amounts of the flexible aromatic diamine and rigid aromatic diamine to the aromatic dianhydride is 100:100.05 to 100.5.

[0024] In an alternative embodiment, in the production method according to the present invention, the monoamine is a monoamine containing an imidazole structure.

[0025] In an alternative embodiment, in the production method according to the present invention, the monoamine containing an imidazole structure is one or more selected from the group consisting of 2-aminoimidazole, 4-aminoimidazole, 5-amino-4-imidazolecarboxamide and 2-aminobenzimidazole, and the molar ratio of the diamine, the dianhydride and the monoamine containing an imidazole structure is 98 to 99.5:100:0.5 to 4.

[0026] In an alternative embodiment, in the production method according to the present invention, in step S1, the molar ratio of the sum of the used molar amounts of the flexible aromatic diamine and rigid aromatic diamine to the aromatic dianhydride is 100:100.05 to 100.5.

[0027] In an alternative embodiment, in the production method according to the present invention, in step S1, the flexible aromatic diamine is one or more selected from the group consisting of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)diphenyl sulfone and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

[0028] As a selective embodiment, in the production method according to the present invention, in step S1, the rigid aromatic diamine is selected from one or more of 4,4'-diaminobiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, paraphenylenediamine, metaphenylenediamine, paraphenylenedimethylamine, and 4,4'-diaminobenzophenone.

[0029] As a selective embodiment, in the production method according to the present invention, in step S1, the aromatic dianhydride is one or more selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-dibenzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride, and 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride.

[0030] As a selective embodiment, in the production method according to the present invention, in step S3, the diamine is one or more selected from the group consisting of 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (TPE-M), 1,4-bis(4-aminophenoxy)benzene (TPE-Q), 4,4'-bis(4-aminophenoxy)diphenyl sulfone (BAPS), and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[0031] As a selective embodiment, in the manufacturing method according to the present invention, in step S3, the dianhydride is one or more selected from the group consisting of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (α-BPDA), 3,3',4,4'-dibenzophenonetetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride (ODPA), and 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride (α-ODPA).

[0032] Based on the same technical concept, the present invention further provides a two-layer flexible copper-clad laminate comprising a copper foil layer and a polyimide layer, wherein the polyimide layer is the high-adhesion polyimide composite film described above. [Effects of the Invention]

[0033] Compared to conventional technology, the beneficial effects of the present invention are as follows:

[0034] (1) In the present invention, by providing a thermoplastic polyimide adhesive layer on at least one surface of the thermosetting polyimide support layer, and by embedding an interface layer formed by the reaction of terminal amino group hyperbranched polyamide graft silica particles between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer, the contact area between the support layer and the adhesive layer can be increased, improving the peel strength of the composite film and increasing its adhesion.

[0035] (2) In the present invention, by mixing terminal amino group hyperbranched polyamide grafted silica particles with a chemical casting reagent and a thermosetting polyamic acid resin solution, inorganic particles can be uniformly distributed on the film, avoiding the occurrence of sedimentation and aggregation problems. At the same time, the relatively large number of amino groups on the surface of the terminal amino group hyperbranched polyamide grafted silica particles enhances the compatibility between the silica particles and the organic system. During high-speed mixing and the formation of the casting film, the terminal anhydride groups of the thermosetting polyamic acid molecular chains react, removing residual active groups and forming a crosslinked network structure, thereby improving the dimensional stability of the film.

[0036] (3) In the present invention, by using a monoamine containing an imidazole structure as a encapsulant for a thermoplastic polyamic acid, the endpoint of the polycondensation reaction can be controlled, excessive growth of the molecular chain in the later stages can be avoided, and the uniformity of the molecular weight distribution can be improved. On the other hand, the adhesion of the composite film can be improved by the formation of a complex between the imidazole ring and copper, and the imidazole ring is introduced as a terminal group, so its proportion in the molecular chain is small and does not reduce the overall thermoplasticity.

[0037] (4) In the present invention, by further optimizing the film, the properties of the material such as adhesion, dimensional stability and heat resistance can be greatly improved and a low glass transition temperature can be maintained. [Brief explanation of the drawing]

[0038] [Figure 1] This shows the microscopic detection results of the polyimide composite film produced in Example 7. [Figure 2] This is a schematic diagram of the reaction of terminal amino group superbranched polyamide grafted silica particles produced in the example. [Figure 3] This is a plan view of the layered film of the polyimide composite film manufactured in Comparative Example 1. The left side shows the results of observation with a 500x magnification mirror, and the right side shows the results of observation with a 1500x magnification mirror. [Figure 4]This is a plan view of the layered film of the polyimide composite film manufactured in Example 3. The left side shows the results of observation with a 500x magnification mirror, and the right side shows the results of observation with a 1500x magnification mirror. [Figure 5] This is a plan view of the layered film of the polyimide composite film manufactured in Comparative Example 3. The left side shows the results of observation with a 500x magnification mirror, and the right side shows the results of observation with a 1500x magnification mirror. [Modes for carrying out the invention]

[0039] To facilitate understanding of the present invention, the following description will be more comprehensive and detailed, combining the drawings and preferred embodiments of the specification. However, the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as those ordinarily understood by those skilled in the art. The technical terms used herein are solely for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, equipment and facilities used in the present invention are commercially available or can be manufactured by existing methods.

[0040] Example 1 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0041] 1, polymerization 31.7 kg of ODA and 36.4 kg of p-PDA were dissolved in 800 kg of dimethylformamide. In batches, 54.4 kg of PMDA, 31.9 kg of BTDA, and 43.7 kg of BPDA were added, and the mixture was reacted for 5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1850 P.

[0042] 11.7 kg of ODA and 31.2 kg of TPE-R were dissolved in 420 kg of dimethylformamide, 36.4 kg of PMDA was added in batches, and finally 0.48 kg of 2-aminoimidazole was added. The mixture was reacted for 4 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 550 P.

[0043] 1 kg of amino-modified silica with a particle size of 0.4 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and obtained terminal amino-group hyperbranched polyamide grafted silica particles. A schematic diagram of the reaction is shown in Figure 2.

[0044] 2, Film forming 1.6 kg of terminally amino group hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with thermosetting polyamic acid resin at a rotational speed of 1850 rpm. The mixture was then delivered to a die head via a pipeline and extruded. Through processes such as casting, longitudinal and transverse stretching, and high-temperature heating, a thermosetting polyimide film with a thickness of 19 μm was obtained.

[0045] 3. Application A thermoplastic polyamic acid resin was applied to both sides of a thermosetting polyimide film, and the temperature was gradually increased within the range of 150°C to 450°C to obtain a composite film with a total thickness of 25 μm, with the thickness of the adhesive layers on each side being 3 μm.

[0046] Example 2 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0047] The polymerization process is the same as in Example 1.

[0048] 1.58 kg of terminal amino group hyperbranched polyamide grafted silica particles with a particle size of 0.5 μm, 18 kg of pyridine, and 21 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 1850 rpm to obtain a thermosetting polyamic acid precursor resin. This was then fed simultaneously with the thermoplastic polyamic acid resin to a three-layer co-extrusion die head for extrusion molding. After processes such as casting, longitudinal and transverse stretching, and high-temperature heating, a composite film with a total thickness of 25 μm was obtained, with the thickness of the adhesive layers on both sides being 3 μm each.

[0049] Example 3 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0050] 1, polymerization 12.7 kg of ODA, 12.4 kg of TPE-M, and 67.5 kg of 4,4'-diamino-2,2'-dimethylbiphenyl were dissolved in 800 kg of dimethylformamide. In batches, 65.2 kg of PMDA and 41 kg of BTDA were added, and the mixture was reacted for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2370 P.

[0051] 14.4 kg of ODA and 25.9 kg of BAPP were dissolved in 420 kg of dimethylformamide. In batches, 9.4 kg of PMDA and 29.6 kg of α-BPDA were added, and finally 0.57 kg of 2-aminobenzimidazole was added. The mixture was reacted for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 510P.

[0052] 1 kg of amino-modified silica with a particle size of 3 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and obtained terminal amino-group hyperbranched polyamide grafted silica particles. A schematic diagram of the reaction is shown in Figure 2.

[0053] 2, Film forming 1 kg of terminal amino group hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with the resin at a rotational speed of 2250 rpm. The mixture was then delivered to a die head via a pipeline and extruded. Through processes such as casting, longitudinal and transverse stretching, and high-temperature heating, a thermosetting polyimide film with a thickness of 19 μm was obtained.

[0054] 3. Application A thermoplastic polyamic acid resin was applied to both sides of a thermosetting polyimide film, and the temperature was gradually increased within the range of 150°C to 450°C to obtain a composite film with a total thickness of 25 μm, with the thickness of the adhesive layers on each side being 3 μm.

[0055] Example 4 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0056] The polymerization process is the same as in Example 2.

[0057] 1 kg of terminal amino group hyperbranched polyamide grafted silica particles with a particle size of 3.2 μm, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2350 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, and the thickness of the adhesive layers on both sides was 3 μm each.

[0058] Example 5 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0059] 1, polymerization 18.2 kg of BAPP, 8.9 kg of 3,4'-ODA, and 75.3 kg of 4,4'-diamino-3,3'-dimethylbiphenyl were dissolved in 800 kg of dimethylformamide, and 97.2 kg of PMDA was added in batches. The mixture was reacted for 4 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1580 P.

[0060] 35.3 kg of BAPS and 10.7 kg of BAPP were dissolved in 420 kg of dimethylformamide. In batches, 16.9 kg of ODPA and 16.0 kg of BPDA were added, and finally 0.23 kg of 3-aminoimidazole was added. The mixture was reacted for 5.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 450 P.

[0061] 1 kg of amino-modified silica with a particle size of 2.8 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added and reacted in methanol. The mixture was filtered by vacuum suction to obtain terminal amino-group hyperbranched polyamide grafted silica particles. A schematic diagram of the reaction is shown in Figure 2.

[0062] 2, Film forming 0.4 kg of terminal amino group hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2550 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, and the thickness of the adhesive layers on both sides was 4 μm each.

[0063] Example 6 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0064] 1, polymerization 10.2 kg of BAPS, 16.1 kg of BAPP, and 69.9 kg of 4,4'-diaminobenzophenone were dissolved in 800 kg of dimethylformamide. In batches, 69.4 kg of BPDA and 34.2 kg of PMDA were added, and the mixture was reacted for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2030P.

[0065] 8.9 kg of BAPS and 33.7 kg of TPE-Q were dissolved in 420 kg of dimethylformamide, and 15 kg of PMDA and 22.1 kg of BTDA were added in batches. Finally, 0.18 kg of 2-aminobenzimidazole was added, and the mixture was reacted for 5.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 620P.

[0066] 1 kg of amino-modified silica with a particle size of 1.5 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added and reacted in methanol. The mixture was then filtered by vacuum suction to obtain terminal amino-group hyperbranched polyamide grafted silica particles.

[0067] 2, Film forming 0.2 kg of terminal amino group hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2550 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 20 μm, and the thickness of the adhesive layers on both sides was 3 μm each.

[0068] Example 7 A method for producing a highly adhesive polyimide composite film includes the following steps.

[0069] 1, polymerization 9.3 kg of TPE-M and 72.8 kg of 4,4'-diaminodiphenylmethane were dissolved in 800 kg of dimethylacetamide, and 117.8 g of BPDA was added in batches. The mixture was reacted for 7 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1730 P.

[0070] 44.2 kg of TPE-M was dissolved in 420 kg of dimethylacetamide, and in batches, 16.6 kg of PMDA, 14.2 kg of α-ODPA, and 4.9 kg of BTDA were added. Finally, 0.14 kg of 2-aminobenzimidazole was added, and the mixture was reacted for 4.7 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 520P.

[0071] 1 kg of amino-modified silica with a particle size of 1 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and obtained terminal amino-group hyperbranched polyamide grafted silica particles. A schematic diagram of the reaction is shown in Figure 2.

[0072] 2, Film forming 0.14 kg of terminal amino group hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2650 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, and the thickness of the adhesive layers on both sides was 3 μm each.

[0073] Comparative Example 1 The differences from Example 1 are that 2-aminoimidazole is not added and terminal amino group hyperbranched polyamide grafted silica particles are not added; otherwise, it is the same as Example 1.

[0074] Comparative Example 2 1, polymerization 85.8 kg of ODA was dissolved in 800 kg of dimethylacetamide, and 47.1 kg of PMDA, 27.6 kg of BTDA, and 37.8 kg of BPDA were added in batches. The mixture was reacted for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2030P.

[0075] 11.7 kg of ODA and 31.3 kg of TPE-R were dissolved in 420 kg of dimethylacetamide, 36.5 kg of PMDA was added in batches, and finally 0.48 kg of 2-aminoimidazole was added. The mixture was reacted for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 580 P.

[0076] 1 kg of amino-modified silica with a particle size of 11.5 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and terminal amino-group hyperbranched polyamide grafted silica particles were obtained.

[0077] 2, Film forming 1.6 kg of terminal amino group hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2250 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, with the adhesive layers on both sides each having a thickness of 3 μm.

[0078] Comparative Example 3 1, polymerization 55.4 kg of m-PDA was dissolved in 770 kg of dimethylacetamide, and in batches, 56.3 kg of PMDA, 33 kg of BTDA, and 45.2 kg of BPDA were added and the mixture was reacted for 6.5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2350 P.

[0079] 10.7 kg of ODA and 30.7 kg of TPE-M were dissolved in 420 kg of dimethylacetamide, 37.5 kg of PMDA was added in batches, and finally 1.142 kg of 2-aminoimidazole was added. The mixture was reacted for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 580 P.

[0080] 1 kg of amino-modified silica with a particle size of 3.5 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and terminal amino-group hyperbranched polyamide grafted silica particles were obtained.

[0081] 2, Film forming 3 kg of terminal amino group hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2250 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, with the adhesive layers on both sides each having a thickness of 3 μm.

[0082] Comparative Example 4 1, polymerization 85.8 kg of ODA was dissolved in 770 kg of dimethylacetamide, and 47.1 kg of PMDA, 27.6 kg of BTDA, and 37.8 kg of BPDA were added in batches. The mixture was reacted for 5.8 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1750 P.

[0083] 22.2 kg of ODA and 20.7 kg of BAPP were dissolved in 420 kg of dimethylacetamide, 36.7 kg of PMDA was added in batches, and finally 0.419 kg of 2-aminoimidazole was added. The mixture was reacted for 3 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 500 P.

[0084] 1 kg of amino-modified silica with a particle size of 3.5 μm and 2.2 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3.35 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and terminal amino-group hyperbranched polyamide grafted silica particles were obtained.

[0085] 2, Film forming 1.6 kg of terminal amino group hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride were added to a high-speed mixer and uniformly mixed with a thermosetting polyamic acid resin at a rotational speed of 2030 rpm to obtain a thermosetting polyamic acid precursor resin. This was then simultaneously fed to a three-layer co-extrusion die head for extrusion molding, casting, longitudinal and transverse stretching, and high-temperature heating to obtain a composite film with a total thickness of 25 μm, with the thickness of the adhesive layers on both sides being 3 μm each.

[0086] Comparative Example 5 The only difference from Example 1 is that terminal amino group hyperbranched polyamide grafted silica particles are not added; otherwise, it is the same as Example 1.

[0087] Comparative Example 6 1, polymerization 31.7 kg of ODA and 36.4 kg of p-PDA were dissolved in 800 kg of dimethylformamide. In batches, 54.4 kg of PMDA, 31.9 kg of BTDA, and 43.7 kg of BPDA were added, and the mixture was reacted for 5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1850 P.

[0088] 11.7 kg of ODA and 31.2 kg of TPE-R were dissolved in 420 kg of dimethylformamide, 36.4 kg of PMDA was added in batches, and finally 0.48 kg of 2-aminoimidazole was added. The mixture was reacted for 4 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 550 P.

[0089] 1 kg of amino-modified silica with a particle size of 0.5 μm and 3.8 kg of methyl acrylate were added to 10 kg of methanol. After reacting at 50°C, the mixture was filtered by vacuum suction, and then 3 kg of ethylenediamine was added. The mixture was reacted in methanol, filtered by vacuum suction, and terminal amino-group hyperbranched polyamide grafted silica particles were obtained.

[0090] The remaining steps are the same as in Example 1.

[0091] Comparative Example 7 The only difference from Example 1 is that 2-aminoimidazole is not added; otherwise, it is the same as Example 1.

[0092] Performance detection A polyimide composite film produced in Example 7 was detected using a microscope, and its cross-section is shown in Figure 1. The core layer is a thermosetting polyimide layer 1, and both sides are thermoplastic polyimide layers 2. These two layers intersect to form an interface layer 3, and terminal amino group hyperbranched polyamide grafted silica particles 4 are distributed inside.

[0093] The polyimide composite films produced in Comparative Example 1, Example 3, and Comparative Example 3 were detected under a microscope, and their core layer film planes are shown in Figures 3 to 5. In Comparative Example 1, no terminal amino group hyperbranched polyamide grafted silica particles were added, and as can be seen from Figure 3, the core layer surface is smooth. Figure 4 shows the layer film plane of the polyimide composite film in Example 3, and Figure 5 shows the layer film plane of the polyimide composite film in Comparative Example 3. As the amount of terminal amino group hyperbranched polyamide grafted silica particles added increases, the core layer surface clearly becomes rougher, increasing the contact area between the core layer and the adhesive layer, and achieving the effect of improving peel strength.

[0094] The polyimide films produced in the above examples and comparative examples were tested for mechanical properties based on ASTM D882, their coefficient of thermal expansion was tested by the TMA method, and their glass transition temperature was tested by the DMA method (heating rate of 5°C / min). Each was then laminated with 18 μm rolled copper foil using industrial methods to produce two-layer, adhesive-free, double-sided copper-clad laminates. The peel strength was then tested based on IPC-TM-650, and the results are shown in Table 1 below.

[0095] Table 1: Overall performance of polyimide films obtained in the examples and comparative examples. When testing the peel strength in Comparative Example 6, the film undergoes brittle fracture, making it impossible to obtain specific values.

[0096] As is clear from Table 1, compared to Example 1, Comparative Example 1 did not use terminal amino group hyperbranched polyamide grafted silica particles and 2-aminoimidazole, resulting in a slight improvement in the film's coefficient of thermal expansion (CTE) and a significant decrease in peel strength. In Comparative Example 2, all thermosetting layer diamines were flexible ODA, and 11.5 μm amino group modified silica was used, resulting in insufficient molecular chain rigidity and excessive silica particle size, significantly reducing the mechanical properties of the polyimide film and increasing the coefficient of thermal expansion (CTE). In Comparative Example 3, all thermosetting layer diamines were rigid PDA, leading to high molecular chain regularity, increased intermolecular forces, inhibiting internal rotation and motion of the molecular chains, and excessive addition of silica particles, resulting in a rapid decrease in film flexibility and failure to meet application requirements. In Comparative Example 4, all thermosetting layers were flexible ODA, and the content was excessive, resulting in decreased film tensile strength, poor dimensional stability, and a high thermoplastic layer Tg, leading to poor peel strength. In Comparative Example 5, terminal amino group hyperbranched polyamide grafted silica particles were not used. The thermal expansion coefficient of the film increased, and the peel strength decreased sharply. In Comparative Example 6, the relatively large amounts of methyl acrylate and ethylenediamine used resulted in excessive hyperbranching and an excessive number of amino groups on the silica particle surface, leading to excessive PI crosslinking, a significant decrease in film elongation, and increased susceptibility to brittle fracture during processing and application. In Comparative Example 7, 2-aminoimidazole was not used in the thermoplastic layer, resulting in decreased film peel strength.

[0097] From the above, it can be seen that, in the present invention, by introducing monoamines containing imidazole structures and terminal amino group hyperbranched polyamide grafted silica particles into the structure of a polyimide composite film, the performance of the film, such as adhesion, dimensional stability, and heat resistance, is greatly improved, while maintaining a relatively low glass transition temperature, and meeting the processing application requirements of materials such as two-layer FCCL.

[0098] The above is a further detailed description of the present invention based on specific preferred embodiments, but the specific implementation of the present invention is not limited to this description. Those skilled in the art can make several simple assumptions and substitutions without departing from the concept of the present invention, all of which should be considered to fall within the scope of protection of the present invention.

Claims

1. A method for producing a highly adhesive polyimide composite film used in a flexible copper-clad laminate, comprising a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer provided on at least one surface of the thermosetting polyimide support layer, An interfacial layer formed by the reaction of terminal amino group superbranched polyamide graft silica particles and thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer. The aforementioned method, Step S1 involves a polycondensation reaction between a flexible aromatic diamine, a rigid aromatic diamine, and an aromatic dianhydride to produce a polyamic acid resin A. Step S2 involves adding amination silica with methyl acrylate or its homologue, then reacting it with an aliphatic diamine or its homologue to produce terminal amino group hyperbranched polyamide grafted silica particles, finally dispersing this in a chemical casting reagent and rapidly mixing it with the polyamic acid resin A produced in step S1 to obtain a mixed solution, wherein the mass ratio of the amination silica, acrylate, and aliphatic diamine is 1:1 to 3:0.7 to 4. Step S3 involves a polycondensation reaction of a diamine, a dianhydride, and a monoamine to produce a polyamic acid resin B, Step S4 includes a step in which a polyimide composite film is manufactured by a film formation process, using the mixed solution from step S2 as a thermosetting polyimide support layer and the polyamic acid resin B manufactured in step S3 as a thermoplastic polyimide adhesive layer. The terminal group of the thermoplastic polyimide contains an imidazole ring capable of forming a complex with copper, The thermosetting polyamic acid is obtained from a flexible aromatic diamine, a rigid aromatic diamine and an aromatic dianhydride, wherein the molar ratio of the flexible aromatic diamine to the rigid aromatic diamine is 5 to 35:65 to 95. The particle size of the terminal amino group hyperbranched polyamide grafted silica particles is 0.1 to 10 μm, and the amount added is 0.05 to 1% of the mass of the thermosetting polyimide support layer. A method for producing a highly adhesive polyimide composite film, characterized by the following features.

2. The method for forming the interface layer is characterized by comprising dispersing the terminal amino group superbranched polyamide graft silica particles in a chemical casting reagent, mixing them with a thermosetting polyamic acid resin, and obtaining the result by polymerization reaction, as described in claim 1.

3. The method for producing a highly adhesive polyimide composite film according to claim 1, characterized in that, in step S2, the chemical casting reagent comprises a catalyst, a dehydrating agent, and an organic solvent, the catalyst is one or more selected from the group consisting of pyridine and its derivatives, quinoline, isoquinoline, and triethylamine, the amount of the catalyst used is 1 to 5% of the mass of the polyamic acid resin A, the dehydrating agent is one or more selected from the group consisting of acetic anhydride, propionic anhydride, and benzoic anhydride, and the amount of the dehydrating agent used is 15 to 35% of the mass of the polyamic acid resin A.

4. The method for producing a highly adhesive polyimide composite film according to claim 1, characterized in that, in step S1, the polyamic acid resin A is produced by polycondensation reaction of a flexible aromatic diamine, a rigid aromatic diamine, and an aromatic dianhydride, and the molar ratio of the sum of the molar amounts used of the flexible aromatic diamine and the rigid aromatic diamine to the aromatic dianhydride is 100:100.05 to 100.

5.

5. The method for producing a highly adhesive polyimide composite film used in a flexible copper-clad laminate according to claim 1, characterized in that in step S3, the monoamine is a monoamine containing an imidazole structure.

6. The method for producing a highly adhesive polyimide composite film used in a flexible copper-clad laminate according to claim 5, characterized in that the monoamine containing the imidazole structure is one or more selected from the group consisting of 2-aminoimidazole, 4-aminoimidazole, 5-amino-4-imidazolecarboxamide, and 2-aminobenzimidazole, and the molar ratio of the diamine, dianhydride, and monoamine containing the imidazole structure is 98 to 99.5:100:0.5 to 4.

7. In step S3, The diamine is one or more selected from the group consisting of 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis(4'-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)diphenyl sulfone, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane. The method for producing a highly adhesive polyimide composite film according to claim 1, characterized in that the dianhydride is one or more selected from the group consisting of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-dibenzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride, and 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride.

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