A high-adhesion polyimide composite film for flexible copper clad laminates and its preparation method

Abstract

The present invention discloses a high - adhesion polyimide composite film for flexible copper - clad laminates and a preparation method thereof. The polyimide composite film is composed of a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer provided on at least one side of the thermosetting polyimide support layer. An interface layer formed by the reaction of amino - terminated hyperbranched polyamide grafted silica particles and thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer. The end group of the thermoplastic polyimide contains an imidazole ring that can form a complex with copper. In the present invention, by embedding amino - terminated hyperbranched 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. At the same time, through the complexing effect of the imidazole ring and copper, a polyimide composite film with high adhesion, high dimensional stability, high heat resistance and low glass transition temperature is prepared.

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 flexible copper clad laminates and a preparation method thereof. Background Art

[0002] Flexible printed circuit boards (FPCs) are widely used in electronic products, household appliances, medical treatment, automobiles, aerospace, and military fields due to their characteristics such as light weight, thin thickness, and free bending and folding. Flexible copper clad laminates (FCCLs) are the key substrates of FPCs. Traditional three-layer FCCLs are composed of copper foil, thermosetting polyimide films, and epoxy or silicone adhesives, while two-layer FCCLs use thermoplastic polyimide layers instead of epoxy or silicone adhesives, making the copper clad laminates have the advantages of being thinner, lighter, and having better heat resistance, and gradually becoming the industry mainstream.

[0003] Chinese Patent Application Document CN103739842A proposes a thermoplastic polyimide film for two-layer FCCLs. In order to ensure a certain dimensional stability, diamines containing benzoxazole, benzimidazole aromatic heterocycles, etc. are introduced, reducing the thermoplasticity of the overall molecular chain, resulting in an adhesion force of only 1.1 - 1.2 N / mm, bringing potential hazards to subsequent applications.

[0004] Chinese Patent Application Document CN115746351A proposes a preparation method of a thermoplastic polyimide film with a low coefficient of thermal expansion. By introducing double bonds into the polyimide molecular chain and achieving photo-crosslinking under the action of a crosslinking agent and a photoinitiator, the coefficient of thermal expansion of the film is reduced. However, the crosslinked structure restricts the movement of the molecular chain, making its glass transition temperature close to 300 °C, which is not conducive to hot pressing processing and difficult to commercialize.

[0005] Chinese Patent Application Document CN1957051A proposes an adhesive film and a preparation method thereof. Using the co-extrusion - casting coating method, a thermoplastic polyimide adhesive layer is compounded on one or both sides of a thermosetting polyimide core layer to obtain a composite film that can be bonded by heating. However, both thermosetting and thermoplastic polyamic acid precursors use diamine or dianhydride polycondensation. The amino end group will cause thermal oxidation, reducing the heat resistance of the film, especially the adhesion force after heating, while the anhydride end group is prone to ring-opening hydrolysis, resulting in uneven molecular weight distribution of polyimide and further affecting the performance uniformity.

[0006] As can be seen from the above, in view of the performance requirements of two-layer FCCLs for high adhesion, high dimensional stability, high heat resistance, and low glass transition temperature of the film substrate, it is necessary to improve the existing technology to meet the increasingly demanding application requirements. Summary of the Invention

[0007] To overcome the problems in the prior art, the present invention provides a high-adhesion polyimide composite film for flexible copper clad laminates and a preparation method thereof, and a polyimide composite film with high adhesion, high dimensional stability, high heat resistance and low glass transition temperature is prepared.

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

[0009] The present invention provides a high-adhesion polyimide composite film for flexible copper clad laminates. The polyimide composite film includes a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer provided on at least one side of the thermosetting polyimide support layer. An interface layer formed by the reaction of amino-terminated hyperbranched polyamide grafted silica particles with a thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer.

[0010] In the present invention, by embedding amino-terminated hyperbranched 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, the peel strength of the composite film is improved, and the adhesion is increased.

[0011] As an optional implementation manner, in the polyimide composite film provided by the present invention, the formation method of the interface layer includes: dispersing the amino-terminated hyperbranched polyamide grafted silica particles in a chemical casting reagent, mixing with a thermosetting polyamic acid resin, and then obtaining it through a polymerization reaction.

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

[0013] In the present invention, the precursor polyamic acid resin is formed by the polycondensation reaction of a flexible aromatic diamine, a rigid aromatic diamine and an aromatic dianhydride. Using a rigid aromatic diamine monomer can reduce the coefficient of linear expansion. At the same time, the close packing of molecules can control the water absorption rate and reduce the risk of delamination and explosion of the copper clad laminate caused by film moisture absorption. However, too much rigid aromatic diamine will cause the flexibility of the film to continue to decline and cannot meet the application requirements. Therefore, the present invention also synchronously introduces a flexible aromatic diamine monomer to improve the elongation rate and application performance.

[0014] As an optional implementation manner, in the polyimide composite film provided by the present invention, the end group of the thermoplastic polyimide adhesive layer contains an imidazole ring that can form a complex with copper.

[0015] Based on the same inventive concept, the present invention also provides a method for preparing a high-adhesion polyimide composite film for the flexible copper clad laminate, comprising the following steps:

[0016] S1. Polycondensing a flexible aromatic diamine, a rigid aromatic diamine and an aromatic dianhydride to generate a polyamic acid resin A.

[0017] S2. Performing an addition reaction between surface-aminated silica and an acrylate or its homolog, then reacting with an aliphatic diamine or its homolog to obtain an amino-terminated hyperbranched polyamide grafted silica particle, and finally dispersing it in a chemical casting reagent and rapidly mixing it with the polyamic acid resin A prepared in step S1 to obtain a mixed solution; the mass ratio of the surface-aminated silica, the acrylate or its homolog and the aliphatic diamine or its homolog is 1:1-3:0.7-4.

[0018] S3. Polycondensing a diamine, a dianhydride and a monoamine to generate a polyamic acid resin B.

[0019] S4. Using the mixed solution in step S2 as a thermosetting polyimide support layer and the polyamic acid resin B prepared in step S3 as a thermoplastic polyimide adhesive layer, and preparing a polyimide composite film through a film-forming process.

[0020] In the present invention, the degree of branching of the amino-terminated hyperbranched polyamide grafted silica particle is controlled by controlling the amounts of the acrylate or its homolog and the aliphatic diamine or its homolog. If the degree of branching is too small, the number of amino groups is small, and the compatibility with the resin is not significantly improved; if the degree of branching is large, polymer crosslinking occurs, which also affects the film properties. The amino-terminated hyperbranched polyamide grafted silica particle is 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, which helps the amino-terminated hyperbranched polyamide grafted silica particle to be uniformly dispersed; the chemical casting reagent is used to promote the gelation of the resin within a short time, locking the distribution of the amino-terminated hyperbranched polyamide grafted silica particle in the film, and avoiding the sedimentation and secondary aggregation of the amino-terminated hyperbranched polyamide grafted silica particle caused by too long storage or reaction time; the unique hyperbranched molecular structure, low chain entanglement and relatively large number of amino groups on the silica surface can enhance the compatibility between the silica inorganic particles and the organic system. When high-speed mixing and casting into a film, it reacts with the terminal anhydride groups of the thermosetting polyamic acid molecular chains, eliminates residual active groups, and can also form a crosslinked network structure, improving the dimensional stability and heat resistance of the film. In the chemical field, homologs refer to organic compounds with similar structures and whose molecular compositions differ by one or several "CH2" atomic groups.

[0021] As an alternative embodiment, in the preparation method provided by the present invention, in step S2, the addition amount of the amino-terminated hyperbranched polyamide grafted silica particles is 0.05 - 1% of the mass of the thermosetting polyimide support layer, and the particle size of the amino-terminated hyperbranched polyamide grafted silica particles is 0.1 - 10 μm.

[0022] Further, the particle size of the amino-terminated hyperbranched polyamide grafted silica particles is preferably 0.2 - 6 μm.

[0023] In the present invention, the addition amount of the amino-terminated hyperbranched polyamide grafted silica particles is calculated according to the total amount of the powders input. By controlling the particle size and the addition amount of the amino-terminated hyperbranched polyamide grafted silica particles, the amino-terminated hyperbranched polyamide grafted silica particles can increase the contact area between the support layer and the adhesive layer by embedding the interface between the thermosetting layer and the thermoplastic layer, improve the peel strength of the composite film, and do not affect other properties.

[0024] As an alternative embodiment, in the preparation method provided by the present invention, in step S2, the chemical casting method reagent consists of a catalyst, a dehydrating agent, and an organic solvent; the catalyst is selected from one or more of pyridine and its derivatives, quinoline, isoquinoline, and triethylamine, and the dosage of the catalyst is 1 - 5% of the mass of the polyamic acid resin A; the dehydrating agent is selected from one or more of acetic anhydride, propionic anhydride, and benzoic anhydride, and the dosage of the dehydrating agent is 15 - 35% of the mass of the polyamic acid resin A. In the chemical field, a derivative refers to a more complex product derived from the substitution of atoms or atomic groups in a compound molecule by other atoms or atomic groups, or it can also be a new substance generated by a chemical reaction from the original substance.

[0025] As an alternative embodiment, in the preparation method provided by the present invention, the film-forming process in step S4 includes the following steps: using the mixed solution in step S2 as the support layer, using the polyamic acid resin B prepared in step S3 as the adhesive layer, and after passing through a two-layer or three-layer co-extrusion die head and then performing a high-temperature treatment, a polyimide composite film can be obtained.

[0026] As an alternative embodiment, in the preparation method provided by the present invention, the film-forming process in step S4 further includes the following steps: preparing a thermosetting polyimide support layer by the chemical casting method, and then coating the polyamic acid resin B on one side or both sides, and obtaining a polyimide composite film through high-temperature imidization.

[0027] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the molar ratio of the sum of the molar amounts of the flexible aromatic diamine and the rigid aromatic diamine to the molar amount of the aromatic dianhydride is 100:100.05 - 100.5.

[0028] As an alternative embodiment, in the preparation method provided by the present invention, the monoamine is a monoamine containing an imidazole structure.

[0029] As an alternative embodiment, in the preparation method provided by the present invention, the monoamine containing an imidazole structure is selected from one or more of 2-aminoimidazole, 4-aminoimidazole, 5-amino-4-imidazolecarboxamide, and 2-aminobenzimidazole; the molar ratio of the diamine, dianhydride, and monoamine containing an imidazole structure is 98-99.5:100:0.5-4.

[0030] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the molar ratio of the total amount of the flexible aromatic diamine and the rigid aromatic diamine to the molar amount of the aromatic dianhydride is 100:100.05-100.5.

[0031] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the flexible aromatic diamine is selected from one or more 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.

[0032] As an alternative embodiment, in the preparation method provided by 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, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, and 4,4'-diaminobenzophenone.

[0033] As an alternative embodiment, in the preparation method provided by the present invention, in step S1, the aromatic dianhydride is selected from one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, and 2,3,3',4'-diphenylethertetracarboxylic dianhydride.

[0034] As an alternative embodiment, in the preparation method provided by the present invention, in step S3, the diamine is selected from one or more 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).

[0035] As an alternative embodiment, in the preparation method provided by the present invention, in step S3, the dianhydride is selected from one or more of pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (α-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA), and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride (α-ODPA).

[0036] Based on the same technical concept, the present invention also provides a two-layer flexible copper clad laminate, including a copper foil layer and a polyimide layer, and the polyimide layer is the above-mentioned high-adhesion polyimide composite film.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) In the present invention, a thermoplastic polyimide adhesive layer is provided on at least one side of the thermosetting polyimide support layer, and an interface layer formed by reacting terminal amino hyperbranched polyamide grafted silica particles is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide adhesive layer, which can increase the contact area between the support layer and the adhesive layer, improve the peel strength of the composite film, and increase the adhesiveness.

[0039] (2) In the present invention, the terminal amino hyperbranched polyamide grafted silica particles are mixed with the chemical casting reagent and the thermosetting polyamic acid resin solution, which can make the inorganic particles evenly distributed in the film and avoid the problems of sedimentation and agglomeration; at the same time, the number of amino groups on the surface of the terminal amino hyperbranched polyamide grafted silica particles is large, which can enhance the compatibility between the silica particles and the organic system; reacting with the terminal anhydride groups of the thermosetting polyamic acid molecular chains during high-speed mixing and casting film formation to eliminate residual active groups, and can also form a crosslinked network structure to improve the dimensional stability of the film.

[0040] (3) In the present invention, the monoamine containing an imidazole structure is used as a capping agent for the thermoplastic polyamic acid. On the one hand, it can control the end point of the polycondensation reaction, avoid excessive growth of the molecular chain in the later stage, and improve the uniformity of the molecular weight distribution. On the other hand, by forming a complex with copper through the imidazole ring, the adhesion of the composite film can be improved; moreover, the imidazole ring is introduced as an end group and accounts for a small proportion in the molecular chain, and will not reduce the overall thermoplasticity.

[0041] (4) Through the further optimization of the film, the present invention can significantly improve the properties such as the adhesion, dimensional stability and heat resistance of the material, and maintain a low glass transition temperature. Brief Description of the Drawings

[0042] Figure 1 Microscopic test results of the polyimide composite film prepared in Example 7;

[0043] Figure 2 Reaction schematic diagram of the amino-terminated hyperbranched polyamide grafted silica particles prepared in the examples;

[0044] Figure 3 Plan view of the layer film of the polyimide composite film prepared in Comparative Example 1. The left side is the observation result under a 500-fold microscope, and the right side is the observation result under a 1500-fold microscope;

[0045] Figure 4 Plan view of the layer film of the polyimide composite film prepared in Example 3. The left side is the observation result under a 500-fold microscope, and the right side is the observation result under a 1500-fold microscope;

[0046] Figure 5 Plan view of the layer film of the polyimide composite film prepared in Comparative Example 3. The left side is the observation result under a 500-fold microscope, and the right side is the observation result under a 1500-fold microscope. Detailed Description of the Invention

[0047] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, all the raw materials, reagents, instruments and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0048] Example 1

[0049] Preparation method of a high-adhesion polyimide composite film, comprising the following steps:

[0050] 1. Polymerization

[0051] Dissolve 31.7 kg of ODA and 36.4 kg of p-PDA in 800 kg of dimethylformamide, and add 54.4 kg of PMDA, 31.9 kg of BTDA, and 43.7 kg of BPDA in batches for reaction for 5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1850 P.

[0052] Dissolve 11.7 kg of ODA and 31.2 kg of TPE-R in 420 kg of dimethylformamide, add 36.4 kg of PMDA in batches, and finally add 0.48 kg of 2-aminoimidazole for reaction for 4 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 550 P.

[0053] Add 1 kg of amino-modified silica with a particle size of 0.4 μm and 2.2 kg of methyl acrylate to 10 kg of methanol, react at 50 °C and then filter by vacuum suction. Then add 3.35 kg of ethylenediamine, react in methanol and filter by vacuum to obtain amino-terminated hyperbranched polyamide grafted silica particles. The reaction schematic diagram is as Figure 2 shown.

[0054] 2. Film formation

[0055] Add 1.6 kg of amino-terminated hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride into a high-speed mixer, mix evenly with the thermosetting polyamic acid resin at a rotation speed of 1850 rpm, transport it through a pipeline to a die head, extrude and form, and then obtain a thermosetting polyimide film with a thickness of 19 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating.

[0056] 3. Coating

[0057] Coat the thermosetting polyimide film on both sides with the thermoplastic polyamic acid resin respectively, and raise the temperature programatically in the range of 150 °C - 450 °C to obtain a composite film with a total thickness of 25 μm, and the thickness of the adhesive layers on both sides is 3 μm respectively.

[0058] Example 2

[0059] A preparation method of a high-adhesion polyimide composite film, comprising the following steps:

[0060] The polymerization process is the same as that in Example 1.

[0061] Add 1.58 kg of amino-terminated hyperbranched polyamide grafted silica particles with a particle size of 0.5 μm, 18 kg of pyridine, and 21 kg of acetic anhydride into a high-speed mixer, mix evenly with a thermosetting polyamic acid resin at a rotation speed of 1850 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously transport it with a thermoplastic polyamic acid resin to a three-layer coextrusion die head, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the adhesive layers on both sides are 3 μm respectively.

[0062] Example 3

[0063] A method for preparing a high-adhesion polyimide composite film, comprising the following steps:

[0064] 1. Polymerization

[0065] Dissolve 12.7 kg of ODA, 12.4 kg of TPE-M, and 67.5 kg of 4,4'-diamino-2,2'-dimethylbiphenyl in 800 kg of dimethylformamide, add 65.2 kg of PMDA and 41 kg of BTDA in batches and react for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2370 P.

[0066] Dissolve 14.4 kg of ODA and 25.9 kg of BAPP in 420 kg of dimethylformamide, add 9.4 kg of PMDA and 29.6 kg of α-BPDA in batches, and finally add 0.57 kg of 2-aminobenzimidazole and react for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 510 P.

[0067] Add 1 kg of amino-modified silica with a particle size of 3 μm and 2.2 kg of methyl acrylate into 10 kg of methanol, react at 50 °C and then perform vacuum filtration, then add 3.35 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles. The reaction schematic diagram is as Figure 2 shown.

[0068] 2. Film making

[0069] Add 1 kg of amino-terminated hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride into a high-speed mixer, mix evenly with the resin at a rotation speed of 2250 rpm, transport it through a pipeline to a die head, extrude and form, and then obtain a thermosetting polyimide film with a thickness of 19 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating.

[0070] 3. Coating

[0071] Thermoplastic polyamic acid resin is coated on both sides of the thermosetting polyimide film, and the temperature is increased in a programmed manner within the range of 150°C - 450°C to obtain a composite film with a total thickness of 25 μm, and the thickness of the adhesive layers on both sides is 3 μm respectively.

[0072] Example 4

[0073] A method for preparing a highly adhesive polyimide composite film, comprising the following steps:

[0074] The polymerization process is the same as that in Example 2.

[0075] 1 kg of amino-terminated hyperbranched polyamide grafted silica particles with a particle size of 3.2 μm, 19 kg of pyridine, and 22 kg of acetic anhydride are added to a high-speed mixer, and are mixed evenly with the thermosetting polyamic acid resin at a rotation speed of 2350 rpm to obtain a thermosetting polyamic acid precursor resin, which is simultaneously transported to a three-layer coextrusion die head with the thermoplastic polyamic acid resin, extruded and formed, and then obtained through processes such as 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 is 3 μm respectively.

[0076] Example 5

[0077] A method for preparing a highly adhesive polyimide composite film, comprising the following steps:

[0078] 1. Polymerization

[0079] 18.2 kg of BAPP, 8.9 kg of 3,4'-ODA, and 75.3 kg of 4,4'-diamino-3,3'-dimethylbiphenyl are dissolved in 800 kg of dimethylformamide, and 97.2 kg of PMDA is added in batches and reacted for 4 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1580 P.

[0080] 35.3 kg of BAPS, 10.7 kg of BAPP are dissolved in 420 kg of dimethylformamide, 16.9 kg of ODPA and 16.0 kg of BPDA are added in batches, and finally 0.23 kg of 3-aminoimidazole is added and reacted for 5.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 450 P.

[0081] 1 kg of amino-modified silica with a particle size of 2.8 μm and 2.2 kg of methyl acrylate are added to 10 kg of methanol, reacted at 50°C and then vacuum filtered, and then 3.35 kg of ethylenediamine is added and reacted in methanol and vacuum filtered to obtain amino-terminated hyperbranched polyamide grafted silica particles. The reaction schematic diagram is as Figure 2 shown.

[0082] 2. Film making

[0083] Add 0.4 kg of amino-terminated hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride into a high-speed mixer, mix evenly with the thermosetting polyamic acid resin at a rotation speed of 2550 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously transport it with the thermoplastic polyamic acid resin to a three-layer coextrusion die head, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the adhesive layers on both sides are 4 μm respectively.

[0084] Example 6

[0085] A method for preparing a high-adhesion polyimide composite film, comprising the following steps:

[0086] 1. Polymerization

[0087] Dissolve 10.2 kg of BAPS, 16.1 kg of BAPP, and 69.9 kg of 4,4'-diaminobenzophenone in 800 kg of dimethylformamide, add 69.4 of BPDA and 34.2 kg of PMDA in batches and react for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2030 P.

[0088] Dissolve 8.9 kg of BAPS and 33.7 kg of TPE-Q in 420 kg of dimethylformamide, add 15 kg of PMDA and 22.1 kg of BTDA in batches, and finally add 0.18 kg of 2-aminobenzimidazole and react for 5.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 620 P.

[0089] Add 1 kg of amino-modified silica with a particle size of 1.5 μm and 2.2 kg of methyl acrylate into 10 kg of methanol, react at 50 °C and then filter by vacuum filtration, then add 3.35 kg of ethylenediamine, react in methanol and filter by vacuum to obtain amino-terminated hyperbranched polyamide grafted silica particles.

[0090] 2. Film making

[0091] Add 0.2 kg of amino-terminated hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride into a high-speed mixer, mix evenly with the thermosetting polyamic acid resin at a rotation speed of 2550 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously transport it with the thermoplastic polyamic acid resin to a three-layer coextrusion die head, extrude and form, and then obtain a composite film with a total thickness of 20 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the adhesive layers on both sides are 3 μm respectively.

[0092] Example 7

[0093] A method for preparing a high-adhesion polyimide composite film, comprising the following steps:

[0094] 1. Polymerization

[0095] Dissolve 9.3 kg of TPE-M and 72.8 kg of 4,4'-diaminodiphenylmethane in 800 kg of dimethylacetamide, and add 117.8 of BPDA in batches for reaction for 7 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1730 P.

[0096] Dissolve 44.2 kg of TPE-M in 420 kg of dimethylacetamide, add 16.6 kg of PMDA, 14.2 kg of α-ODPA and 4.9 kg of BTDA in batches, and finally add 0.14 kg of 2-aminobenzimidazole for reaction for 4.7 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 520 P.

[0097] Add 1 kg of amino-modified silica with a particle size of 1 μm and 2.2 kg of methyl acrylate to 10 kg of methanol, react at 50 °C and then perform vacuum filtration, then add 3.35 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles. The reaction schematic diagram is as Figure 2 shown.

[0098] 2. Film formation

[0099] Add 0.14 kg of amino-terminated hyperbranched polyamide grafted silica particles, 19 kg of pyridine, and 22 kg of acetic anhydride to a high-speed mixer, mix evenly with the thermosetting polyamic acid resin at a rotation speed of 2650 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously transport it with the thermoplastic polyamic acid resin to a three-layer coextrusion die head, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thickness of the glue layers on both sides is 3 μm respectively.

[0100] Comparative Example 1

[0101] The difference from Example 1 is that 2-aminobenzimidazole is not added and amino-terminated hyperbranched polyamide grafted silica particles are not added, and the rest are the same as in Example 1.

[0102] Comparative Example 2

[0103] 1. Polymerization

[0104] Dissolve 85.8 kg of ODA in 800 kg of dimethylacetamide, add 47.1 kg of PMDA, 27.6 kg of BTDA and 37.8 kg of BPDA in batches for reaction for 6 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2030 P.

[0105] Dissolve 11.7 kg of ODA and 31.3 kg of TPE-R in 420 kg of dimethylacetamide. Add 36.5 kg of PMDA in batches, and finally add 0.48 kg of 2-aminoimidazole and react for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 580 P.

[0106] Add 1 kg of amino-modified silica with a particle size of 11.5 μm and 2.2 kg of methyl acrylate to 10 kg of methanol. After reacting at 50 °C, perform vacuum filtration. Then add 3.35 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles.

[0107] 2. Film preparation

[0108] Add 1.6 kg of amino-terminated hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride into a high-speed mixer, and mix evenly with the thermosetting polyamic acid resin at a rotation speed of 2250 rpm to obtain a thermosetting polyamic acid precursor resin. Simultaneously transport it with the thermoplastic polyamic acid resin to a three-layer coextrusion die head, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the two side adhesive layers are 3 μm respectively.

[0109] Comparative Example 3

[0110] 1. Polymerization

[0111] Dissolve 55.4 kg of m-PDA in 770 kg of dimethylacetamide. Add 56.3 kg of PMDA, 33 kg of BTDA, and 45.2 kg of BPDA in batches and react for 6.5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 2350 P.

[0112] Dissolve 10.7 kg of ODA and 30.7 kg of TPE-M in 420 kg of dimethylacetamide. Add 37.5 kg of PMDA in batches, and finally add 1.142 kg of 2-aminoimidazole and react for 4.5 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 580 P.

[0113] Add 1 kg of amino-modified silica with a particle size of 3.5 μm and 2.2 kg of methyl acrylate to 10 kg of methanol. After reacting at 50 °C, perform vacuum filtration. Then add 3.35 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles.

[0114] 2. Film preparation

[0115] Add 3 kg of amino-terminated hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride into a high-speed mixer, mix evenly with a thermosetting polyamic acid resin at a rotation speed of 2250 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously convey it to a three-layer coextrusion die head with a thermoplastic polyamic acid resin, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the adhesive layers on both sides are 3 μm respectively.

[0116] Comparative Example 4

[0117] 1. Polymerization

[0118] Dissolve 85.8 kg of ODA in 770 kg of dimethylacetamide, add 47.1 kg of PMDA, 27.6 kg of BTDA, and 37.8 kg of BPDA in batches and react for 5.8 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1750 P.

[0119] Dissolve 22.2 kg of ODA and 20.7 kg of BAPP in 420 kg of dimethylacetamide, add 36.7 kg of PMDA in batches, and finally add 0.419 kg of 2-aminoimidazole and react for 3 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 500 P.

[0120] Add 1 kg of amino-modified silica with a particle size of 3.5 μm and 2.2 kg of methyl acrylate into 10 kg of methanol, react at 50 °C and then perform vacuum filtration, and then add 3.35 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles.

[0121] 2. Film making

[0122] Add 1.6 kg of amino-terminated hyperbranched polyamide grafted silica particles, 18 kg of pyridine, and 21 kg of acetic anhydride into a high-speed mixer, mix evenly with a thermosetting polyamic acid resin at a rotation speed of 2030 rpm to obtain a thermosetting polyamic acid precursor resin, and simultaneously convey it to a three-layer coextrusion die head with a thermoplastic polyamic acid resin, extrude and form, and then obtain a composite film with a total thickness of 25 μm through processes such as casting, longitudinal and transverse stretching, and high-temperature heating. The thicknesses of the adhesive layers on both sides are 3 μm respectively.

[0123] Comparative Example 5

[0124] The difference from Example 1 is that no amino-terminated hyperbranched polyamide grafted silica particles are added, and the rest is the same as in Example 1.

[0125] Comparative Example 6

[0126] 1. Polymerization

[0127] Dissolve 31.7 kg of ODA and 36.4 kg of p-PDA in 800 kg of dimethylformamide, and add 54.4 kg of PMDA, 31.9 kg of BTDA, and 43.7 kg of BPDA in batches for reaction for 5 hours to obtain a thermosetting polyamic acid resin with a viscosity of 1850 P.

[0128] Dissolve 11.7 kg of ODA and 31.2 kg of TPE-R in 420 kg of dimethylformamide, add 36.4 kg of PMDA in batches, and finally add 0.48 kg of 2-aminoimidazole for reaction for 4 hours to obtain a thermoplastic polyamic acid resin with a viscosity of 550 P.

[0129] Add 1 kg of amino-modified silica with a particle size of 0.5 μm and 3.8 kg of methyl acrylate to 10 kg of methanol, react at 50 °C and then perform vacuum filtration. Then add 3 kg of ethylenediamine, react in methanol and perform vacuum filtration to obtain amino-terminated hyperbranched polyamide grafted silica particles.

[0130] The remaining steps are the same as those in Example 1.

[0131] Comparative Example 7

[0132] The difference from Example 1 is that 2-aminoimidazole is not added, and the rest is the same as in Example 1.

[0133] Performance detection

[0134] Use a microscope to detect the polyimide composite film prepared in Example 7, and its cross-section is as Figure 1 shown. The core layer is the thermosetting polyimide layer 1, and the two sides are the thermoplastic polyimide layer 2. The two intersect to form the interface layer 3, and amino-terminated hyperbranched polyamide grafted silica particles 4 are distributed inside.

[0135] Use a microscope to detect the polyimide composite films prepared in Comparative Example 1, Example 3, and Comparative Example 3, and the plane of the core layer film is as Figures 3 - 5 shown. In Comparative Example 1, amino-terminated hyperbranched polyamide grafted silica particles are not added. It can be obtained from Figure 3 that the surface of the core layer is smooth; Figure 4 is the plane of the layer film of the polyimide composite film in Example 3, Figure 5 is the plane of the layer film of the polyimide composite film in Comparative Example 3. As the addition amount of amino-terminated hyperbranched polyamide grafted silica particles increases, the surface of the core layer becomes significantly rougher, thereby increasing the contact area between the core layer and the adhesive layer and achieving the effect of improving the peel strength.

[0136] The polyimide films prepared in the above examples and comparative examples were tested for mechanical properties according to ASTM D882, the coefficient of linear thermal expansion was tested by the TMA method, and the glass transition temperature was tested by the DMA method (heating rate: 5 °C / min). They were respectively roll-pressed with 18-μm rolled copper foil according to the industrial method to form a two-layer type adhesive-free double-sided copper clad laminate, and the peel strength was tested according to IPC-TM-650. The results are shown in Table 1 below.

[0137] Table 1: Comprehensive properties of the polyimide films obtained in the examples and comparative examples

[0138]

[0139] When the peel strength of Comparative Example 6 was tested, the film fractured brittlely and no specific value could be obtained.

[0140] As can be seen from Table 1, compared with Example 1, in Comparative Example 1, the use of terminal amino hyperbranched polyamide grafted silica particles and 2-aminoimidazole was not used, resulting in a slight increase in the coefficient of thermal expansion (CTE) of the film and a significant decrease in the peel strength. In Comparative Example 2, the diamine in the thermosetting layer was all flexible ODA and 11.5-μm amino-modified silica was used, resulting in insufficient molecular chain rigidity and too large particle size of the silica particles, and the mechanical properties of the prepared polyimide film were significantly reduced, and the coefficient of thermal expansion (CTE) increased. In Comparative Example 3, the diamine in the thermosetting layer was all rigid PDA, with high molecular chain regularity and increased intermolecular force, which hindered the internal rotation and movement of the molecular chain, and too many silica particles were added, resulting in a sharp decrease in the flexibility of the film and unable to meet the application requirements. In Comparative Example 4, the thermosetting layer was all flexible ODA with too high a content, resulting in a decrease in the tensile strength of the film, poor dimensional stability, and too high a Tg of the thermoplastic layer and poor peel force. In Comparative Example 5, the terminal amino hyperbranched polyamide grafted silica particles were not used, the coefficient of thermal expansion of the film increased, and the peel strength decreased sharply. In Comparative Example 6, the amounts of methyl acrylate and ethylenediamine were large, with excessive hyperbranching and too many amino groups on the surface of the silica particles, resulting in excessive crosslinking of PI, a significant decrease in the elongation of the film, and easy brittle fracture during processing and application. In Comparative Example 7, 2-aminoimidazole was not used in the thermoplastic layer, resulting in a decrease in the peel strength of the film.

[0141] As can be seen from the above, introducing a monoamine containing an imidazole structure and terminal amino hyperbranched polyamide grafted silica particles into the structure of the polyimide composite film in the present invention can significantly improve the properties such as the adhesiveness, dimensional stability, and heat resistance of the film, while maintaining a relatively low glass transition temperature, meeting the processing and application requirements of materials such as two-layer FCCL.

[0142] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is limited only to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A highly adhesive polyimide composite film that can be used for a flexible copper-clad laminate, the polyimide composite film comprising a thermosetting polyimide support layer and a thermoplastic polyimide adhesive layer disposed on at least one side of the thermosetting polyimide support layer, characterized in that: An interface layer formed by the reaction of amino-terminated hyperbranched polyamide grafted silica particles and thermosetting polyamic acid is embedded between the thermosetting polyimide support layer and the thermoplastic polyimide bonding layer; The thermosetting polyamic acid is prepared by reacting a flexible aromatic diamine and a rigid aromatic diamine with an aromatic dianhydride, and the end group of the thermoplastic polyimide contains an imidazole ring which can form a complex with copper.

2. The high-adhesive polyimide composite film according to claim 1, characterized in that: The interface layer is formed by dispersing the amino-terminated hyperbranched polyamide grafted silica particles in a chemical casting reagent, mixing the particles with a thermosetting polyamide acid resin, and then performing a polymerization reaction to obtain the interface layer.

3. The high-adhesive polyimide composite film according to claim 1, characterized in that: The molar ratio of the flexible aromatic diamine to the rigid aromatic diamine is 5-35:65-95.

4. The method for preparing a highly adhesive polyimide composite film according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, polycondensing a flexible aromatic diamine, a rigid aromatic diamine and an aromatic dianhydride to generate a polyamic acid resin A; S2, reacting the surface-aminated silica with methyl acrylate or its homologues, and then reacting with aliphatic diamine or its homologues to obtain amino-terminated hyperbranched polyamide grafted silica particles, and finally dispersing the silica particles in a chemical casting reagent, and quickly mixing the silica particles with the polyamide acid resin A prepared in step S1 to obtain a mixed solution; the mass ratio of the surface-aminated silica, acrylate and aliphatic diamine is 1:1-3:0.7-4; S3, polycondensing the diamine, the dianhydride and the monoamine to generate a polyamic acid resin B; S4, using the mixed solution in step S2 as a thermosetting polyimide support layer and the polyamic acid resin B prepared in step S3 as a thermoplastic polyimide adhesive layer, and preparing a polyimide composite film through a film-forming process.

5. The method for preparing a highly adhesive polyimide composite film according to claim 4, characterized in that: In step S2, the amount of the amino-terminated hyperbranched polyamide grafted silica particles added is 0.05%-1% of the mass of the thermosetting polyimide, and the particle size of the amino-terminated hyperbranched polyamide grafted silica particles is 0.1-10 μm.

6. The method for preparing a highly adhesive polyimide composite film according to claim 4, characterized in that: In step S2, the chemical casting reagents are composed of a catalyst, a dehydrating agent and an organic solvent; the catalyst is selected from one or more of pyridine and its derivatives, quinoline, isoquinoline and triethylamine, and the amount of the catalyst is 1-5% of the mass of the polyamic acid resin A; the dehydrating agent is selected from one or more of acetic anhydride, propionic anhydride and benzoic anhydride, and the amount of the dehydrating agent is 15-35% of the mass of the polyamic acid resin A.

7. The method for preparing a highly adhesive polyimide composite film according to claim 4, characterized in that: In step S1, the polyamic acid resin A is prepared by polycondensation of flexible aromatic diamine, rigid aromatic diamine and aromatic dianhydride; the molar ratio of the sum of the molar amounts of the flexible aromatic diamine and the rigid aromatic diamine to the molar amount of the aromatic dianhydride is 100:100.05-100.

5.

8. The method for preparing a highly adhesive polyimide composite film for a flexible copper-clad laminate according to claim 4, characterized in that: In step S3, the monoamine is a monoamine containing an imidazole structure.

9. The method for preparing a highly adhesive polyimide composite film for a flexible copper-clad laminate according to claim 8, characterized in that: The monoamine containing imidazole structure is selected from one or more of 2-aminoimidazole, 4-aminoimidazole, 5-amino-4-imidazolecarboxamide and 2-aminobenzimidazole; the molar ratio of the diamine, dianhydride and monoamine containing imidazole structure is 98-99.5:100:0.5-4.

10. The method for preparing a highly adhesive polyimide composite film according to claim 4, characterized in that: In step S3: The diamine is selected from one or more 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 dianhydride is selected from one or more of pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride and 2,3,3',4'-diphenyl ether tetracarboxylic dianhydride.

11. A two-layer flexible copper-clad laminate, comprising a copper foil layer and a polyimide layer, characterized in that: The polyimide layer is a highly adhesive polyimide composite film according to any one of claims 1 to 3.

Images