A transparent polyimide flexible copper clad plate and a preparation method thereof

Abstract

The application discloses a kind of transparent polyimide flexible copper-clad plate and preparation method thereof, belong to electronic chemical technology field.The preparation method of the transparent polyimide flexible copper-clad plate, including the following steps: after organic solvent, filler is ground and dispersed uniformly, monomer diamino diphenyl ether and monomer 1, 3- (4-aminophenoxy) benzene are dissolved to obtain mixed solution;Monomer bisphenol A type diether dianhydride and monomer hexafluorodinitrile dianhydride are added to mixed solution and polymerization reaction occurs, until the viscosity of reaction system is 4-5 million mpa.s, and polyamide acid precursor is prepared;Polyamide acid precursor is coated on copper foil, and transparent polyimide flexible copper-clad plate is obtained by drying under protective gas atmosphere.The polyimide flexible copper-clad plate prepared by the application not only has high light transmittance, but also has high peel strength, tin soldering resistance, etc., and can meet the processing technology requirements of electronic products.

Description

Technical Field

[0001] This invention relates to the field of electronic chemicals technology, and more specifically to a transparent polyimide flexible copper-clad laminate and its preparation method. Background Technology

[0002] With the advancement of technology, higher demands are being placed on consumer electronics. Beyond traditional features like fast processing speed and slim design, transparency has become a crucial element, continuing to influence product design and market development. According to an IDTechEx report, the transparent electronics industry is projected to exceed $20 billion by around 2040. This trend indicates a clearer development trajectory for the transparent electronics industry. The development of transparent electronics technology brings new opportunities and challenges to consumer electronics. With technological advancements and market demand, the transparent electronics industry is expected to remain a dynamic and high-potential market, bringing more innovation to people's lives and work in the future. Transparent polyimide flexible copper-clad laminates (CCLs) are the substrate for the circuitry of these transparent electronic products and are essential raw materials for the production of transparent flexible circuit boards. The purpose of developing transparent flexible CCLs is to provide a foundation for downstream companies to produce colorless transparent circuit boards. Currently, most flexible circuit boards are golden yellow, which cannot meet the needs of colorless transparent electronic products. Some technologies can produce colorless transparent CCLs but do not meet the process requirements for manufacturing flexible electronic products, for example:

[0003] Chinese patent CN115648760A discloses a method for preparing a transparent copper-clad laminate, which uses a transparent epoxy prepreg to coat copper foil and hot-press it to form a rigid transparent copper-clad laminate.

[0004] Chinese patent CN114133865A describes a copper-clad laminate containing transparent resin. The transparent copper-clad laminate is prepared using saturated polyester resin and polyvinyl acetal resin as the main components. The obvious disadvantages of this transparent copper-clad laminate are its poor heat resistance and poor bending resistance, which cannot meet the manufacturing process of modern electronic circuits and cannot produce the transparent circuit boards required for widely used transparent electronic products.

[0005] Chinese patent CN111556644B describes a flexible and stretchable transparent copper-clad laminate. This laminate uses materials such as PE and PVC as base films and adheres them to a metal layer to prepare a transparent copper-clad laminate. However, due to the large thermal expansion coefficients of PE and PVC and their incompatibility with the copper foil and other metal layers, severe deformation problems occur during the circuit board manufacturing process. Therefore, it can only be used in certain small categories of products and cannot be widely applied.

[0006] Therefore, it is necessary to develop a flexible copper-clad laminate that can meet the requirements of electronic product processing technology and is colorless and transparent. Summary of the Invention

[0007] To address the above problems, this invention provides a transparent polyimide flexible copper-clad laminate and its preparation method. This polyimide flexible copper-clad laminate not only has high light transmittance, but also high peel strength and solderability, which can meet the requirements of electronic product processing technology.

[0008] The first objective of this invention is to provide a method for preparing a transparent polyimide flexible copper-clad laminate, comprising the following steps:

[0009] After grinding and dispersing the organic solvent and filler evenly, add monomers diaminodiphenyl ether and 1,3-bis(4-aminophenoxy)benzene to dissolve and obtain a mixture.

[0010] The monomers bisphenol A diether dianhydride and hexafluorodianhydride were added to a mixed solution to initiate a polymerization reaction until the viscosity of the reaction system reached 40,000-50,000 mPa·s, thus preparing a polyamic acid precursor.

[0011] A polyamic acid precursor is coated onto a copper foil and dried under a protective gas atmosphere to obtain a transparent polyimide flexible copper-clad laminate.

[0012] In one embodiment of the present invention, the filler is silicon dioxide.

[0013] In one embodiment of the present invention, the dispersion time is 24-40 hours.

[0014] In one embodiment of the present invention, during the preparation of the polyamic acid precursor, the mass ratio of the monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 1.7065–3.1229:1.7770–2.2212:1.0012–1.4016:0.8770–1.4617.

[0015] The mass ratio of monomeric diaminodiphenyl ether, filler and organic solvent is 1.7065~3.1229:0.0073~0.0359:610.56-675.1.

[0016] In one embodiment of the present invention, during the preparation of the polyamic acid precursor, the mass ratio of the monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 2.1947:1.9547:1.2014:1.1693.

[0017] The mass ratio of monomeric diaminodiphenyl ether, filler and organic solvent is 2.1947:0.0227:645.10.

[0018] In one embodiment of the present invention, the thickness of the polyamic acid precursor after drying is 15-22 μm.

[0019] In one embodiment of the present invention, the organic solvent comprises dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

[0020] In one embodiment of the present invention, the reaction temperature of the polymerization reaction is 0-5°C.

[0021] A second objective of this invention is to provide a transparent polyimide flexible copper-clad laminate prepared by the above-described preparation method.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] In preparing transparent polyimide flexible copper-clad laminates, this invention first uses bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene monomers, with a small amount of solid filler, to prepare a polyamic acid solution via in-situ copolymerization. This solution is then uniformly coated onto the surface of electronic copper foil and, under nitrogen protection, undergoes hot-press imidization to prepare the transparent polyimide flexible copper-clad laminate. During the preparation process, the addition of these four monomers—hexafluorodianhydride, bisphenol A type diether dianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene—improves the transparency, peel strength, and flexibility of the copper-clad laminate. The addition of filler not only improves the flatness of the copper-clad laminate but also enhances the adhesion between the film and the copper foil.

[0024] The transparent flexible polyimide copper-clad laminate prepared by this invention has a light transmittance of over 85% after etching away the copper foil layer. The peel strength between the transparent polyimide layer and the copper foil exceeds 1.0 N / mm. The sample can withstand up to 5000 bending cycles and can pass the reflow soldering process at 310℃. The transparent flexible polyimide copper-clad laminate prepared by this invention not only meets the processing conditions of electronic products but also has high light transmittance, meeting the needs of colorless and transparent electronic products. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] The development of transparent flexible copper-clad laminates is a technology for downstream companies to produce colorless and transparent circuit boards. However, most existing flexible circuit boards are golden yellow, which cannot meet the needs of colorless and transparent electronic products. Furthermore, the preparation of some colorless and transparent copper-clad laminates cannot meet the process requirements for producing flexible electronic products. Based on this, this invention develops a flexible copper-clad laminate that can both meet the requirements of electronic product processing technology and achieve colorless transparency.

[0027] This invention provides a method for preparing a transparent polyimide flexible copper-clad laminate, comprising the following steps:

[0028] Step 1: After grinding and dispersing the organic solvent and filler evenly, add the monomer diaminodiphenyl ether and the monomer 1,3-bis(4-aminophenoxy)benzene to dissolve and obtain a mixed solution;

[0029] When used on flexible circuit boards, the dimensional stability of the film is critical, requiring the film and copper foil to match in terms of temperature changes. The coefficient of thermal expansion is a crucial parameter for assessing film dimensional stability. In this invention, the addition of fillers can adjust the coefficient of thermal expansion to match that of the copper foil, reducing thermal deformation. Furthermore, fillers can reduce the film's cohesion, thereby improving adhesion to the copper foil.

[0030] Step 2: Add bisphenol A type diether dianhydride and hexafluorodianhydride monomers to the mixed solution to carry out a polymerization reaction until the viscosity of the reaction system is 40,000-50,000 mPa·s to prepare a polyamic acid precursor; after the polyamic acid precursor is tested and confirmed to be qualified, it is coated on copper foil.

[0031] In this step, when the viscosity of the reaction system is below this range, the molecular weight of the product is small, the prepared product is brittle and soft, and it is difficult to use for copper-clad laminates. Its tensile strength and tear resistance are low. When it is above this range, the synthesis reaction is very difficult to control, and the requirements for the purity of raw materials are particularly high. Therefore, it is more appropriate to control the viscosity to this range under the premise of meeting the usage conditions.

[0032] Step 3: Coat the polyamic acid precursor onto copper foil, and heat and bake it under a protective gas atmosphere to dehydrate and imidize it, thereby obtaining a transparent polyimide flexible copper-clad laminate.

[0033] In this step, the polyamic acid precursor is coated onto copper foil, and then heated using an inert gas. The inert gas protects the copper foil from oxidation at high temperatures. Under high temperature conditions, the polyamic acid precursor loses one molecule of water to become polyimide, resulting in a transparent polyimide flexible copper-clad laminate.

[0034] The structure of the polyamic acid precursor after curing is shown below:

[0035]

[0036] In a preferred embodiment of the present invention, during the preparation of the polyamic acid precursor, the mass ratio of the monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 1.7065–3.1229:1.7770–2.2212:1.0012–1.4016:0.8770–1.4617.

[0037] The mass ratio of monomeric diaminodiphenyl ether, filler and organic solvent is 1.7065~3.1229:0.0073~0.0359:610.56-675.1.

[0038] In the specific preparation process of this invention, the mass proportions of each raw material are as follows: 2.6024–3.1229 parts of monomer bisphenol A type diether dianhydride, 1.7770–2.2212 parts of monomer hexafluorodianhydride, 1.0012–1.4016 parts of monomer diaminodiphenyl ether, 0.8770–1.4617 parts of monomer 1,3-bis(4-aminophenoxy)benzene, 0.0073–0.0359 parts of filler, and 0.56–675.1 parts of solvent. It should be noted that during the preparation process, the amount of each component (1 part) is determined according to the required weighing quantity for production. One part can represent 1g, 10g, 500g, 1kg, 10kg, or 50kg, etc., and this invention does not impose any limitations on this.

[0039] Increasing the amount of hexafluorodianhydride monomer does not improve strength but can improve transparency. Increasing the amount of bisphenol A type diether dianhydride monomer can improve peel strength. Increasing the amount of diaminodiphenyl ether monomer can increase the glass transition temperature, improve heat resistance, and thus improve the performance of copper clad laminate.

[0040] In a preferred embodiment of the present invention, during the preparation of the polyamic acid precursor, the mass ratio of the monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 2.1947:1.9547:1.2014:1.1693.

[0041] The mass ratio of monomeric diaminodiphenyl ether, filler and organic solvent is 2.1947:0.0227:645.10.

[0042] The structural formula of the monomer diaminodiphenyl ether (ODA) used in this invention is shown below:

[0043]

[0044] The structural formula of the monomer hexafluorodianhydride (6FDA) used in this invention is shown below:

[0045]

[0046] The structural formula of the monomer bisphenol A type diether dianhydride (BPADA) used in this invention is shown below:

[0047]

[0048] The structural formula of the monomer 1,3-bis(4-aminophenoxy)benzene (TPER) used in this invention is shown below:

[0049]

[0050] In a preferred embodiment of the present invention, the filler is silica. Fumed silica has a suitable particle size, small agglomeration, and good transparency, while other fillers agglomerate and are difficult to control. Therefore, the present invention selects fumed silica ED30.

[0051] In a preferred embodiment of the present invention, the organic solvent is a mixture of dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide. The amount of solvent components used is related to the solvent properties; different proportions of the mixed solvents affect the azeotropic point of the mixture. Especially in the preparation process of encapsulation films, it is desirable to lower the boiling point of the mixture to facilitate control of the volatile content of the product. Therefore, the amount of low-boiling-point solvent is appropriately increased. Meanwhile, high-boiling-point NMP has a high solubility for the polymer; adding an appropriate amount of NMP is beneficial to improving the solubility of the polymer.

[0052] In a preferred embodiment of the present invention, the dispersion time is 24-40 hours, for example, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, or 40 hours, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. A short dispersion time easily leads to undispersed small agglomerates, while a long dispersion time affects production efficiency.

[0053] In a preferred embodiment of the present invention, the polymerization reaction temperature is 0-5°C. For example, the reaction temperature can be 0°C, 1°C, 2°C, 3°C, 4°C, or 5°C, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. During the reaction, the reaction temperature is controlled between 0-5°C, generally controlled at 0°C. The reaction temperature may rise to 3°C, as long as it remains within the 0-5°C range.

[0054] In a preferred embodiment of the present invention, the thickness of the polyamic acid precursor after drying is 15-22 μm. During the preparation process, the thickness of the polyamic acid precursor can be within the range of 15-22 μm.

[0055] The transparent polyimide flexible copper-clad laminate prepared by this invention can be applied to consumer transparent electronic products such as smart bracelets, transparent connecting cables, transparent displays, and transparent communication terminal equipment.

[0056] The present invention will be further described in detail below with reference to specific embodiments. In the following embodiments, the amounts of each component involved in the preparation process of the polyamic acid precursor are as shown in Appendix 1, and the unit of component amount is kg.

[0057] Table 1 Formulation of Transparent Polyimide Adhesive

[0058]

[0059]

[0060] Example 1

[0061] Referring to the formulation of Example 1 in Table 1, an organic solvent consisting of 432.81 kg DMAc, 108.20 kg DMF, and 108.20 kg NMP and 0.0073 kg ED30 were added to a reactor and ground and dispersed for 24 hours. Then, 1.0012 kg monomer ODA and 1.4617 kg monomer TPER were added and heated appropriately to 80°C to dissolve them. After the reaction solution was homogeneous, the temperature was lowered to 0-5°C, and 2.6024 kg monomer BPADA and 2.2212 kg monomer 6FDA were added in three batches, with an interval of 1 hour between each addition. The mixture was stirred at a constant speed for 12 hours, and the viscosity of the reaction solution was tested. It was about 15,000 mPa·s. The reaction was then stirred until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0062] The polyimide resin precursor prepared above was coated onto electronic copper foil using an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃, with a travel speed of 10m / min. After removing gas and controlling the drying process, the resin thickness was 15-22μm. After winding, the resin was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5 hours; 100℃ for 5 hours; 120℃ for 3 hours; 150℃ for 3 hours; 200℃ for 2 hours; 300℃ for 2 hours; 350℃ for 2 hours; and 380℃ for 2 hours. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained. Samples were taken for performance testing, and the test results are shown in Table 2.

[0063] Example 2

[0064] Referring to the formulation of Example 1 in Table 1, an organic solvent consisting of 359.15 kg DMAc, 107.75 kg DMF, and 143.66 kg NMP and 0.0145 kg ED30 were added to a reactor and ground and dispersed for 24 h. Then, 1.7065 kg monomer BPADA and 2.1324 kg monomer 6FDA were added and heated appropriately to dissolve them. After the reaction solution was homogeneous, it was cooled to 0°C, and 1.1013 kg monomer ODA and 1.3155 kg monomer TPER were added in three batches, with an interval of 1 h between each addition. The mixture was stirred at a constant speed for 12 h, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued to be stirred until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0065] The polyimide resin precursor prepared above was coated onto electronic copper foil using an air-float coating machine. The oven temperature was controlled at 70℃~150℃, and the speed at 8~10m / min. After degassing and controlled drying, the resin thickness was 15-22μm. After winding, it was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5h; 100℃ for 5h; 120℃ for 3h; 150℃ for 3h; 200℃ for 2h; 300℃ for 2h; 350℃ for 2h; 380℃ for 2h. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained. Samples were taken for performance testing, and the test results are shown in Table 2.

[0066] Example 3

[0067] Referring to the formulation of Example 1 in Table 1, an organic solvent consisting of 322.55 kg DMAc, 107.52 kg DMF, and 215.03 kg NMP and 0.0227 kg ED30 were added to a reactor and ground and dispersed for 24 h. Then, 2.9147 kg of monomer BPADA and 1.9547 kg of monomer 6FDA were added and heated appropriately to dissolve them. After the reaction solution was homogeneous, it was cooled to 0°C, and 1.2014 kg of monomer ODA and 1.1693 kg of monomer TPER were added in three batches, with an interval of 1 h between each addition. The mixture was stirred at a constant speed for 12 h, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued to be stirred until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0068] The polyimide resin precursor prepared above was coated onto electronic copper foil using an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃, with a travel speed of 10m / min. After removing gas and controlling the drying process, the resin thickness was 15-22μm. After winding, the resin was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5 hours; 100℃ for 5 hours; 120℃ for 3 hours; 150℃ for 3 hours; 200℃ for 2 hours; 300℃ for 2 hours; 350℃ for 2 hours; and 380℃ for 2 hours. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained. Samples were taken for performance testing, and the test results are shown in Table 2.

[0069] Example 4

[0070] Referring to the formulation of Example 1 in Table 1, an organic solvent consisting of 285.49 kg DMAc, 107.06 kg DMF, and 249.80 kg NMP and 0.0288 kg ED30 were added to a reactor and ground and dispersed for 24 h. Then, 3.0188 kg monomer BPADA and 1.8658 kg monomer 6FDA were added and heated appropriately to dissolve them. After the reaction solution was homogeneous, it was cooled to 0°C, and 1.3015 kg monomer ODA and 1.0232 kg monomer TPER were added in three batches, with an interval of 1 h between each addition. The mixture was stirred at a constant speed for 12 h, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0071] The polyimide resin precursor prepared above was coated onto electronic copper foil using an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃, with a travel speed of 10m / min. After removing gas and controlling the drying process, the resin thickness was 15-22μm. After winding, the resin was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5 hours; 100℃ for 5 hours; 120℃ for 3 hours; 150℃ for 3 hours; 200℃ for 2 hours; 300℃ for 2 hours; 350℃ for 2 hours; and 380℃ for 2 hours. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained. Samples were taken for performance testing, and the test results are shown in Table 2.

[0072] Example 5

[0073] Referring to the formulation of Example 1 in Table 1, an organic solvent consisting of 284.275 kg DMAc, 142.13 kg DMF, and 248.74 kg NMP and 0.0359 kg ED30 were added to a reactor and ground and dispersed for 24 hours. Then, 3.1229 kg of monomer BPADA and 1.7770 kg of monomer 6FDA were added and heated appropriately to dissolve them. After the reaction solution was homogeneous, it was cooled to 0°C, and 1.4016 kg of monomer ODA and 0.8770 kg of monomer TPER were added in three batches, with an interval of 1 hour between each addition. The mixture was stirred at a constant speed for 12 hours, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0074] The polyimide resin precursor prepared above was coated onto electronic copper foil using an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃, with a travel speed of 10m / min. After removing gas and controlling the drying process, the resin thickness was 15-22μm. After winding, the resin was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5 hours; 100℃ for 5 hours; 120℃ for 3 hours; 150℃ for 3 hours; 200℃ for 2 hours; 300℃ for 2 hours; 350℃ for 2 hours; and 380℃ for 2 hours. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained. Samples were taken for performance testing, and the test results are shown in Table 2.

[0075] Example 6

[0076] An organic solvent consisting of 356.33 kg DMAc, 108.21 kg DMF, and 199.34 kg NMP, along with 0.0176 kg ED30, was added to a reactor and ground and dispersed for 40 hours. Then, 2.1883 kg of monomer BPADA and 2.2136 kg of monomer 6FDA were added, and the mixture was heated appropriately to dissolve them. After the reaction solution became homogeneous, the temperature was lowered to 5°C, and 1.1894 kg of monomer ODA and 0.9782 kg of monomer TPER were added in three batches, with an interval of 1 hour between each addition. The mixture was stirred at a constant speed for 12 hours, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0077] The polyimide resin precursor prepared above was coated onto electronic copper foil on an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃. The travel speed was controlled at 10m / min. After removing the gas, the resin thickness after drying was controlled to be 15-22μm. After winding, it was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5h; 100℃ for 5h; 120℃ for 3h; 150℃ for 3h; 200℃ for 2h; 300℃ for 2h; 350℃ for 2h; 380℃ for 2h. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained.

[0078] Example 7

[0079] An organic solvent consisting of 300.81 kg DMAc, 128.34 kg DMF, and 187.33 kg NMP, along with 0.0279 kg ED30, was added to a reactor and ground and dispersed for 30 hours. Then, 2.7451 kg of monomer BPADA and 1.9347 kg of monomer 6FDA were added, and the mixture was heated appropriately to dissolve them. After the reaction solution became homogeneous, the temperature was lowered to 3°C, and 1.2097 kg of monomer ODA and 1.3083 kg of monomer TPER were added in three batches, with an interval of 1 hour between each addition. The mixture was stirred at a constant speed for 12 hours, and the viscosity of the reaction solution was tested at 15,000 mPa·s. The reaction was then continued until the viscosity reached 40,000-50,000 mPa·s, at which point the synthesis was stopped, thus preparing the polyamic acid precursor.

[0080] The polyimide resin precursor prepared above was coated onto electronic copper foil on an air-float coating machine. The temperature of the first drying tunnel was controlled at 80℃, the second at 100℃, the third at 120℃, the fourth and fifth at 150℃, and the sixth at 120℃. The travel speed was controlled at 10m / min. After removing the gas, the resin thickness after drying was controlled to be 15-22μm. After winding, it was placed in a nitrogen-filled oven for staged heating. The heating program was as follows: 80℃ for 5h; 100℃ for 5h; 120℃ for 3h; 150℃ for 3h; 200℃ for 2h; 300℃ for 2h; 350℃ for 2h; 380℃ for 2h. After natural cooling, a transparent polyimide flexible copper-clad laminate was obtained.

[0081] Table 2 Performance Test Table for Transparent Polyimide Flexible Copper Clad Laminates

[0082]

[0083] As shown in Table 2, the transparent polyimide flexible copper-clad laminates prepared by this invention all exhibit excellent performance, with light transmittance ranging from 85.32% to 87.21%, indicating good transparency. Meanwhile, with increasing filler content, the peel strength of the transparent polyimide flexible copper-clad laminates initially increases and then decreases.

[0084] The purpose of adding fillers in this invention is as follows: (1) Adding fillers can reduce the coefficient of thermal expansion of the film, thereby improving the flatness of the copper clad laminate; (2) Reduce the cohesion of the film, thereby improving the adhesion between the film and the copper foil. However, excessive fillers will also reduce the adhesion and reduce the transparency of the film.

[0085] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0086] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a transparent polyimide flexible copper-clad laminate, characterized in that, Includes the following steps: After grinding and dispersing the organic solvent and filler evenly, the monomers diaminodiphenyl ether and 1,3-bis(4-aminophenoxy)benzene were added and dissolved to obtain a mixture. The monomers bisphenol A diether dianhydride and hexafluorodianhydride were added to the mixture to carry out a polymerization reaction until the viscosity of the reaction system reached 40,000-50,000 mPa·s, thus preparing a polyamic acid precursor. A polyamic acid precursor is coated onto a copper foil and dried under a protective gas atmosphere to obtain a transparent polyimide flexible copper-clad laminate. The mass ratio of monomeric diaminodiphenyl ether, filler, and organic solvent is 1.7065~3.1229:0.0073~0.0359:610.56-675.1; The mass ratio of the monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 1.7065~3.1229:1.7770~2.2212:1.0012~1.4016:0.8770~1.4617. The reaction temperature for polymerization is 0-5℃; The filler is silicon dioxide.

2. The method for preparing a transparent polyimide flexible copper-clad laminate according to claim 1, characterized in that, The dispersion time is 24-40 hours.

3. The method for preparing a transparent polyimide flexible copper-clad laminate according to claim 1, characterized in that, In the preparation of polyamic acid precursor, the mass ratio of monomers bisphenol A type diether dianhydride, hexafluorodianhydride, diaminodiphenyl ether, and 1,3-bis(4-aminophenoxy)benzene is 2.1947:1.9547:1.2014:1.1693. The mass ratio of monomeric diaminodiphenyl ether, filler and organic solvent is 2.1947:0.0227:645.

10.

4. The method for preparing a transparent polyimide flexible copper-clad laminate according to claim 1, characterized in that, After drying, the thickness of the polyamic acid precursor is 15-22 μm.

5. The method for preparing a transparent polyimide flexible copper-clad laminate according to claim 1, characterized in that, Organic solvents include dimethylacetamide, N-methylpyrrolidone, and N,N-dimethylformamide.

6. A transparent polyimide flexible copper-clad laminate prepared by the preparation method according to any one of claims 1-5.

Images