Composite membrane

Abstract

To provide a composite film that combines high modulus of elasticity and high elongation. [Solution] The present invention provides a composite film comprising a first polyimide layer and a second polyimide layer, wherein the first polyimide layer comprises a first polyimide obtained by polymerizing an acid anhydride containing pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and a diamine containing 4,4'-diaminodiphenyl ether (ODA) and paraphenylenediamine (PDA), and the second polyimide layer is formed on at least one side of the first polyimide layer and comprises a second polyimide obtained by polymerizing an acid anhydride and a diamine containing 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP). As a result, the composite film has an elongation of more than 50%, an elastic modulus of more than 5 Gpa, and a glass transition temperature of more than 350°C.

Description

[Technical Field]

[0001] The present invention relates to a composite membrane for being manufactured together with a flexible metal layer substrate, and particularly relates to a polyimide composite membrane that can be directly compression-bonded to metal and has characteristics of high elastic modulus and high elongation percentage. [Background Art]

[0002] Polyimide has excellent thermal stability, excellent mechanical strength and flexibility, excellent electrical insulation performance, chemical resistance and good operability in post-processing, and has always been the first-choice material for flexible copper-clad substrates. Currently, thermoplastic polyimide that has dimensional stability meeting the demand for flexible boards in the industry and good adhesion to copper foil has already been developed and is widely applied in the flexible circuit board industry.

[0003] Conventional thermoplastic polyimide mainly has a low coefficient of linear expansion and high dimensional stability, and can achieve good adhesion to copper foil. In addition to this, to further improve heat resistance and processing stability, flexible circuit boards are further required to have characteristics of good flexibility, high elongation percentage and high elastic modulus. For flexible circuit boards designed to be thin, when polyimide has both high elastic modulus and high elongation percentage, the thinned flexible circuit board can have processing stability while maintaining good flexibility. However, high elastic modulus and high elongation percentage are often contradictory in structural design. To achieve high elastic modulus, it is necessary to use a formulation that makes the product hard, while to achieve high elongation percentage, a formulation that makes the product soft is usually used. [Summary of the Invention]

[0004] The present invention designs a composite membrane that combines high elastic modulus and high elongation percentage, and can simultaneously retain the excellent properties of both after a thinning design.

[0005] The present invention relates to a composite film comprising a first polyimide layer and a second polyimide layer, wherein the first polyimide layer comprises a first polyimide obtained by polymerizing a first acid anhydride and a first diamine, the first acid anhydride comprises pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) to the total moles of the first acid anhydride is 60-83%, the first diamine comprises 4,4'-diaminodiphenyl ether (ODA) and paraphenylenediamine (PDA), the percentage of moles of paraphenylenediamine (PDA) to the total moles of the first diamine is 65-85%, and the pyromellitic anhydride (PMDA) and the 4,4'-diaminodiphenyl ether (ODA) The copolymer segment accounts for 15% to 30% of the moles of the first polyimide, the second polyimide layer is formed on at least one side of the first polyimide layer and includes a second polyimide obtained by polymerizing a second acid anhydride and a second diamine, the second acid anhydride includes at least 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic anhydride (PMDA), the second diamine includes 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the total moles of the second acid anhydride is 18% to 22%, and the copolymer segment of BPDA and BAPP accounts for 10% to 17% of the moles of the second polyimide, forming a composite film. As a result, the composite film has an elongation rate greater than 50%, an elastic modulus greater than 5 Gpa, and a glass transition temperature greater than 350°C.

[0006] The composite film described above has a total thickness of 10 to 60 μm, and the thickness ratio of the first polyimide layer to the second polyimide layer (support layer / adhesive layer) is 3.6 to 6.3. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of the composite film according to the present invention. [Modes for carrying out the invention]

[0008] Please refer to Figure 1. The present invention is a composite film comprising a first polyimide layer 10 and a second polyimide layer 11.

[0009] The first polyimide layer 10 comprises a first polyimide obtained by polymerizing a first acid anhydride and a first diamine, wherein the first acid anhydride comprises pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the total moles of the first acid anhydride is 60-83%, more preferably 65-75%, and the first diamine is 4,4'-diamine The polyimide comprises minodiphenyl ether (ODA) and paraphenylenediamine (PDA), wherein the percentage of the number of moles of paraphenylenediamine (PDA) relative to the total number of moles of the first diamine is 65-85%, more preferably 65-75%, and the proportion of the copolymer segment of pyromellitic anhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) relative to the number of moles of the first polyimide is 15-30%, more preferably 23-30%.

[0010] The second polyimide layer 11 is formed on at least one side of the first polyimide layer and includes a second polyimide obtained by polymerizing a second acid anhydride and a second diamine, wherein the second acid anhydride includes at least 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic anhydride (PMDA), and the second diamine includes 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) to the total number of moles of the second acid anhydride is 18-22%, more preferably 18-20%, and the proportion of the copolymer segment of BPDA and BAPP to the number of moles of the second polyimide is 10-17%, more preferably 10-15%.

[0011] The method for producing the first polyimide layer 10 involves polymerizing pyromellitic anhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) in a first copolymer segment, wherein the molar ratio of pyromellitic anhydride (PMDA) to 4,4'-diaminodiphenyl ether (ODA) in the first copolymer segment is 0.9 to 0.99, and the molar ratio of the first copolymer segment of pyromellitic anhydride (PMDA) and 4,4'-diaminodiphenyl ether (ODA) to the molars of the first polyimide is The proportion is 15% to 30%, and after the polymerization of the first copolymer segment is completed, paraphenylenediamine (PDA) is added to copolymerize with pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the moles of the first acid anhydride is 60 to 85%, more preferably 65 to 75%, and finally the precursor of the first polyimide layer 10 is completed.

[0012] The method for producing the second polyimide layer 11 involves polymerizing a second copolymer segment using 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP). The molar ratio of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) to 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) in the second copolymer segment is 0.85 to 0.99, and the proportion of the moles of the second copolymer segment of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) to the moles of the second polyimide is 10% to 17%, and the polymerization of the second copolymer segment is completed. Subsequently, a second acid anhydride and a second diamine are added and polymerized. The second acid anhydride comprises at least 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and pyromellitic acid anhydride (PMDA), and the second diamine comprises 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP). The percentage of moles of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) relative to the total number of moles of the second acid anhydride is 18-22%, and the proportion of the copolymer segment of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP) relative to the total number of moles of polyimide is 10-17%, finally completing the precursor of the second polyimide layer 11.

[0013] As a method for producing the composite film, a precursor of the first polyimide layer 10 (for example, polyamic acid) is used, and the first polyimide layer 10 is obtained after imidization by chemical cyclization or thermocyclization. Chemical cyclization is performed by adding a dehydrating agent and a catalyst to the precursor of the first polyimide layer 10 to convert the polyamic acid into a first gel film by chemical cyclization. The dehydrating agent may be acetic anhydride or benzoic anhydride, and in the present invention, acetic anhydride is selected as the dehydrating agent. The catalyst may be pyridine, 3-methylpyridine, 2-methylpyridine, 4-methylpyridine, isoquinoline, quinoline, or triethylamine, and among these, pyridine, 3-methylpyridine, 2-methylpyridine, or 4-methylpyridine are preferred. In the present invention, it is more preferable to select 3-methylpyridine. The catalyst and dehydrating agent may be mixed with a solvent to form a mixed solution, the solvent being dimethylacetamide, and the dilution ratio (catalyst / solvent or dehydrating agent / solvent) may be 1 to 5. The final mixed solution is degassed by centrifugal degassing to remove bubbles from the solution. After degassing is complete, the defoamed mixed solution is applied to a glass substrate using a doctor blade with an appropriate gap. After application is complete, the glass substrate coated with the mixed solution is left in an oven at 60 to 80°C for 60 to 120 minutes, then removed, and the semi-dried film is taken from the glass substrate to complete the first gel film. On the other hand, in thermocyclization, the precursor of the first polyimide layer is diluted to an appropriate solid content, applied, and then the glass substrate coated with the mixed solution is left in an oven at 60 to 80°C for 60 to 120 minutes, then removed, the bake time is adjusted according to the degree of dryness of the gel film, and the semi-dried film is taken from the glass substrate to complete the first gel film.

[0014] A precursor of the second polyimide layer 11 (e.g., polyamic acid) is applied to the surface of the first gel film using a doctor blade, and the second gel film is obtained after imidization by chemical cyclization or thermocyclization. Chemical cyclization is the process of converting polyamic acid into a gel film by chemical cyclization by adding a dehydrating agent and a catalyst to the precursor of the second polyimide layer 11 in an amount smaller than the amount used to produce the first polyimide layer 10. The dehydrating agent may be acetic anhydride or benzoic anhydride, and in this invention, acetic anhydride is selected as the dehydrating agent. The catalyst may be pyridine, 3-methylpyridine, 2-methylpyridine, 4-methylpyridine, isoquinoline, quinoline, or triethylamine, and among these, pyridine, 3-methylpyridine, 2-methylpyridine, or 4-methylpyridine is preferred. In this invention, 3-methylpyridine is more preferred. The catalyst and dehydrating agent may be mixed with a solvent to form a mixed solution, the solvent being dimethylacetamide, and the dilution ratio (catalyst / solvent or dehydrating agent / solvent) may be 1 to 5. The final mixed solution is degassed by centrifugal degassing to remove bubbles from the solution. After degassing is complete, the defoamed mixed solution is applied to the first gel film using a doctor blade with an appropriate gap. After application is complete, the glass substrate coated with the mixed solution is left in an oven at 60 to 80°C for 60 to 120 minutes, then removed, and the semi-dried film is taken from the glass substrate to complete the second gel film. On the other hand, in thermocyclization, the precursor of the second polyimide layer is diluted to an appropriate solid content, applied to the first gel film, baked in an oven at 60-80°C for 60-120 minutes, then removed, the bake time is adjusted according to the degree of dryness of the gel film, the semi-dried film is taken from the glass substrate and fixed to a metal frame, the temperature is raised to above 300°C, and the composite film is completed after baking for 60 minutes. A preferred bake temperature is above 300°C, and more preferably above 320°C.

[0015] The present invention may be applied to a flexible circuit board comprising an insulating material and a cover film, particularly preferably an insulating material. The present invention may also be applied, for example, to a metal laminate, which comprises at least one metal layer and the composite film of the present invention, and is obtained by a continuous crimping method, with a pressure of 10-20 kN and a temperature of 320-370°C, wherein the adhesive strength between the composite film and the metal layer is greater than 1.5 kgf / cm, and the peel interface is located between the first polyimide layer and the second polyimide layer.

[0016] The material of the metal layer is not particularly limited, and individual metals such as copper, nickel, aluminum, and silver, or alloys of the said metals may be used, with copper being the most preferred.

[0017] The composite film has an elastic modulus that is at least 4 GPa, and more preferably 5 GPa or higher.

[0018] The composite film has an elongation of at least 40%, preferably 50% or more, and more preferably 60% or more.

[0019] The composite film has a glass transition temperature (Tg) that is at least greater than 330°C, preferably greater than 340°C, and more preferably greater than 350°C.

[0020] The composite film preferably has a water absorption rate of less than 1.5%, and more preferably less than 1.1%.

[0021] The composite film preferably has a coefficient of thermal expansion less than 22 μm / m°C, more preferably less than 20 μm / m°C, and most preferably less than 18 μm / m°C.

[0022] The composite film has a total thickness of 10 to 60 μm, preferably 12 to 50 μm.

[0023] In the composite membrane, the thickness ratio of the first polyimide layer 10 to the second polyimide layer 11 (first polyimide layer 10 / second polyimide layer 11) is at least 3.6 to 6.3, preferably 3.6 to 5.1, and more preferably 4.0 to 4.6.

[0024] According to functional requirements, other types of inorganic fillers or organic fillers may be added to the composite membrane. For example, adding organic fluorine-containing polymers such as polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ether (PFA) can reduce the dielectric constant. In addition, adding phospholipid-containing organic polymers or fillers such as silicon dioxide and aluminum oxide can improve the antistatic property and heat resistance. Adding alkyne structure-containing fillers or silane-based fillers can improve the surface adhesion.

[0025] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. Details of the raw materials represented by abbreviations in each of the following examples are shown below.

[0026] Structure of the first polyimide layer 10 and the second polyimide layer 12 Regarding dianhydrides 3,3',4,4'-biphenyltetracarboxylic dianhydride: BPDA Pyromellitic dianhydride: PMDA Regarding diamines 2,2'-bis[4-(4-aminophenoxyphenyl)]propane: BAPP p-phenylenediamine: PDA 4,4'-diaminodiphenyl ether: ODA

[0027] solvent DMAc: Dimethylacetamide AA: Acetic anhydride AP: 3-methylpyridine

[0028] Detection method

[0029] The properties of the composite films obtained in the following examples are measured by the following method.

[0030] Modulus of elasticity and elongation: Measured using a Hounsfield H10K-S tensile testing machine in accordance with ASTM D882 standard.

[0031] Coefficient of linear expansion (50~200℃): Measured according to ASTM D696 standard using a TA Instruments Q400 TMA device. The measurement temperature range is 50~200℃, and the heating rate is set to 10℃ / min. The second measurement is taken after the stress in the remaining film material is relieved by the first measurement.

[0032] Glass transition temperature: Measured using a DMA25 instrument manufactured by Metravib. Other measurement conditions are: sample measurement range width 15 mm, jig distance 20 mm.

[0033] Analysis of adhesive strength and delamination interface: Measurements are taken using a Tinius Olsen Model 10ST universal material tester in accordance with the IPC™ 650 standard. [Examples]

[0034] 1.49 g of ODA and 1.20 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.24 g of PMDA, and 4.39 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. Then, 0.98 g of BAPP and 0.70 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. 4.76 g of BAPP, 2.39 g of PMDA, and 0.14 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.02 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture for the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0035] 1.49 g of ODA and 1.29 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.14 g of PMDA, and 4.44 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.80 g of BAPP and 0.58 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.93 g of BAPP, 0.27 g of PMDA, and 2.39 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.015 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0036] 1.49 g of ODA and 1.1 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.34 g of PMDA, and 4.45 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.05 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.70 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.14 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of a precursor for the second polyimide layer with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The precursor and mixture for the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the mixture was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0037] 1.49 g of ODA and 1.44 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.57 g of PDA, 0.14 g of PMDA, and 4.28 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and the mixture was baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer. 0.98 g of BAPP and 0.70 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.77 g of BAPP, 2.39 g of PMDA, and 0.14 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.30 g of AP. The aforementioned precursor and mixture for the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0038] 1.45 g of ODA and 0.70 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.52 g of PDA, 0.09 g of PMDA, and 5.16 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.0 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.92 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.82 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0039] 1.52 g of ODA and 1.32 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.59 g of PDA, 0.63 g of PMDA, and 3.9 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.04 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.2 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.77 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0040] 1.53 g of ODA and 1.29 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.54 g of PDA, 0.14 g of PMDA, and 4.44 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The precursor and mixture for the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the mixture was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0041] 0.67 g of ODA and 0.73 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 2.05 g of PDA, 0.1 g of PMDA, and 5.39 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.2 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0042] 1.49 g of ODA and 1.29 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 4.45 g of PMDA, and 0.14 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.10 g of AA and 1.50 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and the mixture was baked at 60-80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.97 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.75 g of BAPP, 2.34 g of PMDA, and 0.25 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.30 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were degassed by centrifugation and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, it was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0043] 1.49 g of ODA and 1.29 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 4.45 g of PMDA, and 0.14 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.05 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.10 g of AA and 1.50 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.77 g of BAPP, 0.08 g of PMDA, and 2.48 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture for the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. [Examples]

[0044] 1.53 g of ODA and 1.29 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.54 g of PDA, 0.14 g of PMDA, and 4.44 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of PMDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 4.1 g of AA and 1.5 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.57 g of BAPP and 0.41 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 5.16 g of BAPP, 2.39 g of PMDA, and 0.43 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.33 g of AA and 0.3 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were degassed by centrifugation and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, it was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 1

[0045] 1.52 g of ODA and 1.32 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.60 g of PDA, 0.69 g of PMDA, and 3.81 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.5 g of AA and 1.3 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of precursor for the second polyimide layer 12 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 2

[0046] 1.45 g of ODA and 0.70 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.59 g of PDA, 0.05 g of PMDA, and 5.22 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.5 g of AA and 1.3 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and the mixture was baked at 60-80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 3

[0047] 1.57 g of ODA and 1.10 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.51 g of PDA, 0.33 g of PMDA, and 4.43 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.4 g of AA and 1.2 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 4

[0048] 0.64 g of ODA and 0.70 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 2.13 g of PDA, 0.80 g of PMDA, and 4.66 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.6 g of AA and 1.3 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 5

[0049] 1.49 g of ODA and 0.67 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.77 g of PMDA, and 4.45 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.4 g of AA and 1.3 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 6

[0050] 1.50 g of ODA and 1.49 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.57 g of PDA, 0.1 g of PMDA, and 4.15 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.19 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 3.4 g of AA and 1.3 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and the mixture was baked at 60-80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.76 g of BAPP, 2.39 g of PMDA, and 0.19 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 7

[0051] 1.49 g of ODA and 1.30 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.14 g of PMDA, and 4.4 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.1 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 5.6 g of AA and 2.0 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.98 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.78 g of BAPP, 2.51 g of PMDA, and 0.01 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.031 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were degassed by centrifugation and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 8

[0052] 1.49 g of ODA and 1.30 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.14 g of PMDA, and 4.45 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 5.6 g of AA and 2.0 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and the mixture was baked at 60-80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.97 g of BAPP and 0.66 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.80 g of BAPP, 2.30 g of PMDA, and 0.29 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the film was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 9

[0053] 1.49 g of ODA and 1.30 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.14 g of PMDA, and 4.45 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.06 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer 10 with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15 wt%) was added to a mixture of catalyst and dehydrating agent consisting of 5.6 g of AA and 2.0 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 1.03 g of BAPP and 0.74 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 4.69 g of BAPP, 2.31 g of PMDA, and 0.21 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor for the second polyimide layer (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The precursor and mixture for the second polyimide layer 11 described above were centrifuged to remove air bubbles and applied to the first gel film of the first polyimide layer 10. After baking in an 80°C oven for 60 minutes, the mixture was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film. Comparative Example 10

[0054] 1.49 g of ODA and 1.30 g of PMDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 1.56 g of PDA, 0.14 g of PMDA, and 4.45 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.07 g of BPDA, and finally, 60 g of the precursor of the first polyimide layer with a viscosity of 180,000 ± 20,000 cps. was obtained. Subsequently, 60 g of the precursor of the first polyimide layer 10 (solid content 15% by weight) was added to a mixture of catalyst and dehydrating agent consisting of 5.6 g of AA and 2.0 g of AP. The aforementioned precursor and mixture of the first polyimide layer 10 were degassed by centrifugation and applied to a substrate, and baked at 80°C for 60 minutes to form the first gel film of the first polyimide layer 10. 0.52 g of BAPP and 0.37 g of BPDA were added to 51 g of DMAc solvent, the reaction temperature was controlled to 25°C, and the mixture was reacted for 1 hour while continuously stirring. Then, 5.20 g of BAPP, 2.31 g of PMDA, and 0.57 g of BPDA were added, the reaction temperature was controlled to 25°C, and the mixture was reacted for 2-3 hours while continuously stirring. The viscosity was finely adjusted using 0.03 g of PMDA, and finally, 60 g of the precursor of the second polyimide layer 11 with a viscosity of 180,000 ± 20,000 cps. was obtained. Next, 55 g of the precursor of the second polyimide layer 11 (15% by weight solids) was added to 5 g of solvent (the solvent being dimethylacetamide) and a mixture of catalyst and dehydrating agent consisting of 0.36 g of AA and 0.32 g of AP. The aforementioned precursor and mixture of the second polyimide layer 11 were degassed by centrifugation and applied to the first gel film of the first polyimide layer 10. After baking in an oven at 80°C for 60 minutes, it was removed, the semi-dried gel composite film was taken from the glass substrate and fixed to a metal frame, and the temperature was raised to above 300°C and baked for 60 minutes to complete the fabrication of the composite film.

[0055] [Table 1] TIFF0007927131000003.tif146140

[0056] [Table 2] TIFF0007927131000005.tif160140

[0057] Comparative Example 1: In the components of the first polyimide layer, the percentage of moles of the dianhydride BPDA is less than 60% of the moles of the first acid anhydride (i.e., the total acid anhydride in the first polyimide layer). Therefore, the composite film prepared in Comparative Example 1 has an elongation of less than 50%.

[0058] Comparative Example 2: In the components of the first polyimide layer, the percentage of moles of BPDA dianhydride is greater than 83% of the moles of the first acid anhydride. Therefore, the composite film prepared in Comparative Example 2 has an elongation of less than 50%.

[0059] Comparative Example 3: In the components of the first polyimide layer, the percentage of molars of diamine PDA is less than 65% of the molars of the first diamine (i.e., the total diamine in the first polyimide layer). Therefore, the composite film prepared in Comparative Example 3 has an elastic modulus less than 5 GPa.

[0060] Comparative Example 4: In the components of the first polyimide layer, the percentage of molars of diamine PDA is greater than 85% of the molars of the first diamine. Therefore, the composite film prepared in Comparative Example 4 has an elongation of less than 50%.

[0061] Comparative Example 5: In the components of the first polyimide layer, the percentage of moles of PMDA / ODA copolymer segment blocks relative to the moles of the first polyimide (i.e., the total polyimide in the first polyimide layer) is less than 15%. Therefore, the composite film prepared in Comparative Example 5 has an elongation of less than 50% and a glass transition temperature less than 350°C.

[0062] Comparative Example 6: In the components of the first polyimide layer, the percentage of moles of PMDA / ODA copolymer segment blocks relative to the moles of the first polyimide is greater than 30%. Therefore, the composite film prepared in Comparative Example 6 has an elongation of less than 50%.

[0063] Comparative Example 7: In the components of the second polyimide layer, the percentage of moles of BPDA, a dianhydride, is less than 18% of the moles of the second acid anhydride (i.e., the total acid anhydride in the second polyimide layer). Therefore, the composite film prepared in Comparative Example 7 has an elongation of less than 50%.

[0064] Comparative Example 8: In the second polyimide layer, the percentage of moles of BPDA dianhydride is greater than 22% of the moles of the second acid anhydride. Therefore, the composite film prepared in Comparative Example 8 has an elastic modulus less than 5 GPa and an elongation less than 50%.

[0065] Comparative Example 9: In the components of the second polyimide layer, the percentage of moles of BPDA / BAPP copolymer segment blocks relative to the moles of the second polyimide (i.e., the total polyimide in the second polyimide layer) is greater than 17%. Therefore, the composite film prepared in Comparative Example 9 has an elastic modulus less than 5 GPa, an elongation less than 50%, and a glass transition temperature less than 350°C.

[0066] Comparative Example 10: In the components of the second polyimide layer, the percentage of moles of BPDA / BAPP copolymer segment blocks relative to the moles of the second polyimide is less than 10%. Therefore, the composite film prepared in Comparative Example 10 has a glass transition temperature less than 350°C and an elongation less than 50%.

[0067] The details of the aforementioned specific embodiments are provided to illustrate the present invention in detail, but these embodiments are for illustrative purposes only and are not intended to limit the present invention. Those skilled in the art will understand that various modifications or amendments made to the present invention are included in part with the present invention without departing from the scope limited by the claims described below. [Explanation of symbols]

[0068] 10. First polyimide layer 11. Second polyimide layer

Claims

1. A first polyimide layer comprising a first polyimide obtained by polymerizing a first acid anhydride and a first diamine, wherein the first acid anhydride comprises pyromellitic anhydride (PMDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the total moles of the first acid anhydride is 60-83%, and the first diamine is 4,4 A first polyimide layer comprising '-diaminodiphenyl ether (ODA) and paraphenylenediamine (PDA), wherein the percentage of the number of moles of paraphenylenediamine (PDA) relative to the total number of moles of the first diamine is 65 to 85%, and the proportion of the copolymer segment of pyromellitic anhydride (PMDA) and the 4,4'-diaminodiphenyl ether (ODA) relative to the number of moles of the first polyimide is 15 to 30%, A second polyimide layer is formed on at least one side of the first polyimide layer and comprises a second polyimide formed by polymerizing a second acid anhydride and a second diamine, wherein the second acid anhydride comprises at least 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and pyromellitic acid anhydride (PMDA), the second diamine comprises 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), the percentage of moles of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) to the total number of moles of the second acid anhydride is 18 to 22%, and the proportion of the copolymer segment of BPDA and BAPP to the total number of moles of the second polyimide is 10 to 17%. A composite film comprising, The composite film has an elongation rate greater than 50%, an elastic modulus greater than 5 GPa, and a glass transition temperature greater than 350°C.

2. The composite film according to claim 1, having a total thickness of 10 to 60 μm, and the ratio of the thicknesses of the first polyimide layer to the second polyimide layer being 3.6 to 6.3.

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