Polyimide, thin film composition, and thin film formed thereby

Abstract

To provide a polyimide, a thin-film composition comprising the polyimide, and a thin film prepared from the thin-film composition.SOLUTION: A polyimide is a product of a reactant (a) and a reactant (b). The reactant (a) comprises a first dianhydride and a second dianhydride. The first dianhydride has a bisphenol phthalic acid dianhydride ether structure. The second dianhydride has a phenylene phthalic acid dianhydride ether or naphthalene phthalic acid dianhydride ether structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to polyimides, thin film compositions containing polyimides, and thin films formed using the thin film compositions. [Background technology]

[0002] Due to its excellent thermal stability and insulation properties, polyimide is currently most commonly used as an insulating material and special engineering plastic, as well as in flexible printed circuit boards (FPCs). In recent years, the development of mobile and personal information and communication has been remarkable, and the market and needs for lightweight, thin flexible printed circuit boards (flexible substrates - FPCs) have expanded rapidly. Flexible substrate technology must also meet the comprehensive demands for increasingly sophisticated functional integration in end-user applications (IoT and wearable devices), higher resolution, faster response times, and larger storage capacities. Therefore, the speed, frequency, and performance of flexible substrates are advancing, and high-frequency flexible substrates have become one of the major trends in flexible substrate technology, mainly to meet the demands for enhanced functionality and integration in mobile communication electronic products. Substrate materials with low dielectric constant and low transmission loss will be the most important selling points in the coming high-frequency era.

[0003] Under the demands of high frequency and high speed, the development of multi-functional flexible substrates is becoming increasingly important, and this will increase even further with the future operating frequencies of 5G mobile communications. Conventional polyimide resins have a relatively high water absorption rate, making them susceptible to the influence of the operating environment of electronic devices. In high-humidity environments, the dielectric loss (Df) of the polyimide resin layer increases due to moisture absorption, potentially worsening transmission loss. Therefore, liquid crystal polymers (LCPs), which have excellent dielectric properties and water absorption rates, are currently used in parts where low transmission loss is required. Although their dielectric loss (Df) does not change with humidity, they have drawbacks such as relatively low adhesion to metal foils such as copper foil, low heat resistance, and difficulty in processing. [Overview of the project] [Problems that the invention aims to solve]

[0004] Therefore, research into polyimide resins that possess high-frequency dielectric properties and low moisture absorption is currently a key technological development item for material manufacturers and flexible substrate suppliers. [Means for solving the problem]

[0005] This disclosure provides a polyimide which is a reaction product of reactant (a) and reactant (b), wherein reactant (a) consists of a first dianhydride and a second dianhydride, the first dianhydride having a structure represented by formula (I), and the second dianhydride having a structure represented by formula (II).

[0006] [ka]

[0007] In the formula, R 1 and R 2 Each of these is independently hydrogen, fluorine, methyl group, ethyl group, propyl group, fluoromethyl group, fluoroethyl group, or fluoropropyl group. 1 It is one of the following:

[0008] [ka]

[0009] The reactant (b) contains a first diamine. The first diamine is one of the following:

[0010] [ka]

[0011] In the formula, R 3 , R 4, R 5 , or R 6 Each of these is independently hydrogen, fluorine, methyl group, ethyl group, propyl group, fluoromethyl group, fluoroethyl group, or fluoropropyl group.

[0012] Embodiments of this disclosure also provide thin film compositions. The thin film composition may contain the polyimide and solvent according to this disclosure, and the solids content of the thin film composition may be 5 wt% to 30 wt%.

[0013] Embodiments of this disclosure also provide thin films, which may include cured products of the thin film composition. [Effects of the Invention]

[0014] This disclosure provides polyimides, thin film compositions containing polyimides, and thin films formed using the thin film compositions. The polyimides are obtained by reacting two specific dianhydrides (e.g., aryl-moiety-containing dianhydrides) with a specific diamine (e.g., aryl-moiety-containing diamines) in a specific molar ratio. Thin films (i.e., cured products) made using the thin film compositions containing polyimides have low dielectric constant (Dk) and low dielectric loss (Df) at high frequencies (frequency bands of 10 GHz or higher), as well as low moisture absorption. Therefore, thin films made from the thin film compositions according to this disclosure can have stable dielectric properties. According to embodiments of this disclosure, the thin film compositions can be further coated onto metal foil substrates to provide excellent bonding strength, heat resistance, and chemical resistance. According to embodiments of this disclosure, the thin film composition is obtained by dissolving / dispersing the polyimide according to this disclosure using a specific solvent. This not only increases the degree of polymerization of the polymer, but also results in a thin film formed using the thin film composition having a more uniform thickness and higher chemical resistance. Furthermore, the thickness of the resulting thin film can be adjusted by controlling the solid content of the thin film composition. [Modes for carrying out the invention]

[0015] Hereinafter, the polyimide of the present disclosure, the thin film composition containing the polyimide, and the thin film formed using the thin film composition will be described in detail. It should be understood that in the following description, many different embodiments or examples are given so that various different aspects of the present disclosure can be implemented. The specific components and configurations described below are merely for briefly explaining the present disclosure. Of course, these are merely examples and do not limit the present disclosure. In the present disclosure, the term "about" refers to the fact that a given quantity can increase or decrease by an amount that those skilled in the art recognize as being of a common and reasonable magnitude.

[0016] Furthermore, terms such as numbers representing order used in the specification and claims, for example, "first", "second", "third", etc., are used to modify the components related to the claims, and do not themselves mean or represent that there is a number representing the previous order for the components related to that claim. Nor do they represent the order between components related to one claim and components related to another claim, or the order in a manufacturing method. These numbers representing order are merely used to clearly distinguish the components related to one claim with a certain name from the other components of the claim with the same name.

[0017] The present disclosure provides a polyimide, a thin film composition containing the polyimide, and a thin film formed using the thin film composition. The polyimide is obtained by reacting two specific dianhydrides (for example, an aryl-moiety-containing dianhydride) with a specific diamine (for example, an aryl-moiety-containing diamine) in a specific molar ratio. The thin film (i.e., the cured product) produced using the thin film composition containing the polyimide has a low dielectric constant (Dk) and low dielectric loss (Df) at high frequencies (frequency bands of 10 GHz or higher), and also has a low moisture absorption rate. Therefore, the thin film produced from the thin film composition according to the present disclosure can have stable dielectric properties. According to an embodiment of the present disclosure, the thin film composition can be further applied to a metal foil substrate to have excellent bonding strength, heat resistance, and chemical resistance. According to an embodiment of the present disclosure, the thin film composition dissolves / disperses the polyimide according to the present disclosure using a specific solvent, thereby not only increasing the degree of polymerization of the polymer but also enabling the thin film formed using the thin film composition to have a more uniform thickness and higher chemical resistance. Also, by controlling the solid content of the thin film composition, the thickness of the obtained thin film can be adjusted.

[0018] According to an embodiment of the present disclosure, the polyimide according to the present disclosure can be a product formed by the reaction (for example, a polymerization reaction) of reactant (a) and reactant (b). The reactant (a) may be at least one dianhydride (for example, an aryl-moiety-containing dianhydride). According to an embodiment of the present disclosure, the reactant (a) may consist of a first dianhydride and a second dianhydride. According to an embodiment of the present disclosure, the first dianhydride may have a structure represented by formula (I), and the second dianhydride may have a structure represented by formula (II).

[0019] [Chemical formula]

[0020] In the formula, R 1 and R 2 are each independently hydrogen, fluorine, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, or a fluoropropyl group. Ar 1 is any of the following.

[0021]

Chemical formula

[0022] According to an embodiment of the present disclosure, the fluoromethyl group in the present disclosure may be a monofluoromethyl group, a difluoromethyl group, or a perfluoromethyl group, the fluoroethyl group may be a monofluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a tetrafluoroethyl group, or a perfluoroethyl group, and the fluoropropyl group may be a monofluoropropyl group, a difluoropropyl group, a trifluoropropyl group, a tetrafluoropropyl group, a pentafluoropropyl group, a hexafluoropropyl group, or a perfluoropropyl group. According to an embodiment of the present disclosure, the propyl group in the present disclosure may be a normal propyl group or an isopropyl group, and the fluoropropyl group may be a fluoronormal propyl group or a fluoroisopropyl group.

[0023] According to an embodiment of the present disclosure, the first dianhydride may be any of the following.

[0024]

Chemical formula

[0025] According to embodiments of the present disclosure, the first dianhydride may be 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA).

[0026] According to embodiments of this disclosure, the second dianhydride may be any of the following:

[0027] [ka]

[0028] According to embodiments of the present disclosure, the second dianhydride may be p-phenylene bis(trimellitate anhydride), TAHQ, or 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA.

[0029] According to embodiments of the present disclosure, the molar ratio of the first dianhydride to the second dianhydride may be 3:7 to 8:2, for example, about 4:6, 5:5, 6:4, 7:3, or 7.5:2.5. If the molar ratio of the first dianhydride to the second dianhydride is excessively high or excessively low, the thin film made from the thin film composition containing the polyimide may be prone to directional cracking, or the resulting thin film (cured product) may have poor dielectric loss properties (>0.005 (@10 GHz)) and relatively high hygroscopicity (>1.0%).

[0030] According to embodiments of the present disclosure, the reactant (b) may be at least one diamine (for example, an aryl-moiety-containing diamine). According to embodiments of the present disclosure, the reactant (b) includes a first diamine. According to embodiments of the present disclosure, the first diamine may be any of the following:

[0031] [ka]

[0032] In the formula, R 3 , R 4 , R 5 , or R 6 Each of these is independently hydrogen, fluorine, methyl group, ethyl group, propyl group, fluoromethyl group, fluoroethyl group, or fluoropropyl group.

[0033] According to embodiments of the present disclosure, the reactant (b) is the first diamine. According to embodiments of the present disclosure, the first diamine may be any of the following:

[0034] [ka]

[0035] According to embodiments of the present disclosure, the first diamine may be 4,4'-oxybis[3-(trifluoromethyl)aniline] (TMDA), 4,4'-oxydianiline (ODA), or 1,3-bis(3-aminophenoxy)benzene (APB-N).

[0036] According to embodiments of the present disclosure, the ratio of moles of reactant (a) to reactant (b) that participate in the reaction (e.g., polymerization reaction) to form a polyimide may be substantially in the range of about 0.95:1.05 to 1.05:0.95, for example, close to about 1:1.

[0037] According to embodiments of the present disclosure, in addition to the first diamine, the reaction substance (b) may further contain a second diamine, the second diamine being any of the following:

[0038] [ka]

[0039] In the formula, R 7 , R 8 , R 9 , R 10 , R 11 , or R 12 Each of these is independently hydrogen, fluorine, a methyl group, an ethyl group, a propyl group, a fluoromethyl group, a fluoroethyl group, or a fluoropropyl group. Furthermore, the first diamine and the second diamine are different.

[0040] According to embodiments of this disclosure, the second diamine may be any of the following:

[0041] [ka]

[0042] According to embodiments of the present disclosure, the second diamine may be 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-oxydianiline (ODA), or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP). According to embodiments of the present disclosure, when the first diamine is 4,4'-oxydianiline (ODA), the second diamine is 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP).

[0043] According to embodiments of the present disclosure, the reactant (b) may consist of the first diamine and the second diamine. According to embodiments of the present disclosure, the molar ratio of the first diamine to the second diamine may be 1:9 to 9:1, for example 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, or 8:2.

[0044] According to embodiments of the present disclosure, the reactant (b) further comprises a third diamine, the third diamine may be any of the following:

[0045] [ka]

[0046] According to embodiments of this disclosure, the third diamine may be bis(4-aminophenyl)terephthalate (BPTP).

[0047] According to embodiments of the present disclosure, the reactant (b) may consist of the first diamine, the second diamine, and the third diamine. According to embodiments of the present disclosure, the molar ratio of the first diamine to the second diamine may be 1:9 to 9:1 (e.g., 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, or 8:2), and the ratio of the molars of the third diamine to the sum of the molars of the first and second diamines is approximately 1:99 to 1:9 (e.g., approximately 2:98, 3:97, 4:96, 5:95, 6:94, 7:93, 8:92, or 9:91).

[0048] According to embodiments of the present disclosure, the weight-average molecular weight (Mw) of the polyimide relating to the present disclosure may range from approximately 5,000 g / mol to 3,000,000 g / mol, for example, from approximately 8,000 g / mol to 2,500,000 g / mol, from 10,000 g / mol to 2,300,000 g / mol, from 15,000 g / mol to 2,000,000 g / mol, from 10,000 g / mol to 1,000,000 g / mol, from 10,000 g / mol to 500,000 g / mol, or from 10,000 g / mol to 300,000 g / mol. The weight-average molecular weight (Mw) of the polyimide relating to the present disclosure can be measured by gel permeation chromatography (GPC) (a calibration curve is created using polystyrene as a standard).

[0049] According to embodiments of this disclosure, the polyimide according to this disclosure is obtained by the following steps. First, reactant (a) and reactant (b) are placed in a reaction bottle and dissolved in a solvent to obtain a solution. The solid content of the solution can be approximately 5 wt% to 45 wt% (for example, approximately 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, 18 wt%, 20 wt%, 21 wt%, 22 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, 32 wt%, 34 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, or 44 wt%). The definitions of reactant (a) and reactant (b) are as described above. According to embodiments of the present disclosure, the solvent used to prepare the polyimide may include N-methylpyrrolidone, dimethylacetamide, γ-butyrolactone, p-xylene, or a combination thereof, so that the polyimide obtained thereafter can dissolve directly in the solvent used without being replaced with another solvent. According to embodiments of the present disclosure, the solvent may be N-methylpyrrolidone, dimethylacetamide, or γ-butyrolactone. According to embodiments of the present disclosure, the molar ratio of reactant (a) to reactant (b) may be about 1.1 to 0.9 to 0.9 to 1.1, for example, about 1:1. According to embodiments of the present disclosure, a catalyst may be added to the solution as needed to accelerate the polymerization reaction and form the polyimide. The amount of the catalyst may be 0.01 wt% to 1 wt% (for example, about 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, or 0.9 wt%) based on the total weight of reactant (a) and reactant (b). Next, the solution is reacted at 180°C to 250°C for 4 to 12 hours to obtain a solution containing the polyimide according to the present disclosure (polyimide solution). When the solvent used is N-methylpyrrolidone, dimethylacetamide, p-xylene, γ-butyrolactone, or a combination thereof, and the molar ratio of reactant (a) to reactant (b) is about 1, the resulting polyimide can be completely dissolved in the solution and no further purification is necessary. Therefore, the polyimide solution obtained from the reaction can be used as is as the thin film composition according to the present disclosure.According to embodiments of the present disclosure, the catalyst may be any catalyst that can be used in the imidation reaction, such as a tertiary amine. For example, tertiary amines may include triethylenediamine (DABCO), N,N-dimethylcyclohexylamine, 1,2-dimethylimidazole, trimethylamine, triethylamine, tripropylamine, tributylamine, triethanolamine, N,N-dimethylaminoethanol, N,N-diethylethanolamine, triethyldiamine, N-methylpyrrolidine, N-ethylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, imidazole, pyridine, picoline, lutidene, quinoline, or isoquinoline.

[0050] According to embodiments of the present disclosure, the thin film composition according to the present disclosure may contain the polyimide and solvent according to the present disclosure. Also, according to some embodiments of the present disclosure, the thin film composition according to the present disclosure may consist of the polyimide and solvent according to the present disclosure. The solvent may be N-methylpyrrolidone, dimethylacetamide, γ-butyrolactone, p-xylene, or a combination thereof, and the solids content of the thin film composition may be 5 wt% to 45 wt% (for example, about 6 wt%, 8 wt%, 10 wt%, 12 wt%, 14 wt%, 15 wt%, 18 wt%, 20 wt%, 21 wt%, 22 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, 32 wt%, 34 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, or 44 wt%). According to embodiments of this disclosure, the thickness of a thin film produced from the thin film composition is directly proportional to the solid content of the thin film composition. In other words, the thickness of a thin film produced from the thin film composition can be adjusted by the solid content of the thin film composition.

[0051] According to embodiments of the present disclosure, a solution containing polyimide obtained by carrying out a reaction (e.g., an imidation reaction) between reactant (a) and reactant (b) can be used as the thin film composition according to the present disclosure. According to embodiments of the present disclosure, the thin film composition according to the present disclosure consists substantially of the polyimide and solvent according to the present disclosure. In other words, the polyimide and solvent are the main components of the thin film composition, and the total weight of the polyimide and solvent accounts for about 90 wt% to 99.99 wt% (e.g., 93 wt%, 95 wt%, 98 wt%, 99 wt%, or 99.5 wt%) of the thin film composition. Other components in the thin film composition other than the polyimide and solvent are defined as secondary components. According to embodiments of the present disclosure, the secondary components may be a catalyst used to produce the polyimide, reactant (a) and / or reactant (b) used to produce the polyimide but not fully reacted, an additive, or a combination of the above. The total weight of the secondary components accounts for approximately 0.01 wt% to 10 wt% of the thin film composition. According to embodiments of the present disclosure, the additives may be additives well known in the art, such as fillers, flame retardants, viscosity modifiers, thixotropic agents, defoamers, leveling agents, surface treatment agents, stabilizers, antioxidants, or combinations thereof. According to other embodiments of the present disclosure, the thin film composition according to the present disclosure may consist of the above-mentioned main components and secondary components.

[0052] According to embodiments of the present disclosure, the present disclosure also provides a thin film which is a cured product obtained by performing a baking process on a thin film composition according to the present disclosure. According to embodiments of the present disclosure, the thin film according to the present disclosure can be produced by the following steps. First, a coating layer is formed on a substrate by performing a coating process using the thin film composition according to the present disclosure. According to embodiments of the present disclosure, the coating process can be screen printing, spin coating, bar coating, blade coating, roller coating, dip coating, spray coating, or brush coating. Next, a baking process is performed on the coating layer to form a film layer. The temperature of the baking process may be about 50°C to 350°C, or less than 290°C (e.g., 70°C to 260°C), and the duration of the process may be 30 minutes to 8 hours. According to embodiments of the present disclosure, the baking process may be a multi-stage baking process.

[0053] To make the above-mentioned and other purposes, features, and advantages of this disclosure clearer and easier to understand, several examples are described below in detail, corresponding to the attached figures.

[0054] Table 1 lists the reagents used in the examples and comparative examples of this disclosure.

[0055] [Table 1-1] [Table 1-2]

[0056] Polyimide fabrication

[0057] Example 1

[0058] 60 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 40 moles of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA, and 100 moles of 1,3-bis(3-aminophenoxy)benzene (APB-N) were placed in a reaction bottle and dissolved with N-methylpyrrolidone (NMP) to obtain a solution (solids content approximately 25 wt%). Then, isoquinoline (catalyst; dose approximately 0.3 wt%) relative to the total weight of BPADA, 2,6-TANA, and APB-N) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (1) containing the polyimide according to this disclosure. The solid content of the thin film composition (1) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0059] Next, the thin film composition (1) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (NMP). Next, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 2.

[0060] The method for measuring moisture absorption was determined by the following formula: Moisture absorption rate = (W1-W0) / W0×100% However, W0 is the weight of the film layer after baking it in an oven at 110°C for 1 hour and then cooling it to room temperature; W1 is the weight of the film layer after immersing it in water at 30°C for 24 hours.

[0061] The dielectric coefficient (Dk) and dielectric loss factor (Df) were measured at a frequency of 10 GHz using a microwave dielectrometer (purchased from AET).

[0062] Comparative Example 1

[0063] 10 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 90 moles of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA, and 100 moles of 4,4'-oxydianiline (ODA) were placed in a reaction bottle and dissolved with N-methylpyrrolidone (NMP) to obtain a solution (solids content approximately 25 wt%). Then, isoquinoline (catalyst; dose approximately 0.3 wt%) relative to the total weight of BPADA, 2,6-TANA, and ODA) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (2) containing the polyimide according to this disclosure. The solid content of the thin film composition (2) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0064] Next, the thin film composition (2) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (NMP). Subsequently, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes. It was observed that the thin film composition failed to form a film layer, or that the formed film layer was prone to cracking.

[0065] Comparative Example 2

[0066] Comparative Example 2 was carried out in the same manner as described in Example 1, except that it contained 10 mole parts of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) and 90 mole parts of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA, to obtain a thin film composition (3) containing the polyimide according to the present disclosure. The solid content of the thin film composition (3) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0067] Next, the thin film composition (3) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (NMP). Subsequently, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes. It was observed that the thin film composition had not formed a film layer, or that the formed film layer was prone to cracking.

[0068] Example 2

[0069] Example 2 was carried out in the same manner as described in Example 1, except that 1,3-bis(3-aminophenoxy)benzene (APB-N) was replaced with 4,4'-oxydianiline (ODA), to obtain a thin film composition (4) containing the polyimide according to the present disclosure. The solid content of the thin film composition (4) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0070] Next, the thin film composition (4) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (NMP). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 2.

[0071] [Table 2]

[0072] As shown in Table 2, the molar ratio of BPADA and 2,6-TANA (the polyimide dianhydride used to prepare the thin film composition (2) of Comparative Example 1) was 1:9, and therefore the thin film composition (2) of Comparative Example 1 did not form. As can be seen from Examples 1 and 2, the cured product of a thin film composition obtained by preparing a polyimide by combining BPADA and 2,6-TANA in specific molar ratios with APB-N or ODA can have its moisture absorption rate reduced (e.g., less than 0.55%, and even less than 0.35%) without increasing the dielectric constant (Dk) or dielectric loss rate.

[0073] Example 3

[0074] 60 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 40 moles of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA, 40 moles of 4,4'-oxydianiline (ODA), and 60 moles of 1,3-bis(3-aminophenoxy)benzene (APB-N) were placed in a reaction bottle and dissolved with dimethylacetamide (N,N-dimethylacetamid, DMAC) to obtain a solution (solids content approximately 25 wt%). Next, isoquinoline (a catalyst; approximately 0.3 wt% of the total weight of BPADA, 2,6-TANA, ODA, and APB-N) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (5) containing the polyimide according to the present disclosure. The solid content of the thin film composition (5) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0075] Next, the thin film composition (5) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0076] Example 4

[0077] Example 4 was carried out in the same manner as described in Example 3, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was increased from 60 moles to 70 moles, and the amount of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA) was decreased from 40 moles to 30 moles, to obtain a thin film composition (6) containing the polyimide according to the present disclosure. The solid content of the thin film composition (6) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0078] Next, the thin film composition (6) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0079] Example 5

[0080] 60 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 40 moles of 2,6-dihydroxynaphthalene bis(trimellitate anhydride), 2,6-TANA, 40 moles of 4,4'-oxydianiline (ODA), and 60 moles of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) were placed in a reaction bottle and dissolved with dimethylacetamide (N,N-dimethylacetamid, DMAC) to obtain a solution (solids content approximately 25 wt%). Next, isoquinoline (a catalyst; approximately 0.3 wt% of the total weight of BPADA, 2,6-TANA, ODA, and HFBAPP) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (7) containing the polyimide according to the present disclosure. The solid content of the thin film composition (7) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0081] Next, the thin film composition (7) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0082] Example 6

[0083] Example 6 was carried out in the same manner as described in Example 5, except that the amount of 4,4'-oxydianiline (ODA) was increased from 40 moles to 50 moles and the amount of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) was decreased from 60 moles to 50 moles, to obtain a thin film composition (8) containing the polyimide according to the present disclosure. The solid content of the thin film composition (8) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0084] Next, the thin film composition (8) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0085] Example 7

[0086] 80 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 20 moles of p-phenylene bis(trimellitate anhydride), TAHQ, 40 moles of 4,4'-oxydianiline (ODA), and 60 moles of 1,3-bis(3-aminophenoxy)benzene (APB-N) were placed in a reaction bottle and dissolved with dimethylacetamide (N,N-dimethylacetamid, DMAC) to obtain a solution (solids content approximately 25 wt%). Next, isoquinoline (a catalyst; approximately 0.3 wt% of the total weight of BPADA, TAHQ, ODA, and APB-N) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (9) containing the polyimide according to the present disclosure. The solid content of the thin film composition (9) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0087] Next, a thin film composition (9) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked under nitrogen conditions at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0088] Example 8

[0089] 70 moles of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA), 30 moles of p-phenylene bis(trimellitate anhydride), TAHQ, 40 moles of 4,4'-oxydianiline (ODA), and 60 moles of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) were placed in a reaction bottle and dissolved with dimethylacetamide (N,N-dimethylacetamid, DMAC) to obtain a solution (solids content approximately 25 wt%). Next, isoquinoline (a catalyst; approximately 0.3 wt% of the total weight of BPADA, TAHQ, ODA, and HFBAPP) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (10) containing the polyimide according to the present disclosure. The solid content of the thin film composition (10) was approximately 25 wt%, and the solvent was dimethylacetamide.

[0090] Next, a thin film composition (10) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (DMAC). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 3.

[0091] Comparative Example 3

[0092] Comparative Example 3 was carried out in the same manner as described in Example 8, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was reduced from 70 moles to 10 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was increased from 30 moles to 90 moles, to obtain a thin film composition (11) containing the polyimide according to the present disclosure. The solid content of the thin film composition (11) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0093] Next, the thin film composition (11) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (NMP). Subsequently, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes. It was observed that the thin film composition failed to form a film layer, or that the formed film layer was prone to cracking.

[0094] [Table 3]

[0095] As shown in Table 3, Examples 3-4 demonstrate that cured thin film compositions obtained by combining specific molar ratios of BPADA and 2,6-TANA with specific molar ratios of ODA and APB-N can reduce moisture absorption (for example, to less than 0.6%) without increasing dielectric constant (Dk) or dielectric loss. Furthermore, as can be seen from Examples 5-6, cured thin film compositions obtained by combining specific molar ratios of BPADA and 2,6-TANA with specific molar ratios of ODA and HFBAPP can reduce moisture absorption (for example, to less than 0.55%) without increasing dielectric constant (Dk) or dielectric loss. Furthermore, as can be seen from Examples 7 and 8, by replacing 2,6-TANA with TAHQ and maintaining a specific molar ratio of BPADA and TAHQ, the cured thin film composition obtained can have its moisture absorption rate reduced without increasing the dielectric constant (Dk) or dielectric loss rate (for example, it can be less than 0.50). In Comparative Example 3, the molar ratio of BPADA to TAHQ was 1:9, so the thin film composition (11) of Comparative Example 3 could not be fabricated to form a film.

[0096] Example 9

[0097] 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) (60 moles), 2,6-dihydroxynaphthalene bis(trimellitate) 40 molar parts of anhydride, 2,6-TANA, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), and 60 molar parts of 1,3-bis(3-aminophenoxy)benzene (APB-N) were placed in a reaction bottle and dissolved with N-methylpyrrolidinone (NMP) to obtain a solution (solid content approximately 25 wt%). Next, isoquinoline (catalyst; dose approximately 0.3 wt%) relative to the total weight of BPADA, 2,6-TANA, HFBAPP, and APB-N) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (12) containing the polyimide according to the present disclosure. The solid content of the thin film composition (12) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0098] Next, a thin film composition (12) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (NMP). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 4.

[0099] Example 10

[0100] 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) (70 moles), p-phenylene bis(trimellitate) 30 molar parts of anhydride (TAHQ), 60 molar parts of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP), and 40 molar parts of 1,3-bis(3-aminophenoxy)benzene (APB-N) were placed in a reaction bottle and dissolved with N-methylpyrrolidinone (NMP) to obtain a solution (solid content approximately 25 wt%). Next, isoquinoline (catalyst; dose approximately 0.3 wt%) relative to the total weight of BPADA, TAHQ, HFBAPP, and APB-N) was added to the reaction bottle. The resulting mixture was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (13) containing the polyimide according to this disclosure. The solid content of the thin film composition (13) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0101] Next, a thin film composition (13) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (NMP). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 4.

[0102] Example 11

[0103] Example 11 was carried out in the same manner as described in Example 10, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was increased from 70 moles to 75 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ was decreased from 30 moles to 25 moles, to obtain a thin film composition (14) containing the polyimide according to the present disclosure. The solid content of the thin film composition (14) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0104] Next, a thin film composition (14) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (NMP). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 4.

[0105] Example 12

[0106] Example 12 was carried out in the same manner as described in Example 10, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was increased from 70 moles to 80 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was decreased from 30 moles to 20 moles, to obtain a thin film composition (15) containing the polyimide according to the present disclosure. The solid content of the thin film composition (15) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0107] Next, a thin film composition (15) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (NMP). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 4.

[0108] Comparative Example 4

[0109] Comparative Example 4 was carried out in the same manner as described in Example 12, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was reduced from 80 moles to 10 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was increased from 20 moles to 90 moles, to obtain a thin film composition (16) containing the polyimide according to the present disclosure. The solid content of the thin film composition (16) was approximately 25 wt%, and the solvent was N-methylpyrrolidone.

[0110] Next, a thin film composition (16) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (NMP). Subsequently, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes. It was observed that the thin film composition failed to form a film layer, or that the formed film layer was prone to cracking.

[0111] [Table 4]

[0112] As shown in Table 4, Examples 9 to 12 show that cured thin film compositions obtained by combining a first diamine (e.g., APB-N) and a second diamine (e.g., HFBAPP) in specific molar ratios with a first diamine (e.g., BPADA) and a second diamine (e.g., TAHQ) in specific molar ratios to produce polyimides can reduce moisture absorption without increasing dielectric constant or dielectric loss. Comparative Example 4 shows that if the ratios of the first and second dianehydrides used are not within the range defined in this disclosure, the resulting thin film composition will not form a film even if prepared, or the resulting cured product will have inferior dielectric constant and dielectric loss, and a higher moisture absorption rate.

[0113] Example 13

[0114] 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) (75 moles), p-phenylene bis(trimellitate) 25 molar parts of anhydride (TAHQ), 4,4'-oxybis[3-(trifluoromethyl)aniline] (TMDA), 40 molar parts of 4,4'-oxybis[3-(trifluoromethyl)aniline] (TMDA), 50 molar parts of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and 10 molar parts of bis(4-aminophenyl)terephthalate (BPTP) were placed in a reaction bottle and dissolved with gamma-butyrolactone (GBL) to obtain a solution (solids content approximately 25 wt%). Then, isoquinoline (catalyst; dose approximately 0.3 wt%) relative to the total weight of BPADA, TAHQ, TMDA, BAPP, and BPTP) was added to the reaction bottle. The obtained material was reacted at 200°C to 220°C for 6 hours to obtain a thin film composition (17) containing the polyimide according to the present disclosure. The solid content of the thin film composition (17) was approximately 25 wt%, and the solvent was γ-butyrolactone.

[0115] Next, a thin film composition (17) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (GBL). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 5.

[0116] Example 14

[0117] Example 14 was carried out in the same manner as described in Example 13, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was increased from 75 moles to 80 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was decreased from 25 moles to 20 moles, to obtain a thin film composition (18) containing the polyimide according to the present disclosure. The solid content of the thin film composition (18) was approximately 25 wt%, and the solvent was γ-butyrolactone.

[0118] Next, a thin film composition (18) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (GBL). The substrate containing the coating layer was then baked in a nitrogen environment at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 5.

[0119] Comparative Example 5

[0120] Comparative Example 5 was carried out in the same manner as described in Example 13, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was increased from 75 moles to 90 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was decreased from 25 moles to 10 moles, to obtain a thin film composition (19) containing the polyimide according to the present disclosure. The solid content of the thin film composition (19) was approximately 25 wt%, and the solvent was γ-butyrolactone.

[0121] Next, a thin film composition (19) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). The coating layer was then baked at 80°C for 30 minutes to remove the solvent (GBL). The substrate containing the coating layer was then baked under nitrogen conditions at 150°C for 30 minutes and at 220°C for 60 minutes to obtain a cured product. Finally, the dielectric coefficient (Dk), dielectric loss factor (Df), and water adsorption rate of the obtained cured product were measured. The results are shown in Table 5.

[0122] Comparative Example 6

[0123] Comparative Example 6 was carried out in the same manner as described in Example 13, except that the amount of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanedianhydride (BPADA) was reduced from 75 moles to 20 moles, and the amount of p-phenylene bis(trimellitate anhydride), TAHQ, was increased from 25 moles to 80 moles, to obtain a thin film composition (20) containing the polyimide according to the present disclosure. The solid content of the thin film composition (20) was approximately 25 wt%, and the solvent was γ-butyrolactone.

[0124] Next, a thin film composition (20) was applied to a substrate (e.g., a glass substrate) using a blade coating method to form a coating layer (approximately 18 μm thick). Then, the coating layer was baked at 80°C for 30 minutes to remove the solvent (GBL). Subsequently, the substrate containing the coating layer was baked in a nitrogen environment at 150°C for 30 minutes and then at 220°C for 60 minutes. It was observed that the thin film composition failed to form a film layer, or that the formed film layer was prone to cracking.

[0125] [Table 5]

[0126] As shown in Table 5, Examples 13 and 14 show that the cured thin film compositions obtained by combining a specific diamine with a specific molar ratio of a specific dianhydride according to the present disclosure can reduce the moisture absorption rate (for example, to 0.3% or less) without increasing the dielectric constant or dielectric loss rate. Furthermore, Comparative Examples 5 and 6 show that if the first and second dianhydrides used are not within the ratio range defined in the present disclosure, the resulting thin film composition cannot be fabricated or the resulting cured product will have a poor dielectric loss rate (for example, higher than 0.0050) and a high moisture absorption rate (for example, higher than 1%).

[0127] In summary, the cured product of the thin film composition according to this disclosure (including the polyimide according to this disclosure) has a low dielectric constant (Dk) and low dielectric loss (Df) at high frequencies (frequency band of 10 GHz or higher), as well as a low moisture absorption rate. Therefore, thin films made from the thin film composition according to this disclosure can have stable dielectric properties.

[0128] Although the present disclosure has been disclosed in several embodiments as described above, these embodiments are not intended to limit the present disclosure. A person with ordinary skill in the art may make any modifications and alterations, provided that they do not deviate from the spirit and scope of the present disclosure, and the scope of protection of the present disclosure will be determined by the attached claims.

Claims

1. A polyimide is a reaction product of reactant (a) and reactant (b), wherein reactant (a) consists of a first dianhydride and a second dianhydride, the first dianhydride has a structure represented by formula (I), and the second dianhydride has a structure represented by formula (II), and the ratio of the number of moles of the first dianhydride to the second dianhydride is 3:7 to 8:

2. 【Chemistry 1】 (In the formula, R １ and R ２ Each of these is independently hydrogen, fluorine, methyl group, ethyl group, propyl group, fluoromethyl group, fluoroethyl group, or fluoropropyl group. １ It is one of the following: 【Chemistry 2】 Furthermore, the reactant (b) consists only of the first diamine and the second diamine, and the first diamine is 【Transformation 3】 The second diamine is 【Chemistry 4】 (In the formula, R １１ and R １２ These are, independently, hydrogen, fluorine, methyl group, ethyl group, propyl group, fluoromethyl group, fluoroethyl group, or fluoropropyl group. A polyimide wherein the ratio of the number of moles of the first diamine to the second diamine is 1:9 to 9:

1.

2. The polyimide according to claim 1, wherein the weight-average molecular weight of the polyimide is 5,000 to 3,000,000 g / mol.

3. A thin film composition, The polyimide according to claim 1, A solvent, and A thin film composition having a solid content of 5 wt% to 30 wt%.

4. The thin film composition according to claim 3, wherein the solvent is N-methylpyrrolidone, dimethylacetamide, γ-butyrolactone, or p-xylene.

5. A thin film which is a cured product of the thin film composition according to claim 3 or 4.

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