Diamine compounds, polyamic acid compounds derived therefrom, and polyimide films and heat-resistant insulating substrates for flexible printed wiring boards or insulating films for semiconductors made of the films

Abstract

Provided is a diamine compound that is easy to synthesize and exhibits high solubility in organic solvents, and that a polyimide film derived from this diamine compound via a polyamic acid compound has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band. The present invention provides a diamine compound represented by the following general formula (1), a polyamic acid compound derived therefrom, and a polyimide film and a heat-resistant insulating substrate for a flexible printed wiring board, or an insulating film for a semiconductor. TIFF2026043157000044.tif23161 In the above formula, X 1 represents a divalent group represented by the following formula (a) or (b), and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group. TIFF2026043157000045.tif15161

Description

[Technical Field]

[0001] The present invention relates to a diamine compound, a polyamic acid compound derived therefrom, a polyimide film, and a heat-resistant insulating substrate for a flexible printed wiring board or an insulating film for a semiconductor, which comprises the film. [Background technology]

[0002] Polyimides are generally derived from bifunctional monomers, tetracarboxylic dianhydrides and diamine compounds, and their films exhibit excellent electrical insulation, mechanical properties, and heat resistance. Some polyimide films also have excellent thermal dimensional stability. Due to these excellent properties, polyimides have been used as heat-resistant insulating substrates for flexible printed circuit boards (FPCs) and insulating materials for electronic devices, such as insulating films for semiconductors. However, with the advent of 5G, the fifth-generation mobile communication system that enables high speed, large capacity, low latency, and the connection of multiple devices, problems have arisen with communication FPCs that use conventional polyimide. These problems stem from the high operating frequencies (signals) of 5G, ranging from 3.7 to 28 GHz.

[0003] Transmission loss is expressed as the sum of conductor loss due to the conductor and dielectric loss due to the dielectric (insulating material). Transmission loss in the high-frequency band is more strongly affected by dielectric loss than conductor loss. Since the dielectric loss is proportional to the square root of the dielectric constant and the dielectric loss tangent (tanδ) of the insulating material, insulating materials with low dielectric constant and dielectric loss tangent (tanδ), especially those with low dielectric loss tangent (tanδ), are required, as they contribute significantly to reducing dielectric loss. A known conventional polyimide film is Kapton® H (manufactured by DuPont-Toray Co., Ltd.), which is derived from pyromellitic dianhydride and 4,4'-oxydianiline. This polyimide film exhibits a dielectric loss tangent (tanδ) of 0.0140 at 10 GHz, which does not satisfy the low dielectric loss tangent required for insulating materials in FPCs for 5G communications (Non-Patent Document 1). The polyimide film also has a high water absorption rate of approximately 2 to 3% by mass, and the dielectric loss tangent (tanδ) of water is extremely large, at approximately 0.123 at 25°C and 2.45 GHz. When placed in a normal environment (room temperature and normal pressure), the polyimide film absorbs moisture from the atmosphere, and the amount of moisture that can be absorbed in the film is considered to be saturated. Therefore, the low water absorption of the polyimide film is also an important control factor from the viewpoint of suppressing water absorption, which is one of the causes of the high dielectric loss tangent, and reducing the dielectric loss tangent (tanδ). As such, the use of conventional polyimide as an insulating material has the problem of large signal transmission loss in the high-frequency bands of 5G.

[0004] Fluorine-based resins and liquid crystal polymers have emerged as candidates for insulating materials that can suppress transmission loss in the high-frequency band, replacing the conventional polyimides mentioned above. For example, Vecstar (registered trademark, manufactured by Kuraray Co., Ltd.) is known as a liquid crystal polymer film that can suppress transmission loss in the high frequency band. This liquid crystal polymer film has a low water absorption rate of 0.04% by mass and a low dielectric loss tangent (tanδ) of 0.002 at 28 GHz (Non-Patent Document 2). Furthermore, the fluorine-based resin polytetrafluoroethylene (PTFE) has an extremely low dielectric loss tangent (tanδ) of 0.00023 at 10 GHz (Non-Patent Document 4). However, the above-mentioned fluororesins have the problem of poor thermal dimensional stability, and the manufacturing methods of insulating materials such as the above-mentioned fluororesins and liquid crystal polymers are more complicated than those of polyimides, which poses a problem in terms of cost. Against this background, attention has once again been drawn to polyimides, and attempts have been made to reduce their drawback of high dielectric loss tangent (tan δ).

[0005] For example, it has been reported that using a monomer with a large molecular weight to reduce the proportion of "imide rings" in the repeating structural unit of polyimide resulted in a decrease in water absorption and a decrease in the dielectric loss tangent (tanδ) at 10 GHz (Non-Patent Documents 3 and 4). Non-Patent Documents 3 and 4 state that, based on the polyimide polymerization method, it is advantageous to increase the molecular weight of the tetracarboxylic dianhydride. In polyimide polymerization, polyimides are generally insoluble in organic solvents, so a solvent-soluble polyimide precursor, i.e., polyamic acid (PAA), is polymerized first. Polyimide film is then formed using a two-step process: a PAA solution is cast onto a substrate, dried, and then heated to convert it to polyimide. Therefore, to obtain high-quality polyimide films, a high degree of polymerization of PAA is required. The most common method for this is to first dissolve a diamine compound in an organic solvent and then add powdered tetracarboxylic dianhydride. The best method is to add powdered tetracarboxylic dianhydride to the diamine solution, allowing the tetracarboxylic dianhydride to dissolve in the reaction solution while reacting with the diamine compound. If the addition order is reversed, dissolving the tetracarboxylic dianhydride in the solvent first will hydrolyze the tetracarboxylic dianhydride, resulting in a decrease in the degree of polymerization of PAA. Thus, the standard method for PAA polymerization involves first dissolving the diamine compound in an organic solvent. On the other hand, increasing the molecular weight of a diamine compound to lower the dielectric dissipation factor (tanδ) reduces its solubility in organic solvents. Non-Patent Documents 3 and 4 report diamine compounds with five aromatic rings, but the synthesis route is complicated and requires multiple steps. Non-Patent Documents 3 and 4 also describe that diamine compounds with six or more aromatic rings introduced to increase the molecular weight significantly reduce their solubility in organic solvents, making the polymerization of polyamic acid difficult. Thus, there are limitations to using high-molecular-weight diamine compounds to lower the dielectric dissipation factor (tanδ) of polyimide films. Therefore, Non-Patent Documents 3 and 4 aim to reduce the water absorption rate of polyimide and the dielectric loss tangent (tan δ) at 10 GHz by increasing the molecular weight of tetracarboxylic dianhydride, which is not limited by solubility. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] ACS Applied Polymer Materials, 2021, Vol. 3, pp. 362-371 [Non-patent document 2] Journal of the Japan Institute of Electronics Packaging, 2015, Vol. 18, No. 5, pp. 316-318 [Non-patent document 3] Polymer International, 2022, Vol. 71, p. 1164 [Non-patent document 4] Polymers, 2024, Vol. 16, No. 653 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the methods described in Non-Patent Documents 3 and 4 for reducing the water absorption rate of polyimide using a tetracarboxylic dianhydride with a large molecular weight and for reducing the dielectric loss tangent (tan δ) at 10 GHz, the synthesis of the tetracarboxylic dianhydride with a large molecular weight requires multi-step reactions, which poses problems in terms of cost and the environment. The present invention has been made in view of the above problems, and an object of the present invention is to develop a new diamine compound capable of deriving a polyimide film having low water absorption and a low dielectric loss tangent in addition to the excellent properties of the polyimide film (high heat resistance and excellent thermal dimensional stability). That is, an object of the present invention is to provide a diamine compound that is easy to synthesize and exhibits high solubility in organic solvents, and that produces a polyimide film derived from this diamine compound via a polyamic acid compound (polyimide precursor) that has high heat resistance and excellent thermal dimensional stability, as well as low water absorbency and a low dielectric loss tangent in the high frequency band. Another object of the present invention is to provide a polyamic acid compound from which a polyimide film is derived that has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band. Another object of the present invention is to provide a polyimide film that has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band, and a heat-resistant insulating substrate for a flexible printed wiring board or an insulating film for a semiconductor made of this film. [Means for solving the problem]

[0008] As a result of intensive research in view of the above-mentioned problems, the present inventors have found that a compound represented by the following general formula (1) can be obtained by combining an amino group with a specific substituent (R 1 or R 2 The present inventors have found that a diamine compound in which a benzene ring having as a substituent a naphthalenediyl group represented by formula (a) or a biphenylene group represented by formula (b) is introduced via an ester bond to both ends of the naphthalenediyl group represented by formula (a) or the biphenylene group represented by formula (b) is useful. Specifically, the diamine compound represented by the following general formula (1) is easy to synthesize and exhibits high solubility in organic solvents. The diamine compound and a general-purpose tetracarboxylic dianhydride are polymerized in an organic solvent as monomers to form a polyimide precursor, a polyamic acid (PAA) compound solution, which is obtained by casting the solution on a substrate and drying it to form a film on the substrate. The polyamic acid (PAA) compound is then heated on the substrate to dehydrate and ring-close the polyamic acid (PAA) compound, resulting in a polyimide film with high heat resistance (glass transition temperature and 5% mass loss temperature (T) in either nitrogen (N) or air) comparable to that of conventional general-purpose polyimide films. d 5It was discovered that the polyimide film exhibits high thermal dimensional stability (low average coefficient of linear thermal expansion (average CTE)) and excellent thermal dimensional stability (low average coefficient of linear thermal expansion (average CTE)), and furthermore, it can achieve low water absorption (reduced water absorption rate) and a low dielectric loss tangent in the high frequency band (low dielectric loss tangent (tan δ) at 10 GHz), which were difficult to achieve with conventional general-purpose polyimide films. The present invention was completed after further investigations based on this finding.

[0009] That is, the above problems were solved by the following means. <1> A diamine compound represented by the following general formula (1): [ka] In the above formula, X 1 represents a divalent group represented by the following formula (a) or (b), and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group. [ka] In the above formula, * indicates a bond. <2> A polyamic acid compound comprising a structural unit represented by the following general formula (2): [ka] In the above formula, X 1 represents a divalent group represented by the following formula (a) or (b), and Y 1 represents a tetravalent aromatic or aliphatic group, and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group. [ka] In the above formula, * indicates a bond. <3> A polyimide film comprising a structural unit represented by the following general formula (3): [ka] In the above formula, X 1 represents a divalent group represented by the following formula (a) or (b), and Y 1 represents a tetravalent aromatic or aliphatic group, and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group. [ka] In the above formula, * indicates a bond. <4> The average coefficient of linear thermal expansion between 100 and 200°C is 30.0 ppm / K or less. <3> The polyimide film according to claim 1. <5> The water absorption rate is 1.0% by mass or less. <3> or <4> The polyimide film according to claim 1. <6> The dielectric loss tangent at an operating frequency of 10 GHz is 0.00300 or less. <3> ~ <5> 1. The polyimide film according to any one of the above items. <7> <3> ~ <6> 1. A heat-resistant insulating substrate for a flexible printed wiring board or an insulating film for a semiconductor, comprising the polyimide film according to any one of 1 to 8.

[0010] In the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present invention, the high frequency band means a band of 1 GHz or higher, preferably a band of 1 to 30 GHz, and more preferably a band of 3.7 to 28 GHz. [Effects of the Invention]

[0011] The diamine compound of the present invention can be easily synthesized via a known esterification reaction followed by a reduction reaction, and a polyimide film derived from this diamine compound via a polyamic acid compound (polyimide precursor) has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band. Furthermore, the polyamic acid compound of the present invention provides a polyimide film derived therefrom that has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band. Furthermore, the polyimide film of the present invention, as well as the heat-resistant insulating substrate of a flexible printed wiring board and the insulating film for a semiconductor made of this film, have high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows infrared absorption spectra of a polyamic acid film and a polyimide film of Comparative Example 3. [Figure 2] 1 shows infrared absorption spectra of the polyamic acid film and the polyimide film of Example 5. [Figure 3] 1 shows infrared absorption spectra of the polyamic acid film and polyimide film of Example 6. [Figure 4] 1 shows infrared absorption spectra of a polyamic acid film and a polyimide film of Comparative Example 4. [Figure 5] 1 shows infrared absorption spectra of the polyamic acid film and polyimide film of Example 7. [Figure 6] 1 shows infrared absorption spectra of the polyamic acid film and polyimide film of Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Diamine compounds] The diamine compound of the present invention is represented by the following general formula (1).

[0014] [ka]

[0015] In the above formula, X 1 represents a divalent group represented by the following formula (a) or (b), and R 1 and R 2each independently represents a trifluoromethyl group or a methyl group. [ka]

[0016] The diamine compound of the present invention can be suitably used as a raw material (monomer) for polyimide and polyamic acid compound, which is a precursor of polyimide. The diamine compound represented by the above general formula (1) is a compound having an amino group and a specific substituent (R 1 or R 2 ) as a substituent, and the benzene ring has a divalent group (X 1 ) is introduced at both ends via an ester bond. X 1 When X is a divalent group represented by formula (a), the central part constituting the diamine compound is a naphthalene-2,6-diyl group, which can improve the geometric linearity of the entire diamine compound. 1 Similarly, when R is a divalent aromatic group represented by formula (b), the central moiety constituting the diamine compound is a biphenyl-4,4'-diyl group, so that the geometric linearity of the entire diamine compound can be improved. 1 or R 2 The benzene ring having as a substituent a diamine group is bonded so that the amino group is located at the para position relative to the ester bond, resulting in a structure in which the geometric linearity of the entire diamine compound is further enhanced. Generally, the lower the linear thermal expansion of a polyimide film in a glassy state, the more geometrically linear the chemical structure of the polyimide main chain is, the more preferable it is. To achieve this, it is necessary to polymerize a polyamic acid compound by combining highly linear monomers to form a film. As described above, the diamine compound of the present invention contains, in the central portion constituting the diamine compound, a divalent aromatic group X, which can enhance the geometric linearity of the entire diamine compound. 1 X 1Since the geometric linearity from the amine group to the amino groups at both ends is also enhanced, in a polyimide film obtained by a thermal imidization process from a film of a polyamic acid compound (polyamic acid film) derived from the diamine compound of the present invention, the rigidity of the polyimide main chain is increased, making it more likely to aggregate, thereby exhibiting high heat resistance and promoting self-orientation of the polyimide main chain in the film plane, resulting in low thermal expansion (excellent thermal dimensional stability). Furthermore, in a polyimide film derived from the diamine compound of the present invention, the concentration (proportion) of imide groups in the constituent units is reduced compared to the concentration of imide groups in the constituent units of conventional polyimide films, so it also exhibits low water absorption. In addition, the diamine compound in the general formula (1) is R 1 and R 2 The trifluoromethyl group and the methyl group which can be independently taken as the diamine compound can increase the solubility of the diamine compound in an organic solvent. Moreover, the above R 1 and R 2 The trifluoromethyl group and the methyl group, which can be independently adopted as R, can also realize a low dielectric tangent (tanδ) in the high frequency band of the derived polyimide film. The reason for this is speculation, but as mentioned above, in the polyimide main chain derived from the diamine compound represented by general formula (1), in which the geometric linearity of the entire compound is enhanced, local molecular motion at the site derived from the diamine compound represented by general formula (1) occurs. 1 and R 2 This is thought to be due in part to the suppression in the high frequency range caused by the substituent introduced as R (see Examples 5 and 6 for Comparative Example 3, and Examples 7 and 8 for Comparative Example 4, which will be described later). 1 and R 2 When is a methyl group, the dielectric loss tangent (tan δ) in the high frequency band can be further reduced (see Example 5 compared to Example 6 and Example 7 compared to Example 8, which will be described later). On the other hand, the substituent R 1 and R 2Since the substituted position of the ester group does not affect the geometric linearity of the polyimide main chain, there is no particular limitation on the substituted position as represented by general formula (1). In other words, the substituted position may be either the ortho-position or the meta-position relative to the ester bond.

[0017] <Method of producing diamine compound> The diamine compound represented by the general formula (1) can be obtained, for example, by the following reaction formula: That is, a dinitro intermediate is obtained by a known esterification reaction using a 4-nitrophenol compound represented by the general formula (4) and a dicarboxylic acid dichloride compound represented by the general formula (5), and then the nitro group in the obtained dinitro intermediate is reduced to an amino group by a known reduction reaction, thereby producing the diamine compound represented by the general formula (1). The above esterification reaction and reduction reaction are not limited to known reactions, and commonly used esterification reaction and reduction reaction may be used.

[0018] [ka]

[0019] In the above reaction formula, R is R 1 and R 2 correspond to R 1 , R 2 and X 1 is R in the above general formula (1) 1 , R 2 and X 1 are synonymous with each other. Examples of the 4-nitrophenol compound represented by the general formula (4) include 2-methyl-4-nitrophenol, 3-methyl-4-nitrophenol, 2-trifluoromethyl-4-nitrophenol, and 3-trifluoromethyl-4-nitrophenol, whose chemical structures are shown below.

[0020] [ka]

[0021] Examples of the dicarboxylic acid dichloride compound represented by the above general formula (5) include 2,6-naphthalenedicarboxylic acid dichloride and 4,4'-diphenyldicarbonyl chloride.

[0022] [ka]

[0023] The 4-nitrophenol compound represented by the general formula (4) may be one of the compounds having the above chemical structure, or two or more of them may be mixed and used. Depending on the type of the 4-nitrophenol compound represented by the general formula (4), R in the diamine compound represented by the general formula (1) may be 1 and R 2 is determined. The 4-nitrophenol compound represented by general formula (4) may be reacted in a ratio of at least 2 equivalents per equivalent of the compound represented by general formula (5). When two or more 4-nitrophenol compounds represented by general formula (4) are used, the total amount thereof may be reacted in a ratio of at least 2 equivalents per equivalent of the compound represented by general formula (5).

[0024] [Polyamic acid compounds] The polyamic acid compound of the present invention contains a structural unit represented by the following general formula (2). The polyamic acid compound of the present invention can be obtained by reacting (polymerizing) a diamine compound represented by the above general formula (1) with a tetracarboxylic dianhydride by a known method. The polyamic acid compound of the present invention serves as a precursor to the polyimide of the present invention, which contains a structural unit represented by the below-described general formula (3). The polyamic acid compound of the present invention has high solubility in organic solvents.

[0025] [ka]

[0026] In the above formula, X 1is X in the above general formula (1). 1 and represents a divalent group represented by the above formula (a) or (b). 1 represents a tetravalent aromatic or aliphatic group, and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group.

[0027] Y 1 represents a tetravalent aromatic group or an aliphatic group (i.e., a tetravalent aromatic group or a tetravalent aliphatic group). The above-mentioned tetravalent aromatic group is Y 1 The term "aromatic hydrocarbon ring" refers to a group in which all four bonds as the aromatic hydrocarbon ring are aromatic hydrocarbon rings. The aromatic hydrocarbon ring may be either a monocyclic ring or a condensed ring. The number of aromatic hydrocarbon rings having a bond may be one or more. When the tetravalent aromatic group contains two or more aromatic hydrocarbon rings, these two or more aromatic hydrocarbon rings may be directly bonded by a single bond or may be linked via a linking group. Examples of the linking group include aliphatic hydrocarbon groups (alkylene groups, alkenylene groups, alkylene groups), aromatic hydrocarbon groups (arylene groups), -O-, >C=O, and >S(=O)2, or linking groups formed by combining two or more of these. Some or all of the hydrogen atoms in the aliphatic hydrocarbon groups may be substituted with fluorine atoms. Note that linking groups formed by combining two or more may have a structure in which two aromatic hydrocarbon groups are linked by a single bond. Specific examples of the linking group include an alkylene group, an alkynylene group, -O-, >C=O, >S(=O)2, -C(=O)O-arylene group-O-C(=O)-, and -C(=O)O-arylene group-single bond-arylene group-O-C(=O)-. The above-mentioned tetravalent aliphatic group is Y 1It means a group in which three or more of the four bonds as aliphatic hydrocarbons are contained in the ring. The aliphatic hydrocarbon may be either linear or cyclic, and may be either saturated or unsaturated, and the saturated aliphatic hydrocarbon ring and the unsaturated aliphatic hydrocarbon ring may be either a monocyclic ring, a fused ring, or a bridged ring. The saturated aliphatic hydrocarbon ring and the unsaturated aliphatic hydrocarbon ring may be a heterocyclic ring in which at least one of the carbon atoms constituting the ring is replaced with an oxygen atom, a sulfur atom, or a nitrogen atom. When the tetravalent aliphatic group contains two or more aromatic hydrocarbon rings, these two or more aromatic hydrocarbon rings may be directly bonded by a single bond or may be linked via a linking group. Examples of the linking group include those described above for the tetravalent aromatic group. Y 1 Specific examples of the substituent include, but are not limited to, the substituents shown below. In the structural formula below, *1 and *2 represent bonds, with two *1 being bonds to one amide bond and one carboxy group, and two *2 being bonds to the remaining amide bond and one carboxy group. In a polyimide film containing a structural unit represented by the general formula (3) described below, two *1 are bonds to one imide bond, and two *2 are bonds to the other imide bond. In addition, there are no particular limitations on the substituents that may have an asymmetric carbon atom, as long as the chemical structure can adopt them, and the asymmetric carbon atom may adopt either the R or S absolute configuration.

[0028] [ka]

[0029] [ka]

[0030] In the polyamic acid compound of the present invention, the content of the structural unit represented by general formula (2) is preferably 10 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 30 to 100 mass%, when the total of all structural units of the polyamic acid compound is 100 mass%. In the polyamic acid compound, examples of structural units other than the structural unit represented by general formula (2) include structural units containing a structure derived from a copolymerization component described below.

[0031] <Method for producing (polymerizing) polyamic acid compounds> The polyamic acid compound of the present invention can be obtained by reacting (polymerizing) the diamine compound represented by the above general formula (1) with a tetracarboxylic dianhydride by a known method. The diamine compounds represented by the above general formula (1) may be used singly or in combination of two or more kinds.

[0032] (Tetracarboxylic acid dianhydride) The tetracarboxylic acid dianhydride that can be used when polymerizing a polyamic acid compound containing a structural unit represented by the above general formula (2) is not particularly limited as long as it is a compound represented by the following general formula (c):

[0033] [ka]

[0034] In the above formula, Y 1 represents Y in the above general formula (2). 1 and represents a tetravalent aromatic or aliphatic group. Suitable examples of the tetracarboxylic dianhydride represented by the above general formula (c) are not particularly limited, and include commonly used aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides. Examples of aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 4,4'-(ethyne-1,2-diyl)diphthalic anhydride, bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)1,4-phenylene, bis( 1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)4,4'-biphenylene, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenylethertetracarboxylic dianhydride, 3,3',4,4'-biphenylsulfonetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropanoic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propanoic dianhydride, and the like. Examples of the aliphatic tetracarboxylic dianhydride include bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5-(dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, and 1,2,3,4-cyclopentane tetracarboxylic dianhydride. The tetracarboxylic dianhydrides represented by the above general formula (c) may be used alone or in combination of two or more.

[0035] The tetracarboxylic acid dianhydride represented by the general formula (c) preferably has a rigid and linear chemical structure from the viewpoint of further improving thermal dimensional stability and low dielectric loss tangent. Specific examples of the aromatic tetracarboxylic acid dianhydrides include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 4,4'-(ethyne-1,2-diyl)diphthalic anhydride, bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)1,4-phenylene, and bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)4,4'-biphenylene.

[0036] (Copolymerization component) When polymerizing the polyamic acid compound (polyimide precursor) of the present invention, aromatic or aliphatic diamine compounds can be used in combination as copolymerization components in addition to the diamine compound represented by the general formula (1) above, within the scope that does not significantly impair the polymerization reactivity and the properties of the polyimide film obtained from the polyamic acid compound (high heat resistance, excellent thermal dimensional stability, low water absorption, and low dielectric loss tangent in the high frequency band). Aromatic diamine compounds that can be used as copolymerization components include 2,2'-bis(trifluoromethyl)benzidine, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,3,5,6-tetramethyl-p-phenylenediamine (also known as 3,6-diaminodurene), 4,4'-diaminodiphenylmethane, 4,4'-methylenebis(2-methylaniline), 4, 4'-methylenebis(2-ethylaniline), 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-methylenebis(2,6-diethylaniline), 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone Benzidine, 3,3'-dihydroxybenzidine, 3,3'-dimethoxybenzidine, o-tolidine, m-tolidine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl phenyl, bis(4-(3-aminophenoxy)phenyl)sulfone, bis(4-(4-aminophenoxy)phenyl)sulfone, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, and p-terphenylenediamine (for example, 4,4″-diamino-p-terphenyl).

[0037] The aliphatic diamine compound that can be used as a copolymerization component may be either a chain aliphatic diamine compound or an alicyclic diamine compound. Examples of alicyclic diamine compounds include 4,4'-methylenebis(cyclohexylamine), isophoronediamine, trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminoadamantane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane. Examples of the chain aliphatic diamine compound include 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, and diaminosiloxane.

[0038] These diamine compounds may be used alone or in combination of two or more. Among them, from the viewpoint of improving the heat resistance of the polyimide film, p-phenylenediamine, which is a diamine compound having a rigid and linear chemical structure, is suitable as a copolymerization component, and from the viewpoint of improving the film toughness, 4,4'-diaminodiphenyl ether and 2,2-bis(4-(4-aminophenoxy)phenyl)propane are suitable.

[0039] (organic solvent) The organic solvent used in the polymerization of the polyamic acid compound is not particularly limited as long as it is a solvent that dissolves the diamine compound and the resulting polyamic acid compound. Specific examples of the solvent include, but are not limited to, aprotic amide solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, 3-methoxy-N,N-dimethylpropanamide, and 3-butoxy-N,N-dimethylpropanamide; ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, butyl acetate, ethyl acetate, and isobutyl acetate; ethylene carbonate; and propylene carbonate. glycol-based solvents such as diethylene glycol dimethyl ether, triethylene glycol, and triethylene glycol dimethyl ether; phenol-based solvents such as phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, and 4-chlorophenol; ketone-based solvents such as cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, and methyl isobutyl ketone; and ether-based solvents such as tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethoxyethane, and dibutyl ether. Other solvents that can be used include acetophenone, sulfolane, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, butanol, ethanol, xylene, toluene, and petroleum naphtha-based solvents. These solvents may be used alone or in combination of two or more.

[0040] (Polyamic acid compound polymerization method) The method for polymerizing the polyamic acid compound of the present invention is not particularly limited, and any known method, such as ring-opening polyaddition reaction, can be applied. Specifically, the polymerization can be carried out by the following method. First, a diamine compound is dissolved in an organic solvent. To this solution, a powder of tetracarboxylic dianhydride, substantially equimolar to the diamine compound, is gradually added. The mixture is stirred using a mechanical stirrer or the like at a temperature ranging from 0 to 100°C, preferably from 20 to 60°C, for 0.5 to 150 hours, preferably from 1 to 72 hours. The monomer concentration is typically in the range of 5 to 50% by mass, preferably from 10 to 40% by mass. By carrying out polymerization within this monomer concentration range, a uniform polyamic acid compound with a high degree of polymerization can be obtained. If the polymerization degree of the polyamic acid compound increases too much, making the polymerization solution difficult to stir, the solution can be diluted with the same organic solvent as appropriate. To enhance the mechanical strength of the polyimide film obtained from the polyamic acid compound of the present invention, it is preferable that the degree of polymerization of the polyamic acid compound be as high as possible. By carrying out polymerization within the above monomer concentration range, a polymer (polyamic acid compound) with a sufficiently high degree of polymerization can be obtained while ensuring sufficient solubility of the monomer (diamine compound and tetracarboxylic dianhydride) and the polymer (polyamic acid compound).

[0041] The intrinsic viscosity of the polyamic acid compound of the present invention is preferably in the range of 0.1 to 15.0 dL / g, more preferably in the range of 0.3 to 5.0 dL / g. The intrinsic viscosity is a value measured by the method described in the Examples below.

[0042] [Polyamic acid solution] A solution obtained by dissolving the polyamic acid compound of the present invention in an organic solvent is also referred to as the polyamic acid solution of the present invention. The polyamic acid compound of the present invention is soluble in various organic solvents due to the chemical structure of the constituent unit represented by the above-mentioned general formula (1), and the organic solvent contained in the polyamic acid solution of the present invention can be appropriately selected depending on the intended use and / or processing conditions. Specifically, the organic solvent used in the polymerization of the above-mentioned polyamic acid compound is preferred, and the polyamic acid solution obtained by the polymerization of the above-mentioned polyamic acid compound can be used directly or after adjusting the concentration by further adding the organic solvent used in the polymerization, for the production of a polyimide film as described below. The polyamic acid compound of the present invention can be prepared into a homogeneous polyamic acid solution by dissolving the compound in air or a dry inert gas at a temperature ranging from room temperature (20°C) to the boiling point of the organic solvent for 0.1 to 96 hours during polymerization. After dissolution, the solution can be filtered to remove insoluble matter. The concentration of the polyamic acid compound of the present invention in the polyamic acid solution of the present invention varies depending on the intrinsic viscosity of the polyamic acid compound and the method for producing the polyimide film, but is usually preferably 0.1% by mass or more, more preferably 1 to 30% by mass, calculated as the concentration of all monomers used. If necessary, additives such as a photosensitizer, a sensitizer, an adhesion promoter, a silane coupling agent, a crosslinking agent, an end-capping agent, an antioxidant, an ultraviolet absorber, an antifoaming agent, a leveling agent, a surfactant, an inorganic filler, an organic filler, a dye, a pigment, and a mold release agent may be added to the polyamic acid solution of the present invention.

[0043] [Polyimide film] The polyimide film of the present invention contains a structural unit represented by the following general formula (3): That is, it is a polyimide film containing a structural unit represented by the following general formula (3). The polyimide of the present invention can be obtained by a method including the steps of: applying a polyamic acid solution onto a substrate, the polyamic acid solution being prepared by dissolving a polyamic acid compound (polyimide precursor) containing a structural unit represented by the above general formula (2) in an organic solvent; and drying the solution to obtain a film on the substrate; and heating the film on the substrate to dehydrate and ring-close the polyamic acid (thermal imidization), thereby converting the film into a polyimide film. This method can obtain a polyimide film that exhibits high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in the high frequency band.

[0044] [ka]

[0045] In the above formula, X 1 is X in the above general formula (1). 1and represents a divalent group represented by the above formula (a) or (b). 1 is Y in the above general formula (2) 1 and represents a tetravalent aromatic or aliphatic group, and R 1 and R 2 each independently represents a trifluoromethyl group or a methyl group.

[0046] In the polyimide constituting the polyimide film of the present invention, the content of the structural unit represented by general formula (3) is preferably 10 to 100 mass%, more preferably 20 to 100 mass%, and even more preferably 30 to 100 mass%, when the total of all structural units of the polyimide is 100 mass%. In the polyimide, structural units other than the structural unit represented by general formula (3) include structural units obtained by dehydration ring closure of structural units other than the structural unit represented by general formula (2) in the above-mentioned polyamic acid compound. The polyimide film of the present invention may contain additives that may be contained in the polyamic acid solution of the present invention described above. Note that when the additives contained in the polyamic acid solution of the present invention are used in a reaction in the production process of the polyimide film of the present invention and their structure is changed, this means that the additives after the reaction are contained.

[0047] For example, when used for flexible printed wiring boards, the average coefficient of linear thermal expansion (average CTE) of the polyimide film of the present invention is preferably less than about 40 ppm (parts per million) / K, which is the average CTE of each component of the flexible printed wiring board, which is mainly composed of copper circuits, and specifically, 30.0 ppm / K or less. Furthermore, the lower the average CTE, the better. There is no particular lower limit, but a practical lower limit is, for example, -10 ppm / K or more. The smaller the difference in average CTE between the copper circuit (about 20 ppm / K) and the insulating film, the more easily warping and distortion of the laminated member of the copper circuit and the insulating film are eliminated. The water absorption of the polyimide film of the present invention is preferably less than 3.0% by mass, specifically 1.0% by mass or less. There is no particular restriction on the lower limit, but a practical lower limit is, for example, 0.01% by mass or more. As mentioned above, a lower water absorption is advantageous for reducing the dielectric loss tangent (tan δ). The dielectric loss tangent (tanδ) of the polyimide film of the present invention, measured by a cavity resonator perturbation method at an operating frequency of 10 GHz, a relative humidity of 50%, and 23°C, is preferably 0.00300 or less, more preferably 0.00280 or less, and even more preferably 0.00220 or less, from the viewpoint of achieving a dielectric loss tangent as low as that of liquid crystal polymers. The dielectric loss tangent is particularly preferably 0.00200 or less, from the viewpoint of achieving a dielectric loss tangent even lower than that of liquid crystal polymers. While there is no particular restriction on the lower limit, a practical lower limit is, for example, 0.0001 or more. The smaller the dielectric loss tangent (tanδ), the more advantageous it is for reducing dielectric loss. Furthermore, when the dielectric loss tangent (tanδ) of a polyimide film satisfies the requirement of 0.00300 or less at the operating frequency of 10 GHz, the dielectric loss tangent (tanδ) can be kept low (approximately 0.00300 or less) over the entire operating frequency range of approximately 1 to 30 GHz. The glass transition temperature (Tg) of the polyimide film of the present invention is required to be 260° C. or higher, for example, from the viewpoint of being able to withstand the temperature of lead-free solder mounting, and is therefore preferably 260° C. or higher, more preferably 280° C. or higher, and even more preferably does not exhibit glass transition (does not have a glass transition temperature) in the range of room temperature to 450° C. A higher Tg is preferable because it provides better heat resistance, and there is no particular upper limit. The 5% mass loss temperature (T d 5 , N2) and the 5% mass loss temperature in air (T d 5 In both cases, the temperature of the 5% mass loss in nitrogen (T d 5 , N2) and the 5% mass loss temperature in air (T d5 , Air) is higher, the heat resistance is better, so there is no particular upper limit, but a practical upper limit is, for example, 550°C or less. The thickness of the polyimide film of the present invention can be adjusted appropriately depending on the intended use within the range that can be produced, and can be, for example, 1 to 150 μm, and preferably 2 to 100 μm. The above average coefficient of linear thermal expansion (average CTE), water absorption, dielectric loss tangent (tanδ), glass transition temperature (Tg), 5% mass loss temperature in nitrogen (T d 5 , N2), 5% mass loss temperature in air (T d 5 , Air) and film thickness are values ​​measured by the method described in the Examples below. Therefore, the dielectric loss tangent (tan δ) is an average dielectric loss tangent (tan δ).

[0048] <Method of manufacturing polyimide film> The polyimide film of the present invention can be produced by a method including the steps of: applying the polyamic acid solution of the present invention onto a substrate and drying it to obtain a film on the substrate; and heating the film on the substrate to dehydrate and ring-close the polyamic acid compound, thereby converting the film into a polyimide film. The polyamic acid solution of the present invention is applied to a substrate by a known method such as dipping, spin coating, or printing, for example, by casting onto a support substrate such as a glass substrate using a doctor blade. Thereafter, a polyimide film can be produced by drying and heating using a hot air dryer, infrared drying oven, vacuum dryer, inert oven, or the like, typically at a temperature in the range of 40 to 450°C, preferably 50 to 400°C. Specifically, the polyamic acid solution cast onto the support substrate is heated at 40 to 150°C to dry the organic solvent to a certain extent, and then heated at 150 to 450°C to dehydrate and ring-close the polyamic acid, resulting in a high-quality polyimide film. When removing strain remaining at the interface between the polyimide film and the supporting substrate, a known method can be employed. For example, the polyimide film can be peeled off from the supporting substrate and then heated and dried under reduced pressure using a vacuum dryer or the like, thereby obtaining a polyimide film from which strain remaining at the interface with the supporting substrate has been removed. It is also possible to produce a laminate of a substrate and a polyimide film by applying the composition directly to a silicon wafer, copper foil, aluminum foil, a low thermal expansion inorganic substrate, etc., instead of onto a supporting substrate, followed by drying and heating. The polyimide film produced as described above has high heat resistance and excellent thermal dimensional stability, as well as low water absorption and a low dielectric loss tangent in high frequency bands, and therefore can be suitably used as an insulating material for electronic devices such as heat-resistant insulating substrates for flexible wiring boards and insulating films for semiconductors (e.g., interlayer insulating films for semiconductors).In particular, it can be suitably used as an insulating material used in high frequency bands, such as an insulating material for electronic devices for 5G. [Example]

[0049] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the examples shown below. Note that the physical property values ​​in the following examples are values ​​measured by the following evaluation methods. Furthermore, room temperature means "about 20°C" and is also abbreviated as rt.

[0050] <Evaluation method> 1. Infrared absorption spectrum The infrared absorption spectra of compounds such as diamine compounds were measured by the KBr method using a Fourier transform infrared spectrophotometer FT / IR-4X (product name, manufactured by JASCO Corporation). The infrared absorption spectra of polyamic acid films and polyimide films were measured using thin film samples (approximately 5 μm thick). 2. 1 H-NMR spectrum Using a Fourier transform nuclear magnetic resonance JNM-ECP400 (trade name, manufactured by JEOL), synthesized compounds such as diamine compounds were measured in deuterated dimethyl sulfoxide (DMSO-d6). 3. Melting Point The melting points of the synthesized products such as diamine compounds were measured in a nitrogen atmosphere at a heating rate of 5°C / min using a high-sensitivity differential scanning calorimeter DSC8230 (trade name, manufactured by Rigaku Corporation), a differential thermobalance TG8120 (trade name, manufactured by Rigaku Corporation), or a thermogravimetric analyzer TG-DTA2000 (trade name, manufactured by Netsch). The sharper the melting peak of the melting point, the higher the purity. 4.Elemental analysis For elemental analysis of synthesized products such as diamine compounds, the chemical composition of C, H, and N was analyzed using an organic trace elemental analyzer (manufactured by J Science Labs, product name: MICRO CORDER JM10). 5.Intrinsic viscosity:η inh The reduced viscosity of a 0.5% by mass polyamic acid solution was measured at 30°C using an Ostwald viscometer. N-methyl-2-pyrrolidone (NMP) was used as the solvent. This value was considered to be the intrinsic viscosity. 6. Film Thickness The thickness of the polyimide film was determined by measuring the thickness at four points on the film using a Digimatic Micrometer MDC-25MX (trade name, manufactured by Mitutoyo Corporation) and calculating the average value. 7. Glass transition temperature: Tg The glass transition temperature of the polyimide film was determined using a thermomechanical analyzer TMA8310 (trade name, manufactured by Rigaku Corporation) by first heating a polyimide film sample (size: width 5 mm, length 15 mm) to 150°C at 5°C / min (first heating) under a load of film thickness (μm) × 0.5 g, then cooling to 20°C and further heating at 5°C / min (second heating), and then measuring the glass transition temperature by the tangent method (intersection of the tangent in the glassy state and the tangent after Tg) of the TMA (mechanical thermal analysis) curve during the second heating. 8. 5% mass loss temperature in nitrogen (N2) or air: T d 5 Using a thermogravimetric analyzer TG-DTA2000 (trade name, manufactured by Netsch) or a differential thermobalance TG8120 (trade name, manufactured by Rigaku), the temperature at which the polyimide film lost 5% of its initial mass was measured in nitrogen (N2) gas or air during a temperature increase from 20°C at a rate of 10°C / min. A higher value indicates higher thermal stability. 9. Average coefficient of linear thermal expansion: Average CTE The average coefficient of linear thermal expansion (CTE) of the polyimide film was measured using a thermomechanical analyzer (TMA8310, manufactured by Rigaku Corporation) by heating a polyimide film sample (size: 5 mm wide, 15 mm long) to 150°C at 5°C / min (first heating) under a load of film thickness (μm) × 0.5 g, then cooling to 20°C and heating again at 5°C / min (second heating). The average coefficient of linear thermal expansion (CTE) was calculated from the TMA curve during the second heating. The average coefficient of linear thermal expansion (CTE) was calculated as the average value between 100 and 200°C (i.e., the slope of the secant line passing through 100°C and 200°C on the TMA curve).

[0051] 10. Average tensile modulus: E, Average elongation at break: ε b,ave , maximum breaking elongation: ε b,max , average breaking strength: σ b The mechanical properties of polyimide films (specimens: 30 mm long x 3 mm wide x 25 μm thick) were measured using a tensile tester (Tensilon UTM-2, manufactured by A&D Co., Ltd.) at a stretching rate of 8 mm / min at room temperature (number of valid specimens n>15). The average tensile modulus (E) was calculated from the initial slope of the stress-strain curve, and the average breaking elongation (ε) was calculated from the elongation and stress at which the film broke. b,ave ), maximum breaking elongation (ε b,max ) and average breaking strength (σ b The test pieces were cut to the above sizes from polyimide films that had been left at room temperature for 12 hours. 11.Water absorption rate:W A The water absorption rate of polyimide film was measured according to JIS (Japanese Industrial Standards) K 7209 (2000). The mass (W0) of a polyimide film (film thickness 20-30 μm) that had been vacuum dried at 50°C for 24 hours was weighed, and the film was then immersed in water at 23°C for 24 hours. After wiping off excess water, the mass (W) was weighed and the W A = [(W-W0) / W0] x 100 (%), the water absorption rate (W A ) was calculated. 12. High frequency dielectric properties (average relative dielectric constant: ε r , average dielectric tangent: tanδ) The high-frequency dielectric properties of the polyimide film at 10 GHz were measured by placing the polyimide film in an environment of 23°C and 50% RH (relative humidity) for 24 hours, and then measuring the average relative dielectric constant (ε) under the same temperature and humidity conditions using a cavity resonator perturbation method (compliant with IEC (International Electrotechnical Commission) 62810, Keysight Technologies, Inc., N5222B PNA Microwave Network Analyzer, Kanto Electronics Application Development Co., Ltd., 10 GHz cavity resonator, model number: CP531). r ), and the average dielectric loss tangent (tan δ) was measured (number of tests n=2).

[0052] [Comparative Example: Substituent R in General Formula (1)] 1 and R 2 Synthesis of diamine compound not having (Comparative Example 1) (1) Synthesis of dinitro compounds

[0053] [ka]

[0054] 3.1627 g (22.735 mmol) of 4-nitrophenol was added to a 100 mL three-neck flask and dissolved in anhydrous N,N-dimethylformamide (DMF). 5 mL of anhydrous triethylamine was added to prepare solution A. 2.2296 g (8.8099 mmol) of 2,6-naphthalenedicarboxylic acid dichloride was added to a 100 mL recovery flask and dissolved in 60 mL of anhydrous DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred at room temperature (rt) for 1 hour under a dry nitrogen gas atmosphere, and then 40 mL of anhydrous DMF was added. The mixture was then stirred at 45 °C for 4 hours. The temperature was then returned to room temperature, and the reaction solution was slowly added to 800 mL of a mixed solvent of deionized water and methanol (volume ratio 1:1). The precipitate was filtered and thoroughly washed with a mixed solvent of deionized water and methanol (volume ratio 1:1). A silver nitrate solution was added to the wash to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum oven at 120°C for 12 hours. The crude product was added to 100 mL of dimethyl sulfoxide (DMSO), heated to 50°C, and stirred for 1 hour. The mixture was then cooled to room temperature and filtered, washing the precipitate thoroughly with DMSO to recover the target product. The product was then dried at 120°C for 12 hours. The dried product was then added to 100 mL of DMF, stirred at 50°C for 1 hour, washed, and then filtered. The recovered product was then vacuum-dried at 120°C for 12 hours to obtain the white target product. The yield was 68%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 1737cm -1 Ester group C=O stretching, 1518 and 1344 cm -1 Nitro group stretching, 1261 cm -1 The CO stretching of the ester group was also confirmed. 1 The H-NMR spectrum could not be measured because the product was insoluble in deuterated solvents, but it was confirmed that no signals derived from the raw materials 4-nitrophenol and 2,6-naphthalenedicarboxylic acid dichloride were observed, and the product was then subjected to the subsequent reduction reaction.

[0055] (2) Synthesis of diamines by reduction of dinitro compounds

[0056] [ka]

[0057] To a 100 mL three-neck flask, 2.7159 g of the dinitro compound synthesized above, 60 mL of anhydrous DMF, and 0.2815 g of palladium / carbon (Pd 10%) (approximately 55% water-wet) were added. The solution was stirred at 50-80 °C for 6 hours while bubbling hydrogen. The reaction mixture was cooled and filtered, and the filtrate was added to 800 mL of brine to precipitate the target product. The suspension was filtered and washed thoroughly with deionized water. A silver nitrate solution was added to the washes to confirm the removal of chloride ions. The recovered product was dried under vacuum at 120 °C for 12 hours to obtain a beige crude product. 2.1779 g of the resulting crude product and 50 mL of DMF were added to a 200 mL recovery flask, heated to 120 °C to dissolve, and then recrystallized. The purified powder was collected by filtration, washed thoroughly with deionized water and then methanol, and dried at 130 °C for 12 hours to obtain the target product as an orange powder. The yield was 62%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3070 and 3018 cm -1 Aromatic CH stretching, 1719 cm -1 Ester group C=O stretching, 1256cm -1 The CO stretching of the ester group was also confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm) confirmed the following signals: 8.91 (d, J = 0.8 Hz, 2H), 8.37 (d, J = 8.6 Hz, 2H), 8.20 (dd, J = 8.6, 1.4 Hz, 2H), 6.98 (d, J = 8.8 Hz, 4H), 6.63 (d, J = 8.8 Hz, 4H), and 5.14 (s, 4H). Elemental analysis revealed theoretical values ​​of C; 72.35%, H; 4.55%, and N; 7.03%, while the measured values ​​were C; 72.19%, H; 4.59%, and N; 7.19%, with the difference between the theoretical and measured values ​​for all elements being within 0.3%. These analytical results confirmed the identity of the target diamine compound. An attempt was made to measure the melting point using a differential thermobalance TG8120 (trade name, manufactured by Rigaku Corporation), but thermal decomposition began at around 250°C, making it impossible to confirm the melting point.

[0058] (Comparative Example 2) (1) Synthesis of dinitro compounds

[0059] [ka]

[0060] 2.7401 g (19.6974 mmol) of 4-nitrophenol was added to a 100 mL three-neck flask and dissolved in dehydrated DMF. 5 mL of dehydrated triethylamine was added to prepare solution A. 2.3207 g (8.3143 mmol) of 4,4'-diphenyldicarbonyl chloride was added to a 300 mL recovery flask and dissolved in 50 mL of dehydrated DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred under a dry nitrogen atmosphere at room temperature for 2 hours and then at 45 °C for 3 hours. The temperature was then returned to room temperature, and the reaction solution was slowly added to 800 mL of a mixed solvent of deionized water and methanol (1:1 by volume). The precipitate was filtered and thoroughly washed with a mixed solvent of deionized water and methanol (1:1 by volume). Silver nitrate aqueous solution was added to the wash solution to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum oven at 120°C for 12 hours. The dried crude product was added to 100 mL of tetrahydrofuran (hereafter referred to as THF), heated to approximately 60°C, and stirred for 1 hour. After cooling to room temperature and filtering, the precipitate was thoroughly washed with THF to recover the target product. The target product was then dried at 120°C for 12 hours, yielding a white product. The yield was 92%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 1732 cm -1 Ester group C=O stretching, 1517 and 1342 cm -1 Nitro group stretching, 1261 cm -1 The CO stretching of the ester group was also confirmed. 1 In the H-NMR spectrum, signals were observed at (DMSO-d6, δ, ppm): 8.39 (d, J = 9.2 Hz, 4H), 8.31 (d, J = 8.6 Hz, 4H), 8.07 (d, J = 8.6 Hz, 4H), and 7.68 (d, J = 9.2 Hz, 4H). These analytical results confirmed that this was the desired dinitro intermediate. Furthermore, a high-sensitivity differential scanning calorimeter, DSC8230 (Rigaku Corporation), confirmed a melting point of 244 °C, and the melting peak was sharp.

[0061] (2) Synthesis of diamines by reduction of dinitro compounds

[0062] [ka]

[0063] To a 100 mL three-neck flask, 0.9327 g of the dinitro compound synthesized above, 50 mL of anhydrous DMF, and 0.1030 g of palladium / carbon (Pd 10%) (approximately 55% water-wet) were added. The solution was stirred at 30-50 °C for 5 hours while bubbling hydrogen. The reaction mixture was cooled and filtered, and the filtrate was added to 800 mL of deionized water to precipitate the target product. This suspension was filtered, washed with deionized water, and vacuum-dried at 120 °C for 12 hours to obtain a beige crude product. To a 200 mL recovery flask, 0.7514 g of the resulting crude product was added to 50 mL of toluene, heated to 100 °C, dissolved, and then recrystallized. The purified powder was collected by filtration, washed thoroughly with toluene and then hexane, and dried at 120 °C for 12 hours to obtain the brown target product. The yield was 75%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3068 and 3044 cm -1 Aromatic CH stretching, 1724 cm -1 Ester group C=O stretching, 1264cm -1 The CO stretching of the ester group was also confirmed. 1 The H-NMR spectrum of the compound (DMSO-d6, δ, ppm) confirmed the following signals: 8.22 (d, J = 8.5 Hz, 4H), 7.99 (d, J = 8.3 Hz, 4H), 6.94 (d, J = 8.8 Hz, 4H), 6.61 (d, J = 8.8 Hz, 4H), and 5.11 (s, 4H). Elemental analysis revealed theoretical values ​​of C: 73.57%, H: 4.75%, and N: 6.60%, while the measured values ​​were C: 73.28%, H: 4.84%, and N: 6.47%, with the difference between the theoretical and measured values ​​being within 0.3% for all elements. These analytical results confirmed the identity of the target diamine compound. Furthermore, a high-sensitivity differential scanning calorimeter (DSC8230, Rigaku Corporation) confirmed a melting point of 262 °C, with a sharp melting peak.

[0064] [Example: Synthesis of diamine compound represented by general formula (1)] Example 1 (1) Synthesis of dinitro compounds

[0065] [ka]

[0066] 3.2851 g (21.4516 mmol) of 2-methyl-4-nitrophenol was added to a 100 mL three-neck flask and dissolved in 10 mL of dehydrated DMF. 5 mL of dehydrated triethylamine was added to prepare solution A. 2.1986 g (8.6874 mmol) of 2,6-naphthalenedicarboxylic acid dichloride was added to a 100 mL recovery flask and dissolved in 70 mL of dehydrated DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred under a dry nitrogen atmosphere at room temperature for 1 hour and then at 45 °C for 4 hours. The temperature was then returned to room temperature, and the reaction solution was slowly added to 800 mL of a mixed solvent of deionized water and methanol (1:1 by volume). The precipitate was filtered and thoroughly washed with a mixed solvent of deionized water and methanol (1:1 by volume). A silver nitrate solution was added to the wash solution to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum oven at 60°C for 12 hours. The dried crude product was added to 100mL of DMF, heated to 50°C, and stirred for 1 hour. After cooling to room temperature and filtering, the precipitate was thoroughly washed with DMF and then methanol to recover the target product. The product was then dried at 120°C for 12 hours. The dried product was then added to 100mL of DMSO for washing, and the purified product was filtered and washed with DMSO and methanol, after which it was dried at 120°C for 12 hours to obtain the white target product. The yield was 59%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 2965 and 2934 cm -1 Aliphatic CH stretching, 1737cm -1 Ester group C=O stretching, 1522, 1350 cm -1 Nitro group stretching, 1249 cm -1 The CO stretching of the ester group was also confirmed. 1The H-NMR spectrum could not be measured because the product was insoluble in deuterated solvents, but it was confirmed that no signals derived from the raw materials, 2-methyl-4-nitrophenol and 2,6-naphthalenedicarboxylic acid dichloride, were observed, and the product was then subjected to the subsequent reduction reaction.

[0067] (2) Synthesis of diamines by reduction of dinitro compounds

[0068] [ka]

[0069] A 100 mL three-neck flask was charged with 2.4311 g of the dinitro compound synthesized above, 60 mL of anhydrous DMF, and 0.2502 g of palladium / carbon (Pd 10%) (approximately 55% water-wet). The solution was stirred at 50–80°C for 5.5 hours while bubbling with hydrogen. After cooling, the reaction mixture was filtered to remove the catalyst. An appropriate amount of toluene (azeotropic agent) was added, and the filtrate was evaporated to dryness, yielding a crude product as a brown powder. A 200 mL recovery flask was charged with 1.9333 g of the resulting crude product and 38 mL of DMF, heated to 120°C, dissolved, and then recrystallized by adding 18 mL of deionized water. The purified powder was collected by filtration, washed thoroughly with deionized water and then methanol, and dried at 120°C for 12 hours to obtain the desired product as a brown powder. The yield was 70%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3062 and 3039 cm -1 Aromatic CH stretching, 2906 cm -1 Aliphatic CH stretching, 1728 cm -1 Ester group C=O stretching, 1259 cm -1 The CO stretching of the ester group was also confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm): 8.95 (d, J = 0.8 Hz, 2H), 8.39 (d, J = 8.6 Hz, 2H), 8.23 ​​(dd, J = 8.5, 1.3 Hz, 2H), 6.90 (d, J = 8.5 Hz, 2H), 6.52 (d, J = 2.4 Hz, 2H), 6.47 (dd, J = 8.5, 2.6 Hz, 2H), 5.06 (s, 4H), and 2.07 (s, 6H) were observed. Elemental analysis revealed the theoretical values ​​of C; 72.23%, H; 5.20%, and N; 6.57%, while the measured values ​​were C; 73.06%, H; 5.36%, and N; 6.78%, with the difference between the theoretical and measured values ​​being within 0.3% for all elements. These analytical results confirmed the identity of the target diamine compound. Furthermore, a melting point of 230°C was confirmed using a differential thermobalance TG8120 (trade name, manufactured by Rigaku Corporation), and the melting peak was sharp.

[0070] Example 2 (1) Synthesis of 2-trifluoromethyl-4-nitrophenol

[0071] [ka]

[0072] A 100 mL three-neck flask was charged with 11.4377 g (50.7103 mmol) of 1-chloro-4-nitro-2-(trifluoromethyl)benzene, 10.5749 g (188.482 mmol) of potassium hydroxide, 10 mL of deionized water, and 10 mL of DMSO. The mixture was stirred at room temperature for 10 minutes under a nitrogen atmosphere, followed by vigorous stirring at 100 °C for 5 hours. After cooling to room temperature, the reaction solution was transferred to a 300 mL beaker and acidified to approximately pH 2 by slowly adding concentrated hydrochloric acid to give a yellow-white suspension. The yellow suspension was transferred to a separatory funnel and extracted three times with 100 mL of ethyl acetate. The organic layer was washed with 100 mL of brine and recovered. The organic layer was dehydrated over anhydrous sodium sulfate, evaporated to dryness, and then vacuum-dried at 30 °C for 12 hours. The dried product was then purified by sublimation under reduced pressure at 80 °C to obtain a pale yellow-white product. The yield was 74%. In the infrared absorption spectrum of the obtained target substance, -1 Wide OH stretch, 3102cm -1 Aromatic CH stretching, 1526 cm -1 Nitro group stretching, 1116cm -1 CF expansion and contraction was confirmed. 1 In the H-NMR spectrum, signals were confirmed at (DMSO-d6, δ, ppm): 12.36 (s, 1H), 8.38 (dd, J = 2.9, 9.1 Hz, 1H), 8.32 (d, J = 2.8 Hz, 1H), and 7.22 (d, J = 9.1 Hz, 1H). These analytical results confirmed that the target compound was 2-trifluoromethyl-4-nitrophenol.

[0073] (2) Synthesis of dinitro compounds

[0074] [ka] 4.3988 g (21.2390 mmol) of 2-trifluoromethyl-4-nitrophenol synthesized above was added to a 100 mL three-neck flask and dissolved in 10 mL of dehydrated DMF. 5 mL of dehydrated triethylamine was added to prepare solution A. 2.5273 g (9.9862 mmol) of 2,6-naphthalenedicarboxylic acid dichloride was added to a 100 mL recovery flask and dissolved in 60 mL of dehydrated DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred at room temperature under a dry nitrogen gas atmosphere for 4 hours. The reaction solution was then slowly added to 800 mL of a mixed solvent of deionized water and methanol (1:1 by volume). The precipitate was filtered and thoroughly washed with a mixed solvent of deionized water and methanol (1:1 by volume). Silver nitrate aqueous solution was added to the wash solution to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum dryer at 60°C for 12 hours. The dried crude product was added to 50 mL of toluene and heated to 100°C. 19 mL of DMF was added, and the insoluble matter was removed by filtration. The filtrate was collected, concentrated in an evaporator, and recrystallized. The resulting crystals were collected by filtration and washed thoroughly with a mixed solvent of toluene and DMF (volume ratio 5:2), and the target product was recovered. The product was then dried at 120°C for 12 hours to obtain the white target product. The yield was 51%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 1734cm -1 Ester group C=O stretching, 1532 and 1357 cm -1 Nitro group stretching, 1248 cm -1 Ester group CO stretching, 1143cm -1 CF expansion and contraction was confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm): 9.01 (d, J = 1.8 Hz, 2H), 8.74 (dd, J = 8.8, 2.7 Hz, 2H), 8.63 (d, J = 2.8 Hz, 2H), 8.52 (d, J = 8.6 Hz, 2H), 8.26 (dd, J = 8.5, 1.7 Hz, 2H), and 8.11 (d, J = 9.2 Hz, 2H) were observed. Furthermore, a differential thermobalance (TG8120, Rigaku Corporation) confirmed a melting point of 249 °C, with a sharp melting peak.

[0075] (3) Synthesis of diamines by reduction of dinitro compounds

[0076] [ka]

[0077] A 200 mL three-neck flask was charged with 2.9385 g of the dinitro compound synthesized above, 100 mL of ethyl acetate, and 0.3042 g of palladium / carbon (Pd10%) (approximately 55% water-wet). The solution was stirred at 40–60°C for 6 hours while bubbling with hydrogen. After cooling, the reaction mixture was filtered to remove the catalyst. An appropriate amount of toluene (azeotropic agent) was added to the filtrate, and the solvent was removed by evaporation to dryness, yielding a crude product as a yellow powder. A 200 mL recovery flask was charged with 2.3423 g of the resulting crude product and 30 mL of DMF, and the mixture was heated to 120°C to dissolve the product. Then, 6 mL of deionized water and 1 mL of DMF were added, and the insoluble matter was filtered off. The filtrate was then recrystallized. The purified powder was collected by filtration, thoroughly washed with a mixture of deionized water and DMF (6:1 by volume), and dried at 120°C for 12 hours to obtain the target product as a yellow powder. The yield was 66%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3081 and 3063 cm -1 Aromatic CH stretching, 1733 cm -1 Ester group C=O stretching, 1264cm -1 Ester group CO stretching, 1135cm -1 CF expansion and contraction was confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm) confirmed the following signals: 8.90 (d, J = 1.4 Hz, 2H), 8.43 (d, J = 8.6 Hz, 2H), 8.20 (dd, J = 8.5, 1.4 Hz, 2H), 7.25 (d, J = 8.8 Hz, 2H), 6.98 (d, J = 2.6 Hz, 2H), 6.90 (dd, J = 8.8, 2.6 Hz, 2H), and 5.65 (s, 4H). Elemental analysis revealed the theoretical values ​​of C: 58.44%, H: 3.02%, and N: 5.24%, while the measured values ​​were C: 58.31%, H: 3.24%, and N: 5.37%, with the difference between the theoretical and measured values ​​being within 0.3% for all elements. These analytical results confirmed the identity of the target diamine compound. An attempt was made to measure the melting point using a differential thermobalance TG8120 (trade name, manufactured by Rigaku Corporation), but thermal decomposition began at around 255°C, making it impossible to confirm the melting point.

[0078] Example 3 (1) Synthesis of dinitro compounds

[0079] [ka]

[0080] 1.5428 g (10.0074 mmol) of 2-methyl-4-nitrophenol was added to a 100 mL three-neck flask and dissolved in 10 mL of dehydrated DMF. 5 mL of dehydrated triethylamine was added to prepare solution A. 1.1209 g (4.0158 mmol) of 4,4'-diphenyldicarbonyl chloride was added to a 300 mL recovery flask and dissolved in 30 mL of dehydrated DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred under a dry nitrogen atmosphere at room temperature for 2.5 hours, followed by another 2.5 hours at 45 °C. The temperature was then returned to room temperature, and the reaction solution was slowly added to 800 mL of a 1:1 volumetric mixture of deionized water and methanol. The precipitate was collected by filtration and thoroughly washed with a 1:1 volumetric mixture of deionized water and methanol. The resulting washes were then added with aqueous silver nitrate solution to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum oven at 100°C for 12 hours. The dried crude product was added to 200 mL of THF, heated to approximately 66°C, and stirred for 1 hour. The mixture was then cooled to room temperature and filtered, washing the precipitate thoroughly with THF to recover the target product. The product was then dried at 120°C for 12 hours, yielding a white target product. The yield was 73%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 2971 and 2927 cm -1 Aliphatic CH stretching, 1742 cm -1 Ester group C=O stretching, 1523 and 1343 cm -1 Nitro group stretching, 1257cm -1 The CO stretching of the ester group was also confirmed. 1 The H-NMR spectrum confirmed the following signals (DMSO-d6, δ, ppm): 8.33 (d, J = 8.6 Hz, 6H), 8.21 (dd, J = 2.9, 9.0 Hz, 2H), 8.07 (d, J = 8.6 Hz, 4H), 7.63 (d, J = 8.8 Hz, 2H), and 2.34 (s, 6H). These analytical results confirmed that this was the desired dinitro intermediate. Furthermore, a high-sensitivity differential scanning calorimeter (DSC8230, Rigaku Corporation) confirmed a melting point of 266 °C, with a sharp melting peak.

[0081] (2) Synthesis of diamines by reduction of dinitro compounds

[0082] [ka]

[0083] To a 100 mL three-neck flask, 1.8401 g of the dinitro compound synthesized above, 60 mL of anhydrous DMF, and 0.1894 g of palladium / carbon (Pd10%) (approximately 55% water-wet) were added. The solution was stirred at 40–60 °C for 5 hours while bubbling hydrogen. The reaction mixture was cooled and filtered, and the filtrate was added to 900 mL of brine to precipitate the target product. The suspension was filtered and washed thoroughly with deionized water. A silver nitrate solution was added to the washes to confirm the removal of chloride ions. After washing with methanol, the mixture was vacuum-dried at 100 °C for 12 hours to obtain a pale beige crude product. To a 300 mL recovery flask, 1.4637 g of the resulting crude product and 100 mL of toluene were added, heated to 100 °C, and 16 mL of DMSO was added. The insoluble material was filtered and removed without cooling. 100 mL of toluene was added to the filtrate, cooled to room temperature, and recrystallized in a refrigerator. The purified orange crystals were collected by filtration, washed thoroughly with toluene, and dried at 130°C for 12 hours to obtain the target product as orange needles in a yield of 88%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3015cm -1 Aromatic CH stretching, 2941 cm -1 Aliphatic CH stretching, 1719 cm -1 Ester group C=O stretching, 1263cm -1 The CO stretching of the ester group was also confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm) confirmed the following signals: 8.25 (d, J = 8.6 Hz, 4H), 8.00 (d, J = 8.6 Hz, 4H), 6.85 (d, J = 8.5 Hz, 2H), 6.50 (d, J = 2.3 Hz, 2H), 6.45 (dd, 2.5, 8.4 Hz, 2H), 5.04 (s, 4H), and 2.03 (s, 6H). Elemental analysis revealed the theoretical values ​​of C; 74.32%, H; 5.35%, and N; 6.19%, while the measured values ​​were C; 74.56%, H; 5.52%, and N; 5.83%, with the difference between the theoretical and measured values ​​being within 0.4% for all elements. These analytical results confirmed the identity of the target diamine compound. We also attempted to measure the melting point using a differential thermobalance TG8120 (trade name, manufactured by Rigaku Corporation), but thermal decomposition began at around 180°C, making it impossible to confirm the exact melting point.

[0084] Example 4 (1) Synthesis of dinitro compounds

[0085] [ka]

[0086] 3.8616 g (18.6452 mmol) of 2-trifluoromethyl-4-nitrophenol synthesized in Example 2 was added to a 100 mL three-neck flask and dissolved in 10 mL of dehydrated DMF. 4.5 mL of dehydrated triethylamine was added to prepare solution A. 2.3289 g (8.3437 mmol) of 4,4'-diphenyldicarbonyl chloride was added to a 300 mL recovery flask and dissolved in 60 mL of dehydrated DMF to prepare solution B. Solution B was slowly added dropwise to solution A, resulting in a yellow suspension. This yellow suspension was stirred at room temperature under a dry nitrogen gas atmosphere for 4 hours. The reaction solution was then slowly added to 800 mL of a mixed solvent of deionized water and methanol (1:1 by volume). The precipitate was collected by filtration and thoroughly washed with a mixed solvent of deionized water and methanol (1:1 by volume). A silver nitrate solution was added to the wash solution to confirm the removal of chloride ions. The resulting white crude product was dried in a vacuum oven at 120°C for 12 hours. The dried crude product was added to 15 mL of acetic acid and heated to approximately 110°C, and an additional 20 mL of acetic acid was added to dissolve it. After removing the insoluble matter by filtration, the filtrate was again heated to approximately 110°C and 5 mL of acetic acid was added to recrystallize it. The white needles were collected by filtration, washed thoroughly with acetic acid, and dried at 120°C for 12 hours to obtain the target product as white needles. The yield was 73%. In the infrared absorption spectrum of the obtained target substance, -1 Aromatic CH stretching, 1755cm -1 Ester group C=O stretching, 1532 and 1355 cm -1 Nitro group stretching, 1254 cm -1 Ester group CO stretching, 1115cm -1 CF expansion and contraction was confirmed. 1The H-NMR spectrum confirmed the following signals (DMSO-d6, δ, ppm): 8.71 (dd, J = 2.7, 9.0 Hz, 2H), 8.61 (d, J = 2.7 Hz, 2H), 8.28 (d, J = 8.6 Hz, 4H), 8.11 (d, J = 8.7 Hz, 4H), and 8.06 (d, J = 9.0 Hz, 2H). These analytical results confirmed that this was the desired dinitro intermediate. Furthermore, a high-sensitivity differential scanning calorimeter (DSC8230, Rigaku Corporation) confirmed a melting point of 186 °C, with a sharp melting peak.

[0087] (2) Synthesis of diamines by reduction of dinitro compounds

[0088] [ka]

[0089] To a 100 mL three-neck flask, 2.8795 g of the dinitro compound synthesized above, 60 mL of anhydrous ethyl acetate, and 0.2918 g of palladium / carbon (Pd 10%) (approximately 55% water-wet) were added. The solution was stirred at 40-60 °C for 4.5 hours while bubbling hydrogen. The reaction mixture was cooled and filtered, and the filtrate was evaporated to dryness to obtain a pale yellow powder of crude product. 2.2691 g of the resulting crude product and 100 mL of toluene were added to a 300 mL recovery flask, heated to 100 °C, and 2.5 mL of DMSO was added to dissolve and recrystallize. The purified product, a pale green powder, was collected by filtration, washed thoroughly with toluene, and dried at 100 °C for 12 hours to obtain the target product as a pale green powder. The yield was 79%. In the infrared absorption spectrum of the obtained target substance, -1 NH stretching, 3050cm -1 Aromatic CH stretching, 1731 cm -1 Ester group C=O stretching, 1264cm -1 Ester group CO stretching, 1107cm -1 CF expansion and contraction was confirmed. 1The H-NMR spectrum (DMSO-d6, δ, ppm) confirmed the following signals: 8.21 (d, J = 8.6 Hz, 4H), 8.02 (d, J = 8.6 Hz, 4H), 7.19 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 2.7 Hz, 2H), 6.88 (dd, 2.6, 8.7 Hz, 2H), and 5.62 (s, 4H). Elemental analysis revealed theoretical values ​​of C; 60.01%, H; 3.24%, and N; 5.00%, while the measured values ​​were C; 60.06%, H; 3.33%, and N; 4.92%, with the difference between the theoretical and measured values ​​for all elements being within 0.3%. These analytical results confirmed the identity of the target diamine compound. Furthermore, a melting point of 244°C was confirmed using a high-sensitivity differential scanning calorimeter DSC8230 (trade name, manufactured by Rigaku Corporation), and the melting peak was sharp.

[0090] [Comparative Example: Substituent R in General Formula (1)] 1 and R 2 Synthesis of polyamic acid and polyimide film derived from diamine compound not having (Comparative Example 3)

[0091] [ka]

[0092] A dry 70 mL sealed reaction vessel was placed with a Teflon® stir bar. 3.00 mmol of the diamine compound synthesized in Comparative Example 1, previously dried in a vacuum oven at 50°C for 12 hours, was added to anhydrous N-methyl-2-pyrrolidone (hereinafter referred to as "NMP") and dissolved at 100°C. After dissolution, the mixture was allowed to cool to room temperature. 3.00 mmol of 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter referred to as "s-BPDA"), previously dried in a vacuum oven at 200°C for 12 hours, was added with magnetic stirring (initial total monomer concentration: 25.0% by mass). As the polymerization progressed, the solution viscosity increased, making sufficient stirring impossible. Therefore, the minimum necessary amount of anhydrous NMP was added and the mixture was stirred for 72 hours to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 16.7% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 2.71 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried at 80°C for 3 hours in a forced convection hot air oven to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 320°C for 1 hour. The resulting polyimide film was approximately 20 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness: approximately 5 μm) measured before and after thermal imidization. Specifically, the peaks at 1660 and 1540 cm originating from polyamic acid were observed. -1 The disappearance of the amide C=O stretching vibration absorption band near 1770 cm and the appearance of the imide group characteristic absorption bands at 1770 and 1377 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Comparative Example 3 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and had a small average coefficient of linear thermal expansion (average CTE) of 10.0 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 7.57 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 519°C and 494°C, respectively, demonstrating sufficient heat resistance. AHowever, the average relative permittivity (ε r ) was 3.18, and the average dielectric tangent (tan δ) was 0.00360, which meant that the target dielectric tangent (tan δ) of 0.00300 or less was not achieved.

[0093] Comparative Example 4 [ka]

[0094] A dry 70 mL sealed reaction vessel was placed with a Teflon stir bar, and 3.00 mmol of the diamine compound synthesized in Comparative Example 2, which had been dried in a vacuum oven at 50°C for 12 hours, and dehydrated NMP were added and dissolved as much as possible at 100°C (some of the solution remained undissolved). The mixture was then allowed to cool to room temperature, and 3.00 mmol of s-BPDA, which had been dried in a vacuum oven at 200°C for 12 hours, was added while stirring with a magnetic stirrer (initial total monomer concentration: 10.0% by mass). As the polymerization progressed, the solution viscosity increased, but the mixture was stirred for 72 hours without adding additional dehydrated NMP to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 10.0% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 1.60 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried in a forced convection hot air oven at 80°C for 3 hours to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and the polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 280°C for 1 hour. The resulting polyimide film was approximately 17 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness: approximately 5 μm) measured before and after thermal imidization. Specifically, the peaks at 1660 and 1540 cm originating from polyamic acid were observed. -1 The disappearance of the amide C=O stretching vibration absorption band near 1773 cm and the appearance of the imide group characteristic absorption bands at 1773 and 1379 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Comparative Example 4 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and had a small average coefficient of linear thermal expansion (average CTE) of 8.4 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 6.35 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 520°C and 496°C, respectively, demonstrating sufficient heat resistance. A However, the average relative permittivity (ε r ) was 2.76, and the average dielectric tangent (tan δ) was 0.00322, which meant that the target dielectric tangent (tan δ) of 0.00300 or less was not achieved.

[0095] Example: Synthesis of polyamic acid and polyimide film derived from diamine compound represented by general formula (1) Example 5

[0096] [ka]

[0097] A dry 70 mL sealed reaction vessel was placed with a Teflon stir bar, and 3.00 mmol of the diamine compound synthesized in Example 1, previously dried in a vacuum oven at 50°C for 12 hours, and dehydrated NMP were added and dissolved as much as possible at 100°C (some of the solution remained undissolved). The mixture was then allowed to cool to room temperature, and 3.00 mmol of s-BPDA, previously dried in a vacuum oven at 200°C for 12 hours, was added while stirring with a magnetic stirrer (initial total monomer concentration: 15.0% by mass). As the polymerization progressed, the solution viscosity increased, but the mixture was stirred for 72 hours without adding additional dehydrated NMP to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 15.0% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 1.06 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried in a forced convection hot air oven at 80°C for 3 hours to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and the polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 280°C for 1 hour. The resulting polyimide film was approximately 20 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness approximately 5 μm) measured before and after thermal imidization. Specifically, the 1661 and 1544 cm -1 The disappearance of the amide C=O stretching vibration absorption band near 1772 cm and the appearance of the imide group characteristic absorption bands at 1772 and 1380 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Example 5 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and had a low average coefficient of linear thermal expansion (average CTE) of 9.9 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 8.64 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 468°C and 440°C, respectively, demonstrating sufficient heat resistance. A ) was 0.69 mass%. Furthermore, the average relative permittivity (ε r The dielectric loss tangent (tanδ) was 2.97, and the average dielectric loss tangent (tanδ) was an extremely low 0.00187, achieving the target dielectric loss tangent (tanδ) of 0.00300 or less. This polyimide film is a groundbreaking insulating material that combines the inherently excellent properties of polyimide, such as high heat resistance and excellent thermal dimensional stability, with low water absorption and a dielectric loss tangent (tanδ) in the high frequency band that is lower than that of liquid crystal polymers, which were difficult to achieve with conventional polyimide films.

[0098] Example 6 [ka]

[0099] A dry 70 mL sealed reaction vessel was placed with a Teflon stir bar, and 3.00 mmol of the diamine compound synthesized in Example 2, previously dried in a vacuum oven at 50°C for 12 hours, and dehydrated NMP were added and dissolved as much as possible at 100°C (some of the solution remained undissolved). The mixture was then allowed to cool to room temperature, and 3.00 mmol of s-BPDA, previously dried in a vacuum oven at 200°C for 12 hours, was added while stirring with a magnetic stirrer (initial total monomer concentration: 20.0% by mass). As the polymerization progressed, the solution viscosity increased, but the mixture was stirred for 72 hours without adding additional dehydrated NMP to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 20.0% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 1.74 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried in a forced convection hot air oven at 80°C for 3 hours to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 320°C for 1 hour. The resulting polyimide film was approximately 20 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness: approximately 5 μm) measured before and after thermal imidization. Specifically, the peaks at 1665 and 1549 cm derived from polyamic acid were observed. -1 The disappearance of the amide C=O stretching vibration absorption band near 1774 cm and the appearance of the imide group characteristic absorption bands at 1774 and 1378 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Example 6 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and had a small average coefficient of linear thermal expansion (average CTE) of 14.8 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 8.06 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 426°C and 414°C, respectively, demonstrating sufficient heat resistance. A ) was 0.44 mass%. Furthermore, the average relative permittivity (ε r The dielectric loss tangent (tanδ) was 3.08, and the average dielectric loss tangent (tanδ) was a low 0.00234, achieving the target dielectric loss tangent (tanδ) of 0.00300 or less. This polyimide film combines the inherently excellent properties of polyimide, such as high heat resistance and excellent thermal dimensional stability, with low water absorption and a low dielectric loss tangent (tanδ) in the high-frequency range, which were difficult to achieve with conventional polyimide films. The low dielectric loss tangent (tanδ) in the high-frequency range was reduced to a value equivalent to that of liquid crystal polymers.

[0100] Example 7 [ka]

[0101] A dry 70 mL sealed reaction vessel was placed with a Teflon stir bar, and 3.00 mmol of the diamine compound synthesized in Example 3, previously dried in a vacuum oven at 50°C for 12 hours, and dehydrated NMP were added at 100°C until fully dissolved (some of the solution remained undissolved). The mixture was then allowed to cool to room temperature, and 3.00 mmol of s-BPDA, previously dried in a vacuum oven at 200°C for 12 hours, was added while stirring with a magnetic stirrer (initial total monomer concentration: 10.0% by mass). As the polymerization progressed, the solution viscosity increased, but the mixture was stirred for 72 hours without adding additional dehydrated NMP to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 10.0% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 1.32 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried in a forced convection hot air oven at 80°C for 3 hours to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 280°C for 1 hour. The resulting polyimide film was approximately 17 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness approximately 5 μm) measured before and after thermal imidization. Specifically, the 1656 and 1546 cm spectra derived from polyamic acid were obtained. -1 The disappearance of the amide C=O stretching vibration absorption band near 1773 cm and the appearance of the imide group characteristic absorption bands at 1773 and 1378 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Example 7 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and had a low average coefficient of linear thermal expansion (average CTE) of 7.9 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 7.34 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 463°C and 423°C, respectively, demonstrating sufficient heat resistance. A ) was 0.59 mass%. Furthermore, the average relative permittivity (ε r The dielectric loss tangent (tanδ) was 2.98, and the average dielectric loss tangent (tanδ) was an extremely low 0.00182, achieving the target dielectric loss tangent (tanδ) of 0.00300 or less. This polyimide film is a groundbreaking insulating material that combines the inherently excellent properties of polyimide, such as high heat resistance and excellent thermal dimensional stability, with low water absorption and a dielectric loss tangent (tanδ) in the high frequency band that is lower than that of liquid crystal polymers, which were difficult to achieve with conventional polyimide films.

[0102] Example 8 [ka]

[0103] A dry 70 mL sealed reaction vessel was placed with a Teflon® stir bar, and 3.00 mmol of the diamine compound synthesized in Example 4, previously dried in a vacuum oven at 50°C for 12 hours, and dehydrated NMP were added and dissolved at room temperature. Subsequently, 3.00 mmol of s-BPDA, previously dried in a vacuum oven at 200°C for 12 hours, was added while stirring with a magnetic stirrer (initial total monomer concentration: 40.0% by mass). As the polymerization progressed, the solution viscosity increased and sufficient stirring became impossible. Therefore, the minimum amount of dehydrated NMP necessary was added appropriately, and the mixture was stirred for 72 hours to obtain a homogeneous, viscous polyamic acid solution (final total monomer concentration: 21.2% by mass). The reduced viscosity of the resulting polyamic acid solution was measured using an Ostwald viscometer at 30°C in dehydrated NMP at a concentration of 0.5% by mass, resulting in a value of 3.30 dL / g, indicating a sufficiently high degree of polymerization. This polyamic acid solution was applied to a glass substrate and dried in a forced convection hot air oven at 80°C for 3 hours to obtain a clear polyamic acid film. The glass substrate was then placed in an electric furnace and heated in a vacuum at 250°C for 1 hour, followed by 350°C for 1 hour, to complete the imidization and obtain a polyimide film. Residual strain at the interface between the glass substrate and the polyimide film was removed by peeling the film from the glass substrate and heat-treating it in a vacuum at 310°C for 1 hour. The resulting polyimide film was approximately 18 μm thick and was clear and flexible. The completion of imidization was confirmed separately by infrared absorption spectroscopy (transmission method) using a thin film sample (film thickness: approximately 5 μm) measured before and after thermal imidization. Specifically, the peaks at 1664 and 1550 cm originating from polyamic acid were observed. -1 The disappearance of the amide C=O stretching vibration absorption band near 1774 cm and the appearance of the imide group characteristic absorption bands at 1774 and 1377 cm after thermal imidization. -1 It was confirmed that the imidization reaction was completed under these heating conditions. The polyimide film of Example 8 thus obtained did not exhibit a clear glass transition in the temperature range from room temperature to 450°C, and the average coefficient of linear thermal expansion (average CTE) was a small 10.5 ppm / K. Furthermore, evaluation of the mechanical properties revealed a high average tensile modulus (E) of 7.36 GPa. These results are thought to be due to the rigidity and linearity of the entire polyimide main chain, which is achieved by using monomers with rigid, geometrically linear structures, both for the tetracarboxylic dianhydride and the diamine compound, and the high degree of in-plane orientation of the main chain induced by thermal imidization. In addition, the 5% mass loss temperature (T d 5 ) were 418°C and 418°C, respectively, demonstrating sufficient heat resistance. A ) was 0.48 mass%. Furthermore, the average relative permittivity (ε r The dielectric loss tangent (tanδ) was 2.82, and the average dielectric loss tangent (tanδ) was a low 0.00274, achieving the target dielectric loss tangent (tanδ) of 0.00300 or less. This polyimide film combines the inherently excellent properties of polyimide, such as high heat resistance and excellent thermal dimensional stability, with low water absorption and a low dielectric loss tangent (tanδ) in the high-frequency band, which were difficult to achieve with conventional polyimide films. The low dielectric loss tangent (tanδ) in the high-frequency band was reduced to a value equivalent to that of liquid crystal polymers.

[0104] The intrinsic viscosity (η inh ), and the 5% mass loss temperature (T d 5 ), average coefficient of linear thermal expansion (average CTE), average tensile modulus (E), average breaking strength (σ b ), average elongation at break (ε b,ave ), maximum breaking elongation (ε b,max ), water absorption rate (W A ), average relative permittivity at 10 GHz (ε r) and average dielectric tangent (tan δ) are summarized in Table 1. 1 to 6 show the infrared absorption spectra of the polyamic acid films and polyimide films of Comparative Example 3, Examples 5 and 6, Comparative Example 4, and Examples 7 and 8. In Figs. 1 to 6, the upper side shows the infrared absorption spectrum of the polyimide film, and the lower side shows the infrared absorption spectrum of the polyamic acid film.

[0105] [Table 1]

[0106] (Table notes) In the column for diamine compound, the structure of the diamine compound used as the starting material for the polyimide films of Comparative Examples 3 and 4 and Examples 5 to 8 is described. The diamine compounds used in Comparative Examples 3 and 4 were those represented by the general formula (1) R 1 and R 2 In that it does not have a group corresponding to the following, it is not a diamine compound of the present invention.

[0107] The polyimide films of Comparative Examples 3 and 4 each have a substituent R 1 and R 2 The polyimide films were derived using the diamine compounds of Comparative Examples 1 and 2. As shown in Table 1, the average dielectric loss tangents (tanδ) at 10 GHz of the polyimide films of Comparative Examples 3 and 4 exceeded 0.00300, and a low dielectric loss tangent in the high frequency band was not achieved. In contrast, the polyimide films of Examples 5 to 8 had R 1 and R 2The polyimide films were derived using diamine compounds (diamine compounds of Examples 1 to 4) represented by general formula (1) having a methyl group or a trifluoromethyl group as the carboxyl group. The polyimide films of Examples 5 to 8 exhibited average dielectric loss tangents (tanδ) at 10 GHz ranging from 0.00182 to 0.00274, achieving low dielectric loss tangents (tanδ) in the high frequency band. Furthermore, none of the polyimide films of Examples 5 to 8 exhibited a glass transition temperature (no glass transition temperature was observed) in the range of room temperature to 450°C, and the 5% mass loss temperature (T d 5 ) was 400°C or higher, and they had high heat resistance. The polyimide films of Examples 5 to 8 also had an average coefficient of linear thermal expansion (average CTE) in the range of 7.9 to 14.8 ppm / K, which was lower than the average CTE of copper foil: 20±2 ppm / K, and they had excellent thermal dimensional stability. Furthermore, the water absorption (W A ) was 0.7% by mass or less, which was significantly smaller than the water absorption of Kapton (registered trademark) H (manufactured by DuPont-Toray Co., Ltd.), a conventional polyimide derived from pyromellitic dianhydride and 4,4'-oxydianiline, which has a water absorption rate of approximately 2 to 3% by mass, indicating low water absorption. Furthermore, the diamine compounds of Examples 1 to 4 used to derive the polyimide films of Examples 5 to 8 all exhibited high solubility in dehydrated NMP, an organic solvent. Thus, the diamine compounds of Examples 1 to 4, which are diamine compounds of the present invention, exhibited high solubility in organic solvents, and the derived polyimide films of Examples 5 to 8 realized high heat resistance, excellent thermal dimensional stability, low water absorption, and low dielectric loss tangent (tan δ) in the high frequency band. Furthermore, all of the polyimide films of Examples 5 to 8 had an average tensile modulus (E) of 7.34 GPa or more and an average relative dielectric constant (ε) at 10 GHz of 7.34 GPa or more. r ) was 3.08 or less, and the elastic modulus and relative dielectric constant were at the same levels as those of conventional polyimide films. These results demonstrate that the polyimide films derived from the diamine compounds of the present invention are extremely useful as heat-resistant insulating substrates (heat-resistant insulating films) for flexible printed wiring boards and insulating films and insulating films for electronic devices such as insulating films for semiconductors. In particular, among Examples 5 to 8, R 1 and R 2 The polyimide films of Examples 5 and 7, which had methyl groups as the cations, exhibited even lower average dielectric loss tangents (tanδ) of 0.00187 and 0.00182 at 10 GHz, respectively, which were comparable to the dielectric loss tangent (tanδ) of 0.002 (28 GHz) of the liquid crystal polymer Vecstar (registered trademark, manufactured by Kuraray Co., Ltd.).

Claims

1. A diamine compound represented by the following general formula (1): 【Chemistry 1】 In the above formula, X １ represents a divalent group represented by the following formula (a) or (b), and R １ and R ２ each independently represents a trifluoromethyl group or a methyl group. 【Chemistry 2】 In the above formula, * indicates a bond.

2. A polyamic acid compound comprising a structural unit represented by the following general formula (2): 【Transformation 3】 In the above formula, X １ represents a divalent group represented by the following formula (a) or (b), and Y １ represents a tetravalent aromatic or aliphatic group, and R １ and R ２ each independently represents a trifluoromethyl group or a methyl group. 【Chemistry 4】 In the above formula, * indicates a bond.

3. A polyimide film comprising a structural unit represented by the following general formula (3): 【Transformation 5】 In the above formula, X １ represents a divalent group represented by the following formula (a) or (b), and Y １ represents a tetravalent aromatic or aliphatic group, and R １ and R ２ each independently represents a trifluoromethyl group or a methyl group. 【Transformation 6】 In the above formula, * indicates a bond.

4. 4. The polyimide film according to claim 3, wherein the average coefficient of linear thermal expansion between 100 and 200° C. is 30.0 ppm / K or less.

5. The polyimide film according to claim 3 , which has a water absorption rate of 1.0% by mass or less.

6. 4. The polyimide film according to claim 3, which has a dielectric loss tangent of 0.00300 or less at an operating frequency of 10 GHz.

7. A heat-resistant insulating substrate for a flexible printed wiring board or an insulating film for a semiconductor, comprising the polyimide film according to any one of claims 3 to 6.

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