Polyimide, and polyimide thin film

Abstract

The present invention addresses the problem of providing a polyimide resin material which has excellent dielectric characteristics of a polyimide that uses bis(trimellitic anhydride) having a naphthalene skeleton. The present invention provides, as a solution, a polyimide which has a repeating unit represented by general formula (1) (in the formula, each R1 independently represents a methyl group, a trifluoromethyl group, or a halogen atom, and each n independently represents 1 or 2) and a repeating unit represented by general formula (2) (in the formula, each R1 independently represents a methyl group, a trifluoromethyl group or a halogen atom, each R2 independently represents a methyl group, a trifluoromethyl group or a halogen atom, each n independently represents 1 or 2, and each m independently represents 0, 1, 2, or 3).

Description

Polyimide, polyimide thin film

[0001] The present invention relates to a polyimide having excellent dielectric properties, specifically to a polyimide having excellent dielectric properties, which is made using bis(trimellitate anhydride) having a naphthalene skeleton and a monomer having a biphenyl skeleton.

[0002] Polyimide resins obtained by reacting tetracarboxylic dianhydrides with diamine compounds are generally insoluble, infusible, and ultra-heat-resistant resins, possessing excellent properties such as thermal oxidation resistance, heat resistance, radiation resistance, low-temperature resistance, and chemical resistance. For this reason, polyimide resins are used as materials in fields such as insulating coatings, insulating films, semiconductors, electrode protection films, flexible printed circuit boards, and other electrical and electronic components, as well as in aerospace and transportation equipment, and as heat-resistant adhesives. In recent years, wireless internet and communication devices have become increasingly faster and higher in transmission speed and frequency, requiring the insulating parts that insulate the metal wiring in these devices to accommodate higher frequencies. The higher the frequency, the greater the dielectric loss in the insulating parts, resulting in attenuation of the electrical signal. Therefore, to accommodate higher frequencies, materials with excellent dielectric properties that can reduce dielectric loss are needed.

[0003] It is known that polyimides using 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) are suitable for use as, for example, base films for flexible printed circuit boards, carrier tapes for TAB, or resins for laminates (Patent Document 1), and that polyesterimides obtained by polymerizing 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) with 4,4'-oxydianiline can be used as hybrid films with organically modified hectorite (Non-Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2004-285364

[0005] Macromolecular Research, 2014, Vol. 22, pp. 549-556

[0006] An object of the present invention is to provide a polyimide resin material that uses bis(trimellitate anhydride) having a naphthalene skeleton and has excellent dielectric properties.

[0007] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a polyimide having repeating units derived from a bis(trimellitate anhydride) having a naphthalene skeleton, a bis(trimellitate anhydride) having a biphenyl skeleton, and a diamine compound having a biphenyl skeleton has excellent dielectric properties, and have completed the present invention.

[0008] 1. Repeating units represented by general formula (1) (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group or a halogen atom, and each n independently represents 1 or 2.) and a repeating unit represented by general formula (2): (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group, or a halogen atom; R ２ each independently represent a methyl group, a trifluoromethyl group, or a halogen atom, each n independently represent 1 or 2, and each m independently represent 0, 1, 2, or 3. 2. A polyimide having the following repeating unit represented by general formula (1): (In the formula, R １ is the same as defined in general formula (1). The repeating unit represented by general formula (2) is a repeating unit represented by general formula (2a): (In the formula, R １、 R ２ and m are the same as defined in general formula (2). 1. A polyimide according to 1. 3. The repeating unit represented by general formula (1a) is a repeating unit represented by chemical formula (1a-1) or chemical formula (1a-2), The repeating unit represented by the general formula (2a) is at least one selected from the repeating units represented by chemical formulas (2a-1) to (2a-6). 2. The polyimide according to 4., wherein the combination of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is the combination of the chemical formula (1a-1) and the chemical formula (2a-1), the chemical formula (1a-1) and the chemical formula (2a-3), or the chemical formula (1a-1) and the chemical formula (2a-5). 5. The polyimide according to 1., wherein the content ratio of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is in the range of 50 mol % to 100 mol % of the entire polyimide. 6. The polyimide according to 5., wherein the content ratio of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is 100 mol % of the entire polyimide, and the ratio of the repeating unit represented by the general formula (1) to the repeating unit represented by the general formula (2) is in the range of 50:50 to 90:10 (general formula (1):general formula (2)). 7. A polyimide thin film comprising the polyimide according to any one of items 1. to 6.

[0009] The polyimide of the present invention has excellent dielectric properties and can therefore be suitably used as a material for electronic devices and electronic equipment, particularly for high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz.

[0010] (Polyimide of the Invention) The polyimide of the invention has a repeating unit represented by general formula (1) and a repeating unit represented by general formula (2). (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group, or a halogen atom, and each n independently represents 1 or 2. (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group, or a halogen atom; R ２ each independently represents a methyl group, a trifluoromethyl group, or a halogen atom; each n independently represents 1 or 2; and each m independently represents 0, 1, 2, or 3. １ are each independently preferably a methyl group or a trifluoromethyl group, and particularly preferably a trifluoromethyl group. ２are each independently preferably a methyl group or a trifluoromethyl group, and particularly preferably a methyl group. n is particularly preferably 1. m is each independently preferably 0, 2 or 3, and particularly preferably 0. The repeating unit represented by general formula (1) is preferably a repeating unit represented by general formula (1a), more preferably a repeating unit represented by chemical formula (1a-1) or chemical formula (1a-2), and particularly preferably a repeating unit represented by chemical formula (1a-1). (In the formula, R １ is the same as defined in general formula (1). The repeating unit represented by general formula (2) is preferably a repeating unit represented by general formula (2a), more preferably a repeating unit represented by chemical formulas (2a-1) to (2a-6), and particularly preferably a repeating unit represented by chemical formula (2a-1). (In the formula, R １ , R ２ and m are defined as in general formula (1).

[0011] (Proportion of Repeating Units) The repeating units of the polyimide of the present invention preferably have a total content of repeating units represented by general formula (1) and repeating units represented by general formula (2) in the range of 50 mol% to 100 mol% of the entire polyimide. The lower limit of this content is preferably 60 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. 100 mol%, i.e., the repeating units are particularly preferably composed of only repeating units represented by general formula (1) and repeating units represented by general formula (2). The repeating units represented by general formula (1) and the repeating units represented by general formula (2) may be arranged regularly or may be present randomly in the polyimide. Furthermore, the polyimide may contain only one type of repeating unit selected from the range of the repeating units represented by general formula (1) and the repeating units represented by general formula (2), or may contain two or more types, but preferably contains only one type. When the polyimide of the present invention contains repeating units represented by general formula (1) and repeating units represented by general formula (2) in a ratio of 50 mol% or more to less than 100 mol%, it may contain repeating units other than those represented by general formulas (1) and (2), and one or more compounds selected from the tetracarboxylic acid dianhydrides and diamine compounds described below that form such repeating units may be used in combination. The repeating units other than those represented by general formula (1) may be one type, or two or more types. The remaining repeating units of the polyimide of the present invention are such repeating units. The ratio of repeating units represented by general formula (1) to repeating units represented by general formula (2) contained in the polyimide of the present invention is preferably in the range of 50:50 to 90:10 (general formula (1):general formula (2)). This ratio is more preferably in the range of 60:40 to 90:10, even more preferably in the range of 70:30 to 90:10, and particularly preferably in the range of 80:20 to 90:10.The repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) of the polyimide of the present invention can be combined with each other, but among them, combinations of chemical formula (1a-1) and chemical formula (2a-1), chemical formula (1a-1) and chemical formula (2a-3), and chemical formula (1a-1) and chemical formula (2a-5) are preferred, and the combination of chemical formula (1a-1) and chemical formula (2a-1) is particularly preferred.

[0012] (Dielectric Constant) The dielectric constant of the polyimide of the present invention measured at a frequency of 5 GHz is preferably 3.5 or less. If the dielectric constant is 3.5 or less, it can be suitably used as a polyimide resin material for electronic devices and devices, particularly for high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz. The dielectric constant is more preferably 3.4 or less, and particularly preferably 3.3 or less. The lower the dielectric constant, the better, so there is no particular restriction on the lower limit, but it may be 2.0 or more.

[0013] (Intrinsic Viscosity) In the polyimide of the present invention, the intrinsic viscosity of the polyimide precursor (polyamic acid) before imidization is preferably in the range of 0.1 dL / g or more and 10.0 dL / g or less, more preferably 0.2 dL / g or more and 5.0 dL / g or less, even more preferably 0.5 dL / g or more and 5.0 dL / g or less, and particularly preferably 1.0 dL / g or more and 5.0 dL / g or less.

[0014] (Method for Producing Polyimide of the Present Invention) The method for producing the polyimide of the present invention is not particularly limited, and the polyimide can be produced, for example, by reacting 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) (hereinafter, sometimes referred to as Compound 3A) (3A) as a bis(trimellitate anhydride) having a naphthalene skeleton represented by general formula (3) described below, 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride) (hereinafter, sometimes referred to as Compound 4A) (4A) as a bis(trimellitate anhydride) having a biphenyl skeleton represented by general formula (4) described below, and 2,2'-bis(trifluoromethyl)benzidine (5A) as a diamine compound having a biphenyl skeleton represented by general formula (5) described below to obtain a polyimide precursor (polyamic acid), and then imidizing the polyimide precursor. The reaction formula for the polyimide production in this case is shown below.

[0015] (Bis(trimellitate anhydride) having a naphthalene skeleton represented by general formula (3)) Specific examples of bis(trimellitate anhydride) having a naphthalene skeleton represented by general formula (3) include 2,6-dihydroxynaphthalene-bis(trimellitate anhydride), 1,5-dihydroxynaphthalene-bis(trimellitate anhydride), and 2,7-dihydroxynaphthalene-bis(trimellitate anhydride). At least one selected from 2,6-dihydroxynaphthalene-bis(trimellitate anhydride), 1,5-dihydroxynaphthalene-bis(trimellitate anhydride), and 2,7-dihydroxynaphthalene-bis(trimellitate anhydride) is preferred, with 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) being particularly preferred.

[0016] (Bis(trimellitate anhydride) having a biphenyl skeleton represented by general formula (4)) (In the formula, R ２and m are defined as in general formula (2). ２ Preferred embodiments of and m are the same as those in general formula (2). Specific examples of the bis(trimellitate anhydride) having a biphenyl skeleton represented by general formula (4) include 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride), 4,4'-dihydroxy-3,3'-dimethylbiphenyl-bis(trimellitate anhydride), 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl-bis(trimellitate anhydride), and 4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl-bis(trimellitate anhydride). At least one selected from 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride), 4,4'-dihydroxy-3,3'-dimethylbiphenyl-bis(trimellitate anhydride), 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl-bis(trimellitate anhydride) and 4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl-bis(trimellitate anhydride) is preferred. , 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride), 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl-bis(trimellitate anhydride), and 4,4'-dihydroxy-2,2',3,3',5,5'-hexamethylbiphenyl-bis(trimellitate anhydride) are more preferred, and 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride) is particularly preferred.

[0017] (Diamine compound having a biphenyl skeleton represented by general formula (5)) (In the formula, R １ and n are the same as those in the general formula (1). １The preferred embodiments of n and n are the same as those for general formula (1). Specific examples of the diamine compound represented by general formula (5) include 2,2'-dimethylbenzidine, 3,3'-dimethylbenzidine, 3,3',5,5'-tetramethylbenzidine, 2,2',6,6'-tetramethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine, 3,3',5,5'-tetrafluorobenzidine, 2,2'-dichlorobenzidine, 3,3'-dichlorobenzidine, 3,3',5,5'-tetrachlorobenzidine, 2,2'-dibromobenzidine, 3,3'-dibromobenzidine, and 3,3',5,5'-tetrabromobenzidine. Among these, 2,2'-dimethylbenzidine, 3,3'-dimethylbenzidine, 3,3',5,5'-tetramethylbenzidine, 2,2',6,6'-tetramethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,2'-difluorobenzidine, and 2,2'-dichlorobenzidine are preferred, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, and 2,2'-difluorobenzidine are more preferred, 2,2'-dimethylbenzidine and 2,2'-bis(trifluoromethyl)benzidine are even more preferred, and 2,2'-bis(trifluoromethyl)benzidine is particularly preferred. When the polyimide of the present invention has two or more repeating units selected from the range of the repeating units represented by general formula (1) and the repeating units represented by general formula (2), two or more diamine compounds represented by general formula (5) are used. The polyimide of the present invention preferably has only one type selected from the range of repeating units represented by general formula (1) and repeating units represented by general formula (2), and therefore it is preferable to use one type of diamine compound represented by general formula (5).

[0018] In the polyimide of the present invention, when the content ratio of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is in the range of 50 mol % or more and less than 100 mol %, examples of diamine compounds that can be used as repeating units other than these include m-phenylenediamine (MPD), 5-trifluoromethyl-1,3-phenylenediamine (TFMPD), 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl Phenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, bis(3-aminophenyl)methane, bis(4-aminophenyl)methane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl) 1,1-bis(4-aminophenyl)cyclohexane, 4,4''-diamino-p-terphenyl, 4,4''-diamino-m-terphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, 1,2-ethylenediamine, 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, ethylenediamine, 1,9-nonamethylenediamine, 4,4'-methylenebis(cyclohexylamine), 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, bicyclo[2.2.2]octane-1,4-diamine, decahydro-1,4-naphthalenediamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-Diaminoadamantane, 2,2-bis(4-aminocyclohexyl)propane, 2,2-bis(4-aminocyclohexyl)hexafluoropropane, etc. can be used.

[0019] In the polyimide of the present invention, when the content ratio of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is in the range of 50 mol % or more and less than 100 mol %, examples of tetracarboxylic dianhydrides as repeating units other than these include 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfidetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, Acid dianhydride, 4,4'-(hexafluoroisopropylidene)bis(phthalic) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)biphenyl dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)-3,3'-dimethylbiphenyl dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]ether dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]sulfone dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane dianhydride, 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclohexane dianhydride, 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]cyclodecane dianhydride, 1,1-bis[4-(3,4-dicarboxyphenoxy)phenyl]-3,3,5-trimethylcyclohexane dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]- xyphenoxy)-3-methylphenyl]fluorene dianhydride, hydroquinone-bis(trimellitate anhydride), resorcinol-bis(trimellitate anhydride), 4,4'-dihydroxydiphenyl ether-bis(trimellitate anhydride), 4,4'-dihydroxydiphenyl sulfide-bis(trimellitate anhydride), 4,4'-dihydroxydiphenyl sulfone-bis(trimellitate anhydride), 4,4'-dihydroxybenzophenone-bis(trimellitate anhydride), 1,1'-bis(4-hydroxyphenyl)ethane-bis(trimellitate anhydride), 2,2'-bis(4-hydroxyphenyl)propane-bis(trimellitate anhydride), 2,2'-bis(4-hydroxy-3-methylphenyl)propane-bis(trimellitate anhydride), 2,2'-bis(4-hydroxyphenyl)hexafluoropropane-bis(trimellitate anhydride), 1,1'-bis(4-hydroxyphenyl)cyclohexane-bis(trimellitate anhydride), 1,1'-bis(4-hydroxyphenyl) Examples of suitable cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride include 1,1'-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane-bis(trimellitate anhydride), 1,1'-bis(4-hydroxyphenyl)cyclodecane-bis(trimellitate anhydride), 9,9'-bis(4-hydroxy-3-methylphenyl)fluorene-bis(trimellitate anhydride), cyclobutane-1,2,3,4-tetracarboxylic acid dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic acid dianhydride, and 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic acid dianhydride.

[0020] Specifically, when producing the polyimide of the present invention using the above process, it can be synthesized, for example, by the following method. First, a diamine compound is dissolved in a polymerization solvent, and tetracarboxylic dianhydride is gradually added to this solution. The amount of tetracarboxylic dianhydride used is typically 0.9 to 1.2 molar equivalents, preferably 0.95 to 1.1 molar equivalents, and more preferably 1.0 to 1.1 molar equivalents, relative to the diamine compound. The solution is stirred using a mechanical stirrer or the like, typically at a temperature ranging from 0 to 100°C, preferably 20 to 60°C, for typically 0.5 to 150 hours, preferably 1 to 72 hours. The monomer concentration is typically 5 to 50 wt%, preferably 10 to 40 wt%. By carrying out polymerization within this monomer concentration range, a uniform polyimide precursor (polyamic acid) with a high degree of polymerization can be obtained. If the degree of polymerization of the polyimide precursor (polyamic acid) becomes too high, making the polymerization solution difficult to stir, it can be diluted with the same solvent as appropriate. By carrying out polymerization within the above monomer concentration range, the degree of polymerization of the polymer can be sufficiently high, and the solubility of the monomer and the polymer can be sufficiently ensured. If the polymerization is carried out at a concentration lower than the above range, the degree of polymerization of the polyimide precursor (polyamic acid) may not be sufficiently high, and if the polymerization is carried out at a monomer concentration higher than the above range, the solubility of the monomer and the resulting polymer may be insufficient.

[0021] As the solvent used in the polymerization of the polyimide precursor (polyamic acid), an aprotic solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, or dimethyl sulfoxide is preferred. However, any solvent can be used without any problem as long as it dissolves the raw material monomer, the resulting polyimide precursor (polyamic acid), and the imidized polyimide, and there are no particular limitations on the structure or type of the solvent. Specific examples of the solvent include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; 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; carbonate solvents such as ethylene carbonate and propylene carbonate; glycol solvents such as diethylene glycol dimethyl ether, triethylene glycol, and triethylene glycol dimethyl ether; phenol solvents such as phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, and 4-chlorophenol; ketone solvents such as cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, and methyl isobutyl ketone; and ether solvents such as tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethoxyethane, and dibutyl ether. Other commonly used solvents include acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, butanol, ethanol, xylene, toluene, chlorobenzene, turpentine, mineral spirits, and petroleum naphtha-based solvents. Two or more of these solvents may be mixed and used. The polymerization reaction to obtain the polyimide precursor (polyamic acid) can be carried out in air or an inert gas such as nitrogen, and is preferably carried out in an inert gas such as nitrogen.

[0022] The polyimide precursor (polyamic acid) of the present invention can be made into a varnish containing the polyimide precursor (polyamic acid) and an organic solvent. The organic solvent for dissolving the polyimide precursor (polyamic acid) can be appropriately selected depending on the intended use and processing conditions of the varnish and is not particularly limited. Examples of the organic solvent include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone; carbonate solvents such as ethylene carbonate and propylene carbonate; glycol solvents such as diethylene glycol dimethyl ether, triethylene glycol, and triethylene glycol dimethyl ether; and phenol solvents such as phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, and 4-chlorophenol. Examples of solvents that can be used include alcohol-based solvents, ketone-based solvents such as cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, and methyl isobutyl ketone; ether-based solvents such as tetrahydrofuran, 1,4-dioxane, dimethoxyethane, diethoxyethane, and dibutyl ether; and other general-purpose solvents such as acetophenone, 1,3-dimethyl-2-imidazolidinone, sulfolane, dimethyl sulfoxide, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, chloroform, butanol, ethanol, xylene, toluene, chlorobenzene, turpentine, mineral spirits, and petroleum naphtha-based solvents. Among these, from the viewpoint of solubility, it is preferable to use amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, ester solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, and α-methyl-γ-butyrolactone, and carbonate solvents such as ethylene carbonate and propylene carbonate. Two or more of these solvents may be mixed and used.

[0023] When the polyimide precursor (polyamic acid) of the present invention is dissolved in a solvent to form a varnish, the solids concentration can be appropriately selected depending on the intended use of the varnish and is not particularly limited. For example, when forming a thin film, the solids concentration is preferably 5 wt % or more, although this depends on the molecular weight of the polyimide, the production method, and the thickness of the thin film to be produced. If the solids concentration is too low, it becomes difficult to form a thin film of sufficient thickness. Conversely, if the solids concentration is too high, the solution viscosity may be too high, making coating difficult. Methods for preparing a varnish containing the polyimide precursor (polyamic acid) of the present invention and an organic solvent include, for example, a method of preparing a varnish by polymerizing the polyimide precursor (polyamic acid) as described above, or a method of mixing a polyimide precursor (polyamic acid) that has been previously polymerized and isolated with the above-mentioned solvent and dissolving the mixture in air or an inert gas such as nitrogen at a temperature ranging from room temperature to the boiling point of the solvent for 1 to 48 hours. Furthermore, additives such as a mold release agent, a filler, a silane coupling agent, a crosslinking agent, an end-capping agent, an antioxidant, an antifoaming agent, and a leveling agent can be added to the varnish containing the polyimide precursor (polyamic acid) of the present invention as needed. The resulting varnish can be used, for example, to produce a thin film or tape-shaped polyimide. The varnish can also be used to produce polyimide processed products such as polyimide thin films and laminates. For example, the polyimide precursor (polyamic acid) varnish can be cast onto a support such as a glass substrate using a doctor blade or the like, and the polyimide precursor (polyamic acid) can be imidized by the "thermal imidization method" described below using a hot air dryer, an infrared drying oven, a vacuum dryer, an inert oven, or the like to form a polyimide thin film.

[0024] The method for imidizing the obtained polyimide precursor (polyamic acid) will now be described. Known imidization methods can be used for imidization, including the "thermal imidization method" in which a polyimide precursor (polyamic acid) film is thermally ring-closed, the "solution thermal imidization method" in which a polyimide precursor (polyamic acid) solution is ring-closed at high temperature, and the "chemical imidization method" in which a dehydrating agent is used. Among these, the "thermal imidization method" is preferred for producing the polyimide of the present invention.

[0025] Specifically, in the "thermal imidization method," a polyimide precursor (polyamic acid) solution is cast onto a substrate or the like, and dried typically at 50 to 200°C, preferably 60 to 150°C, to form a polyimide precursor (polyamic acid) film, which is then heated in an inert gas or under reduced pressure typically at 150 to 400°C, preferably 200 to 380°C, for 1 to 12 hours to thermally dehydrate and ring-close the film, thereby completing the imidization, thereby obtaining the polyimide of the present invention. Also, in this manner, the polyimide thin film of the present invention can be obtained.

[0026] In the "solution thermal imidization method," a polyimide precursor (polyamic acid) solution to which a basic catalyst or the like has been added is heated in the presence of an azeotropic agent such as xylene, usually at 100 to 250°C, preferably 150 to 220°C, for 0.5 to 12 hours, thereby removing by-product water from the system and completing the imidization, thereby obtaining a solution of the polyimide of the present invention.

[0027] In the "chemical imidization method," a polyimide precursor (polyamic acid) solution, adjusted to an appropriate solution viscosity for easy stirring, is stirred using a mechanical stirrer or the like while a dehydration ring-closing agent (chemical imidization agent) consisting of an organic acid anhydride and an amine as a basic catalyst is added dropwise. The mixture is typically stirred at 0 to 100°C, preferably 10 to 50°C, for 1 to 72 hours to complete the chemical imidization. The organic acid anhydride that can be used in this process is not particularly limited, but examples include acetic anhydride and propionic anhydride. Acetic anhydride is preferred for ease of reagent handling and purification. Pyridine, triethylamine, quinoline, and the like can be used as basic catalysts, with pyridine being preferred for ease of reagent handling and separation, but is not limited thereto. The amount of organic acid anhydride in the chemical imidization agent is preferably 1 to 10 times, more preferably 1 to 5 times, the theoretical dehydration amount of the polyimide precursor (polyamic acid). The amount of the basic catalyst is preferably in the range of 0.1 to 2 times by mole, more preferably 0.1 to 1 time by mole, relative to the amount of the organic acid anhydride.

[0028] In the "solution thermal imidization method" and "chemical imidization method," by-products such as catalysts, chemical imidization agents, and carboxylic acids (hereinafter referred to as impurities) are present in the reaction solution, and these may be removed and purified. Known purification methods can be used. For example, the simplest method is to drop the imidized reaction solution into a large amount of poor solvent while stirring to precipitate polyimide, and then recover the polyimide powder and repeatedly wash it until the impurities are removed. Suitable solvents for this purpose include water, methanol, ethanol, isopropanol, and other alcohols, which can precipitate polyimide, efficiently remove impurities, and are easy to dry. Mixtures of these may also be used. If the concentration of the polyimide solution used for precipitation by dropping into a poor solvent is too high, the precipitated polyimide may form agglomerates, with impurities remaining in the coarse particles. It may also take a long time to dissolve the resulting polyimide powder in the solvent. On the other hand, if the concentration of the polyimide solution is too low, a large amount of poor solvent is required, which is undesirable because it increases the environmental impact of waste solvent disposal and increases production costs. Therefore, the concentration of the polyimide solution when dropped into the poor solvent is preferably 20% by weight or less, more preferably 10% by weight or less. The amount of poor solvent used at this time is preferably equal to or greater than the amount of the polyimide solution, and is preferably 1.5 to 3 times the amount. The resulting polyimide powder is recovered, and the residual solvent is removed by vacuum drying or hot air drying, to obtain polyimide. There are no limitations on the drying temperature and time, as long as the temperature does not alter the polyimide or decompose the residual solvent. Drying at a temperature in the range of 30 to 200°C for 48 hours or less is preferred.

[0029] (Molded Articles) The polyimide of the present invention can be used to produce various processed articles, such as those listed below. The polyimide of the present invention can be used to produce molded articles, such as thin films, sheets, tapes, containers, threads, lenses, tubes, pellets, and foams. The polyimide of the present invention can also be used as a resin material for, and molded into, the following articles: electronic devices and electronic devices used therein (hereinafter collectively referred to as "electronic devices"), as described below, and electronic devices and devices used therein, particularly electronic devices and devices used for high-speed communication using radio waves in the high-frequency band of 1 GHz to 300 GHz (high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz). It can also be used as a resin material for, and molded into, articles such as machine parts (e.g., impellers, fan gears, gears, bearings, motor parts, cases), automobile parts (e.g., automobile mechanism parts, engine parts, engine room parts, electrical parts, interior parts), cooking utensils and tools, dental instruments, optical equipment parts (e.g., lenses, films), medical equipment parts and materials, dental equipment parts and materials, valves, pipes, nozzles, filters, membranes, sporting goods, leisure goods, and cable ties. The polyimide thin film of the present invention preferably has a dielectric constant of 3.5 or less measured at a frequency of 5 GHz. A dielectric constant of 3.5 or less makes it suitable for use as a polyimide resin material for electronic devices and devices, particularly for high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz. The dielectric constant is more preferably 3.4 or less, and particularly preferably 3.3 or less. Since a lower dielectric constant is preferable, the lower limit is not particularly limited, but it may be 2.0 or more. The polyimide of the polyimide thin film of the present invention has an intrinsic viscosity of the polyimide precursor (polyamic acid) before imidization in the range of preferably 0.1 dL / g to 10.0 dL / g, more preferably 0.2 dL / g to 5.0 dL / g, even more preferably 0.5 dL / g to 5.0 dL / g, and particularly preferably 1.0 dL / g to 5.0 dL / g.

[0030] (Polyimide Resin Material for Electronic Devices and Devices) The polyimide of the present invention has excellent dielectric properties in the high-frequency band. Therefore, a resin material containing the polyimide of the present invention is suitable as a polyimide resin material (polyimide resin material for electronic devices and devices) for use in electronic devices and electronic devices (electronic devices and devices) used therein, and is particularly suitable as a polyimide resin material (polyimide resin material for high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz) for use in electronic devices and devices used in high-speed communication using radio waves in the high-frequency band in the range of 1 GHz to 300 GHz.

[0031] (Electronic Devices and Devices) In the present invention, electronic devices and electronic devices used therein are collectively referred to as "electronic devices and devices." In particular, electronic devices and devices used for high-speed communication using radio waves in a high-frequency band ranging from 1 GHz to 300 GHz are collectively referred to as "high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz." Because the polyimide of the present invention has excellent dielectric properties in high-frequency bands, it is preferable to use the polyimide of the present invention in electronic devices and devices, particularly high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz. Specific examples of the electronic devices include mobile phones, smartphones, personal computers, mobile routers, data center communication equipment, base stations, radar, robots, drones, wearable computers, measuring and measurement instruments used in various industries such as automobiles, aircraft, industry, agriculture, logistics, and civil engineering, high-speed wireless communication equipment, electronic organizers, digital still cameras, video cameras, electronic paper, televisions, players, various audio equipment, in-vehicle displays such as car navigation systems and instrument panels, calculators, printers, scanners, copiers, refrigerators, and washing machines. Among these, electronic devices used for high-speed communication using high-frequency radio waves include mobile phones, smartphones, personal computers, mobile routers, data center communication equipment, base stations, radar, robots, drones, wearable computers, measurement and measuring instruments used in various industries such as automobiles, aircraft, industry, agriculture, logistics, and civil engineering, and high-speed wireless communication equipment. Specific examples of such electronic devices include semiconductors, electronic displays, and electric and electronic components. Examples of such electric and electronic components include capacitors, printed circuits, connectors, various sensors, inductors, switches, and housings. These are also used in electronic devices used for high-speed communication using high-frequency radio waves.More specifically, the polyimide of the present invention can be suitably used in, for example, flexible printed circuit board base films, adhesive layers, cover films, thin-film adhesives, rigid substrates, TAB carrier tapes, antenna element members, copper-clad laminates, filters, substrate packaging materials, liquid crystal alignment films, semiconductor packaging materials, semiconductor encapsulants, or structural members for these electronic devices and devices (preferably high-frequency communication electronic devices and devices in the range of 1 GHz to 300 GHz). Among these, the polyimide of the present invention can be suitably used in flexible printed circuit board base films, adhesive layers, cover films, thin-film adhesives, copper-clad laminates, rigid substrates, TAB carrier tapes, antenna element members, or filter substrate packaging materials for electronic devices and devices, more suitably used in flexible printed circuit board base films, adhesive layers, cover films, thin-film adhesives, and copper-clad laminates for electronic devices and devices, and particularly suitably used in flexible printed circuit board base films, cover films, and copper-clad laminates for electronic devices and devices.

[0032] (High-Frequency Band Radio Waves) In the present invention, high-frequency band radio waves refer to radio waves with a frequency in the range of 1 GHz to 300 GHz, and include microwaves, centimeter waves (SHF: Super High Frequency), millimeter waves (EHF: Extremely High Frequency), etc. The frequency range of such high-frequency band radio waves is preferably in the range of 3 GHz to 100 GHz, more preferably in the range of 5 GHz to 80 GHz, and particularly preferably in the range of 5 GHz to 30 GHz.

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The analytical methods used in the present invention are as follows. <Analysis Method> (1) Measurement of Reduced Viscosity: A 0.5 wt % polyimide precursor solution was prepared, and the reduced viscosity at 40°C was measured using an Ostwald viscometer. (2) Measurement of Crystallinity: The prepared polyimide thin film measurement sample was set in a sample holder, and measurements were performed under the following conditions using the X-ray diffractometer described below. From the measurement results, the crystallinity was calculated from the ratio of the integrated intensity of the peaks in the crystalline portion to the integrated intensity of all peaks in the diffraction spectrum within the diffraction angle (2θ) range of 5° to 40°. Crystallinity (%) = crystalline peak area ÷ (crystalline peak area + amorphous peak area) × 100 Apparatus: MiniFlex 600 (manufactured by Rigaku Corporation) Conditions: Scan axis: 2θ / θ Mode: 1D (scan) Measurement range: 2θ = 5° to 40° Step: 0.1° Speed ​​measurement time: 2θ = 0.5° / min Output: 40 kV-15 mA (3) Dielectric property evaluation (relative dielectric constant ε ｒ The prepared polyimide thin film was processed to a predetermined size and measured and evaluated by the cavity resonator perturbation method (compliant with IEC 62810). Apparatus: PNA network analyzer N5222B (manufactured by Keysight Technologies, Inc.), cavity resonator CP511 for 5 GHz (manufactured by Kanto Electronics Application Development Co., Ltd.) Conditions: frequency 5 GHz, measurement temperature 23°C, number of measurements n = 2 Conditioning: 23°C ± 1°C, 50% RH ± 5% RH × 24 h < Test environment: 23°C ± 1°C, 50% RH ± 5% RH

[0034] Example 1: 1.2811 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 30.9832 g of N-methyl-2-pyrrolidone (NMP) were placed in a 100 mL screw vial and dissolved at room temperature. Subsequently, 1.7062 g of premixed 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) (Compound 3A) and 0.4495 g of 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride) (Compound 4A) were added to the completely dissolved diamine solution and stirred under a nitrogen atmosphere. The molar ratio of Compound 3A to Compound 4A was 8:2. Stirring was terminated when the solution reached a sufficiently high viscosity, yielding a polyamic acid solution with a resin content of 10 wt %. The reduced viscosity of the resulting polyamic acid was 1.88 dL / g (40°C, 0.5 wt %). This polyamic acid solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under a nitrogen stream for 3 hours. The solution was then heated stepwise up to 350°C to imidize the polyamic acid. The imidized thin film was immersed in water, peeled off, and then dried at 250°C and 0.1 kPa for 1 hour. The resulting polyimide thin film was flexible and strong, and did not break even when bent 180°. The dielectric properties of the resulting polyimide thin film were evaluated using the analytical method described above. The results are summarized in Table 1. The crystallinity of the resulting polyimide thin film was measured using the analytical method described above and found to be 11%.

[0035] Example 2: 1.2811 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 31.1576 g of N-methyl-2-pyrrolidone (NMP) were placed in a 100 mL screw vial and dissolved at room temperature. Subsequently, 1.2787 g of premixed 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) (Compound 3A) and 0.8999 g of 4,4'-dihydroxybiphenyl-bis(trimellitate anhydride) (Compound 4A) were added to the completely dissolved diamine solution and stirred under a nitrogen atmosphere. The molar ratio of Compound 3A to Compound 4A was 6:4. Stirring was terminated when the solution reached a sufficiently high viscosity, yielding a polyamic acid solution with a resin content of 10 wt %. The reduced viscosity of the resulting polyamic acid was 2.29 dL / g (40°C, 0.5 wt %). This polyamic acid solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under a nitrogen stream for 3 hours. The solution was then heated stepwise up to 350°C to imidize the polyamic acid. The imidized thin film was immersed in water, peeled off, and then dried at 250°C and 0.1 kPa for 1 hour. The resulting polyimide thin film was flexible and strong, and did not break even when bent 180°. The dielectric properties of the resulting polyimide thin film were evaluated using the analytical method described above. The results are summarized in Table 1. The crystallinity of the resulting polyimide thin film was measured using the analytical method described above and found to be 10%.

[0036] Comparative Example 1: 1.2811 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 31.6611 g of N-methyl-2-pyrrolidone (NMP) were added to a 100 mL screw vial and dissolved at room temperature. Subsequently, 2.2367 g of 2,6-dihydroxynaphthalene-bis(trimellitate anhydride) (Compound 3A) was added to the completely dissolved diamine compound solution and stirred under a nitrogen atmosphere. Stirring was terminated when the viscosity of the solution reached a sufficient level, yielding a polyamic acid solution with a resin content of 10 wt %. The reduced viscosity of the resulting polyamic acid was 1.37 dL / g (40°C, 0.5 wt %). This polyamic acid solution was cast onto a smooth glass support, and the solvent was removed at 80°C under a nitrogen stream for 3 hours. The solution was then heated stepwise up to 350°C to imidize the polyamic acid. The imidized thin film was immersed in water, peeled off, and then dried at 250°C and 0.1 kPa for 1 hour. The resulting polyimide thin film was flexible and strong, and did not break even when bent 180°. The dielectric properties of the resulting polyimide thin film were evaluated using the analytical method described above. The results are summarized in Table 1. The crystallinity of the resulting polyimide thin film was measured using the analytical method described above and found to be 77%.

[0037] Comparative Example 2: 0.4329 g of 1,4-diaminobenzene (p-PDA) and 24.0272 g of N-methyl-2-pyrrolidone (NMP) were added to a 100 mL screw vial and dissolved at room temperature. Subsequently, 2.2369 g of Compound 3A was added to the completely dissolved diamine compound solution and stirred under a nitrogen atmosphere. Stirring was terminated when the solution reached a sufficiently high viscosity, yielding a polyamic acid solution with a resin content of 10 wt %. The reduced viscosity of the resulting polyamic acid was 1.28 dL / g (40°C, 0.5 wt %). This polyamic acid solution was cast onto a smooth glass support, and the solvent was removed at 80°C under a nitrogen stream for 3 hours. The polyamic acid was then heated stepwise up to 350°C to imidize it. The imidized thin film was immersed in water, peeled off, and then dried at 250°C and 0.1 kPa for 1 hour. The obtained polyimide thin film was brittle and broke when bent 180°. The dielectric properties of the obtained polyimide thin film were evaluated using the above-mentioned analytical method. The results are summarized in Table 1. The crystallinity of the obtained polyimide thin film was measured using the above-mentioned analytical method and was found to be 56%.

[0038] Comparative Example 3: 0.4329 g of 1,3-diaminobenzene (m-PDA) and 24.0263 g of N-methyl-2-pyrrolidone (NMP) were added to a 100 mL screw vial and dissolved at room temperature. Subsequently, 2.2374 g of Compound 3A was added to the completely dissolved diamine compound solution and stirred under a nitrogen atmosphere. Stirring was terminated when the solution reached a sufficiently high viscosity, yielding a polyamic acid solution with a resin content of 10 wt %. The reduced viscosity of the resulting polyamic acid was 0.97 dL / g (40°C, 0.5 wt %). This polyamic acid solution was cast onto a smooth glass support, and the solvent was removed at 80°C under a nitrogen stream for 3 hours. The polyamic acid was then heated stepwise up to 350°C to imidize it. The imidized thin film was immersed in water, peeled off, and then dried at 250°C and 0.1 kPa for 1 hour. The obtained polyimide thin film was flexible and strong, and did not break even when bent 180°. The dielectric properties of the obtained polyimide thin film were evaluated using the above-mentioned analytical method. The results are summarized in Table 1. The crystallinity of the obtained polyimide thin film was measured using the above-mentioned analytical method and was found to be 48%.

[0039]

[0040] The polyimides obtained in Examples 1 and 2 of the present invention have a lower relative dielectric constant than the polyimides obtained in Comparative Examples 1 to 3, and therefore, it is clear that they have excellent dielectric properties.

Claims

1. Repeating unit represented by formula (1) (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group or a halogen atom, and each n independently represents 1 or 2; and a repeating unit represented by general formula (2): (In the formula, R １ each independently represents a methyl group, a trifluoromethyl group, or a halogen atom; R ２ each independently represents a methyl group, a trifluoromethyl group or a halogen atom; each independently represents an integer of 1 or 2; and each independently represents an integer of 0, 1, 2 or 3.

2. The repeating unit represented by the general formula (1) is a repeating unit represented by the general formula (1a), (In the formula, R １ is the same as defined in formula (1). The repeating unit represented by formula (2) is a repeating unit represented by formula (2a): (In the formula, R １、 R ２ and m are defined as in general formula (2). The polyimide according to claim 1 .

3. The repeating unit represented by the general formula (1a) is a repeating unit represented by chemical formula (1a-1) or chemical formula (1a-2), The repeating unit represented by the general formula (2a) is at least one selected from the repeating units represented by chemical formulas (2a-1) to (2a-6). The polyimide according to claim 2.

4. The polyimide according to claim 3, wherein a combination of the repeating unit represented by general formula (1) and the repeating unit represented by general formula (2) is the combination of the chemical formula (1a-1) and the chemical formula (2a-1), the chemical formula (1a-1) and the chemical formula (2a-3), or the chemical formula (1a-1) and the chemical formula (2a-5).

5. The polyimide according to claim 1, wherein the content of the repeating unit represented by the general formula (1) and the repeating unit represented by the general formula (2) is in the range of 50 mol % or more and 100 mol % or less of the entire polyimide.

6. The polyimide according to claim 5, wherein the content of the repeating units represented by the general formula (1) and the repeating units represented by the general formula (2) is 100 mol % of the entire polyimide, and the ratio of the repeating units represented by the general formula (1) to the repeating units represented by the general formula (2) is in the range of general formula (1):general formula (2)=50:50 to 90:

10.

7. A polyimide thin film comprising the polyimide according to any one of claims 1 to 6.