TW202434669A - Polyimide, polyimide film - Google Patents

Abstract

An object of the present invention is to provide a polyimide resin material with improved dielectric properties. As a solution, a polyimide having repeating units represented by the general formula (1) in a range of 60 mol % or more and 100 mol % or less of the entire polyimide is provided. (In the formula, R1 each independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched halogenated alkyl group having 1 to 6 carbon atoms or a halogen atom, n represents 1 or 2).

Description

Polyimide, polyimide film

The present invention relates to a polyimide with improved dielectric properties, and more specifically, to a polyimide with improved dielectric properties using 2,6-dihydroxynaphthalene-bis(trimellitic anhydride).

Polyimide resins obtained by the reaction of tetracarboxylic dianhydride and diamine compounds are generally insoluble and infusible super heat-resistant resins with excellent properties such as thermal oxidation resistance, heat resistance, radiation resistance, low temperature resistance, and chemical resistance. Therefore, polyimide resins are used as materials or heat-resistant adhesives in insulating coatings, insulating films, semiconductors, electrode protection films, flexible printed circuit boards and other electrical/electronic parts, aerospace machinery, transportation machinery, and other fields.

In recent years, the transmission speed of electronic signals circulated in wireless network equipment and communication equipment has been moving towards extremely high speed/high frequency, and the insulation parts that insulate the metal wiring of these equipment are also required to be able to cope with high frequencies. The higher the frequency, the greater the dielectric loss of the insulation part, which leads to the attenuation of the circulated electronic signals. Therefore, in order to cope with high frequencies, materials with excellent dielectric properties that can reduce dielectric loss are sought.

It is known that polyimide using 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) is suitable for use, for example, as a base film for flexible printed circuit boards, a carrier tape for TAB, or a resin for laminates (Patent Document 1). In addition, it is known that polyesterimide obtained by polymerizing it with 4,4'-oxydiphenylamine can be used as a hybrid film with organically modified lithium bentonite (Non-Patent Document 1).

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 2004-285364

[Non-patent literature]

[Non-patent document 1] Macromolecular Research, 2014, Vol. 22, pp. 549-556

The subject of the present invention is to provide a polyimide resin material with improved dielectric properties in polyimide using 2,6-dihydroxynaphthalene-bis(trimellitic anhydride).

As a result of the inventors' dedicated research to solve the above problems, they found that polyimide having a structure derived from 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) and a structure derived from a specific diamine compound has improved dielectric properties, and thus completed the present invention.

The present invention is as follows.

1. A polyimide having a repeating unit represented by the general formula (1) in a range of 60 mol% to 100 mol% of the entire polyimide.

(wherein, _R1 independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom, and n represents 1 or 2).

2. The polyimide as described in 1., wherein the repeating unit represented by the aforementioned general formula (1) is a repeating unit represented by the general formula (1a).

(wherein, R ₁ is independently a methyl group, a trifluoromethyl group or a fluorine atom).

3. The polyimide as described in 2., wherein R ₁ in the repeating unit represented by the general formula (1a) is a trifluoromethyl group.

4. The polyimide as described in 1., which has a repeating unit represented by the general formula (1) in a range of 60 mol% or more and less than 100 mol%, and has a repeating unit represented by the general formula (1') in the remaining proportion relative to the repeating unit.

(wherein Ar represents a p-phenylene group or a 4,4'-biphenylene group, and _R1 and n have the same definitions as in the general formula (1)).

5. The polyimide described in 1. has a dielectric loss tangent of less than 0.004 when measured at a frequency of 5 GHz.

6. The polyimide described in 1. has an inherent viscosity of the polyimide precursor before imidization in the range of 0.1 to 10.0 dL/g.

7. A polyimide film comprising the polyimide described in any one of 1. to 6.

The polyimide of the present invention has improved dielectric properties. Therefore, it can be suitably used in electronic machines and/or devices, especially materials for high-frequency communication electronic machines and/or devices in the range of above 1 GHz and below 300 GHz.

(Polyimide of the present invention)

The polyimide of the present invention has repeating units represented by the general formula (1) in a range of 60 mol% to 100 mol% of the entire polyimide.

(wherein, _R1 independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkyl group having 1 to 6 carbon atoms, or a halogen atom, and n represents 1 or 2).

_R1 is preferably independently a linear or branched alkyl group having 1 to 4 carbon atoms, a linear or branched alkyl group having 1 to 4 carbon atoms, or a halogenated atom, more preferably independently a methyl group, a trifluoromethyl group, or a fluorine atom, further preferably independently a methyl group or a trifluoromethyl group, and particularly preferably a trifluoromethyl group.

Preferably n is 1.

In the repeating unit represented by the general formula (1), when n is 1, the bonding position including R ₁ is preferably a repeating unit represented by the general formula (1a), more preferably a repeating unit represented by the chemical formula (1a-1) or the chemical formula (1a-2), and particularly preferably a repeating unit represented by the chemical formula (1a-1).

(wherein, the definition of R ₁ is the same as in general formula (1)).

(Proportions with repeated units)

The polyimide of the present invention has a repeating unit represented by the general formula (1) in a range of 60 mol% to 100 mol% of the entire polyimide. The lower limit of the content ratio of the repeating unit represented by the general formula (1) is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and particularly preferably 100 mol%, that is, only the repeating unit represented by the general formula (1). It is speculated that by making the ratio of the repeating unit represented by the general formula (1) in the polyimide within this range, the polyimide has improved dielectric properties.

The repeating units of general formula (1) can be arranged regularly or randomly in the polyimide.

Furthermore, it may have only one type selected from the range of repeating units represented by general formula (1), or it may have two or more types, but it is preferred to have only one type.

When the polyimide of the present invention has a repeating unit represented by the general formula (1) in a range of 60 mol% or more and less than 100 mol%, for example, it may have a repeating unit other than the repeating unit represented by the general formula (1), and one or more compounds selected from the tetracarboxylic dianhydride and diamine compounds described later may be used in combination to constitute the repeating unit. The repeating unit other than the repeating unit represented by the general formula (1) may be one or more. With respect to the repeating unit of the polyimide of the present invention, the remaining proportion has the repeating unit.

As a repeating unit other than the repeating unit represented by the general formula (1), for example, the repeating unit represented by the general formula (1') can be cited, and the repeating unit represented by the general formula (1') is preferred.

(wherein Ar represents a p-phenylene group or a 4,4'-biphenylene group, and _R1 and n have the same definitions as in the general formula (1)).

Among the repeating units represented by the general formula (1'), the repeating unit represented by the general formula (1'a) is preferred, and one or more repeating units selected from the repeating units represented by the chemical formulas (1'a-1) to (1'a-4) are more preferred, and the repeating unit represented by the chemical formula (1'a-1) or (1'a-3) is still more preferred, and the repeating unit represented by the chemical formula (1'a-3) is particularly preferred.

(wherein Ar represents a p-phenylene group or a 4,4'-biphenylene group, and _R1 and n have the same definitions as in the general formula (1)).

Regarding the repeating units of the polyimide of the present invention, various combinations can be made for the combination of the repeating units represented by the aforementioned general formula (1) and the repeating units other than the aforementioned ones, among which the combination of chemical formula (1a-1) and chemical formula (1'a-1), chemical formula (1a-1) and chemical formula (1'a-3), chemical formula (1a-2) and chemical formula (1'a-2), or chemical formula (1a-2) and chemical formula (1'a-4) is preferred, the combination of chemical formula (1a-1) and chemical formula (1'a-1) or chemical formula (1a-1) and chemical formula (1'a-3) is more preferred, and the combination of chemical formula (1a-1) and chemical formula (1'a-1) is particularly preferred.

(Dielectric loss tangent)

The dielectric loss tangent of the polyimide of the present invention measured at a frequency of 5 GHz is preferably 0.004 or less. If the dielectric loss tangent is 0.004 or less, it can be suitably used as a polyimide resin material for electronic equipment and/or devices, especially for high-frequency communication electronic equipment and/or devices in the range of 1 GHz to 300 GHz. The dielectric loss tangent is preferably 0.0035 or less, more preferably 0.0030 or less, and particularly preferably 0.0025 or less. The lower the dielectric loss tangent, the better, so the lower limit is not particularly limited, and it can also be 0.0010 or more.

(Relative dielectric constant)

The relative dielectric constant of the polyimide of the present invention measured at a frequency of 5 GHz is preferably 3.5 or less. If the relative dielectric constant is below 3.5, it can be suitably used as a polyimide resin material for electronic equipment and/or devices, especially for high-frequency communication electronic equipment and/or devices in the range of 1 GHz to 300 GHz. The relative dielectric constant is more preferably below 3.4, and particularly preferably below 3.3. The lower the relative dielectric constant, the better, so there is no special limit on the lower limit, and it can also be above 2.0.

(Crystallinity)

The crystallinity of the polyimide of the present invention is preferably in the range of 60% to 90%, more preferably in the range of 60 to 85%, still more preferably in the range of 65 to 85%, and particularly preferably in the range of 70 to 85%. It is speculated that the crystallinity of the polyimide within this range is one of the reasons why the polyimide has improved dielectric properties.

The crystallinity in the present invention is calculated by using an X-ray diffraction device to separate the total scattering intensity curve of X-rays into a range showing the scattering effect of the crystal part and a range showing the scattering effect of the amorphous part. Specifically, the measurement sample is placed on a sample carrier, and the diffraction spectrum with a diffraction angle (2θ) in the range of 5 to 40° is obtained by the X-ray diffraction device. The crystallinity is calculated from the ratio of the integrated intensity of the peak of the crystalline part to the integrated intensity of all peaks.

Crystallinity (%) = peak area of crystalline material ÷ (peak area of crystalline material + peak area of amorphous material) × 100

(Intrinsic viscosity)

The inherent viscosity of the polyimide precursor (polyamide) of the polyimide of the present invention before imidization is preferably in the range of 0.1 to 10.0 dL/g, more preferably in the range of 0.2 to 5.0 dL/g, still more preferably in the range of 0.5 to 5.0 dL/g, and particularly preferably in the range of 1.0 to 5.0 dL/g.

(The method for producing polyimide of the present invention)

The method for producing the polyimide of the present invention is not particularly limited, and can be produced, for example, by the following steps: a step of reacting 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) (hereinafter sometimes referred to as compound A) (A) with a diamine compound represented by general formula (2) to obtain a polyimide precursor (polyamide), and a step of imidizing the polyimide precursor.

(wherein, _R1 and n have the same definitions as in general formula (1)).

As a specific example, a reaction formula of a method for producing a polyimide using 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) (A) and 2,2'-bis(trifluoromethyl)benzidine (2a) as a diamine compound represented by general formula (2) is presented. Compound A and compound (2a) are polymerized to obtain a polyimide precursor (polyamide) having the following repeating units, and the polyimide precursor is imidized to obtain the target polyimide (1a) having the following repeating units.

In the diamine compound represented by the general formula (2), _R1 and n have the same definitions as in the general formula (1), and the preferred embodiments are also the same. Specific examples of the diamine compound represented by the general formula (2) 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 them, 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, 2,2'-dichlorobenzidine are preferred, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 2,2'-difluorobenzidine are more preferred, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine are further 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 general formula (1), two or more diamine compounds represented by the general formula (2) are used. The polyimide of the present invention preferably has only one repeating unit selected from the range of the general formula (1), so it is preferred to use one diamine compound represented by the general formula (2).

In the polyimide of the present invention, when the repeating unit represented by the general formula (1) is present in an amount of 60 mol% or more and less than 100 mol%, the diamine compound constituting the repeating unit other than the repeating unit represented by the general formula (1) may be, for example, m-phenylenediamine (m-PDA), p-phenylenediamine (p-PDA), 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 sulfide. 、4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 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)-1,1,1,3,3, 3-Hexafluoropropane, 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-propylenediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, 4,4'-methylenebis(cyclohexylamine), trans-1 ,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 2,5-bis(aminomethyl)biscyclo[2.2.1]heptane, 2,6-bis(aminomethyl)biscyclo[2.2.1]heptane, biscyclo[2.2.2]octane-1,4-diamine, decahydro-1,4-naphthalenediamine, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminobenzidine, 2,2-bis(4-aminocyclohexyl)propane and 2,2-bis(4-aminocyclohexyl)hexafluoropropane, etc.

In the polyimide of the present invention, when the repeating unit represented by the general formula (1) is present in an amount of 60 mol% or more and less than 100 mol%, the tetracarboxylic dianhydride constituting the repeating unit other than the repeating unit represented by the general formula (1) may be, for example, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenyl sulfide tetracarboxylic dian ... -diphenylsulfonate tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)bis(phthalic acid) dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)phthalic 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]sulfonium 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 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)-3-methylphenyl]fluorene dianhydride, hydroquinone-bis(trimellitic anhydride), resorcinol-bis(trimellitic anhydride), 1,5-dihydroxy Naphthalene-bis(trimellitic anhydride), 2,7-dihydroxynaphthalene-bis(trimellitic anhydride), 4,4'-dihydroxybiphenyl-bis(trimellitic anhydride), 4,4'-dihydroxy-3,3'-dimethylbiphenyl-bis(trimellitic anhydride), 4,4'-dihydroxy-3,3',5,5'-tetramethylbiphenyl-bis(trimellitic anhydride), 4,4'-dihydroxy-2,2',3,3',5,5' -Hexamethylbiphenyl-bis(trimellitic anhydride), 4,4'-dihydroxydiphenyl ether-bis(trimellitic anhydride), 4,4'-dihydroxydiphenyl sulfide-bis(trimellitic anhydride), 4,4'-dihydroxydiphenyl sulfide-bis(trimellitic anhydride), 4,4'-dihydroxydiphenyl sulfide-bis(trimellitic anhydride), 4,4'-dihydroxydiphenyl sulfone-bis(trimellitic anhydride), 4,4'-dihydroxybenzophenone-bis(trimellitic anhydride), 1,1'-bis(4-hydroxyphenyl)ethane-bis(trimellitic anhydride), 2,2'-bis( (4-Hydroxyphenyl)propane-bis(trimellitic anhydride), 2,2'-bis(4-hydroxy-3-methylphenyl)propane-bis(trimellitic anhydride), 2,2'-bis(4-hydroxyphenyl)hexafluoropropane-bis(trimellitic anhydride), 1,1'-bis(4-hydroxyphenyl)cyclohexane-bis(trimellitic anhydride), 1,1'-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane-bis(trimellitic anhydride), trimellitic anhydride), 1,1'- bis(4-hydroxyphenyl)cyclodecane-bis(trimellitic anhydride), 9,9'-bis(4-hydroxy-3-methylphenyl)fluorene-bis(trimellitic anhydride), cyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride and 1,2,3,4-tetramethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, etc.

As for the tetracarboxylic dianhydride used together with compound A, the tetracarboxylic dianhydride represented by general formula (3) is preferred.

(In the formula, Ar represents paraphenylene or 4,4'-biphenylene).

Among the specific examples of the above-mentioned tetracarboxylic dianhydride, the tetracarboxylic dianhydride represented by the general formula (3) is hydroquinone-bis(trimellitic anhydride) and 4,4'-dihydroxybiphenyl-bis(trimellitic anhydride). Among them, 4,4'-dihydroxybiphenyl-bis(trimellitic anhydride) is more preferred.

The repeating unit represented by the general formula (1') is formed by polymerizing the tetracarboxylic dianhydride represented by the general formula (3) and the diamine compound represented by the general formula (2) and performing imidization.

When the polyimide of the present invention is manufactured by the above steps, specifically, it can be synthesized by, for example, the following method.

First, the diamine compound is dissolved in a polymerization solvent, and tetracarboxylic dianhydride is slowly added to the solution. The amount of tetracarboxylic dianhydride used is generally in the range of 0.9 to 1.2 molar times relative to the diamine compound, preferably in the range of 0.95 to 1.1 molar times, and more preferably in the range of 1.0 to 1.1 molar times. The solution is stirred at a temperature of generally 0 to 100° C., preferably 20 to 60° C., using a mechanical stirrer, etc., and is generally stirred for 0.5 to 150 hours, preferably 1 to 72 hours. At this time, the monomer concentration is generally in the range of 5 to 50% by weight, preferably in the range of 10 to 40% by weight. By performing polymerization in such a monomer concentration range, a uniform and highly polymerized polyimide precursor (polyamide) can be obtained. When the polymerization degree of the polyimide precursor (polyamide) increases excessively and the polymerization solution becomes difficult to stir, it can also be appropriately diluted with the same solvent. By performing polymerization within the above monomer concentration range, the polymerization degree of the polymer is sufficiently increased, and the solubility of the monomer and the polymer can be fully ensured. If the polymerization is performed at a concentration lower than the above range, the polymerization degree of the polyimide precursor (polyamide) may not be sufficiently increased. If the polymerization is performed at a concentration higher than the above monomer concentration range, the solubility of the monomer or the generated polymer may become insufficient.

烷、二甲氧基乙烷、二乙氧基乙烷、二丁醚等醚系溶劑。其他泛用溶劑亦可使用：苯乙酮、1,3-二甲基-2-咪唑啶酮、環丁碸、二甲基亞碸、丙二醇甲基乙酸酯、乙基賽路蘇、丁基賽路蘇、2-甲基賽路蘇乙酸酯、乙基賽路蘇乙酸酯、丁基賽路蘇乙酸酯、丁醇、乙醇、二甲苯、甲苯、氯苯、松節油(Turpentine)、礦油精、石油腦(naphtha)系溶劑溶劑等。此等的溶劑亦可混合兩種以上使用。 As for the solvent used in the polymerization of the polyimide precursor (polyamic acid), preferably, it is a non-protonic solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, etc., but as long as it can dissolve the raw material monomers and the generated polyimide precursor (polyamic acid), and the imidized polyimide, any kind of solvent can be used without any problem, and in particular, the structure and type of the solvent are not particularly limited. Specifically, for example, 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, and carbonate solvents such as butyl acetate. Carbonate solvents such as ethyl ester and propylene carbonate, glycol solvents such as diethylene glycol dimethyl ether, triethylene glycol, triethylene glycol dimethyl ether, phenol solvents such as m-cresol, p-cresol, o-cresol, 3-chlorophenol, 4-chlorophenol, ketone solvents such as cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone, tetrahydrofuran, 1,4-dimethoxybenzene,

Ether solvents such as oxane, dimethoxyethane, diethoxyethane, and dibutyl ether can be used. Other general solvents that can be used include acetophenone, 1,3-dimethyl-2-imidazolidinone, cyclobutane sulfone, dimethyl sulfoxide, propylene glycol methyl acetate, ethyl thiourea, butyl thiourea, 2-methyl thiourea acetate, ethyl thiourea acetate, butyl thiourea acetate, butanol, ethanol, xylene, toluene, chlorobenzene, turpentine, mineral spirits, and naphtha solvents. Two or more of these solvents can also be used in combination.

In addition, the polymerization reaction to obtain the polyimide precursor (polyamide) can be carried out in air or in an inert gas such as nitrogen, preferably in an inert gas such as nitrogen.

烷、二甲氧基乙烷、二乙氧基乙烷、二丁醚等醚系溶劑，其他泛用溶劑亦可使用：苯乙酮、1,3-二甲基-2-咪唑啶酮、環丁碸、二甲基亞碸、乙酸丁酯、乙酸乙酯、乙酸異丁酯、丙二醇甲基乙酸酯、乙基賽路蘇、丁基賽路蘇、2-甲基賽路蘇乙酸酯、乙基賽路蘇乙酸酯、丁基賽路蘇乙酸酯、氯仿、丁醇、乙醇、二甲苯、甲苯、氯苯、松節油(Turpentine)、礦油精、石油腦系溶劑等。其中，從溶解性的觀點來看，較佳係使用N,N-二甲基甲醯胺、N,N-二甲基乙醯胺、N-甲基-2-吡咯啶酮等醯胺溶劑、γ-丁內酯、γ-戊內酯、δ-戊內酯、γ-己內酯、ε-己內酯、α-甲基-γ-丁內酯等酯溶劑、碳酸伸乙酯、碳酸伸丙酯等碳酸酯溶劑。亦可將此等的溶劑混合兩種以上使用。 The polyimide precursor (polyamide) of the present invention can be made into a varnish containing the polyimide precursor (polyamide) and an organic solvent. As for the organic solvent for dissolving the polyimide precursor (polyamide), the solvent can be appropriately selected according to the use of the varnish and the processing conditions, and there is no particular limitation. For example, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α -methyl-γ-butyrolactone and other ester solvents, ethyl carbonate, propyl carbonate and other carbonate solvents, diethylene glycol dimethyl ether, triethylene glycol, triethylene glycol dimethyl ether and other glycol solvents, phenol, m-cresol, p-cresol, o-cresol, 3-chlorophenol, 4-chlorophenol and other phenol solvents, cyclopentanone, cyclohexanone, acetone, methyl ethyl ketone, diisobutyl ketone, methyl isobutyl ketone and other ketone solvents, tetrahydrofuran, 1,4-dimethoxybenzene,

Ether solvents such as oxane, dimethoxyethane, diethoxyethane, and dibutyl ether can also be used. Other general solvents can also be used: acetophenone, 1,3-dimethyl-2-imidazolidinone, cyclobutane sulfone, dimethyl sulfoxide, butyl acetate, ethyl acetate, isobutyl acetate, propylene glycol methyl acetate, ethyl thiourea, butyl thiourea, 2-methyl thiourea acetate, ethyl thiourea acetate, butyl thiourea acetate, chloroform, butanol, ethanol, xylene, toluene, chlorobenzene, turpentine, mineral spirits, and naphtha-based solvents. Among them, from the viewpoint of solubility, it is preferred 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 ethyl carbonate and propyl carbonate. These solvents may be mixed and used in combination of two or more.

When the polyimide precursor (polyamide) of the present invention is dissolved in a solvent to form a varnish, the solid content concentration can be appropriately selected according to the purpose of the varnish without any particular limitation. For example, when it is used as a film, although it is related to the molecular weight of the polyimide, the manufacturing method and the thickness of the manufactured film, it is preferred to make the solid content concentration above 5% by weight. If the solid content concentration is too low, it is difficult to form a film with sufficient film thickness. On the contrary, if the solid content concentration is high and the solution viscosity is too high, there is a risk that coating will become difficult. As for the method for preparing a varnish containing the polyimide precursor (polyamide) of the present invention and an organic solvent, for example, there can be listed: a method of preparing the polyimide precursor (polyamide) by subjecting the polyimide precursor (polyamide) to the above-mentioned polymerization reaction, or a method of mixing the polyimide precursor (polyamide) obtained by pre-polymerization and monolysis with the above-mentioned solvent, and dissolving it in the air or inert gas such as nitrogen at a temperature range from room temperature to below the boiling point of the solvent for 1 hour to 48 hours.

In addition, the varnish containing the polyimide precursor (polyamide) of the present invention may also contain additives such as release agents, fillers, silane coupling agents, crosslinking agents, end-capping agents, antioxidants, defoaming agents, and leveling agents as required.

The obtained varnish can be used to manufacture polyimide in the form of a film or a strip, for example. In addition, the varnish can be used to manufacture polyimide processed products such as polyimide films or laminates. As for its manufacturing method, for example, a scraper is used to cast the polyimide precursor (polyamide) varnish onto a support such as a glass substrate, and a hot air dryer, an infrared drying furnace, a vacuum dryer, an inert gas oven, etc. are used to perform imidization of the polyimide precursor (polyamide) by the "thermal imidization method" described later, thereby forming a polyimide film.

The imidization method of the obtained polyimide precursor (polyamide) is described.

Imidization can be carried out by known imidization methods, such as the "thermal imidization method" for thermally ring-closing a polyimide precursor (polyamide) film, the "solution thermal imidization method" for ring-closing a polyimide precursor (polyamide) solution at high temperature, and the "chemical imidization method" using a dehydrating agent. In order to produce the polyimide of the present invention, the imidization method by the "thermal imidization method" is preferred.

Specifically, in the "thermal imidization method", a polyimide precursor (polyamide) solution is cast onto a substrate, etc., and is usually dried at 50 to 200°C, preferably 60 to 150°C, to form a polyimide precursor (polyamide) film. After that, it is heated in an inert gas or under reduced pressure, usually at 150°C to 400°C, preferably 200°C to 380°C, for 1 to 12 hours to perform thermal dehydration and ring closure to complete imidization, thereby obtaining the polyimide of the present invention. In addition, the polyimide film of the present invention can be obtained in this way.

In the "solution thermal imidization method", a polyimide precursor (polyamide) solution to which an alkaline catalyst is added is heated in the presence of an azeotropic agent such as xylene, usually at 100 to 250°C, preferably at 150 to 220°C for 0.5 to 12 hours, thereby removing the by-product water from the system to complete the imidization, thereby obtaining the polyimide solution of the present invention.

In the "chemical imidization method", a polyimide precursor (polyamide) solution having been adjusted to a suitable solution viscosity for easy stirring is stirred by a mechanical stirrer or the like, and a dehydrating ring-closing agent (chemical imidization agent) composed of an anhydride of an organic acid and an amine as an alkaline catalyst is added dropwise, usually at 0 to 100°C, preferably at 10 to 50°C, for 1 to 72 hours, thereby chemically completing the imidization. The organic anhydride that can be used at this time is not particularly limited, and acetic anhydride, propionic anhydride, etc. can be listed. From the perspective of the ease of handling and purification of the reagent, acetic anhydride is suitable. In addition, as for the alkaline catalyst, pyridine, triethylamine, quinoline, etc. can be used. From the perspective of the ease of handling and purification of the reagent, pyridine is suitable, but it is not limited to these. The amount of organic acid anhydride in the chemical imidization agent is preferably in the range of 1 to 10 times the theoretical dehydration amount of the polyimide precursor (polyamide), and more preferably in the range of 1 to 5 times the molar amount. In addition, relative to the amount of organic acid anhydride, the amount of alkaline catalyst is preferably in the range of 0.1 to 2 times the molar amount, and more preferably in the range of 0.1 to 1 times the molar amount.

In the "solution thermal imidization method" and the "chemical imidization method", by-products such as catalysts, chemical imidization agents, carboxylic acids (hereinafter referred to as impurities) will be mixed into the reaction solution, so these can also be removed for purification. Purification can be performed using known methods. For example, as for the simplest method, there is the following method: while stirring the imidized reaction solution, it is dripped into a large amount of poor solvent to precipitate polyimide, and then the polyimide powder is recovered and repeatedly washed until the impurities are removed. At this time, as for the solvent that can be used, it is suitable to be water, methanol, ethanol, isopropyl alcohol and other alcohols that can precipitate polyimide, can remove impurities efficiently and are easy to dry, and these can also be used in combination. If the concentration of the polyimide solution when dropping into a bad solvent to precipitate it is too high, the precipitated polyimide will become lumps, impurities may remain in the coarse particles, and there is a risk that it will take a long time to dissolve the obtained polyimide powder in the solvent. On the other hand, if the concentration of the polyimide solution is too thin, a large amount of bad solvent is required, the environmental burden caused by the waste solvent treatment increases, and the manufacturing cost becomes high, which is not good. Therefore, the concentration of the polyimide solution when dropping into the bad solvent is preferably less than 20% by weight, and more preferably less than 10% by weight. The amount of the bad solvent used at this time is preferably equal to or more than the amount of the polyimide solution, and is preferably 1.5 to 3 times the amount.

The obtained polyimide powder is recovered and the residual solvent is removed by reduced pressure drying or hot air drying to obtain polyimide. The drying temperature and time are not limited as long as the polyimide does not deteriorate and the residual solvent does not decompose. It is preferably dried within a temperature range of 30 to 200°C for less than 48 hours.

(Molding products)

The polyimide of the present invention can be used to produce the various processed products listed below.

The polyimide of the present invention can be used to manufacture films, sheets, tapes, containers, wires, lenses, tubes, particles, foams and other molded products.

Furthermore, the polyimide of the present invention can be used as mechanical parts (e.g., impellers, fan gears, etc.) in addition to the electronic equipment and electronic devices used therein (hereinafter sometimes collectively referred to as electronic equipment and/or devices) described below and electronic equipment and/or devices used in high-speed communications using high-frequency radio waves in the range of 1 GHz to 300 GHz (high-frequency communication electronic equipment and/or devices in the range of 1 GHz to 300 GHz). gear), gears, bearings, motor parts, housings), automotive parts (e.g. automotive mechanism parts, engine parts, engine room internal parts, electrical parts, interior parts), cooking utensils/appliances, dental instruments, optical machine parts (e.g. lenses, films), medical machine parts/materials, dental machine parts/materials, valves, pipes, nozzles, filters, films, sports equipment, leisure equipment, straps, etc., which can be formed into such articles.

The dielectric loss tangent of the polyimide film of the present invention measured at a frequency of 5 GHz is preferably 0.004 or less. If this dielectric loss tangent is below 0.004, it can be used as a material for electronic equipment and/or devices, especially high-frequency communication electronic equipment and/or devices in the range of 1 GHz to 300 GHz, which requires high-frequency communication equipment such as polyimide resin. This dielectric loss tangent is more preferably 0.0035 or less, more preferably 0.0030 or less, and particularly preferably 0.0025 or less. The lower the dielectric loss tangent, the better, so the lower limit is not particularly limited, and it can also be above 0.0010.

The relative dielectric constant of the polyimide film of the present invention measured at a frequency of 5 GHz is preferably 3.5 or less. If the relative dielectric constant is 3.5 or less, it can be suitable for use in electronic equipment and/or devices, especially polyimide resin materials for high-frequency communication electronic equipment and/or devices in the range of 1 GHz to 300 GHz. The relative dielectric constant is more preferably 3.4 or less, and particularly preferably 3.3 or less. The lower the relative dielectric constant, the better, so the lower limit is not particularly limited, and can also be 2.0 or more.

The crystallinity of the polyimide film of the present invention is preferably in the range of 60% to 90%, more preferably in the range of 60 to 85%, still more preferably in the range of 65 to 85%, and particularly preferably in the range of 70 to 85%. It is speculated that the crystallinity of polyimide in this range is one of the reasons why polyimide has improved dielectric properties.

The crystallinity in the present invention is calculated by using an X-ray diffraction device to separate the total scattering intensity curve of X-rays into a range showing the scattering effect of the crystal part and a range showing the scattering effect of the amorphous part. Specifically, the crystallinity is calculated from the ratio of the integrated intensity of the peak of the crystalline part to the integrated intensity of all peaks in the diffraction spectrum with a diffraction angle (2θ) of 5 to 40° obtained by the X-ray diffraction device when the measurement sample is placed on a sample carrier.

Crystallinity (%) = peak area of crystalline material ÷ (peak area of crystalline material + peak area of amorphous material) × 100

The polyimide of the polyimide film of the present invention preferably has an inherent viscosity of the polyimide precursor (polyamide acid) before imidization in the range of 0.1 to 10.0 dL/g, more preferably in the range of 0.2 to 5.0 dL/g, still more preferably in the range of 0.5 to 5.0 dL/g, and particularly preferably in the range of 1.0 to 5.0 dL/g.

(Polyimide resin materials for electronic equipment and/or devices)

Since the polyimide of the present invention has improved dielectric properties in the high frequency band, the resin material containing the polyimide of the present invention is suitable as a polyimide resin material (polyimide resin material for electronic equipment and/or equipment) for electronic equipment and electronic devices (electronic equipment and/or equipment) used therein, and is particularly suitable as a polyimide resin material (polyimide resin material for high frequency communication electronic equipment and/or equipment in the range of 1 GHz to 300 GHz) for electronic equipment and/or equipment used in high-speed communication using high frequency band radio waves in the range of 1 GHz to 300 GHz.

(Electronic machines and/or devices)

In the present invention, electronic machines and electronic devices used therein are collectively referred to as electronic machines and/or devices. In particular, electronic machines and/or devices used in high-speed communications using high-frequency radio waves in the range of 1 GHz to 300 GHz are collectively referred to as high-frequency communication electronic machines and/or devices in the range of 1 GHz to 300 GHz.

The polyimide of the present invention has excellent dielectric properties in the high-frequency band, so the electronic machines and/or devices using the polyimide of the present invention, especially high-frequency communication electronic machines and/or devices in the range of 1 GHz to 300 GHz, are preferred.

Specifically, the aforementioned electronic devices include: mobile phones, smart phones, personal computers, mobile routers, data center communication devices, base stations, radars, robots, drones, wearable computers, measurement/measuring devices used in various industries such as automobiles/aircrafts/industry/agriculture/logistics/civil engineering, high-speed wireless communication devices, electronic notebooks, digital cameras, video cameras, electronic paper, televisions, players, various audio devices, car navigation devices and dashboards and other in-vehicle displays, calculators, printers, scanners, copiers, refrigerators, washing machines, etc.

Among them, electronic equipment used in high-speed communications using high-frequency radio waves can be listed as follows: mobile phones, smartphones, personal computers, mobile routers, data center communication equipment, base stations, radars, robots, drones, wearable computers, measurement/measuring equipment used in various industries such as automobiles/aircrafts/industry/agriculture/logistics/civil engineering, and high-speed wireless communication equipment.

The aforementioned electronic devices specifically include semiconductors, electronic displays, and electrical/electronic components. For example, the aforementioned electrical/electronic components include capacitors, printed circuits, connectors, various sensors, inductors, switches, and frames. These can also be used in electronic equipment used in high-speed communications using high-frequency radio waves.

The polyimide of the present invention, in more detail, can be suitably used in: base films for flexible printed circuit boards of such electronic machines and/or devices (preferably high-frequency communication electronic machines and/or devices in the range of 1 GHz to 300 GHz), adhesive layers, protective films, thin film adhesives, rigid boards, TAB carrier tapes, antenna element components, copper-clad laminates, filters, substrate exterior materials, liquid crystal orientation films, semiconductor mounting materials, semiconductor sealing materials or structural components. Among these, the base film, adhesive layer, protective film, thin film adhesive, copper clad laminate, hard substrate, TAB carrier tape, antenna component or filter, and substrate exterior material for flexible printed circuit substrates of electronic machines and/or devices are more suitable, and the base film, adhesive layer, protective film, thin film adhesive, and copper clad laminate for flexible printed circuit substrates of electronic machines and/or devices are further suitable, and the base film, protective film, and copper clad laminate for flexible printed circuit substrates of electronic machines and/or devices are particularly suitable.

(High frequency radio waves)

The high-frequency band radio waves in the present invention are radio waves with a frequency range of 1 GHz to 300 GHz, including microwaves, centimeter waves (SHF: Super High Frequency), millimeter waves (EHF: Extremely High Frequency) and other radio waves. The frequency range of this high-frequency band radio wave 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.

[Implementation example]

The present invention is specifically described below through examples, but the present invention is not limited to these examples.

The analysis method in the present invention is as follows.

<Analysis method>

(1) Determination of reduced viscosity

Prepare a 0.5 wt% polyimide precursor solution and use an Ostwald viscometer to measure the reduced viscosity at 40°C.

(2) Determination of crystallinity

The prepared polyimide film sample is placed on a sample carrier and measured using the following X-ray diffraction device under the following conditions. Then, the crystallinity is calculated from the ratio of the integrated intensity of the peak of the crystalline part to the integrated intensity of all peaks in the diffraction spectrum with a diffraction angle (2θ) of 5 to 40°.

Crystallinity (%) = peak area of crystalline material ÷ (peak area of crystalline material + peak area of amorphous material) × 100

Device: MiniFlex600 (manufactured by Rigaku Co., Ltd.)

Condition: Scanning axis: 2θ/θ

Mode: 1D (scan)

Measuring range: 2θ=5° to 40°

Step: 0.1°

Speed measurement time: 2θ=0.5°/min

Power: 40kV-15mA

(3) Dielectric property evaluation (relative dielectric constant ε _r , dielectric loss tangent tanδ)

The manufactured polyimide film is processed into a predetermined size and measured and evaluated by the Cavity Resonator Perturbation Method (according to IEC 62810).

Device: PNA network analyzer N5222B (manufactured by Keysight Technologies, Inc.)

Cavity resonator 5GHz CP511 (manufactured by Kanto Electronics Application Development Co., Ltd.)

Conditions: frequency 5GHz, measurement temperature 23℃, measurement constant n=2

Condition adjustment: 23℃±1℃, 50%RH±5%RH×24h<

Test environment: 23℃±1℃, 50%RH±5%RH

<Implementation Example 1>

Add 1.2811g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 31.6611g of N-methyl-2-pyrrolidone (NMP) to a 100mL screw-cap bottle and dissolve them at room temperature. Then, add 2.2367g of 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) (Compound A) to the completely dissolved diamine compound solution and stir in a nitrogen environment. Stop stirring when the viscosity of the solution becomes sufficiently high to obtain a polyamide solution with a resin component of 10% by weight. The reduced viscosity of the obtained polyamide is 1.37dL/g (40°C, 0.5% by weight).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was heated to 350°C in stages to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film does not break even when bent 180° and is soft and tough.

The dielectric properties of the obtained polyimide film were evaluated by the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 77%.

<Implementation Example 2>

1.2811 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 30.9832 g of N-methyl-2-pyrrolidone (NMP) were added to a 100 mL screw bottle and dissolved at room temperature. Then, 1.7062 g of 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) (Compound A) and 0.4495 g of 4,4'-dihydroxybiphenyl-bis(trimellitic anhydride) (referred to as Compound B) which had been premixed were added to the completely dissolved diamine compound solution and stirred in a nitrogen atmosphere (at this time, the mass ratio of Compound A to Compound B was 8:2). Stirring was stopped when the viscosity of the solution became sufficiently high to obtain a polyamide solution containing 10% by weight of the resin component. The reduced viscosity of the obtained polyamine is 1.88dL/g (40℃, 0.5wt%).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was heated to 350°C in stages to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film does not break even when bent 180° and is soft and tough.

The dielectric properties of the obtained polyimide film were evaluated by the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 11%.

<Implementation Example 3>

1.2811 g of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 31.1576 g of N-methyl-2-pyrrolidone (NMP) were added to a 100 mL screw bottle and dissolved at room temperature. Then, 1.2787 g of 2,6-dihydroxynaphthalene-bis(trimellitic anhydride) (Compound A) and 0.8999 g of 4,4'-dihydroxybiphenyl-bis(trimellitic anhydride) (Compound B) which had been premixed were added to the completely dissolved diamine compound solution and stirred in a nitrogen atmosphere (at this time, the mass ratio of Compound A to Compound B was 6:4). Stirring was stopped when the viscosity of the solution became sufficiently high to obtain a polyamide solution containing 10% by weight of the resin component. The reduced viscosity of the obtained polyamine is 2.29dL/g (40℃, 0.5wt%).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was heated to 350°C in stages to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film does not break even when bent 180° and is soft and tough.

The dielectric properties of the obtained polyimide film were evaluated by the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 10%.

<Comparison Example 1>

Add 0.8010g of 4,4'-diaminodiphenyl ether (ODA) and 27.3411g of N-methyl-2-pyrrolidone (NMP) to a 100mL screw-cap bottle and dissolve them at room temperature. Then, add 2.2375g of compound A to the completely dissolved diamine compound solution and stir in a nitrogen environment. Stop stirring when the viscosity of the solution becomes sufficiently high to obtain a polyamide solution with a resin component of 10% by weight. The reduced viscosity of the obtained polyamide is 1.73dL/g (40℃, 0.5% by weight).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was gradually heated to 350°C to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film does not break even when bent 180° and is soft and tough.

The dielectric properties of the obtained polyimide film were evaluated by the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 62%.

<Comparison Example 2>

Add 0.4329g of 1,4-diaminobenzene (p-PDA) and 24.0272g of N-methyl-2-pyrrolidone (NMP) to a 100mL screw-cap bottle and dissolve them at room temperature. Then, add 2.2369g of compound A to the completely dissolved diamine compound solution and stir in a nitrogen environment. Stop stirring when the viscosity of the solution becomes sufficiently high to obtain a polyamide solution with a resin component of 10% by weight. The reduced viscosity of the obtained polyamide is 1.28dL/g (40°C, 0.5% by weight).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was heated to 350°C in stages to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film will break if bent 180°, and is brittle.

The dielectric properties of the polyimide film were evaluated using the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 56%.

<Comparison Example 3>

Add 0.4329g of 1,3-diaminobenzene (m-PDA) and 24.0263g of N-methyl-2-pyrrolidone (NMP) to a 100mL screw-cap bottle and dissolve them at room temperature. Then, add 2.2374g of compound A to the completely dissolved diamine compound solution and stir in a nitrogen environment. Stop stirring when the viscosity of the solution becomes sufficiently high to obtain a polyamide solution with a resin component of 10% by weight.

The reduced viscosity of the obtained polyamine is 0.97dL/g (40℃, 0.5wt%).

This polyamide solution was cast onto a smooth glass plate support, and the solvent was removed at 80°C under nitrogen flow for 3 hours. After that, it was heated to 350°C in stages to imidize the polyamide. The imidized film was immersed in water and peeled off, and then dried at 250°C and 0.1kPa for 1 hour.

The resulting polyimide film does not break even when bent 180° and is soft and tough.

The dielectric properties of the obtained polyimide film were evaluated by the above analysis method. The results are summarized in Table 1.

The crystallinity of the obtained polyimide film was measured by the above analysis method and the result was 48%.

[Table 1]

The polyimide obtained in Example 1 of the present invention has a lower dielectric loss tangent than the polyimide obtained in Comparative Examples 1 to 3 which use diamine compounds different from Compound A as raw materials, and it is obvious that it has improved dielectric properties.

Dielectric loss can be expressed as the product of a given constant, the square root of the relative dielectric constant, and the dielectric loss tangent, with the dielectric loss tangent making a greater contribution. The dielectric loss values calculated from the measured relative dielectric constant and dielectric loss tangent values by the following formula are shown in Table 1.

[Formula]

Signal loss = (relative dielectric constant ε _r ) ^0.5 × (dielectric loss tangent tanδ)

It is obvious that the polyimide obtained in Example 1 of the present invention is particularly suitable for use as a polyimide material for electronic devices that are required to cope with high frequencies.

Compared with Example 1, the polyimide obtained in Examples 2 and 3 of the present invention is a copolymerized polyimide obtained by using compound B and compound A together as tetracarboxylic dianhydride, and changing the mass ratio to 8:2 and 6:4 respectively.

The polyimide obtained in Examples 2 and 3 containing a specific amount of repeating units represented by general formula (1) has small relative dielectric constant, dielectric loss tangent and dielectric loss values. Compared with the polyimide of Example 1, the dielectric loss tangent and dielectric loss values are large, but the relative dielectric constant value is small, so it is obvious that it has excellent dielectric properties.

Claims (7)

A polyimide having a repeating unit represented by the general formula (1) in a range of 60 mol% to 100 mol% of the entire polyimide;

In the formula, _R1 independently represents a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched halogenated alkyl group having 1 to 6 carbon atoms, or a halogen atom, and n represents 1 or 2. The polyimide as described in claim 1, wherein the repeating unit represented by the aforementioned general formula (1) is a repeating unit represented by the general formula (1a);

In the formula, R ₁ is independently a methyl group, a trifluoromethyl group or a fluorine atom. The polyimide as described in claim 2, wherein R ₁ in the repeating unit represented by the general formula (1a) is a trifluoromethyl group. The polyimide as described in claim 1 has a repeating unit represented by the general formula (1) in a range of 60 mol% or more and less than 100 mol%, and has a repeating unit represented by the general formula (1') in the remaining proportion relative to the repeating unit;

In the formula, Ar represents a p-phenylene group or a 4,4'-biphenylene group, and _R1 and n have the same meanings as in the general formula (1). The polyimide as described in claim 1 has a dielectric loss tangent of less than 0.004 when measured at a frequency of 5 GHz. For the polyimide described in claim 1, the inherent viscosity of the polyimide precursor before imidization is in the range of 0.1 to 10.0 dL/g. A polyimide film comprising the polyimide as described in any one of claims 1 to 6.