Polyamic acid, polyimide, polyimide film, materials for electronic substrates and electronic substrates

Abstract

To provide a polyimide suitable for high-frequency substrate materials that retains high heat resistance and mechanical strength inherent in the polyimide while offering reductions in dielectric constant and dielectric loss tangent, a polyamide acid serving as its precursor, and a polyimide film, an electronic board material, and an electronic board, each including the polyimide.SOLUTION: A polyamide acid is polymerized from a diamine component containing 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzene amine and an acid component containing 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid, a polyimide, a polyimide film, a material for an electronic substrate, and an electronic substrate. [Background technology]

[0002] Aromatic polyimides, which are obtained by condensation polymerization of aromatic diamine compounds and aromatic tetracarboxylic acid compounds and then curing (imidization), are widely used as materials for electronic substrates because of their excellent mechanical strength, heat resistance, electrical insulation, and chemical resistance. However, with the recent trend toward higher frequencies associated with high-speed signal transmission in electronic devices, there is a growing demand for lower dielectric constants and lower dielectric dissipation factors for polyimides, which are used as electronic circuit board materials. Because the signal propagation speed in electronic circuits decreases with an increase in the dielectric constant of the board material, and signal transmission loss increases with an increase in the dielectric constant and dielectric dissipation factor, lowering the dielectric constant and dielectric dissipation factor of polyimides, which are used as board materials, is essential for improving the performance of electronic devices. In particular, a reduction in the dielectric dissipation factor is required for communication devices used at high frequencies.

[0003] Examples of polyimides currently widely used as electronic substrate materials include p-phenylenediamine (PDA)-3,3',4,4'-biphenyltetracarboxylic dianhydride (sBPDA)-based polyimides (Patent Document 1). All of these polyimides have relatively high dielectric constants and dielectric loss tangents due to the high polarity of the imide group.

[0004] To address the issue of reducing the relatively high dielectric constant and dielectric loss tangent of polyimides, which are caused by the high polarity of such imide groups, a method has been proposed (Patent Document 2), in which, for example, a monomer having a long chain skeleton is introduced to reduce the number of imide groups per unit molecular length (imide group concentration), thereby reducing the polarity of the entire molecule and lowering the dielectric constant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 60-42817 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-106891 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 2 has the disadvantage that the inherent properties of polyimide, such as mechanical strength and heat resistance, are reduced due to the presence of many aliphatic chain structures.

[0007] Therefore, an object of the present invention is to provide a polyimide useful as a high-frequency substrate material, which has a reduced dielectric constant and dielectric loss tangent while maintaining the inherent high heat resistance and mechanical strength of polyimide, a polyamic acid which is its precursor, and a polyimide film, a material for electronic substrates, and an electronic substrate each containing the polyimide. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that a polyimide obtained using a diamine component containing 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine (hereinafter sometimes referred to as "BPCMAN") and an acid component containing 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (hereinafter sometimes referred to as "BPADA") has a reduced dielectric constant and dielectric dissipation factor while maintaining the inherent high heat resistance and mechanical strength of polyimides, and is useful as a high-frequency substrate material, thereby completing the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0009] (1) A polyamic acid obtained by polymerizing a diamine component containing 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine and an acid component containing 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. (2) A polyimide obtained by curing the polyamic acid described in (1) above. (3) A polyimide obtained by polymerizing a diamine component containing 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine and an acid component containing 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride. (4) The polyimide according to (2) or (3) above, which has a dielectric loss tangent of 0.004 or less at a frequency of 1 GHz. (5) The polyimide according to any one of (2) to (4) above, which has a relative dielectric constant of 2.9 or less at a frequency of 1 GHz. (6) The polyimide according to any one of (2) to (5) above, which has a glass transition temperature of 220° C. or higher. (7) The polyimide according to any one of (2) to (6) above, which has a tensile modulus of elasticity of 2.1 GPa or more. (8) The polyimide according to any one of (2) to (7) above, which has a tensile strength of 80 MPa or more. (9) A polyimide film containing the polyimide according to any one of (2) to (8) above. (10) A material for electronic substrates, containing the polyimide according to any one of (2) to (8) above. (11) An electronic substrate containing the polyimide according to any one of (2) to (8) above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a polyimide useful as a high-frequency substrate material, which has a reduced dielectric constant and dielectric loss tangent while maintaining the inherent high heat resistance and mechanical strength of polyimide, a polyamic acid which is its precursor, and a polyimide film, an electronic substrate material, and an electronic substrate each containing the polyimide.

[0011] The polyimide of the present invention achieves both high heat resistance and mechanical strength and a reduced dielectric constant and dielectric loss tangent, and is useful as a high-frequency substrate material. Furthermore, the polyamic acid of the present invention is useful as a precursor of the polyimide of the present invention, since it can be imidized and cured to obtain the polyimide of the present invention, which achieves both high heat resistance and mechanical properties and reduced dielectric constant and dielectric loss tangent. Furthermore, the high-frequency substrate of the present invention is useful because it achieves both high heat resistance and mechanical strength and reduced dielectric constant and dielectric loss tangent. DETAILED DESCRIPTION OF THE INVENTION

[0012] The polyamic acid, polyimide, polyimide film, material for electronic substrates, and electronic substrates of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. Furthermore, "the dielectric constant and dielectric loss tangent can be reduced while maintaining high heat resistance and mechanical strength of the resulting polyimide" is also simply referred to as "the effect of the present invention is excellent."

[0013] [Polyamic acid] The polyamic acid of the present invention is a polyamic acid obtained by polymerizing a diamine component containing 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine (BPCMAN) and an acid component containing 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA).

[0014] By imidizing and curing the polyamic acid of the present invention, a polyimide having a reduced dielectric constant and dielectric loss tangent while maintaining the inherent high heat resistance and mechanical strength of polyimide (hereinafter, sometimes referred to as the "polyimide of the present invention") can be obtained. The polyimide of the present invention is useful as a high-frequency substrate material, and the polyamic acid of the present invention is useful as a precursor of the polyimide of the present invention.

[0015] <Diamine component> The diamine component includes BPCMAN. Since BPCMAN is a long-chain molecule having a polyaromatic ring and a spiro structure, it can reduce the dielectric constant and dielectric loss tangent while maintaining the high heat resistance and mechanical strength of the polyimide of the present invention obtained by imidizing and curing the polyamic acid of the present invention.

[0016] Instead of BPCMAN, 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4'-tetramethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine or 4,4'-[(3,3',4,4'-tetrahydro-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine (both compounds differing from BPCMAN only in the presence or absence of a methyl group) can be used, but BPCMAN is preferred because it provides better effects for the present invention.

[0017] The diamine component may also contain a diamine compound other than BPCMAN. Examples of diamine compounds other than BPCMAN include 4,4'-diaminodiphenyl ether (hereinafter sometimes abbreviated as "ODA"), 1,4-phenylenediamine (p-phenylenediamine; hereinafter sometimes abbreviated as "PDA"), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes abbreviated as "BAPP"), 4,4'-[1,4-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy] ]bisbenzenamine, 4,4'-[1,3-phenylenebis[(1-methylethylidene)-4,1-phenyleneoxy]]bisbenzenamine, 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4'-tetramethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine, and other aromatic diamines; 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, linear aliphatic diamines such as pentane, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine; 1,2-diaminopropane, 1,2-diamino-2-methylpropane, 1,3-diamino-2-methylpropane, 1,3-diamino-2,2-dimethylpropane, 1,3-diaminopentane, and 1,5-diamino-2-methylpentane; Branched aliphatic diamines such as 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 1,3-cyclohexanebis(methylamine), 4,4'-diaminodicyclohexylmethane, bis(4-amino-3-methylcyclohexyl)methane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.0] 2,6 ]decane, 2,5(6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-diaminoadamantane, 3,3'-diamino-1,1'-biadamantyl, 1,6-diaminoadamantane and other alicyclic diamines; The diamine compounds other than BPCMAN can be used either alone or in combination of two or more.

[0018] The content of BPCMAN in the diamine component is not particularly limited, but is preferably 50 mol % or more, and more preferably 80 mol % or more, because this allows the dielectric constant and dielectric dissipation factor of the polyimide obtained by imidizing and curing a polyamic acid to be further reduced while maintaining high heat resistance and mechanical strength.

[0019] <Acid component> The acid component includes BPADA. BPADA can impart high mechanical strength, heat resistance, chemical resistance and electrical insulation to the polyimide of the present invention obtained by imidizing and curing the polyamic acid of the present invention.

[0020] The acid component may also contain a polycarboxylic acid anhydride other than BPADA. Examples of polycarboxylic acid anhydrides other than BPADA include aromatic tetracarboxylic acid dianhydrides such as pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (sBPDA), 4,4'-oxydiphthalic anhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), and 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA). The polycarboxylic acid compounds other than BPADA can be used either alone or in combination of two or more.

[0021] The content of BPADA in the acid component is not particularly limited, but from the viewpoint of reducing the dielectric constant and dielectric loss tangent, it is preferably 50 mol % or more, and more preferably 80 mol % or more.

[0022] <Amount of Diamine Component and Acid Component> The amounts of the diamine component and the acid component are not particularly limited, but in order to sufficiently increase the molecular weight of the polymer obtained by polymerizing the diamine component and the acid component, the amount of the acid anhydride group of the acid component is preferably 0.9 to 1.1 equivalents relative to the amino group of the diamine component.

[0023] <Structure of Polyamic Acid> The polyamic acid of the present invention is not particularly limited in terms of its molecular structure, and examples thereof include random copolymers, alternating copolymers, and block copolymers.

[0024] <Method for producing polyamic acid> The method for producing polyamic acid of the present invention includes a step of polymerizing a diamine component containing BPCMAN and an acid component containing BPADA.

[0025] The polymerization of the diamine component and the acid component is carried out, for example, by adding the diamine component and the acid component to a solvent in amounts such that the total amount of the diamine component and the total amount of the acid component are approximately equimolar, and polymerizing the diamine component and the acid component in the solvent. In addition to the diamine component and the acid component, additives described below may also be added to the solvent.

[0026] The conditions for polymerizing the diamine component and the acid component are not particularly limited. For example, a method can be used in which the diamine component and the acid component are added to N,N-dimethylacetamide (solvent), the resulting mixture is stirred at a temperature of 80°C or less in air or nitrogen atmosphere, and the mixture is reacted to produce a polyamic acid solution (polyamic acid composition).

[0027] The polyamic acid solution (polyamic acid composition) obtained by the above production method is preferably prepared so as to contain 10 to 30 mass % of polyamic acid in the solvent (concentration).

[0028] [Polyamic acid composition] The polyamic acid composition of the present invention is a composition containing the above-mentioned polyamic acid of the present invention. The polyamic acid composition of the present invention may contain only one type of polyamic acid of the present invention, or may contain two or more types of polyamic acids of the present invention. The polyimide of the present invention can be obtained by curing the polyamic acid composition of the present invention. The polyimide of the present invention thus obtained has a reduced dielectric constant and dielectric loss tangent while maintaining the inherent high heat resistance and mechanical strength of polyimides, and is useful as a high-frequency substrate material. The polyamic acid composition of the present invention is useful as a precursor of the polyimide of the present invention.

[0029] Furthermore, the polyamic acid composition of the present invention may contain components other than the polyamic acid of the present invention in addition to the polyamic acid of the present invention, which is an essential component.

[0030] <Components other than polyamic acid> Examples of components other than the polyamic acid of the present invention include solvents, other additives, and reaction intermediates.

[0031] (solvent) Examples of the solvent include N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide, dimethyl sulfone, cyclohexanone, cyclopentanone, tetrahydrofuran, dichloromethane, trichloromethane, toluene, and methyl ethyl ketone, but are not particularly limited as long as they are soluble. The above solvents can be used alone or in combination of two or more.

[0032] (Other additives) Examples of the additives include dehydrating agents and catalysts used to convert polyamic acid into polyimide by dehydrating and cyclizing (imidizing) the polyamic acid.

[0033] Examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride, and aromatic carboxylic acid anhydrides such as phthalic anhydride. The above dehydrating agents can be used alone or in combination of two or more.

[0034] Examples of the catalyst include heterocyclic tertiary amines such as pyridine, picoline, and quinoline; aliphatic tertiary amines such as triethylamine; and aromatic tertiary amines such as N,N-dimethylaniline. The above catalysts can be used alone or in combination of two or more.

[0035] (reaction intermediates, etc.) The polyamic acid composition of the present invention may contain reaction intermediates and the like that are by-produced during the polymerization reaction between the diamine component and the acid component.

[0036] <varnish> The polyamic acid composition of the present invention can be used as a varnish for high-frequency substrate materials.

[0037] [Polyimide] The polyimide of the present invention is a polyimide (cured product) obtained by polymerizing a diamine component containing BPCMAN and an acid component containing BPADA.

[0038] The polyimide of the present invention can also be obtained by imidizing the polyamic acid of the present invention and then curing it.

[0039] The polyimide of the present invention obtained by using a diamine component containing BPCMAN and an acid component containing BPADA has excellent heat resistance and mechanical properties, and can also have a reduced dielectric constant and dielectric loss tangent.

[0040] <Diamine component / Acid component> The diamine component and the acid component are the same as those explained for the polyamic acid of the present invention.

[0041] <Polyimide structure> The polyimide of the present invention obtained by polymerizing a diamine component containing BPCMAN and an acid component containing BPADA and then imidizing the polymer is not particularly limited in terms of its molecular structure, and examples thereof include a random copolymer, an alternating copolymer, and a block copolymer.

[0042] <Polyimide manufacturing method> The method for producing a polyimide of the present invention includes a step of polymerizing a diamine component containing BPCMAN and an acid component containing BPADA.

[0043] "polymerization" The polymerization of the diamine component and the acid component is carried out, for example, by adding the diamine component and the acid component to a solvent in amounts such that the total amount of the diamine component and the total amount of the acid component are approximately equimolar, and polymerizing the diamine component and the acid component in the solvent. In addition to the diamine component and the acid component, the solvent may further contain the above-mentioned additives.

[0044] The polyimide of the present invention may be produced by directly polymerizing a diamine component and an acid component in a solvent, or by dehydrating and cyclizing (imidizing) the polyamic acid of the present invention or the polyamic acid composition of the present invention.

[0045] <Imidization> Methods for converting polyamic acid to polyimide by dehydration and cyclization include, for example, a chemical ring-closure method in which dehydration is performed using a dehydrating agent and a catalyst, and a thermal ring-closure method in which dehydration is performed thermally. Either one of these methods or a combination of both may be used. The dehydrating agent and catalyst used in the chemical ring-closure method are the same as those described above.

[0046] In the thermal ring-closure method, the heating temperature is usually 100 to 400°C, more preferably 150 to 250°C. The heating time is usually 1 minute to 6 hours, more preferably 30 minutes to 2 hours. The heating atmosphere is not particularly limited, but from the viewpoint of suppressing coloration of the surface of the polyimide obtained by curing, an inert atmosphere such as a nitrogen gas atmosphere or a nitrogen / hydrogen mixed gas atmosphere is preferred.

[0047] Specifically, for example, a film containing the polyimide of the present invention can be produced by heating a film containing the polyamic acid of the present invention to a high temperature. A chemical ring-closure method may also be used in combination.

[0048] When forming a film containing the polyimide of the present invention from a film containing the polyamic acid of the present invention, the removal of the solvent and the heating for imidization may be carried out successively, or the removal of the solvent and the imidization may be carried out simultaneously.

[0049] The polyimide of the present invention obtained by polymerizing a diamine component containing BPCMAN and an acid component containing BPADA may contain reaction intermediates and the like that are by-produced during the polymerization reaction.

[0050] <varnish> A polyimide solution (varnish) can be obtained by dissolving the polyimide of the present invention in a solvent, or by dehydrating and imidizing the polyamic acid solution of the present invention by heating it directly or by adding a catalyst, thereby obtaining a polyimide solution (varnish).

[0051] The polyimide solution (varnish) is dropped into a poor solvent such as water or methanol, filtered, and dried to obtain a polyimide solid.

[0052] A polyimide film can also be produced by casting the polyimide solution (varnish) on the substrate and drying it. Furthermore, the polyimide solid can be heated and compressed to form a molded polyimide body.

[0053] <Mechanical strength> The mechanical strength of the polyimide of the present invention is evaluated by the tensile modulus and tensile strength (tensile strength). The tensile modulus is preferably 2.1 GPa or more, and more preferably 2.2 GPa or more. The tensile strength is preferably 70 MPa or more, and more preferably 80 MPa or more. Here, the tensile modulus and tensile strength are values ​​measured in accordance with JIS K 7127:1999 (ISO 527-3:1995).

[0054] <Heat resistance> The heat resistance of the polyimide of the present invention is evaluated by the glass transition temperature. The glass transition temperature is preferably 220°C or higher, and more preferably 230°C or higher.

[0055] <Dielectric properties: relative permittivity, dielectric loss tangent> The dielectric properties of the polyimide of the present invention are evaluated by the relative dielectric constant and the dielectric loss tangent at a frequency of 1 GHz. The relative dielectric constant at the frequency of 1 GHz is preferably 2.9 or less. The dielectric loss tangent at the frequency of 1 GHz is preferably 0.004 or less. The dielectric constant ε, the dielectric constant of a vacuum ε0 and the relative dielectric constant ε r Between ε=ε r Because of the relationship of ·ε0, when discussing the level of dielectric constant, the relative permittivity may be used instead of the dielectric constant.

[0056] The polyimide of the present invention has high heat resistance and mechanical strength, and a reduced dielectric constant and dielectric loss tangent, and is therefore useful as a high-frequency substrate material.

[0057] [Polyimide composition] The polyimide composition of the present invention is a composition containing the above-described polyimide of the present invention. The polyimide acid composition of the present invention may contain only one type of polyimide of the present invention, or may contain two or more types of polyimides of the present invention.

[0058] The polyimide composition of the present invention may contain components other than the polyimide of the present invention in addition to the polyimide of the present invention, which is an essential component.

[0059] <Components other than polyimide> Examples of components other than the polyimide of the present invention include solvents, other additives, and reaction intermediates.

[0060] (solvent) Specific examples of the solvent are the same as those for the polyamic acid composition of the present invention described above.

[0061] (Other additives) Examples of other additives include an oxidation stabilizer, a filler, a silane coupling agent, a photosensitizer, a photopolymerization initiator, and a sensitizer.

[0062] [Electronic boards, high frequency boards] A polyimide film for high-frequency substrates (hereinafter, sometimes referred to as the "polyimide film of the present invention") can be produced using the polyamic acid of the present invention or the polyamic acid composition of the present invention, or the polyimide of the present invention or the polyimide composition of the present invention.

[0063] The method for producing the polyimide film of the present invention is not particularly limited, and examples thereof include a method in which the polyamic acid or polyamic acid composition of the present invention is applied to a support (e.g., a glass plate, a stainless steel plate, a copper plate, an aluminum plate, etc.) and then dried and heated to dehydrate and ring-close (imidize), or a method in which the polyimide of the present invention is dissolved in an organic solvent and then applied to a glass plate and the solvent is removed. The method for applying the polyimide to these supports is not particularly limited, and any conventionally known coating method can be used.

[0064] From the viewpoint of solubility, the organic solvent is preferably an aprotic polar solvent. Specific examples of aprotic polar solvents include N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethyl sulfoxide, γ-butyrolactone, and 1,3-dimethyl-2-imidazolidinone, but there are no particular limitations as long as they dissolve the polyimide of the present invention. The above solvents can be used alone or in combination of two or more. In this case, the content of polyimide is preferably in the range of 5 to 50% by mass, and more preferably in the range of 10 to 30% by mass.

[0065] Specifically, polyamic acid or polyamic acid composition applied to a glass plate is dried at a temperature of 50 to 150°C for about 0.5 to 80 minutes, and then heat-treated at a temperature of 100 to 400°C, more preferably about 150 to 250°C, to obtain a polyimide film. From the viewpoint of suppressing discoloration of the polyimide film, a temperature of 400°C or less is preferred. Furthermore, imidization is preferably carried out under reduced pressure or in a nitrogen atmosphere to suppress discoloration of the polyimide film, but may also be carried out in air as long as the temperature is not particularly high.

[0066] Furthermore, when reducing the pressure, the lower the pressure, the better. However, there are no particular limitations as long as the pressure satisfies the heating conditions and water can be removed, and specifically, it is about 0.09 MPa to 0.0001 MPa.

[0067] The polyimide film thus obtained may be blended with other crosslinkable resins, thermosetting resins, etc., when producing the polyimide from the polyamic acid or polyamic acid composition, as long as the effects of the present invention are not impaired. Furthermore, if necessary, additives such as inorganic fibers, e.g., glass fiber and carbon fiber, oxidation stabilizers, end-capping agents, fillers, silane coupling agents, photosensitizers, photopolymerization initiators, and sensitizers may also be blended.

[0068] A conductive film can be formed on the polyimide film thus obtained, and then an electronic circuit or a high frequency circuit can be constructed, whereby the polyimide film can be used as an electronic substrate or a high frequency substrate.

[0069] [Coverlay film] The coverlay film of the present invention is a coverlay film having, on a polyimide film made of the polyimide of the present invention, an adhesive layer containing the polyimide obtained by imidizing the polyamic acid of the present invention or the polyamic acid composition of the present invention. The coverlay film of the present invention can be used for flexible printed circuit boards (FPC boards) and the like. Examples of methods for forming an adhesive layer of a coverlay film using the polyamic acid of the present invention or the polyamic acid composition of the present invention as a material include a method in which the polyamic acid of the present invention or the polyamic acid composition of the present invention is applied to the surface of the polyimide film of the present invention, the solvent is removed, and the resulting mixture is cured to form a film. [Example]

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0071] The abbreviations used in the following examples and comparative examples have the following meanings. BPCMAN: 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane PDA: p-phenylenediamine sBPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BPADA: 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride DMAc: N,N-dimethylacetamide

[0072] [Example 1] 51.4 g of BPCMAN and 48.6 g of BPADA were added to 400 g of DMAc and stirred at room temperature and atmospheric pressure for 3 hours to produce a polyamic acid solution. 15 g of the resulting polyamic acid solution was applied to a glass plate using a bar coater and heated at 100°C for 20 minutes and then at 250°C for 20 minutes to produce a polyimide film approximately 50 μm thick. The prepared polyimide films were evaluated according to the evaluation methods described below, and the results are shown in Table 1. The "molar ratio of each component" refers to the molar ratio within the total diamine components and total acid components.

[0073] [Comparative Example 1] As shown in Table 1, a polyamic acid solution was prepared and a polyimide film was produced in the same manner as in Example 1, except that PDA was used instead of BPCMAN as the diamine component, sBPDA was used instead of BPADA as the acid component, and PDA and sBPDA were mixed in a molar ratio of 1.0:1.0. The prepared polyimide films were evaluated according to the evaluation methods described below, and the results are shown in Table 1.

[0074] Comparative Example 2 As shown in Table 1, a polyamic acid solution was prepared and a polyimide film was produced in the same manner as in Example 1, except that BAPP was used instead of BPCMAN as the diamine component and BAPP and BPADA were mixed in a molar ratio of 1.0:1.0. The prepared polyimide films were evaluated according to the evaluation methods described below, and the results are shown in Table 1.

[0075] [Evaluation method] The prepared polyimide films were evaluated for mechanical strength (tensile modulus, tensile strength), heat resistance (glass transition temperature), and dielectric properties (relative permittivity, dielectric loss tangent).

[0076] <Mechanical strength> The tensile modulus (Young's modulus) and tensile strength (tensile strength) were measured under the following conditions in accordance with JIS K 7127:1999 (ISO 527-3:1995). Tensile speed: 102 mm / min (minutes) Chuck distance: 30mm

[0077] <Heat resistance> The glass transition temperature was measured under the following conditions in accordance with JIS K 7244-1:1998 (ISO 6721-1:1994). In Table 1, "300<" indicates that the temperature is above 300°C. Heating rate: 3°C / min Temperature range: 50~450℃ Frequency: 1Hz

[0078] <Dielectric properties: relative permittivity, dielectric loss tangent> The relative permittivity and dielectric loss tangent were measured under the following conditions in accordance with JIS C 2138:2007. Measurement method: Resonance method Measurement frequency: 1GHz

[0079] [Table 1]

[0080] The polyimide of Example 1 obtained by polymerization using BPCMAN as the diamine component and BPADA as the acid component had high tensile modulus and tensile strength, high heat resistance, low dielectric constant and dielectric loss tangent, and good dielectric properties. That is, the polyimide of Example 1 achieved a balance between heat resistance, mechanical strength, and dielectric properties. In contrast, the polyimide of Comparative Example 1, which used PDA instead of BPCMAN as the diamine component and sBPDA instead of BPADA as the acid component, had higher heat resistance and mechanical strength than the polyimide of Example 1, but had a higher dielectric dissipation factor and inferior dielectric properties. In other words, the polyimide of Comparative Example 1 did not achieve a balance between heat resistance, mechanical strength, and dielectric properties. Furthermore, the polyimide of Comparative Example 2, which used BAPP instead of BPCMAN as the diamine component, had lower heat resistance and mechanical strength than the polyimide of Example 1, and also had a higher dielectric constant and dielectric dissipation factor, resulting in poorer mechanical strength and dielectric properties. In other words, the polyimide of Comparative Example 2 did not achieve a balance between heat resistance, mechanical strength, and dielectric properties. [Industrial Applicability]

[0081] The polyimide of the present invention is suitable for use as a substrate material (high frequency substrate material) for electronic devices used in high frequency regions, and is thought to contribute to improving the performance of electronic devices.

Claims

1. A polyamic acid obtained by polymerizing a diamine component consisting of 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine and an acid component consisting of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.

2. A polyimide obtained by curing the polyamic acid according to claim 1.

3. A polyimide obtained by polymerizing a diamine component consisting of 4,4'-[(3,3',4,4'-tetrahydro-4,4,4',4',7,7'-hexamethyl-2,2'-spirobi[2H-1-benzopyran]-6,6'-diyl)bis(oxy)]bisbenzenamine and an acid component consisting of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.

4. A polyimide film comprising the polyimide according to claim 2 or 3.

5. A material for electronic substrates, comprising the polyimide according to claim 2 or 3.

6. An electronic substrate comprising the polyimide according to claim 2 or 3.

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