JP2022001622A - Polyamic acid, polyimide, polyimide film, electronic board material, and electronic board - Google Patents

Abstract

To provide a polyimide that has excellent mechanical strength and heat resistance, and that has low dielectric constant and dielectric loss tangent.SOLUTION: Provided is a polyamic acid that is obtained by polymerizing a diamine component comprising 4,4'-[9H-fluorene-9-ylidenebis[(2-methyl-4,1-phenylene)oxy]]bisbenzeneamine, and an acid component comprising 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride.SELECTED DRAWING: None

Description

The present invention relates to polyamic acids, polyimides, polyimide films, materials for electronic substrates and electronic substrates.

Conventionally, a polyimide obtained by condensation polymerizing an aromatic diamine compound and an aromatic tetracarboxylic acid compound and further curing (imidizing) the aromatic diamine compound is known (Patent Documents 1 and 2). Such polyimide is widely used as a material for electronic substrates because it is excellent in mechanical strength, heat resistance, electrical insulation, chemical resistance, and the like.

In recent years, with the increase in high frequency accompanying high-speed signal transmission of electronic devices, there is an increasing demand for low dielectric constant and low dielectric loss tangent of polyimide, which is a material for electronic substrates.
The signal propagation velocity in an electronic circuit decreases as the dielectric constant of the electronic substrate material increases, and the signal transmission loss increases as the dielectric constant and dielectric loss tangent of the electronic substrate material increase.
Therefore, lowering the dielectric constant and lowering the dielectric loss tangent of polyimide, which is a material for electronic substrates, is indispensable for improving the performance of electronic devices. In particular, in communication equipment used at high frequencies, reduction of dielectric loss tangent is required.

Special Publication No. 60-42817 Japanese Unexamined Patent Publication No. 2007-106891

For example, p-phenylenediamine (PDA) -3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (sBPDA) -based polyimide (Patent Document 1) is relatively free due to the high polarity of the imide group. It has a high dielectric constant and dielectric loss tangent.
Therefore, a method (Patent Document 2) has been proposed in which the polarity of the entire molecule is reduced and the dielectric constant is lowered by reducing the number of imide groups (imide group concentration) per unit molecular length.
However, in the method described in Patent Document 2, the original properties of polyimide such as mechanical strength and heat resistance may be deteriorated by increasing the number of aliphatic chain structures.

Therefore, an object of the present invention is to provide a polyimide having excellent mechanical strength and heat resistance, and having a low dielectric constant and dielectric loss tangent.

As a result of diligent studies, the present inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention.

That is, the present invention provides the following [1] to [11].
[1] 4,4'-[9H-fluorene-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] A diamine component composed of bisbenzeneamine and 2,2-bis [4- (3). , 4-Dicarboxyphenoxy) Phenyl] Polyamide acid obtained by polymerizing an acid component consisting of propane dianhydride.
[2] 4,4'-[9H-fluorene-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] A diamine component consisting of bisbenzeneamine and 2,2-bis [4- (3). , 4-Dicarboxyphenoxy) Phenyl] Polyimide obtained by polymerizing an acid component consisting of propane dianhydride.
[3] A polyimide obtained by imidizing the polyamic acid according to the above [1].
[4] The polyimide according to the above [2] or [3], wherein the dielectric loss tangent at a frequency of 1 GHz is 0.005 or less.
[5] The polyimide according to any one of [2] to [4] above, wherein the relative permittivity at a frequency of 1 GHz is 3.0 or less.
[6] The polyimide according to any one of [2] to [5] above, wherein the glass transition temperature is 230 ° C. or higher.
[7] The polyimide according to any one of the above [2] to [6], which has a tensile elastic modulus of 2.0 GPa or more.
[8] The polyimide according to any one of the above [2] to [7], which has a tensile strength of 80 MPa or more.
[9] A polyimide film having a film made of the polyimide according to any one of the above [2] to [8].
[10] A material for an electronic substrate having the polyimide according to any one of the above [2] to [8].
[11] An electronic substrate having the polyimide according to any one of the above [2] to [8].

According to the present invention, it is possible to provide a polyimide having excellent mechanical strength and heat resistance, and having a low dielectric constant and a dielectric loss tangent.

[Polyamide acid]
The polyamic acid of the present invention may be abbreviated as 4,4'-[9H-fluorene-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] bisbenzeneamine (hereinafter, "BCFAN"). ) And an acid component consisting of 2,2-bis [4- (3,4-dicarboxyphenoxy) phenyl] propane dianhydride (hereinafter, may be abbreviated as "BPADA"). , Is obtained by polymerizing.

By imidizing and curing the polyamic acid of the present invention, a polyimide (hereinafter, may be referred to as "polyimide of the present invention") can be obtained. The polyimide of the present invention has a reduced dielectric constant and dielectric loss tangent while maintaining the high mechanical strength and heat resistance inherent in the polyimide.
The molecular structure of the polyamic acid of the present invention is not particularly limited, and examples thereof include random copolymers, alternate copolymers, and block copolymers.
The polyimide of the present invention is useful as a material for a high frequency substrate. The polyamic acid of the present invention is useful as a precursor of the polyimide of the present invention.

<Diamine component>
The diamine component contains BC FAN.
BCFAN is a long-chain molecule having a polycyclic aromatic cyclic structure. Therefore, in the polyimide of the present invention obtained by imidizing and curing the polyamic acid of the present invention, the dielectric constant and the dielectric loss tangent can be lowered while maintaining high mechanical strength and heat resistance.

The diamine component may contain a diamine compound other than BCFAN.
Examples of the diamine compound other than BCPAN include 4,4'-diaminodiphenyl ether (hereinafter, may be abbreviated as "ODA") and 1,4-phenylenediamine (p-phenylenediamine) (hereinafter, "PDA"). , 2,2-Bis [4- (4-aminophenoxy) phenyl] propane (hereinafter, may be abbreviated as "BAPP"), 4,4'-[9H-fluorene. -9-Ilidenbis [(4,1-phenylene) oxy]] Aromatic diamines such as bisbenzeneamine; 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino Pentan, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonandiamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine, etc. Linear aliphatic diamines; 1,2-diaminopropane, 1,2-diamino-2-methylpropane, 1,3-diamino-2-methylpropane, 1,3-diamino-2,2-dimethylpropane, Branched aliphatic diamines such as 1,3-diaminopentane and 1,5-diamino-2-methylpentane; 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), 1,4-diamino Cyclohexane, 1,3-diaminocyclohexane, 1,4-cyclohexanebis (methylamine), 1,3-cyclohexanebis (methylamine), 4,4'-diaminodicyclohexylmethane, bis (4-amino-3-methylcyclohexyl) ) Diamine, 3 (4), 8 (9) -bis (aminomethyl) tricyclo [5.2.1.0 ^2,6 ] diamine, 2,5 (6) -bis (aminomethyl) bicyclo [2.2 .1] Alicyclic diamines such as heptane, 1,3-diaminoadamantan, 3,3'-diamino-1,1'-viadamantyl, 1,6-diaminoadamantan, and the like.
The diamine compound other than BCPAN may be used alone or in combination of two or more.

The content of BCWAN in the diamine component is preferably 50 mol% or more, more preferably 80 mol% or more, because the mechanical strength and heat resistance are more excellent, and the dielectric constant and the dielectric loss tangent can be further reduced.

<Acid component>
The acid component comprises 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.

The acid component may contain a polycarboxylic acid anhydride other than BPADA.
Examples of polycarboxylic acid anhydrides other than BPADA include pyromellitic acid dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (sBPDA), and 4,4'-oxydiphthal. Acid Anhydride (ODPA), 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA), 3,3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride (DSDA), Aromatic tetracarboxylic acid diacid anhydrides such as 9,9-bis (3,4-dicarboxyphenyl) fluorene diacid anhydride (BPAF) can be mentioned.
The polycarboxylic acid compound other than BPADA may be used alone or in combination of two or more.

The content of BPADA in the acid component is preferably 50 mol% or more, more preferably 80 mol% or more, because the dielectric constant and the dielectric loss tangent can be further reduced.

<Amount of diamine component and acid component>
The amounts of the diamine component and the acid component are not particularly limited, but the acid of the acid component with respect to the amino group of the diamine component 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 anhydride group is preferably 0.9 equivalent or more.

<Manufacturing method of polyamic acid>
The method for producing a polyamic acid of the present invention comprises a step of polymerizing a diamine component and an acid component.
In the polymerization of the diamine component and the acid component, for example, the diamine component and the acid component are added to the solvent in an amount such that the total of the diamine component and the total of the acid components are approximately equal molars, and the diamine component is added to the solvent. It is carried out by polymerizing with an acid component.
Examples of the solvent include the solvents described below. In addition to the diamine component and the acid component, an additive described later may be added to the solvent.

The conditions for polymerizing the diamine component and the acid component are not particularly limited.
For example, first, a diamine component and an acid component are added to a solvent such as N, N-dimethylacetamide to obtain a mixture. Next, the obtained mixture is stirred and reacted in an atmosphere or a nitrogen atmosphere under a temperature condition of 80 ° C. or lower.
In this way, a solution containing polyamic acid (polyamic acid composition) is produced.
The solution containing polyamic acid (polyamic acid composition) is preferably prepared so that the content of polyamic acid in the solvent is 10 to 30% by mass.

[Polyamic acid composition]
The polyamic acid composition of the present invention contains the polyamic acid of the present invention.
The polyamic acid composition of the present invention may contain only one kind of polyamic acid of the present invention, or may contain two or more kinds of the polyamic acid of the present invention.

<Ingredients other than polyamic acid>

The polyamic acid composition of the present invention may further 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.
Examples of the components other than the polyamic acid of the present invention include solvents, additives, reaction intermediates and the like.

"solvent"
Examples of the solvent include N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, dimethylsulfone, cyclohexanone, and the like. Examples thereof include cyclopentanone, tetrahydrofuran, dichloromethane, trichloromethane, toluene, methyl ethyl ketone, γ-butyrolactone and the like, and the present invention is not particularly limited as long as the above-mentioned components can be dissolved.
The solvent may be used alone or in combination of two or more.

"Additive"
Examples of the additive include a dehydrating agent, a catalyst and the like used for dehydrating and cyclizing (imidizing) the polyamic acid to convert it into polyimide.
Examples of the dehydrating agent include aliphatic carboxylic acid anhydrides such as acetic anhydride; aromatic carboxylic acid anhydrides such as phthalic anhydride; and the like, and these may be used alone or in combination of two or more. May be used together.
Examples of the catalyst include heterocyclic tertiary amines such as pyridine, picoline and quinoline; aliphatic tertiary amines such as triethylamine; aromatic tertiary amines such as N, N-dimethylaniline; and the like. These may be used alone or in combination of two or more.

《Reaction Intermediate》
The reaction intermediate is produced as a by-product during the polymerization reaction between the diamine component and the acid component.

[Polyimide]
The polyimide of the present invention is obtained by polymerizing a diamine component made of BCPAN and an acid component made of BPADA.
The polyimide of the present invention has excellent mechanical strength and heat resistance, and has a low dielectric constant and dielectric loss tangent, like the polyimide obtained by using the polyamic acid of the present invention.
The molecular structure of the polyimide of the present invention is not particularly limited, and examples thereof include random copolymers, alternate copolymers, and block copolymers.

<Diamine component and acid component>
The diamine component and the acid component are the same as the diamine component and the acid component described above.

<Manufacturing method of polyimide>
The method for producing the polyimide of the present invention is, for example, a method of polymerizing a diamine component made of BCPAN and an acid component made of BPADA.
For example, the diamine component and the acid component are added to the solvent in an amount such that the total of the diamine component and the total of the acid components are approximately equal molars, and the diamine component and the acid component are polymerized in the solvent. In addition to the diamine component and the acid component, the above-mentioned additives may be further added to the solvent.
The polyimide of the present invention obtained by polymerizing a diamine component and an acid component may contain a reaction intermediate produced as a by-product during the polymerization reaction.

In order to produce the polyimide of the present invention, the diamine component and the acid component may be directly polymerized in a solvent, or the polyamic acid of the present invention or the polyamic acid composition of the present invention is dehydrated and cyclized (imidized). May be manufactured.

Examples of the method of dehydrating and cyclizing polyamic acid to convert it to polyimide include a chemical ring closure method of dehydrating using a dehydrating agent and a catalyst; a thermal ring closure method of thermally dehydrating; and the like, and one of these methods is used. It may be used alone or in combination of two or more.
Examples of the dehydrating agent and catalyst used in the chemical ring closure method include the above-mentioned dehydrating agent and catalyst.

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

In the case of the heat-closed ring method, specifically, for example, a film containing the polyimide of the present invention (polyimide film) can be produced by heating the coating film containing the polyamic acid of the present invention to a high temperature. A chemical ring closure method may be used in combination.
Heating for removing and imidizing the solvent when forming the film containing the polyimide of the present invention from the coating film containing the polyamic acid of the present invention may be continuously performed, and the solvent removal and imidization may be performed. It may be done at the same time.

<Mechanical strength>
The mechanical strength of the polyimide of the present invention is evaluated by the tensile elastic modulus and the tensile strength.
The tensile elastic modulus is preferably 2.0 GPa or more, more preferably 2.3 GPa or more, and even more preferably 2.5 GPa or more.
The tensile strength is preferably 80 MPa or more, more preferably 90 MPa or more, still more preferably 100 MPa or more.
The tensile modulus and tensile strength are measured according to JIS K 7127: 1999 (ISO 527-3: 1995).

<Heat-resistant>
The heat resistance of the polyimide of the present invention is evaluated by the glass transition temperature.
The glass transition temperature is preferably 230 ° C. or higher, more preferably 240 ° C. or higher.
The glass transition temperature is measured according to JIS K 7424-1: 1998 (ISO 6721-1: 1994).

<Dielectric property>
The dielectric property of the polyimide of the present invention is evaluated by the relative permittivity and the dielectric loss tangent at a frequency of 1 GHz.
The relative permittivity at a frequency of 1 GHz is preferably 3.0 or less.
The dielectric loss tangent at a frequency of 1 GHz is preferably 0.005 or less.
Relative permittivity and dielectric loss tangent are measured according to JIS C 2565: 1992.
Since there is a relationship of ε = ε _r · ε ₀ between the permittivity ε, the permittivity ε _{0 of the} vacuum, and the relative permittivity ε _r , when discussing the high and low of the permittivity, the ratio is used instead of the permittivity. Permittivity may be used.

[varnish]
By dissolving the polyimide of the present invention in a solvent, a polyimide solution (varnish) can be obtained. Further, a polyimide solution (varnish) can be obtained by dehydrating and imidizing the polyamic acid composition of the present invention as it is by heating or adding a catalyst.
A polyimide solid is obtained by dropping, filtering, and drying a polyimide solution (varnish) in a poor solvent such as water or methanol. A polyimide molded body can be formed by heating and compressing a polyimide solid material.
A polyimide film can be produced by applying a polyimide solution (varnish) on a support and drying it.

[Polyimide film]
A polyimide film (hereinafter, may be referred to as "polyimide film of the present invention") can be produced by using the polyamic acid of the present invention, the polyamic acid composition of the present invention, or the polyimide of the present invention. That is, the polyimide film of the present invention has a film made of the polyimide of the present invention.

The method for producing the polyimide film of the present invention is not particularly limited, and for example, the polyamic acid of the present invention or the polyamic acid composition of the present invention is used as a support (for example, a glass plate, a stainless plate, a copper plate, an aluminum plate, etc.). A method of coating on a glass plate and then drying and heating to dehydrate and close the ring (imidization); a method of dissolving the polyimide of the present invention in an organic solvent and applying the obtained solution on a glass plate to remove the solvent. ; Etc. can be mentioned. The coating method on the support is not particularly limited, and a conventionally known coating method can be applied.

The organic solvent is preferably an aprotic polar solvent from the viewpoint of solubility.
Specific examples of the aprotic polar solvent include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethyl sulfoxide, and γ-butyrolactone. Examples thereof include 1,3-dimethyl-2-imidazolidinone, but the present invention is not particularly limited as long as the polyimide of the present invention can be dissolved.
The aprotic polar solvent may be used alone or in combination of two or more.
In this case, the polyimide content is preferably 5 to 50% by mass, more preferably 10 to 30% by mass.

The drying temperature is preferably 50 to 150 ° C. The drying time is preferably 0.5 to 80 minutes.
The heating temperature is preferably 100 to 400 ° C, more preferably 150 to 250 ° C. On the other hand, from the viewpoint of suppressing the coloring of the polyimide film, the heating temperature is preferably 400 ° C. or lower.
In order to suppress the coloring of the polyimide film, the imidization is preferably carried out under reduced pressure or in a nitrogen atmosphere, but may be carried out in air unless the temperature is particularly high.
The pressure when the pressure is reduced is preferably as small as possible, and specifically, it is about 0.09 MPa to 0.0001 MPa.

The polyimide film of the present invention thus obtained includes other crosslinkable resins, thermosetting resins and the like when producing a polyimide from a polyamic acid or a polyamic acid composition as long as the effects of the present invention are not impaired. May be blended.
Inorganic fibers such as glass fiber and carbon diver; additives such as oxidation stabilizers, terminal sealants, fillers, silane coupling agents, photosensitizers, photopolymerization initiators, and sensitizers may be added as required. It may be blended.

The polyimide film of the present invention can be used as an electronic substrate such as a high frequency substrate by forming a conductive film on the polyimide film and further forming an electronic circuit or a high frequency circuit.

[Coverlay film]
The coverlay film using the polyimide of the present invention (hereinafter, also referred to as “the coverlay film of the present invention”) is obtained by placing the polyamic acid of the present invention or the polyamic acid composition of the present invention on the polyimide film of the present invention. It has an adhesive layer containing a polyimide obtained by imidization.
The coverlay film of the present invention is used for a flexible printed circuit board (FPC board) or the like.
As a method for forming an adhesive layer using the polyamic acid of the present invention or the polyamic acid composition of the present invention, for example, the polyamic acid of the present invention or the polyamic acid composition of the present invention can be used on the surface of the polyimide film of the present invention. A method of forming a film by applying it to a film, removing the solvent, and curing the film can be mentioned.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

The abbreviations used in the following examples and comparative examples have the following meanings, respectively.
BCCAN: 4,4'-[9H-fluoren-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] bisbenzeneamine-PDA: p-phenylenediamine-BAPP: 2,2-bis [ 4- (4-Aminophenoxy) phenyl] propane ・ sBPDA: 3,3 ′, 4,4 ′-biphenyltetracarboxylic acid dianhydride ・ BPADA: 2,2-bis [4- (3,4-dicarboxyphenoxy) ) Phenyl] propane dianhydride ・ DMAc: N, N-dimethylacetamide

<Example 1>
BCFAN (47.8 g) and BPADA (52.2 g) are added to DMAc (400 g) and reacted by stirring at room temperature and atmospheric pressure for 3 hours to form a solution containing polyamic acid (polyamic acid composition). ) Was obtained.
The obtained polyamic acid-containing solution (15 g) was applied to a glass plate using a bar coater and heated at 100 ° C. for 20 minutes, 200 ° C. for 20 minutes, and 300 ° C. for 20 minutes to obtain a polyimide having a thickness of about 50 μm. I got a film.

<Comparative Example 1>
Polyamide acid and a polyimide film were obtained according to the same procedure as in Example 1 except that PDA was used instead of BCPAN as a diamine component and sBPDA was used instead of BPADA as an acid component.

<Comparative Example 2>
Polyamide acid and a polyimide film were obtained according to the same procedure as in Example 1 except that BAPP was used instead of BCWAN as the diamine component.

<evaluation>
The prepared polyimide film was evaluated for mechanical strength (tensile modulus and tensile strength), heat resistance (glass transition temperature), and dielectric properties (dielectric modulus and dielectric loss tangent). The results are shown in Table 1 below.

《Mechanical strength》
According to JIS K 7127: 1999 (ISO 527-3: 1995), the tensile elastic modulus (Young's modulus) and tensile strength of the polyimide film were measured under the following conditions.
Tensile speed: 102 mm / min
Distance between chucks: 30 mm

"Heat-resistant"
According to JIS K 7424-1: 1998 (ISO 6721-1: 1994), the glass transition temperature of the polyimide film was measured under the following conditions.
Temperature rise rate: 3 ° C / min
Temperature range: 50-450 ° C
Frequency: 1Hz

《Dielectric property》
According to JIS C 2565: 1992, the relative permittivity and the dielectric loss tangent of the polyimide film were measured under the following conditions.
Measurement method: Cavity resonator method Measurement frequency: 1 GHz

<Summary of evaluation results>
The polyimide of Example 1 using BCFAN and BPADA was excellent in mechanical strength and heat resistance, and had a low dielectric constant and a dielectric loss tangent.
On the other hand, the polyimide of Comparative Example 1 in which PDA was used instead of BCPAN and sBPDA was used instead of BPADA had a higher relative permittivity and dielectric loss tangent than the polyimide of Example 1, and had insufficient dielectric properties. there were.
Further, the polyimide of Comparative Example 2 in which BAPP was used instead of BCPAN had a lower tensile elastic modulus and tensile strength than the polyimide of Example 1, and the mechanical strength was insufficient. In addition, the glass transition temperature was low and the heat resistance was insufficient. Further, the dielectric loss tangent was high and the dielectric properties were insufficient.

Claims (11)

4,4'-[9H-fluorene-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] A diamine component consisting of bisbenzeneamine and 2,2-bis [4- (3,4-) Dicarboxyphenoxy) Phenyl] Polyamide acid obtained by polymerizing an acid component consisting of propane dianhydride. 4,4'-[9H-fluorene-9-iridenbis [(2-methyl-4,1-phenylene) oxy]] A diamine component consisting of bisbenzeneamine and 2,2-bis [4- (3,4-) Dicarboxyphenoxy) Phenyl] Polyimide obtained by polymerizing an acid component consisting of propane dianhydride. A polyimide obtained by imidizing the polyamic acid according to claim 1. The polyimide according to claim 2 or 3, wherein the dielectric loss tangent at a frequency of 1 GHz is 0.005 or less. The polyimide according to any one of claims 2 to 4, wherein the relative permittivity at a frequency of 1 GHz is 3.0 or less. The polyimide according to any one of claims 2 to 5, wherein the glass transition temperature is 230 ° C. or higher. The polyimide according to any one of claims 2 to 6, which has a tensile elastic modulus of 2.0 GPa or more. The polyimide according to any one of claims 2 to 7, which has a tensile strength of 80 MPa or more. A polyimide film having a film made of the polyimide according to any one of claims 2 to 8. The material for an electronic substrate having the polyimide according to any one of claims 2 to 8. The electronic substrate having the polyimide according to any one of claims 2 to 8.