Polyamic acid and polyimide

Abstract

The present disclosure pertains to a polyamic acid that includes diamine units and tetracarboxylic acid units. At least one selected from the group consisting of the diamine units and the tetracarboxylic acid units includes at least one nonaromatic hydrocarbon group and includes a unit (X) having a group (X) in which the total number of carbon atoms of the at least one nonaromatic hydrocarbon group is 9 or more. The percentage content of the unit (X) is 12.0 mol% or more based on the total amount of the diamine units and the tetracarboxylic acid units.

Description

Polyamic acids and polyimides

[0001] This disclosure relates to polyamic acid, printed circuit board materials, antenna substrate materials, transmission line cable materials, compositions, polyimides, printed circuit boards, antenna substrates, and transmission line cables.

[0002] With the increasing adoption of Driving Safety Support Systems (DSSS), the demand for in-vehicle millimeter-wave radar is growing. Insulating materials used for in-vehicle millimeter-wave radar substrates require low dielectric constant and dielectric loss tangent to minimize transmission signal loss, as well as excellent heat resistance and dimensional stability.

[0003] For example, Patent Document 1 discloses polyimide as an insulating resin for metal-clad laminates. According to Patent Document 1, by using a combination of a dimer acid type diamine, a specific tetracarboxylic dianhydride component, and a specific diamine compound, it is possible to suppress the amount of dimer acid type diamine used, thereby improving dimensional stability through heat treatment, and to obtain a polyimide with low dielectric loss tangent that is less dependent on heat treatment conditions.

[0004] Japanese Patent Publication No. 2016-188298

[0005] This disclosure provides a polyamic acid that can produce polyimides having low dielectric constant and low dielectric loss tangent, and excellent dimensional stability. Furthermore, this disclosure provides printed circuit board materials, antenna substrate materials, transmission line cable materials, and compositions containing the polyamic acid. In addition, this disclosure provides printed circuit boards, antenna substrates, and transmission line cables with excellent dimensional stability.

[0006] The present invention includes, but is not limited to, the following embodiments. One embodiment relates to a polyamic acid comprising diamine units and tetracarboxylic acid units, wherein at least one selected from the group consisting of the diamine units and the tetracarboxylic acid units comprises a unit (X) having a group (X) which comprises at least one non-aromatic hydrocarbon group, and the total number of carbon atoms of the at least one non-aromatic hydrocarbon group is 9 or more, and the content of the unit (X) is 12.0 mol% or more based on the total amount of the diamine units and the tetracarboxylic acid units. Another embodiment relates to a printed circuit board material, an antenna substrate material, and a transmission line cable material comprising the polyamic acid. Another embodiment relates to a composition comprising the polyamic acid and a solvent. Another embodiment relates to a polyimide obtained using the polyamic acid or the composition. Another embodiment relates to a printed circuit board, an antenna substrate, and a transmission line cable obtained using the polyamic acid, any of the materials, or the composition.

[0007] This disclosure provides a polyamic acid that can be used to obtain a polyimide having a low dielectric constant and low dielectric loss tangent, and excellent dimensional stability. This disclosure also provides printed circuit board materials, antenna substrate materials, transmission line cable materials, and compositions containing the polyamic acid. Furthermore, this disclosure provides printed circuit boards, antenna substrates, and transmission line cables having excellent dimensional stability.

[0008] Embodiments of the present invention will now be described. The present invention is not limited to the following embodiments. Furthermore, the following embodiments can be implemented individually or in combination. Combinations of multiple embodiments are also included in the present invention.

[0009] In numerical ranges described stepwise in this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. Furthermore, the upper or lower limit of a numerical range described in this disclosure may be replaced with the values ​​shown in the examples. A numerical value may be selected from the upper and lower limits described stepwise in this disclosure to form a stepwise numerical range. Furthermore, the upper and lower limits described in this disclosure may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component exist in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each structure in the polymer may contain multiple types of the corresponding structure. If multiple types of the structure corresponding to each structure exist in the polymer, the content or amount of each structure means the total content or amount of the multiple types of structures present in the polymer, unless otherwise specified. In this disclosure, the term "layer" includes not only layers that form over the entire region in which the layer exists, but also layers that form over only a portion of that region when the region in which the layer exists is observed. The same applies to "film."

[0010] <Polyamic Acids> In some embodiments, polyamic acids contain diamine units and tetracarboxylic acid units. Polyamic acids contain amide acid bonds (also called "amide acid structures" or "amide acid groups") in the polymer chain. Polyamic acids may further contain imide bonds (also called "imide groups"). Polyamic acids may contain one or more diamine units. Polyamic acids may contain one or more tetracarboxylic acid units.

[0011] At least one selected from the group consisting of diamine units and tetracarboxylic acid units includes a unit (X) having a group (X) which includes at least one non-aromatic hydrocarbon group and the total number of carbon atoms of the at least one non-aromatic hydrocarbon group is 9 or more. In this disclosure, "a group (X) which includes at least one non-aromatic hydrocarbon group and the total number of carbon atoms of the at least one non-aromatic hydrocarbon group is 9 or more" may be referred to as "group (X)" or "hydrocarbon group (X)". In this disclosure, "a unit (X) having a hydrocarbon group (X)" may be referred to as "unit (X)". The hydrocarbon group (X) may be an amidic acid group and an amidic acid group, an amidic acid group and an imide group, or an imide group and an imide group. The number of carbon atoms in the amidic acid group and the imide group is not included in the total number of carbon atoms of the at least one non-aromatic hydrocarbon group in the hydrocarbon group (X). The polyamic acid may contain a hydrocarbon group (X), an amidic acid group, and an imide group if an imide group is also present, in the polymer chain.

[0012] At least one selected from the group consisting of diamine units and tetracarboxylic acid units may further include a unit (Y) having an organic group (Y) but not a hydrocarbon group (X). The "organic group (Y)" is an organic group other than a hydrocarbon group (X) that does not correspond to a hydrocarbon group (X). In this disclosure, the "organic group" is a group containing at least one carbon atom. In this disclosure, the "unit (Y) having an organic group (Y) but not a hydrocarbon group (X)" may be referred to as "unit (Y)". The organic group (Y) may be a group located between two amidic acid groups, an amidic acid group and an imide group, or an imide group and an imide group. The number of carbon atoms in the amidic acid group and the imide group is not included in the number of carbon atoms of the organic group (Y). The polyamic acid may contain the organic group (Y), the amidic acid group, and, if an imide group is also present, the imide group in the polymer chain.

[0013] [Diamine Units and Tetracarboxylic Acid Units] In some embodiments, the diamine unit may be a unit represented by the following formula (N). The tetracarboxylic acid unit may be a unit represented by the following formula (C).

[0014]

[0015] In the formula, R Ｎ The symbol (x) represents an organic group, and P represents the bond position with a tetracarboxylic acid unit or a hydrogen atom. * represents the bond position with another atom. The organic group may be a hydrocarbon group (X) or an organic group (Y).

[0016]

[0017] In the formula, R Ｃ The symbol (X) represents an organic group, and Q represents the bonding position with a diamine unit or a hydroxyl group. The asterisk (*) indicates the bonding position with another atom. The organic group may be a hydrocarbon group (X) or an organic group (Y).

[0018] In some embodiments, the diamine unit may be a unit derived from a diamine or diisocyanate. The tetracarboxylic acid unit may be a unit derived from a tetracarboxylic dianhydride. In this disclosure, “diamine or diisocyanate” means “at least one compound selected from the group consisting of diamines and diisocyanates.”

[0019] In some embodiments, the diamine unit may be a unit introduced into the polyamic acid using a diamine or diisocyanate. The tetracarboxylic acid unit may be a unit introduced into the polyamic acid using a tetracarboxylic dianhydride.

[0020] In this disclosure, the unit represented by formula (N) may be referred to as "unit (N)". The same may apply to other units represented by formulas, structural units, polymers, etc.

[0021] [Unit (X)] In polyamic acid, either only the diamine unit or the tetracarboxylic acid unit contains unit (X), or both the diamine unit and the tetracarboxylic acid unit contain unit (X). When the diamine unit contains unit (X), the unit (X) contained in the diamine unit is a "diamine unit having a hydrocarbon group (X)". When the tetracarboxylic acid unit contains unit (X), the unit (X) contained in the tetracarboxylic acid unit is a "tetracarboxylic acid unit having a hydrocarbon group (X)". That is, polyamic acid contains "diamine units having a hydrocarbon group (X)", "tetracarboxylic acid units having a hydrocarbon group (X)", or both of these units. The diamine unit and the tetracarboxylic acid unit may each independently contain one or more types of unit (X). When polyamic acid has a hydrocarbon group (X), it is thought that a polyimide with a low dielectric constant and low dielectric loss tangent can be obtained due to reasons such as an increase in free volume and a decrease in polarity. Note that the discussions, speculations, etc. described in this disclosure do not limit the present invention.

[0022] (Content) In polyamic acid, the content of unit (X) is, for example, 12.0 mol% or more, 13.0 mol% or more, 14.0 mol% or more, or 15.0 mol% or more, based on the total amount of diamine units and tetracarboxylic acid units. When the content of unit (X) is 12.0 mol% or more, polyimides with low dielectric constant and dielectric loss tangent are easily obtained. The content of unit (X) is, for example, 50.0 mol% or less, 40.0 mol% or less, 35.0 mol% or less, 30.0 mol% or less, or 25.0 mol% or less, based on the total amount of diamine units and tetracarboxylic acid units. When the content of unit (X) is 50.0 mol% or less, the mechanical strength and heat resistance of the polyimide are easily maintained. The content of unit (X) may be 12.0 to 50.0 mol%, 13.0 to 40.0 mol%, or 14.0 to 30.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units.

[0023] For example, metal-clad laminates used in the manufacture of printed circuit boards typically have a resin layer and a metal layer. To improve the dimensional stability of printed circuit boards, it is desirable for the warping of the metal-clad laminate to be small. One of the causes of warping in metal-clad laminates is thought to be that the thermal expansion coefficient of the resin layer is greater than that of the metal layer. In this disclosure, according to some embodiments, the tensile modulus of polyimide can be reduced by including units (X) having hydrocarbon groups (X) containing non-aromatic hydrocarbon groups in the polyamic acid. When the tensile modulus of polyimide is small, the resin layer is more likely to follow the dimensional changes of the metal, even when the thermal expansion coefficient is large. For example, a metal-clad laminate can be manufactured by applying a composition containing polyamic acid to a metal layer to form a layer containing polyamic acid, and then heating it to obtain a layer containing polyimide. If the tensile modulus of polyimide is small during the process of the heated polyimide-containing layer cooling to room temperature, the polyimide-containing layer is more likely to follow the dimensional changes (in this case, small shrinkage) of the metal layer. If the layer containing polyimide can follow the dimensional changes of the metal layer, warping of the metal-clad laminate can be suppressed. From the viewpoint of reducing the tensile modulus of polyimide, it is preferable that the content of unit (X) be higher, for example, 20.0 mol% or more, 25.0 mol% or more, or 30.0 mol% or more, based on the total amount of diamine units and tetracarboxylic acid units. The content of unit (X) may be 20.0 to 50.0 mol%, 25.0 to 40.0 mol%, or 30.0 to 35.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units.

[0024] (Hydrogen group (X)) The hydrocarbon group (X) includes at least one non-aromatic hydrocarbon group. In the hydrocarbon group (X), the total number of carbon atoms of at least one non-aromatic hydrocarbon group is 9 or more. If the hydrocarbon group (X) includes one non-aromatic hydrocarbon group, the total number of carbon atoms means the total number of carbon atoms contained in that one non-aromatic hydrocarbon group. If the hydrocarbon group (X) includes two or more non-aromatic hydrocarbon groups, the total number of carbon atoms means the total number of carbon atoms contained in those two or more non-aromatic hydrocarbon groups. If the hydrocarbon group (X) includes two or more non-aromatic hydrocarbon groups, the non-aromatic hydrocarbon groups may be the same or different from each other. The hydrocarbon group (X) may further include any group other than a non-aromatic hydrocarbon group. The hydrocarbon group (X) is, for example, a 1- to 4-valent group. The unit (X) preferably includes a 2- to 4-valent hydrocarbon group (X), more preferably a 2- or 4-valent hydrocarbon group (X), and even more preferably a 2-valent hydrocarbon group (X).

[0025] A non-aromatic hydrocarbon group is a hydrocarbon group that does not contain an aromatic ring and is non-aromatic. Examples of non-aromatic hydrocarbon groups include saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, unsaturated alicyclic hydrocarbon groups, or groups consisting of two or more selected from these. Saturated aliphatic hydrocarbon groups may be linear or branched. Unsaturated aliphatic hydrocarbon groups may be linear or branched. If hydrocarbon group (X) contains two or more non-aromatic hydrocarbon groups, the two or more non-aromatic hydrocarbon groups may be the same or different from each other.

[0026] Examples of hydrocarbon groups (X) and the total number of carbon atoms of at least one non-aromatic hydrocarbon group contained in the hydrocarbon group (X) are given below. Also, as a reference example, examples of organic groups (Y) and the total number of carbon atoms of at least one non-aromatic hydrocarbon group contained in the organic group (Y) are given. As will be described later, the number of carbon atoms contained in the -C(O)- group is not included in the total number of carbon atoms. In this disclosure, "*" in the formulas represents the bond position with other atoms.

[0027]

[0028] The total number of carbon atoms in at least one non-aromatic hydrocarbon group contained in the hydrocarbon group (X) may be 9 to 50. For example, the number of carbon atoms may be 12 or more, 16 or more, 20 or more, 24 or more, 28 or more, 32 or more, or 36 or more. For example, the number of carbon atoms may be 48 or less, 44 or less, 40 or less, or 36 or less. For example, the number of carbon atoms may be 12 to 48, 20 to 44, or 28 to 40. When the total number of carbon atoms in the non-aromatic hydrocarbon groups is 9 or more, it is thought that a polyimide with a low dielectric constant and a low dielectric loss tangent can be obtained due to reasons such as an increase in free volume and a decrease in polarity. Furthermore, when the total number of carbon atoms in the non-aromatic hydrocarbon groups is 9 or more, it is thought that the tensile modulus of the polyimide can be reduced. When the total number of carbon atoms in the non-aromatic hydrocarbon groups is 50 or less, good solubility in the solvent can be maintained. Even if the polyamic acid has groups in place of hydrocarbon groups (X) where the total number of carbon atoms of aromatic hydrocarbon groups and heteroaromatic ring compound groups is 9 or more, it is not possible to obtain a polyimide with a low dielectric constant and a low dielectric loss tangent due to its small free volume.

[0029] Examples of saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, unsaturated alicyclic hydrocarbon groups, and groups consisting of two or more selected from these, which may comprise the hydrocarbon group (X), are given below. The following examples may apply to saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, unsaturated alicyclic hydrocarbon groups, and groups consisting of two or more selected from these, as described herein.

[0030] The number of carbon atoms in a saturated aliphatic hydrocarbon group is, for example, 1 to 50, 2 to 40, 3 to 30, 4 to 20, or 5 to 10. A saturated aliphatic hydrocarbon group is, for example, an atomic group obtained by removing 1 to 4 hydrogen atoms from a linear or branched alkane. Examples of alkanes include methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, hexacosane, octacosane, triacontane, tetracontane, and pentacontane.

[0031] The number of carbon atoms in the unsaturated aliphatic hydrocarbon group is, for example, 2 to 50, 2 to 40, 3 to 30, 4 to 20, or 5 to 10. The unsaturated aliphatic hydrocarbon group contains one or more carbon-carbon unsaturated bonds, which may be, for example, five or fewer, four or fewer, three or fewer, or two or fewer. The unsaturated aliphatic hydrocarbon may be an alkene containing one carbon-carbon double bond, or an alkyne containing one carbon-carbon triple bond. The unsaturated aliphatic hydrocarbon group is, for example, an atomic group obtained by removing one to four hydrogen atoms from a linear or branched alkene, or an atomic group obtained by removing one to four hydrogen atoms from a linear or branched alkyne. Examples of alkenes include ethene, propene, butene, pentene, hexene, heptene, octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene, octadecene, nonadecene, eicosene, heneicosene, docosene, tricosene, tetracosene, pentacosene, hexacosene, heptacosene, octacosene, nonacosene, triacontene, tetracontene, and pentacosene. Examples of alkynes include ethin, propine, butin, pentin, hexin, heptin, octin, nonine, desine, undesine, dodesine, tridecine, tetradecine, pentadesine, hexadesine, heptadesine, octadecine, nonadesine, eicosine, heneicosine, docosine, tricosine, tetracosine, pentacosine, hexacosine, heptacosine, octacosine, nonacosine, triacontin, tetracontin, and pentacontin.

[0032] The number of carbon atoms in a saturated alicyclic hydrocarbon group is, for example, 3 to 20, 4 to 16, 5 to 10, or 6 to 8. A saturated alicyclic hydrocarbon group is, for example, an atomic group obtained by removing 1 to 4 hydrogen atoms from a cycloalkane. Examples of cycloalkanes include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, norbornane, decalin, bicyclobutane, bicyclohexane, bicyclooctane, spiropentane, spiroheptane, guadricyclane, and adamantane.

[0033] The number of carbon atoms in an unsaturated alicyclic hydrocarbon group is, for example, 4 to 20, 5 to 10, or 6 to 8. The number of carbon-carbon unsaturated bonds in an unsaturated aliphatic hydrocarbon group is one or more, and may be, for example, 5 or fewer, 4 or fewer, 3 or fewer, or 2 or fewer. The unsaturated aliphatic hydrocarbon may be a cycloalkene containing one carbon-carbon double bond, or a cycloalkyne containing one carbon-carbon triple bond. The unsaturated alicyclic hydrocarbon group is, for example, an atomic group obtained by removing 1 to 4 hydrogen atoms from a cycloalken, or an atomic group obtained by removing 1 to 4 hydrogen atoms from a cycloalkyne. Examples of unsaturated alicyclic hydrocarbons include cyclobutene, cyclopentene, cyclopentadiene, cyclohexene, cyclohexadiene, cycloheptene, norbornene, norbornadiene, and bicyclooctadiene.

[0034] The number of carbon atoms in a group consisting of two or more types selected from these is, for example, 4 to 50, 9 to 50, 16 to 48, 24 to 44, or 32 to 40. The group consisting of two or more types selected from these is a group consisting of two or more types selected from the group consisting of saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, and unsaturated alicyclic hydrocarbon groups, wherein the two or more types of groups are bonded to each other. The group consisting of two or more types selected from these includes, for example, at least one selected from the group consisting of a group consisting of a saturated aliphatic hydrocarbon group and a saturated alicyclic hydrocarbon group, a group consisting of a saturated aliphatic hydrocarbon group and an unsaturated alicyclic hydrocarbon group, a group consisting of an unsaturated aliphatic hydrocarbon group and a saturated alicyclic hydrocarbon group, and a group consisting of an unsaturated aliphatic hydrocarbon group and an unsaturated alicyclic hydrocarbon group.

[0035] Examples of groups that the hydrocarbon group (X) may contain include aromatic hydrocarbon groups, aromatic heterocyclic compound groups, and groups containing heteroatoms. The following examples may apply to aromatic hydrocarbon groups, aromatic heterocyclic compound groups, and groups containing heteroatoms in this disclosure. From the viewpoint of reducing polarity, the hydrocarbon group (X) does not need to contain an oxygen atom, and furthermore, does not need to contain a heteroatom.

[0036] The number of carbon atoms in an aromatic hydrocarbon group is, for example, 6 to 30, 6 to 20, or 6 to 10. An aromatic hydrocarbon group is, for example, an atomic group obtained by removing 1 to 4 hydrogen atoms from an aromatic hydrocarbon. Examples of aromatic hydrocarbons include benzene, naphthalene, anthracene, pyrene, and perylene. The number of carbon atoms in an aromatic heterocyclic compound group is 2 to 30, 4 to 20, or 5 to 10. An aromatic heterocyclic compound group is, for example, an atomic group obtained by removing 1 to 4 hydrogen atoms from an aromatic heterocyclic compound. Examples of aromatic heterocyclic compounds include pyridine, furan, benzofuran, thiophene, and benzothiophene.

[0037] Examples of heteroatom-containing groups include heteroatom-containing linking groups (excluding amidic acid groups and imide groups) and heteroatom-containing substituents. Examples of heteroatom-containing linking groups include oxy groups, thio groups, sulfonyl groups, sulfinyl groups, carbonyl groups, carbonyloxy groups, and imino groups. Examples of heteroatom-containing substituents include hydroxyl groups, mercapto groups, sulfo groups, sulfino groups, carboxyl groups, fluoro groups, and chloro groups. In this disclosure, the number of carbon atoms in the -C(O)- group included in the heteroatom-containing group is not included in the total number of carbon atoms of at least one non-aromatic hydrocarbon group.

[0038] The hydrocarbon group (X) consists, for example, a non-aromatic hydrocarbon group having 9 or more carbon atoms. When the hydrocarbon group (X) consists of a non-aromatic hydrocarbon group, the hydrocarbon group (X) does not contain aromatic hydrocarbon groups, aromatic heterocyclic compound groups, or groups containing heteroatoms. The hydrocarbon group (X) is, for example, a saturated aliphatic hydrocarbon group having 9 or more carbon atoms; an unsaturated aliphatic hydrocarbon group having 9 or more carbon atoms; a saturated alicyclic hydrocarbon group having 9 or more carbon atoms; an unsaturated alicyclic hydrocarbon group having 9 or more carbon atoms; or a group having 9 or more carbon atoms consisting of two or more selected from saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, and unsaturated alicyclic hydrocarbon groups. Saturated aliphatic hydrocarbon groups may be linear or branched. Unsaturated aliphatic hydrocarbon groups may be linear or branched. When the hydrocarbon group (X) consists of a non-aromatic hydrocarbon group having 9 or more carbon atoms, it is easier to lower the concentration of polar groups contained in the polyamic acid.

[0039] The hydrocarbon group (X) preferably comprises at least one group selected from the group consisting of saturated alicyclic hydrocarbon groups and unsaturated alicyclic hydrocarbon groups, and more preferably comprises saturated alicyclic hydrocarbon groups. When the polyamic acid contains at least one of saturated alicyclic hydrocarbon groups and unsaturated alicyclic hydrocarbon groups, there is a tendency to obtain polyimides with lower dielectric constants. This is presumed to be because the free volume of the polyimide increases due to its alicyclic structure.

[0040] The hydrocarbon group (X) preferably comprises at least one group selected from the group consisting of a linear saturated aliphatic hydrocarbon group having 6 or more carbon atoms and a linear unsaturated aliphatic hydrocarbon group having 6 or more carbon atoms, and more preferably comprises a linear saturated aliphatic hydrocarbon group having 6 or more carbon atoms. When the polyamic acid contains at least one of a linear saturated aliphatic hydrocarbon group having 6 or more carbon atoms and a linear unsaturated aliphatic hydrocarbon group having 6 or more carbon atoms, it is easier to obtain a polyimide with a lower dielectric loss tangent. The reason for this is presumed to be that the concentration of imide groups in the polyimide decreases due to the long chain structure of the polyimide, that is, the number of polar groups in the polyimide decreases relatively.

[0041] In some embodiments, the total number of carbon atoms in the saturated aliphatic hydrocarbon group and the unsaturated aliphatic hydrocarbon group contained in the hydrocarbon group (X) may be greater than the total number of carbon atoms in the saturated alicyclic hydrocarbon group and the unsaturated alicyclic hydrocarbon group contained in the hydrocarbon group (X).

[0042] In some embodiments, the hydrocarbon group (X) does not have to include aromatic hydrocarbon groups and aromatic heterocyclic compound groups.

[0043] The hydrocarbon group (X) preferably includes a group represented by the following formula (G1).

[0044]

[0045] In the formula, R ｘ This represents a hydrocarbon group (X). Examples of hydrocarbon groups (X) are as described above.

[0046] The hydrocarbon group (X) more preferably contains at least one selected from the group consisting of the groups represented by the following formula (G2) to the groups represented by the following formula (G6).

[0047]

[0048] In the formula, R ａ each independently represents a linear or branched saturated aliphatic hydrocarbon group (the number of carbon atoms is, for example, 1 or more, 6 or more, or 8 or more), or a linear or branched unsaturated aliphatic hydrocarbon group (the number of carbon atoms is, for example, 1 or more, 6 or more, or 8 or more), and preferably represents a linear saturated aliphatic hydrocarbon group (the number of carbon atoms is, for example, 1 or more, 6 or more, or 8 or more) or a linear unsaturated aliphatic hydrocarbon group (the number of carbon atoms is, for example, 1 or more, 6 or more, or 8 or more). R ｂ each independently represents a saturated alicyclic hydrocarbon group or an unsaturated alicyclic hydrocarbon group, and preferably represents a saturated alicyclic hydrocarbon group (the number of carbon atoms is, for example, 6 (cyclohexane group) or 7 (norbornane group)). L represents a single bond or a linking group containing a heteroatom (excluding an amino acid group and an imide group). R ａ and R ｂ each independently may or may not have a substituent. R ａ and R ｂ The upper limit of the number of carbon atoms of is, for example, 48 or less, 44 or less, 40 or less, or 36 or less.

[0049] The hydrocarbon group (X) more preferably contains at least one selected from the group consisting of the group represented by the following formula (G7), the group represented by the following formula (G8), and the group represented by the following formula (G9). These groups can be introduced into the polyamic acid by using, for example, a dimer diamine as a monomer for obtaining the polyamic acid. The hydrocarbon group (X) particularly preferably contains the group represented by the formula (G8). When the polyamic acid contains at least one selected from the group consisting of the group represented by the formula (G7), the group represented by the formula (G8), and the group represented by the formula (G9), sufficient effects of low dielectric constant, low dielectric tangent, and low thermal expansion coefficient tend to be obtained.

[0050]

[0051] In the formula, R ｃ Each independently represents a linear alkylene group or a linear alkenylene group (with, for example, 6 or more carbon atoms, 8 or more carbon atoms, or 9 or more carbon atoms), R ｄ Each of these independently represents a linear alkyl group or a linear alkenyl group (with, for example, 6 or more carbon atoms, 8 or more, or 9 or more carbon atoms). ｃ and R ｄ Each of these elements may independently have substituents or not. ｃ and R ｄ The upper limit for the number of carbon atoms is, for example, 48 or less, 44 or less, 40 or less, or 36 or less.

[0052] (Examples of Unit (X)) In some embodiments, the "unit (X) included in the diamine unit" may be a unit represented by the following formula (NX), and may be at least one selected from the group consisting of the unit represented by the following formula (NXA) and the unit represented by the following formula (NXI). The "unit (X) included in the tetracarboxylic acid unit" may be a unit represented by the following formula (CX), and may be at least one selected from the group consisting of the unit represented by the following formula (CXA) and the unit represented by the following formula (CXI).

[0053]

[0054] In the formula, R ｘ represents a hydrocarbon group (X), and P represents a bond position to a tetracarboxylic acid unit or a hydrogen atom. * represents a bond position to another atom, and may be a bond position to a tetracarboxylic acid unit.

[0055]

[0056] In the formula, R ｘ represents a hydrocarbon group (X). * indicates a bonding position with another atom, and may be a bonding position with a tetracarboxylic acid unit.

[0057]

[0058] In the formula, R ｘ represents a hydrocarbon group (X). * indicates a bonding position with another atom, and may be a bonding position with a tetracarboxylic acid unit.

[0059]

[0060] In the formula, R ｘ represents a hydrocarbon group (X), and Q represents the bonding position to a diamine unit or a hydroxyl group. * represents the bonding position to another atom, and may be the bonding position to a diamine unit.

[0061]

[0062] In the formula, R ｘ represents a hydrocarbon group (X). * indicates a bonding position with another atom, and may be a bonding position with a diamine unit.

[0063]

[0064] In the formula, R ｘ represents a hydrocarbon group (X). * indicates a bonding position with another atom, and may be a bonding position with a diamine unit.

[0065] In some embodiments, the "unit (X) included in the diamine unit" may be a unit derived from a diamine or diisocyanate having a hydrocarbon group (X). The "unit (X) included in the tetracarboxylic acid unit" may be a unit derived from a tetracarboxylic dianhydride having a hydrocarbon group (X).

[0066] In some embodiments, the "unit (X) included in the diamine unit" may be a unit introduced into the polyamic acid using a diamine or diisocyanate having a hydrocarbon group (X). The "unit (X) included in the tetracarboxylic acid unit" may be a unit introduced into the polyamic acid using a tetracarboxylic dianhydride having a hydrocarbon group (X).

[0067] (Diamines having a hydrocarbon group (X)) Diamines having a hydrocarbon group (X) can be represented, for example, by the following formula (Ax).

[0068]

[0069] In the formula, R ｘ R represents a hydrocarbon group (X). ｘ Examples include the group represented by formula (G2) to the group represented by formula (G9).

[0070] Specific examples of diamines having a hydrocarbon group (X) include: Diamines with 9 or more carbon atoms having a saturated aliphatic hydrocarbon group, such as 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,14-diaminotetradecane, and 1,16-diaminohexadecane; Diamines with 9 or more carbon atoms having an unsaturated aliphatic hydrocarbon group, such as 1,9-diaminononene, 1,10-diaminodecene, 1,11-diaminoundecene, 1,12-diaminododecene, 1,14-diaminotetradecene, and 1,16-diaminohexadecane; Diamines with 9 or more carbon atoms having a saturated alicyclic hydrocarbon group, such as isophoronediamine, bis(aminomethyl)norbornane, 1,3-diaminoadamantane, and 4,4'-diaminodicyclohexylmethane; Diamines having 9 or more carbon atoms and possessing an unsaturated alicyclic hydrocarbon group, such as bis(aminomethyl)norbornene and 4,4'-diaminodicyclohexenylmethane; monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, and nervonic acid; diunsaturated fatty acids such as linoleic acid, eicosadienoic acid, and docosadienoic acid; and diamines derived from dimers (also called dimer acids) of unsaturated fatty acids such as linolenic acid, pinolenic acid, eleostearic acid, meadic acid, dihomo-γ-linolenic acid, and eicosatrienoic acid; and dimer amines having 9 or more carbon atoms, such as diamines in which the carbon-carbon double bond contained in the molecule is hydrogenated.

[0071] In some embodiments, unit (X) includes a dimeramine unit. The dimeramine structural unit may be a group of atoms obtained by removing two or four hydrogen atoms from a dimeramine.

[0072] Examples of commercially available dimer amines with 9 or more carbon atoms include "PRIAMINE 1075" and "PRIAMINE 1074" manufactured by Croda Japan Co., Ltd.

[0073] (Diisocyanates having a hydrocarbon group (X)) Diisocyanates having a hydrocarbon group (X) can be represented, for example, by the following formula (Ix).

[0074]

[0075] In the formula, R ｘ R represents a hydrocarbon group (X). ｘ Examples include the group represented by formula (G2) to the group represented by formula (G9).

[0076] Specific examples of diisocyanates having a hydrocarbon group (X) include compounds that have the same structure as the compounds shown above as examples of diamines, except that the amino group is replaced with an isocyanate group.

[0077] (Tetracarboxylic dianhydrides having a hydrocarbon group (X)) Tetracarboxylic dianhydrides having a hydrocarbon group (X) can be represented, for example, by the following formula (Cx).

[0078]

[0079] In the formula, R ｘ This represents a hydrocarbon group (X). Examples of hydrocarbon groups (X) are as described above.

[0080] The following are specific examples of tetracarboxylic dianhydrides having a hydrocarbon group (X). The "number of carbon atoms" below refers to the number of carbon atoms in the hydrocarbon group (X), and does not include the number of carbon atoms in the carboxylic acid anhydride group. Tetracarboxylic dianhydrides with 9 or more carbon atoms having an alicyclic hydrocarbon group, such as 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride and 2,2-bis(3,4-dicarboxycyclohexyl)propane dianhydride.

[0081] [Unit (Y)] In polyamic acids, either a diamine unit or a tetracarboxylic acid unit alone may contain unit (Y), or both a diamine unit and a tetracarboxylic acid unit may contain unit (Y). When a diamine unit contains unit (Y), the unit (Y) contained in the diamine unit is a "diamine unit having an organic group (Y) and no hydrocarbon group (X)". When a tetracarboxylic acid unit contains unit (Y), the unit (Y) contained in the tetracarboxylic acid unit is a "tetracarboxylic acid unit having an organic group (Y) and no hydrocarbon group (X)". In other words, polyamic acids may contain "diamine units having an organic group (Y) and no hydrocarbon group (X)", "tetracarboxylic acid units having an organic group (Y) and no hydrocarbon group (X)", or both of these units. Diamine units and tetracarboxylic acid units may each independently contain one or more types of unit (Y).

[0082] (Content) In polyamic acid, the content of unit (Y) is, for example, 88.0 mol% or less, 87.0 mol% or less, 86.0 mol% or less, or 85.0 mol% or less, based on the total amount of diamine units and tetracarboxylic acid units. When the content of unit (Y) is 88.0 mol% or less, the content of unit (X) is sufficient, and polyimides with low dielectric constant and dielectric loss tangent are easily obtained. From the viewpoint of reducing the tensile modulus of polyimide, the content of unit (Y) is, for example, 80.0 mol% or less, 75.0 mol% or less, or 70.0 mol% or less, based on the total amount of diamine units and tetracarboxylic acid units. The content of unit (Y) is, for example, 50.0 mol% or more, 60.0 mol% or more, 65.0 mol% or more, 70.0 mol% or more, or 75.0 mol% or more, based on the total amount of diamine units and tetracarboxylic acid units. When the content of unit (Y) is 50.0 mol% or more, it is easier to maintain the mechanical strength and heat resistance of the polyimide. From the viewpoint of obtaining good mechanical strength and heat resistance, it is preferable that unit (Y) contains at least one of an aromatic hydrocarbon group and an aromatic heterocyclic compound group, and it is preferable that the content of such unit (Y) is high. In particular, when the content of unit (Y) containing at least one of an aromatic hydrocarbon group and an aromatic heterocyclic compound group is 70.0 mol% or more, it is easier to obtain a polyimide with better mechanical strength and heat resistance. The content of unit (Y) may be 50.0 to 88.0 mol%, 60.0 to 87.0 mol%, or 70.0 to 86.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units. The content of unit (Y) may be 50.0 to 80.0 mol%, 65.0 to 75.0 mol%, or 65.0 to 70.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units.

[0083] (Organic group (Y)) The organic group (Y) is a group that includes, for example, at least one selected from the group consisting of saturated aliphatic hydrocarbon groups, unsaturated aliphatic hydrocarbon groups, saturated alicyclic hydrocarbon groups, unsaturated alicyclic hydrocarbon groups, aromatic hydrocarbon groups, aromatic heterocyclic compound groups, and groups consisting of two or more selected from these. If the organic group (Y) includes at least one non-aromatic hydrocarbon group, the total number of carbon atoms in the at least one non-aromatic hydrocarbon group is 8 or less. The organic group (Y) preferably includes an aromatic hydrocarbon group. The organic group (Y) may further include linking groups containing heteroatoms, substituents containing heteroatoms, etc. The organic group (Y) is, for example, a 1- to 4-valent group. The unit (Y) preferably includes a 2- to 4-valent organic group (Y), and more preferably includes a 4-valent organic group (Y) and a 2-valent organic group (Y).

[0084] The organic group (Y) preferably includes a group represented by the following formula (G11).

[0085]

[0086] In the formula, R ｙ This represents an organic group (Y).

[0087] The organic group (Y) more preferably includes at least one selected from the group consisting of a group represented by the following formula (G12) to a group represented by the following formula (G14a).

[0088]

[0089] In the formula, R ｅ Each of these independently represents an aromatic hydrocarbon group or an aromatic heterocyclic compound group, preferably an aromatic hydrocarbon group, and more preferably a benzene group. ｆ R represents a linear or branched saturated aliphatic hydrocarbon group, or a linear or branched unsaturated aliphatic hydrocarbon group. ｆ The number of carbon atoms is 8 or less. L represents a linking group containing a single bond or a heteroatom (excluding amide groups and imide groups). ｅ and R ｆ Each of these elements may independently have substituents or not.

[0090] According to some embodiments, the organic group (Y) includes at least one selected from the group consisting of a group represented by formula (G14) and a group represented by formula (G14a), preferably represented by formula (G14) and R ｅ A group in which is a benzene group and L is a linking group containing a single bond or heteroatom (for example, a carbonyl group), and a group represented by formula (G14a), R ｅ The organic group (Y) contains at least one selected from the group consisting of "a benzene group and a linking group containing a heteroatom (e.g., a carbonyloxy group)". When the organic group (Y) contains these groups, a rigid structure is introduced to the polyamic acid, making it easier for the polyimide to orient within the layer, and a low coefficient of thermal expansion tends to be obtained. For example, the organic group (Y) is represented by formula (G14), R ｅ "A is a benzene group, and L is a single bond" and "It is represented by formula (G14), R ｅ It includes a group in which L is a benzene group and L is a linking group containing a heteroatom (for example, a carbonyl group), and is further represented by formula (G14a), R ｅ The group may include a benzene group and a linking group containing a heteroatom (for example, a carbonyloxy group).

[0091] According to some embodiments, the organic group (Y) preferably includes a group represented by formula (G11) and a group represented by the following formula (G15), and more preferably includes at least one selected from the group consisting of a group represented by formula (G12) to a group represented by formula (G14a) and at least one selected from the group consisting of a group represented by the following formula (G16) to a group represented by the following formula (G18b).

[0092]

[0093] In the formula, R ｙ This represents an organic group (Y).

[0094] The organic group (Y) more preferably includes at least one selected from the group consisting of a group represented by the following formula (G16) to a group represented by the following formula (G18b).

[0095]

[0096] In the formula, R ｅEach of these independently represents an aromatic hydrocarbon group or an aromatic heterocyclic compound group, preferably an aromatic hydrocarbon group, and more preferably a benzene group. ｆ R represents a linear or branched saturated aliphatic hydrocarbon group, or a linear or branched unsaturated aliphatic hydrocarbon group. ｆ The number of carbon atoms is 8 or less. L represents a linking group containing a single bond or a heteroatom (excluding amide groups and imide groups). ｅ and R ｆ Each of these elements may independently have substituents or not.

[0097] According to some embodiments, the organic group (Y) includes at least one group selected from the group consisting of a group represented by formula (G18) (where L is a linking group containing a heteroatom) to a group represented by formula (G18b) (where L is a linking group containing a heteroatom). When the organic group includes the at least one such group, it tends to maintain good solubility in the solvent. According to some embodiments, the organic group (Y) includes at least one group selected from the group consisting of a group represented by formula (G18) (where L is an oxy group or a carbonyl group) to a group represented by formula (G18b) (where L is an oxy group or a carbonyl group). When the organic group includes the at least one such group, an ether bond or a carbonyl bond can be introduced into the block chain.

[0098] According to some embodiments, the organic group (Y) has a group represented by formula (G18) (L is a single bond). When the organic group contains the said group, a rigid structure can be introduced into the polyimide. According to some embodiments, the organic group (Y) has a group represented by formula (G18) (L is a single bond, R ｅ The organic group has one or both of the substituents being non-aromatic hydrocarbon groups. When the organic group contains the aforementioned group, it is possible to increase the free volume while introducing a rigid structure to the polyimide. The non-aromatic hydrocarbon group as a substituent is, for example, an alkyl group having 1 to 4 carbon atoms.

[0099] (Examples of unit (Y)) In some embodiments, the "unit (Y) included in the diamine unit" may be a unit represented by the following formula (NY), a unit represented by the following formula (NYA), or a unit represented by the following formula (NYI). The "unit (Y) included in the tetracarboxylic acid unit" may be a unit represented by the following formula (CY), a unit represented by the following formula (CYA), or a unit represented by the following formula (CYI).

[0100]

[0101] In the formula, R ｙ * represents an organic group (Y), and P represents a bond position to a tetracarboxylic acid unit or a hydrogen atom. * represents a bond position to another atom, and may be a bond position to a tetracarboxylic acid unit.

[0102]

[0103] In the formula, R ｙ * represents an organic group (Y). * indicates a bonding position with another atom, and may be a bonding position with a tetracarboxylic acid unit.

[0104]

[0105] In the formula, R ｙ * represents an organic group (Y). * indicates a bonding position with another atom, and may be a bonding position with a tetracarboxylic acid unit.

[0106]

[0107] In the formula, R ｙ * represents an organic group (Y), and Q represents a bond position with a diamine unit or a hydroxyl group. * represents a bond position with another atom, and may be a bond position with a diamine unit.

[0108]

[0109] In the formula, R ｙ * represents an organic group (Y). * indicates a bonding position with another atom, and may also be a bonding position with a diamine unit.

[0110]

[0111] In the formula, R ｙ* represents an organic group (Y). * indicates a bonding position with another atom, and may also be a bonding position with a diamine unit.

[0112] In some embodiments, the "unit (Y) included in the diamine unit" may be a unit derived from a diamine or diisocyanate having an organic group (Y) but no hydrocarbon group (X). The "unit (Y) included in the tetracarboxylic acid unit" may be a unit derived from a tetracarboxylic dianhydride having an organic group (Y) but no hydrocarbon group (X).

[0113] In some embodiments, the "unit (Y) included in the diamine unit" may be a unit introduced into the polyamic acid using a diamine or diisocyanate having an organic group (Y) but no hydrocarbon group (X). The "unit (Y) included in the tetracarboxylic acid unit" may be a unit introduced into the polyamic acid using a tetracarboxylic dianhydride having an organic group (Y) but no hydrocarbon group (X).

[0114] (Diamines having an organic group (Y)) Diamines having an organic group (Y) can be represented, for example, by the following formula (Ay).

[0115]

[0116] In the formula, R ｙ R represents an organic group (Y). ｙ Examples include the group represented by formula (G16) to the group represented by formula (G18b).

[0117] Specific examples of diamines having an organic group (Y) include: diamines with 8 or fewer carbon atoms having a saturated aliphatic hydrocarbon group, such as 1,2-ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane; diamines with 8 or fewer carbon atoms having a saturated aliphatic hydrocarbon group, such as 1,4-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl)cyclohexane; Diamines having aromatic hydrocarbon groups such as 1,4-phenylenediamine, 4,4'-diaminodiphenyl ether, 4,4'-diamino-3,3'-dimethyldiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diamino-2,2'-dimethylbiphenyl, and having non-aromatic hydrocarbon groups with 8 or fewer carbon atoms.

[0118] (Diisocyanates having an organic group (Y)) Diisocyanates having an organic group (Y) can be represented, for example, by the following formula (Iy).

[0119]

[0120] In the formula, R ｙ R represents an organic group (Y). ｙ Examples include the group represented by formula (G16) to the group represented by formula (G18b).

[0121] Specific examples of diisocyanates having an organic group (Y) include compounds that have the same structure as the compounds shown above as examples of diamines, except that the amino group is replaced with an isocyanate group.

[0122] (Tetracarboxylic dianhydrides having an organic group (Y)) Tetracarboxylic dianhydrides having an organic group (Y) can be represented, for example, by the following formula (Cy).

[0123]

[0124] In the formula, Rｙ R represents an organic group (Y). ｙ Examples include the group represented by formula (G12) to the group represented by formula (G14a).

[0125] Specific examples of tetracarboxylic dianhydrides having an organic group (Y) are listed below. The "number of carbon atoms" below refers to the number of carbon atoms in the non-aromatic hydrocarbon group contained in the organic group (Y), and does not include the number of carbon atoms in the aromatic ring and carboxylic acid anhydride group. Tetracarboxylic dianhydrides with 8 or fewer carbon atoms having a saturated aliphatic hydrocarbon group, such as 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,5,6-hexanetetracarboxylic dianhydride; Tetracarboxylic dianhydrides with 8 or fewer carbon atoms having a saturated alicyclic hydrocarbon group, such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetracarboxylic dianhydride; Dianhydrides of tetracarboxylic acids having 8 or fewer carbon atoms and possessing aromatic hydrocarbon groups such as pyromellitic acid dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid anhydride, 3,4'-oxydiphthalic acid anhydride, bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)1,4-phenylene; Dianhydrides of tetracarboxylic acids having 8 or fewer carbon atoms and possessing aromatic heterocyclic compound groups such as pyromellitic acid dianhydride and thiophenetetracarboxylic acid dianhydride.

[0126] In some embodiments, unit (Y) includes a biphenyltetracarboxylic acid unit. The biphenyltetracarboxylic acid unit may be an atomic group obtained by removing two or four hydrogen atoms from biphenyltetracarboxylic acid.

[0127] [Structural Units] Polyamic acids contain structural units (S) having one diamine unit and one tetracarboxylic acid unit. Structural units (S) can be represented, for example, by the following formula (SA) or formula (SI). Polyamic acids contain structural units (SA) and may further contain structural units (SI).

[0128]

[0129] In the formula, R ｎａ and R ｃａ Each of these independently represents an organic group. The organic group may be a hydrocarbon group (X) or an organic group (Y).

[0130]

[0131] In the formula, R ｎｉ and R ｃｉ Each of these independently represents an organic group. The organic group may be a hydrocarbon group (X) or an organic group (Y).

[0132] Polyamic acids may contain other arbitrary structural units in addition to structural unit (S). The content of other arbitrary structural units in polyamic acids is, for example, 0.0 to 10.0 mol%, or 0.0 to 5.0 mol%, based on the total amount of all structural units contained in the polyamic acid. The content of structural unit (S) in polyamic acids is, for example, 90.0 to 100.0 mol%, or 95.0 to 100.0 mol%, based on the total amount of all structural units contained in the polyamic acid. Examples of other arbitrary structural units include structural units containing structures derived from trifunctional or more polyamines or structures derived from trifunctional or more polyisocyanates, structural units having amide bonds (also called amide groups), structural units having an imide group and an amide group, structural units having an amidoic acid group and an amide group, etc. These arbitrary structural units may or may not contain a hydrocarbon group (X).

[0133] [Homopolymers / Copolymers] Polyamic acid may be a homopolymer or a copolymer. A homopolymer may be a polymer containing only one type of structural unit. A copolymer may be a polymer containing two or more types of structural units. Examples of copolymers include random copolymers, alternating copolymers, block copolymers, or graft copolymers.

[0134] In some embodiments, the polyamic acid may be a homopolymer or copolymer comprising a structure represented by the following formula (PA). The copolymer may be a random copolymer.

[0135]

[0136] In the formula, R ｎａ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and R ｃａ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and n is a number of 2 or more. ｎａ They may be identical to each other, or they may be different in part or in whole. Two or more R ｃａ They may be identical to each other, or they may be different in part or in whole. Two or more R ｎａ and 2 or more R ｃａ At least one selected from the group comprises a hydrocarbon group (X).

[0137] For example, polyamic acid may be a homopolymer containing a structure represented by the following formula (PA-1).

[0138]

[0139] In the formula, R ｘ represents a hydrocarbon group (X), and R ｙ R represents an organic group (Y), and n is a number greater than or equal to 2. ｘ These are identical to each other, and there are two or more R ｙ They are identical to each other.

[0140] [Polyamic Acid Block / Polyimide Block Copolymer] In some embodiments, the polyamic acid may be a block copolymer comprising a polyamic acid block (BA) and a polyimide block (BI). The polyamic acid block (BA) may be a block that becomes a different polyimide block (BI-A) from the polyimide block (BI) by ring closure of the amidic acid bond. The block copolymer may further contain any block different from the polyamic acid block (BA) and the polyimide block (BI). The block copolymer may contain one or more of any blocks.

[0141] In block copolymers, either only the polyimide block (BI) or the polyamic acid block (BA) contains unit (X), or both the polyimide block (BI) and the polyamic acid block (BA) contain unit (X). Each polyimide block (BI) and the polyamic acid block (BA) may independently contain one or more types of unit (X). If the block copolymer contains unit (Y), either only the polyimide block (BI) or the polyamic acid block (BA) may contain unit (Y), or both the polyimide block (BI) and the polyamic acid block (BA) may contain unit (Y). Each polyimide block (BI) and the polyamic acid block (BA) may independently contain one or more types of unit (Y).

[0142] According to some embodiments, a polyimide with a low coefficient of thermal expansion can be obtained by using a block copolymer of polyamic acid. This is thought to be because the polyimide molecules are more easily oriented when the block copolymer contains both polyimide blocks (BI) and polyamic acid blocks (BA). If the coefficient of thermal expansion of polyimide can be reduced to approach that of metals, for example, warping of metal-clad laminates can be suppressed. Generally, polyimides tend to exhibit low dielectric constant and low dielectric loss tangent as the free volume within the molecule increases. On the other hand, polyimides tend to have a lower coefficient of thermal expansion as the amount of rigid structures within the molecule increases. From the viewpoint of achieving both low dielectric constant and low dielectric loss tangent and a low coefficient of thermal expansion in polyimide, the polyamic acid may, for example, have blocks containing unit (X) and blocks not containing unit (X).

[0143] (Polyamic acid block (BA)) The inclusion of a polyamic acid block in the block copolymer tends to result in good solubility in solvents. In this disclosure, the polyamic acid block (BA) has a content of amide acid groups relative to the total of amide acid groups and imide groups that is, for example, more than 50 mol%, 80 mol% or more, or 90 mol% or more. The upper limit of the content of amide acid groups may be 100 mol%. The content can be measured by a Fourier transform infrared spectrophotometer (FTIR).

[0144] The number-average molecular weight of the polyamic acid block (BA) is, for example, 500 or more, 1,000 or more, 3,000 or more, or 6,000 or more. The number-average molecular weight of the polyamic acid block (BA) is, for example, 30,000 or less, 25,000 or less, 20,000 or less, or 10,000 or less. When the number-average molecular weight is 500 or more, good film-forming properties tend to be easily obtained. When the number-average molecular weight is 30,000 or less, the composition containing the block copolymer and solvent tends to be easily adjusted to a viscosity suitable for coating. The number-average molecular weight of the polyamic acid block (BA) is, for example, 500 to 30,000, 1,000 to 25,000, 3,000 to 20,000, or 6,000 to 10,000. In this disclosure, the number-average molecular weight can be measured by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene. Specifically, it can be obtained by the method described in the examples.

[0145] The polyamic acid block (BA) may be a linear polymer block or a branched polymer block, and is preferably a linear polymer block.

[0146] In the polyamic acid block (BA), the content of unit (X) is, for example, 0.0 to 80.0 mol%, 0.0 to 50.0 mol%, or 0.0 to 30.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units. In the polyamic acid block (BA), the content of unit (Y) is, for example, 20.0 to 100.0 mol%, 50.0 to 100.0 mol%, or 70.0 to 100.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units. In particular, when the content of unit (Y) containing at least one of an aromatic hydrocarbon group and an aromatic heterocyclic compound group is 20.0 mol% or more, polyimides with good mechanical strength and heat resistance are easily obtained.

[0147] The total amount of diamine units and tetracarboxylic acid units contained in the polyamic acid block (BA) in the block copolymer (hereinafter referred to as "polyamic acid block (BA) content") is greater than 0 mol% and less than 100 mol%, based on the total amount of diamine units and tetracarboxylic acid units contained in the block copolymer. The polyamic acid block (BA) content is, for example, greater than 0 mol%, 30 mol% or more, 60 mol% or more, or 90 mol% or more. The higher the polyamic acid block (BA) content, the more easily the block copolymer dissolves in organic solvents. The polyamic acid block (BA) content is, for example, less than 100 mol%, 70 mol% or less, 40 mol% or less, or 10 mol% or less. The polyamic acid block (BA) content is, for example, 10 to 90 mol%, 20 to 80 mol%, 30 to 70 mol%, 50 to 70 mol%, or 60 to 70 mol%.

[0148] (Polyimide Block (BI)) The presence of a polyimide block (BI) in the block copolymer prevents exchange reactions or crosslinking from occurring when obtaining the block copolymer or when ring-closing the amidic acid groups. In this disclosure, the polyimide block (BI) has an imide group content of, for example, more than 50 mol%, 80 mol% or more, or 90 mol% or more relative to the total of amidic acid groups and imide groups. The upper limit of the imide group content may be 100 mol%. In this disclosure, the content can be measured by FTIR.

[0149] The number-average molecular weight of polyimide blocks (BI) is, for example, 500 or more, 1,000 or more, 2,000 or more, or 3,000 or more. The number-average molecular weight of polyimide blocks (BI) is, for example, 10,000 or less, 8,000 or less, 7,000 or less, or 5,000 or less. When the number-average molecular weight is 500 or more, it is easier to obtain polyimides with a low coefficient of expansion. When the number-average molecular weight is 10,000 or less, it is easier to ensure the solubility of the block copolymer in the solvent. The number-average molecular weight of polyimide blocks (BI) is, for example, 500 to 10,000, 1,000 to 8,000, 2,000 to 7,000, or 3,000 to 5,000.

[0150] The polyimide block (BI) may be a linear polymer block or a branched polymer block, and is preferably a linear polymer block.

[0151] In polyimide blocks (BI), the content of unit (X) is, for example, 0.0 to 70.0 mol%, 10.0 to 60.0 mol%, or 20.0 to 50.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units. In particular, when the content of unit (X) is 20.0 mol% or more, polyimides with low dielectric constant and low dielectric loss tangent are easily obtained. In polyimide blocks (BI), the content of unit (Y) is, for example, 30.0 to 100.0 mol%, 40.0 to 90.0 mol%, or 50.0 to 80.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units. In particular, when the content of unit (Y) containing at least one of an aromatic hydrocarbon group and an aromatic heterocyclic compound group is 30.0 mol% or more, polyimides with good mechanical strength and heat resistance are easily obtained.

[0152] The total amount of diamine units and tetracarboxylic acid units contained in the polyimide block (BI) in the block copolymer (hereinafter referred to as "polyimide block (BI) content") is greater than 0.0 mol% and less than 100.0 mol%, based on the total amount of diamine units and tetracarboxylic acid units contained in the block copolymer. For example, the polyimide block (BI) content is greater than 0.0 mol%, 30.0 mol% or more, 60.0 mol% or more, or 90.0 mol% or more. The higher the polyimide block (BI) content, the more likely it is to prevent exchange reactions or crosslinking when obtaining the block copolymer or when cyclizing the amidic acid group. For example, the polyimide block (BI) content is less than 100.0 mol%, 70.0 mol% or less, 40.0 mol% or less, or 10.0 mol% or less. The polyimide block (BI) content is, for example, 10-90 mol%, 20-80 mol%, 30-70 mol%, 30-50 mol%, or 30-40 mol%.

[0153] (Example of block copolymer) For example, polyamic acid may be a block copolymer comprising a block having a structure represented by the following formula (BA) and a block having a structure represented by the following formula (BI). Block (BA) may be a homopolymer block or a copolymer block. Block (BI) may be a homopolymer block or a copolymer block. The copolymer block may be a random copolymer block.

[0154]

[0155] In formula (BA), R ｎａ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and R ｃａ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and m represents a number of 2 or more. ｎａ They may be identical to each other, or they may be different in part or in whole. Two or more R ｃａ They may be identical to each other, or they may be different in part or in whole. In formula (BI), R ｎｉ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and R ｃｉ Each of these independently represents a hydrocarbon group (X) or an organic group (Y), and n is a number of 2 or more. ｎｉ They may be identical to each other, or they may be different in part or in whole. Two or more R ｃｉ They may be identical to each other, or they may be partially or completely different from each other. Two or more R ｎａ , 2 or more R ｃａ , 2 or more R ｎｉ , and 2 or more R ｃｉ At least one selected from the group comprises a hydrocarbon group (X).

[0156] For example, the polyamic acid may be a block copolymer comprising a block having a structure represented by the following formula (BA-1) and a block having a structure represented by the following formula (BI-1).

[0157]

[0158] In formula (BA-1), R ｙａ Each of these independently represents an organic group (Y), and Rｙｃ each independently represents an organic group (Y), and m represents a number of 2 or more. Two or more R ｙａ may be the same as each other, or some or all of them may be different from each other. Two or more R ｙｃ may be the same as each other, or some or all of them may be different from each other. In formula (BI-1), R ｘ each independently represents a hydrocarbon group (X), and R ｙ each independently represents an organic group (Y), and n is a number of 2 or more. Two or more R ｘ may be the same as each other, or some or all of them may be different from each other. Two or more R ｙ may be the same as each other, or some or all of them may be different from each other.

[0159] For example, block (BA-1) is a homopolymer block. In formula (BA-1), R ｙａ represents an organic group (Y), and R ｙｃ represents an organic group (Y), and two or more R ｙａ are the same as each other, and two or more R ｙｃ may be the same as each other. For example, block (BI-1) is a homopolymer block. In formula (BI-1), R ｘ represents a hydrocarbon group (X), and R ｙ represents an organic group (Y), and two or more R ｘ are the same as each other, and two or more R ｙ may be the same as each other.

[0160] For example, block (BA-1) is a random copolymer block. In formula (BA-1), R ｙａ represents an organic group (Y), and R ｙｃ represents an organic group (Y), and two or more R ｙａ may be the same as each other, or some or all of them may be different from each other, and two or more R ｙｃ may be the same as each other, or some or all of them may be different from each other. For example, block (BI-1) is a random copolymer block. In formula (BI-1), R ｘ represents a hydrocarbon group (X), Y ｙ represents an organic group (Y), and two or more R ｘThey may be identical to each other, or they may be partially or completely different from each other, and there may be two or more Y ｙ They may be identical to each other, or they may be different in part or in whole.

[0161] For example, block (BA-1) is a random copolymer block, and in formula (BA-1), R ｙａ represents an organic group (Y), R ｙｃ represents an organic group (Y), and 2 or more R ｙａ They may be identical to each other, or they may be partially or completely different from each other, and there may be two or more R ｙｃ They may be identical to each other, or they may be different in part or in whole. For example, block (BI-1) is a homopolymer block, and in formula (BI-1), R ｘ represents a hydrocarbon group (X), and Y ｙ represents an organic group (Y), and 2 or more R ｘ They are identical to each other, and there are two or more Y ｙ They may be identical to each other.

[0162] [Molecular Weight of Polyamic Acid] The number-average molecular weight of polyamic acid is, for example, 5,000 or more, 10,000 or more, or 20,000 or more. The number-average molecular weight of polyamic acid is, for example, 100,000 or less, 50,000 or less, or 30,000 or less. When the number-average molecular weight is 5,000 or more, good film-forming properties tend to be easily obtained. When the number-average molecular weight is 100,000 or less, the composition containing polyamic acid and solvent tends to be easily adjusted to a viscosity suitable for coating. The number-average molecular weight of polyamic acid is, for example, 5,000 to 100,000, 10,000 to 50,000, or 20,000 to 30,000.

[0163] The weight-average molecular weight of polyamic acid is, for example, 10,000 or more, 30,000 or more, or 60,000 or more. The number-average molecular weight of polyamic acid is, for example, 700,000 or less, 100,000 or less, or 70,000 or less. When the weight-average molecular weight is 5,000 or more, good film-forming properties tend to be easily obtained. When the weight-average molecular weight is 100,000 or less, the composition containing polyamic acid and solvent tends to be easily adjusted to a viscosity suitable for coating. The weight-average molecular weight of polyamic acid is, for example, 10,000 to 150,000, 30,000 to 100,000, or 40,000 to 70,000.

[0164] When the polyamic acid is a block copolymer, for example, the number-average molecular weight of the polyimide block (BI) is smaller than the number-average molecular weight of the polyamic acid block (BA). Preferably, the block copolymer comprises a polyimide block (BI) and a polyamic acid block (BA) with a number-average molecular weight larger than that of the polyimide block (BI). When the number-average molecular weight of the polyimide block (BI) is smaller than that of the polyamic acid block (BA), the block copolymer tends to be easier to synthesize and the solubility of the block copolymer tends to be ensured. Including a polyamic acid block (BA) with a number-average molecular weight larger than that of the polyimide block (BI) tends to facilitate the synthesis of a block copolymer with a sufficient number-average molecular weight.

[0165] [Applications] In some embodiments, polyimides with low dielectric constant, low dielectric loss tangent, and low thermal expansion coefficient can be obtained using polyamic acid. The obtained polyimides can be used in various electronic and mechanical components, such as displays, solar cells, touch panels, organic EL lighting, millimeter-wave radar, high-frequency antennas, high-speed transmission substrates, and transmission lines and cables. Of these, they can be preferably used in equipment used in the high-frequency range, such as millimeter-wave radar, high-frequency antennas, high-speed transmission substrates, and high-frequency transmission lines and cables. A millimeter-wave radar is a radar that emits millimeter waves to an object and receives reflected waves from the object to detect the object. Automotive millimeter-wave radars mounted on vehicles are applied to collision avoidance systems, autonomous driving systems, etc. In high-frequency antennas, there is a demand for high frequency and high-speed transmission for high-speed communication in communication equipment, etc., and when a high-frequency antenna is housed in a housing in small communication equipment, a material with even lower dielectric constant and low dielectric loss tangent is desired. Examples of high-speed transmission substrates include printed circuit boards and antenna substrates. Examples of high-frequency transmission line cables include coaxial cables and flat cables.

[0166] It is preferable that the polyimide obtained using the polyamic acid satisfies one or more of the following: relative permittivity, dielectric loss tangent, thermal expansion coefficient, glass transition temperature, and tensile modulus. Particularly preferable is that the polyimide obtained using the polyamic acid satisfies the tensile modulus described later.

[0167] <Method for Producing Polyamic Acid> In some embodiments, the method for producing polyamic acid includes obtaining polyamic acid (PA) using a diamine or diisocyanate and a tetracarboxylic dianhydride, wherein at least one selected from the group consisting of diamine or diisocyanate and tetracarboxylic dianhydride used to obtain the polyamic acid (PA) has a unit (X). According to this method, the polyamic acid of the above-described embodiments can be easily produced.

[0168] In some embodiments, when the polyamic acid is a block copolymer, the method for producing the block copolymer includes: obtaining polyimide (PI) using a diamine or diisocyanate and a tetracarboxylic dianhydride; obtaining polyamic acid (PA) using a diamine and a tetracarboxylic dianhydride; and obtaining a block copolymer using the polyimide (PI) and the polyamic acid (PA), wherein at least one selected from the group consisting of the diamine or diisocyanate and tetracarboxylic dianhydride used to obtain the polyimide (PI), and the diamine and tetracarboxylic dianhydride used to obtain the polyamic acid (PA), has unit (X). According to this production method, polyamic acid which is a block copolymer of the embodiments described above can be easily produced.

[0169] For the synthesis of polyimides (PI) and polyamic acids (PA), monomers such as the aforementioned diamines, diisocyanates, tetracarboxylic dianhydrides, polyamines, polyisocyanates, dicarboxylic acid compounds, and tricarboxylic acid compounds can be used.

[0170] The monomer reaction can be carried out by solution polymerization. Suitable solvents for the reaction include, for example, polar solvents such as N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), 3-methoxy-N,N-dimethylpropanamide (MPA), N,N'-dimethylformamide, N,N'-dimethylpropylene urea [1,3-dimethyl-3,4,5,6-tetrahydropyridimine-2(1H)-one], dimethyl sulfoxide, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and sulfolane; aromatic hydrocarbon solvents such as xylene and toluene; and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone. The solvent preferably contains at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), and 3-methoxy-N,N-dimethylpropanamide (MPA), and more preferably contains at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), and 3-methoxy-N,N-dimethylpropanamide (MPA).

[0171] The amount of solvent used is preferably 100 to 600 parts by mass, and more preferably 200 to 400 parts by mass, per 100 parts by mass of the total amount of monomers. Using 100 parts by mass or more of solvent allows each monomer to react homogeneously. Using 600 parts by mass or less of solvent can accelerate the polymerization reaction. Furthermore, using a small amount of solvent allows for the production of a polyimide (PI) or polyamic acid (PA)-containing solution with a high concentration of polyimide (PI) or polyamic acid (PA).

[0172] The reaction temperature when synthesizing polyamic acids using monomers is not particularly limited. The reaction temperature may be, for example, 10 to 50°C or 20 to 40°C. The reaction time may be, for example, 30 minutes to 24 hours, 1 to 12 hours, or 3 to 6 hours. The reaction product can be sampled to measure the number-average molecular weight, the concentration of remaining amino groups or isocyanate groups, etc., and the reaction time can be adjusted to obtain the desired reaction product.

[0173] The temperature used to obtain polyimide using polyamic acid (i.e., imidation) is not particularly limited. The imidation temperature may be, for example, 120 to 200°C or 160 to 180°C. The reaction time may be, for example, 30 minutes to 24 hours, 1 to 12 hours, or 3 to 6 hours. The reaction product can be sampled to measure the number-average molecular weight, the concentration of remaining amidic acid groups, etc., and the reaction time can be adjusted to obtain the desired reaction product.

[0174] When obtaining block copolymers, it is preferable that the polymer chains of polyimide (PI) have carboxylic acid anhydride groups at their ends and the polymer chains of polyamic acid (PA) have amino groups at their ends, as this facilitates synthesis. The ratio of diamine or diisocyanate to tetracarboxylic dianhydride used to obtain polyimide (PI) is such that, based on the diamine or diisocyanate, the tetracarboxylic dianhydride is, for example, greater than 1.00 mol%, 1.05 mol% or more, or 1.10 mol% or more. The ratio of diamine to tetracarboxylic dianhydride used to obtain polyamic acid (PA) is such that, based on the diamine, the tetracarboxylic dianhydride is, for example, less than 1.00 mol%, 0.98 mol% or less, or 0.97 mol% or less.

[0175] Block copolymers can be synthesized using polyimide (PI) and polyamic acid (PA). Any additional polymer may be used in the synthesis. The reaction between polyimide (PI) and polyamic acid (PA) can be carried out by solution polymerization. The solvents mentioned above can be used as the solvent during the reaction. The reaction temperature is not particularly limited. From the viewpoint of allowing the reaction to proceed sufficiently, the reaction temperature may be, for example, 20-100°C, 30-80°C, or 40-70°C. The reaction time may be, for example, 30 minutes to 24 hours, 1-12 hours, or 3-6 hours. The reaction product can be sampled, and the number-average molecular weight, the concentration of remaining amino groups or isocyanate groups, etc., can be measured, and the reaction time can be adjusted to obtain the desired reaction product.

[0176] <Printed circuit board material, antenna substrate material, and transmission line cable material> In some embodiments, the printed circuit board material, antenna substrate material, and transmission line cable material contain the polyamic acid of any of the embodiments described above. Polyamic acid can be preferably used as a printed circuit board material, antenna substrate material, and transmission line cable material because the polyimide obtained using it has a low dielectric constant, a low dielectric loss tangent, and a low coefficient of thermal expansion.

[0177] In some embodiments, the printed circuit board material, antenna substrate material, and transmission line cable material may further contain any components such as thermoplastic resin, organic filler, flame retardant, flame retardant aid, ultraviolet absorber, peroxide, antioxidant, photopolymerization initiator, fluorescent whitening agent, and adhesion improver. The content of any component can be within a range suitable for the application of the printed circuit board material, antenna substrate material, and transmission line cable material. The content of any component is, for example, 0 to 50% by mass, 0 to 30% by mass, or 0 to 10% by mass, based on the mass of the printed circuit board material, antenna substrate material, and transmission line cable material. The content of polyamic acid is, for example, 50 to 100% by mass, 70 to 100% by mass, or 90 to 100% by mass, based on the mass of the printed circuit board material, antenna substrate material, and transmission line cable material.

[0178] <Composition> In some embodiments, the composition contains a polyamic acid, a printed circuit board material, an antenna substrate material, or a transmission line cable material according to any of the embodiments described above, and a solvent. Examples of solvents included in the composition include the reaction solvents described above that can be used in the synthesis of polyamic acid. The solvent preferably contains at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), and 3-methoxy-N,N-dimethylpropanamide (MPA), and more preferably contains at least one selected from the group consisting of N-ethyl-2-pyrrolidone (NEP), γ-butyrolactone (GBL), and 3-methoxy-N,N-dimethylpropanamide (MPA). The composition can preferably be used as a printed circuit board composition, an antenna substrate composition, or a transmission line cable material.

[0179] The polyamic acid content can be set to a range suitable for the intended use of the composition. The polyamic acid content is, for example, 5 to 50% by mass, 8 to 40% by mass, or 10 to 30% by mass, based on the mass of the composition.

[0180] The composition may further contain any components such as polyamide, polyethersulfone, acrylic polymer, epoxy compound, isocyanate compound, melamine compound, filler, defoamer, preservative, and surfactant. The composition can be produced, for example, by mixing and stirring a polyamic acid and a solvent with any components used as needed. The composition may be, for example, a composition that does not contain a photoacid generator, a composition that does not contain a crosslinking agent, a composition that does not contain a photosensitizer, a composition that does not contain a photopolymerization initiator, etc. The composition may be a thermosetting composition or a photosensitive composition. The composition may be a non-photosensitive composition from the viewpoint of having excellent storage stability and being able to form polyimide materials in the shape of films, layers, membranes, etc., by a simple method. According to some embodiments, the composition may be a composition except in the case that it contains at least one selected from the group consisting of a photoacid generator, a crosslinking agent, a photosensitizer, and a photopolymerization initiator.

[0181] <Polyimide> In some embodiments, polyimide can be obtained using the polyamic acid of any of the embodiments described above, or the composition of any of the embodiments described above. For example, polyimide can be obtained by cyclizing the amide acid groups contained in the polyamic acid and converting them to imide groups (in this disclosure, this conversion may be referred to as "imidization"). The method of imidization is not particularly limited. A method of heating the polyamic acid is preferred because it is simple. The heating temperature is, for example, 250 to 400°C.

[0182] When the polyamic acid is a block copolymer, the polyimide obtained from the block copolymer includes a polyimide block (BI) and a polyimide block (BI-A) which is a block in which the polyamic acid block (BA) is imidized. The polyimide block (BI) and the polyimide block (BI-A) may be different blocks. Due to its block structure, the polyimide exhibits a low coefficient of thermal expansion. Due to the presence of hydrocarbon groups (X), the polyimide exhibits a low dielectric constant and a low dielectric loss tangent. Furthermore, due to the presence of hydrocarbon groups (X), the polyimide tends to exhibit a low water absorption rate.

[0183] The relative permittivity of polyimide is, for example, 3.5 or less, 3.0 or less, or 2.8 or less, from the viewpoint of obtaining excellent insulating properties. The relative permittivity of polyimide is not particularly limited, but for example, it is 2.0 or more. The relative permittivity (Dk) can be measured using a polyimide film (for example, 25 μm thick) with the cavity resonator method (TE mode) under the conditions of a frequency of 10 GHz and a measurement temperature of 25°C. The relative permittivity (Dk) may be a value obtained by measuring after the polyimide film has been thoroughly dried. Alternatively, the relative permittivity (Dk) may be a value obtained after immersing the polyimide film in water, for example, a value obtained by measuring immediately after immersion in water for 24 hours in an atmosphere of 25°C.

[0184] The dielectric loss tangent of polyimide is, for example, 0.0100 or less, 0.0050 or less, or 0.0020 or less, from the viewpoint of suppressing transmission loss. The dielectric loss tangent of polyimide is not particularly limited, but for example, it is 0.0005 or more. The dielectric loss tangent (Df) can be measured using a polyimide film (for example, 25 μm thick) with the cavity resonator method (TE mode) under the conditions of a frequency of 10 GHz and a measurement temperature of 25°C. The dielectric loss tangent (Df) may be a value obtained by measuring after the polyimide film has been thoroughly dried. Alternatively, the dielectric loss tangent (Df) may be a value obtained after immersing the film in water, for example, a value obtained by measuring immediately after immersion in water for 24 hours in an atmosphere of 25°C.

[0185] The coefficient of thermal expansion (CTE) of polyimide is, for example, 100 ppm / K or less, 80 ppm / K or less, 50 ppm / K or less, 40 ppm / K or less, 30 ppm / K or less, or 20 ppm / K or less, from the viewpoint of obtaining excellent heat resistance. The coefficient of thermal expansion of polyimide is, for example, -5 ppm / K or more, 0 ppm / K or more, 10 ppm / K or more, or 15 ppm / K or more, considering that the polyimide film is used by being bonded to other materials. The coefficient of thermal expansion (ppm / K) can be determined by converting the average linear thermal expansion coefficient (ppm / °C) measured at 30 to 200°C using a thermomechanical analyzer under the condition of a heating rate of 10°C / min with a polyimide film (for example, 25 μm thick).

[0186] The glass transition temperature (Tg) of polyimide is, for example, 200°C or higher, 250°C or higher, or 300°C or higher, from the viewpoint of the heat resistance of the molded article. There are no particular restrictions on the glass transition temperature (Tg) of polyimide, but for example, it is 600°C or lower. The glass transition temperature can be determined as the temperature (°C) corresponding to the inflection point in the linear thermal expansion coefficient curve between 30 and 200°C, measured using a polyimide film (for example, 25 μm thick) with a thermomechanical analyzer at a heating rate of 10°C / min.

[0187] The tensile modulus of polyimide is, for example, 4.5 GPa or less, 4.0 GPa or less, 3.5 GPa or less, or 3.0 GPa or less, from the viewpoint of suppressing warping of metal-clad laminates. The tensile modulus of polyimide is, for example, 0.5 GPa or more, 0.7 GPa or more, 1.0 GPa or more, 2.0 GPa or more, or 3.0 GPa or more, considering the mechanical strength of the polyimide film. A tensile test is performed using a polyimide film (for example, 25 μm thick) under the measurement conditions of a test speed of 5 mm / min, a chuck distance of 20 mm, and a measurement temperature of room temperature (25°C). Young's modulus (MPa) is calculated from the slope of the elastic deformation region at the initial stage of stress rise, and the obtained value is taken as the tensile modulus (MPa). Other detailed conditions and calculation methods can be carried out in accordance with the international standard ISO 5271 (1993).

[0188] More specifically, the relative permittivity, dielectric loss tangent, thermal expansion coefficient, glass transition temperature, and tensile modulus of polyimide can be measured, respectively, by preparing a polyimide film according to the method described in the Examples and then using the prepared polyimide film according to the method described in the Examples.

[0189] <Metal-clad laminates> In some embodiments, metal-clad laminates are obtained using the polyamic acid, printed circuit board material, antenna substrate material, or composition of any of the embodiments described above. Metal-clad laminates can be used to obtain printed circuit boards or antenna substrates. Metal-clad laminates may be flexible or rigid substrates. A metal-clad laminate has a layer containing polyimide (hereinafter referred to as the "polyimide layer") and a metal layer in contact with the polyimide layer. The metal-clad laminate may have the metal layer on only one side of the polyimide layer, or on both sides of the polyimide layer. A metal-clad laminate may have an adhesive layer between the polyimide layer and the metal layer. Due to the good adhesion of the polyimide layer, a metal-clad laminate does not need to have an adhesive layer between the polyimide layer and the conductive layer. If the metal-clad laminate has the metal layer on only one side of the polyimide layer, the metal-clad laminate may have the adhesive layer on the other side of the polyimide layer. The polyimide layer may consist of a single polyimide layer or may contain multiple polyimide layers. When the metal-clad laminate contains multiple polyimide layers, the metal-clad laminate may have metal layers, adhesive layers, etc., between the polyimide layers.

[0190] The material of the metal layer may be, for example, copper, aluminum, gold, silver, or alloys thereof. The metal layer is preferably copper foil. The polyimide layer has high adhesion even to copper foil with low surface roughness, such as unroughened copper foil or low-roughness copper foil. Transmission loss can be suppressed by using copper foil with low surface roughness. The copper foil may have a surface roughness (ten-point average roughness, Rz) according to JIS B 0601:2013, for example. ＪＩＳThe surface roughness is 3.0 μm or less, 2.0 μm or less, or 1.0 μm or less. The lower limit of the surface roughness is not particularly limited, but for example, it is 0.5 μm or more. An example of a metal-clad laminate is a flexible copper-clad laminate (FCCL). A metal-clad laminate obtained using the polyamic acid, printed circuit board material, antenna substrate material, or composition of any of the embodiments described above has suppressed curling and good handling properties even when manufactured by a roll-to-roll method. Electronic components or mechanical components using metal-clad laminates with suppressed warping have excellent dimensional stability, thus preventing defects such as delamination after mounting.

[0191] <Printed Circuit Boards and Antenna Substrates> In some embodiments, the printed circuit board is obtained using the polyamic acid, material, or composition of any of the embodiments described above, or contains the polyimide of any of the embodiments described above. The printed circuit board according to the embodiment of the present invention has low transmission loss and excellent dimensional stability. The printed circuit board may be an antenna substrate.

[0192] Examples of printed circuit boards include printed wiring boards and printed circuit boards. Examples of printed circuit boards include flexible boards and rigid boards. Examples of printed circuit boards include single-sided boards, double-sided boards, and multilayer boards. For example, the materials, protective films, insulating layers, etc., of these boards may be obtained using polyamic acid or may include polyimide, etc.

[0193] Examples of flexible substrates include substrates comprising a base film, wherein the base film is obtained using polyamic acid or contains polyimide, etc. Other examples of flexible substrates include substrates comprising a base film and a heat-resistant insulating layer formed on the base film, wherein at least the heat-resistant insulating layer is obtained using polyamic acid or contains polyimide, etc.

[0194] According to some embodiments, distortion of the pattern after the formation of the wiring pattern or circuit pattern can be reduced, and component mounting can be performed in the correct position. Therefore, handling in the manufacturing process is simplified, and substrates with precise wiring patterns or circuit patterns can be reliably produced. Printed circuit boards can be used for communication modules, memory modules, camera modules, sensor modules, and the like.

[0195] <Transmission Line Cable> In some embodiments, the transmission line cable is obtained using the polyamic acid, material, or composition of any of the embodiments described above, or contains the polyimide of any of the embodiments described above. The transmission line cable according to the embodiments of the present invention has low transmission loss and excellent dimensional stability.

[0196] Examples of transmission line cables include coaxial cables and flat cables. A coaxial cable, for example, comprises an inner conductor, an insulating layer covering the outer circumference of the inner conductor, an outer conductor located on the outer circumference of the insulating layer, and an insulating layer covering the outer circumference of the outer conductor, wherein at least one of the insulating layers is obtained using polyamic acid or contains polyimide, etc.

[0197] <Examples of Embodiments> (1) A polyamic acid comprising diamine units and tetracarboxylic acid units, wherein at least one selected from the group consisting of the diamine units and the tetracarboxylic acid units comprises a unit (X) having a group (X) which comprises at least one non-aromatic hydrocarbon group and the total number of carbon atoms of the at least one non-aromatic hydrocarbon group is 9 or more, and the content of the unit (X) is 12.0 mol% or more based on the total amount of the diamine units and the tetracarboxylic acid units. (2) A polyamic acid comprising unit (N) and unit (C), wherein unit (N) and unit (C) comprise at least one selected from the group consisting of unit (NX) and unit (CX), and the total content of unit (NX) and unit (CX) is 12.0 mol% or more based on the total amount of unit (N) and unit (C). Either the content of unit (NX) or the content of unit (CX) may be 0.0 mol%. (3) A polyamic acid comprising units derived from diamine or diisocyanate and units derived from tetracarboxylic acid, wherein the units derived from diamine or diisocyanate and the units derived from tetracarboxylic acid each comprise at least one selected from the group consisting of "units derived from diamine or diisocyanate having a hydrocarbon group (X)" and "units derived from tetracarboxylic dianhydride having a hydrocarbon group (X)", and the total content of the "units derived from diamine or diisocyanate having a hydrocarbon group (X)" and the "units derived from tetracarboxylic dianhydride having a hydrocarbon group (X)" is 12.0 mol% or more based on the total amount of units derived from diamine or diisocyanate and units derived from tetracarboxylic acid. Either the content of the "units derived from diamine or diisocyanate having a hydrocarbon group (X)" or the content of the "units derived from tetracarboxylic dianhydride having a hydrocarbon group (X)" may be 0.0 mol%. (4) The polyamic acid according to any one of (1) to (3) above, which is a block copolymer having a polyamic acid block and a polyimide block. (5) A polyamic acid according to any one of (1) to (4) above, wherein the tensile modulus is 4.0 GPa or less.(6) The polyamic acid according to any one of (1) to (5), wherein the unit (X) comprises a unit (X) having a group (X) having 28 or more carbon atoms. (7) The polyamic acid according to any one of (1) to (6), wherein the unit (X) comprises a dimeramine unit. (8) The polyamic acid according to any one of (1) to (7), wherein the diamine unit and the tetracarboxylic acid unit further comprises a unit (Y) having an organic group (Y) and not having the group (X). (9) The polyamic acid according to any one of (1) to (8), wherein the unit (Y) comprises a 3,3',4,4'-biphenyltetracarboxylic acid unit. (10) The polyamic acid according to any one of (1) to (9), wherein the content of the unit (X) is 20.0 mol% or more based on the total amount of the diamine unit and the tetracarboxylic acid unit. (11) A polyamic acid according to any one of (1) to (10), wherein the tensile modulus is 1.0 GPa or more. (12) A polyamic acid according to any one of (1) to (11), wherein the diamine unit is a unit represented by formula (N) and the tetracarboxylic acid unit is a unit represented by formula (C). (13) A polyamic acid according to any one of (1) to (12), wherein the diamine unit is a unit derived from at least one compound selected from the group consisting of diamines and diisocyanates, and the tetracarboxylic acid unit is a unit derived from a tetracarboxylic dianhydride. (14) A printed circuit board material containing the polyamic acid according to any one of (1) to (13). (15) An antenna substrate material containing the polyamic acid according to any one of (1) to (13). (16) A transmission line cable material containing the polyamic acid according to any one of (1) to (13). (17) A composition containing the polyamic acid described in any of (1) to (13) above and a solvent. (18) A polyimide obtained using the polyamic acid described in any of (1) to (13) above or the composition described in (17). (19) A printed circuit board obtained using the polyamic acid described in any of (1) to (13) above, the printed circuit board material described in (14) above, or the composition described in (17) above.(20) An antenna substrate obtained using the polyamic acid described in any of (1) to (13) above, the antenna substrate material described in (15) above, or the composition described in (17) above. 7 (21) A transmission line cable obtained using the polyamic acid described in any of (1) to (13) above, the transmission line cable material described in (16) above, or the composition described in (17) above.

[0198] Embodiments of the present invention will be specifically described by reference to examples. Embodiments of the present invention are not limited to the following examples.

[0199] <Synthesis of Polyimide (PI) and Polyamic Acid (PA)> [Polyimide (PI-3)] 41.06 g (0.0767 mol) of dimeramine ("PRIAMINE 1075", Croda Japan Co., Ltd., containing the dimeramine represented by the following formula) (hereinafter referred to as "DDA") was dissolved in 233.35 g of dimethylacetamide and 35.00 g of xylene to obtain a diamine solution. 31.57 g (0.0980 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (hereinafter referred to as "BTDA") was added to the diamine solution and the reaction was carried out until a clear solution was obtained. The reaction was carried out by stirring the solution at 50°C or below for more than 1 hour. Thereafter, a dehydration thermal imidation reaction was carried out with the clear solution while stirring at 180°C for more than 4 hours to obtain a polyimide (PI-3) solution (varnish) having an acid anhydride structure derived from BTDA at the end.

[0200]

[0201] [Polyimides (PI-1), (PI-2), (PI-4) to (PI-8)] Solutions of polyimides (PI-1), (PI-2), (PI-4) to (PI-8) were obtained in the same manner as for polyimide (PI-3), except that the diamines and tetracarboxylic dianhydrides shown in Table 2 were used.

[0202] [Polyamic Acid (PA-3)] 39.89 g (0.188 mol) of 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter referred to as "mTB") was dissolved in 371.65 g of dimethylacetamide to obtain a diamine solution. 47.48 g (0.161 mol) of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter referred to as "BPDA") was added to the diamine solution and reacted to obtain a solution (varnish) of polyamic acid (PA-3) having an amine structure derived from mTB at its terminals. The reaction was carried out by stirring the solution at a temperature of 50°C or below for at least 8 hours.

[0203] [Polyamic acids (PA-1), (PA-2), (PA-4) to (PA-8)] Solutions of polyamic acids (PA-1), (PA-2), (PA-4) to (PA-8) were obtained in the same manner as for polyamic acid (PA-3), except that the diamines and tetracarboxylic dianhydrides shown in Table 2 were used, and dimethylacetamide and N-methyl-2-pyrrolidone were used as solvents.

[0204] <Synthesis of Block Copolymer (Blocked Polyamido Acid Imide)> [Example 3] 340.99 g of a solution of polyimide (PI-3) and 459.01 g of a solution of polyamic acid (PA-3) were mixed and reacted to obtain a varnish of blocked polyamido acid imide (polyimide precursor). The reaction was carried out by stirring the solution at 100°C or below for more than one hour. The varnish is a composition containing polyamic acid, which is a block copolymer, and a solvent.

[0205] [Examples 1, 2, 4-7, Comparative Example 1] Varnishes of blocked polyamido acid imides of Examples 1, 2, 4-7 were obtained in the same manner as in Example 3, except that solutions of polyimide and polyamic acid shown in Table 2 were used. The number-average molecular weight of the blocked polyamido acid imide of Example 7 was 25,000, and the weight-average molecular weight was 53,000. The number-average molecular weight and weight-average molecular weight were measured according to the following method.

[0206] <Synthesis of Polyamic Acid (PA-9)> [Example 8] 101.00 g (0.189 mol) of DDA was dissolved in 556.52 g of dimethylacetamide and 83.48 g of xylene to obtain a diamine solution. 59.00 g (0.183 mol) of BTDA was added to the diamine solution and the reaction was carried out until a clear solution was obtained to obtain a varnish of polyamic acid (polyimide precursor) (PA-9). The reaction was carried out by stirring the solution at 50°C or below for more than 1 hour. The varnish is a composition containing polyamic acid and a solvent.

[0207] Table 2 shows the types and amounts of diamines and tetracarboxylic dianhydrides used in the synthesis of polyimides and polyamic acids, and the types and amounts of polyimides and polyamic acids used in the synthesis of blocked polyamic acid imides.

[0208] The meanings of the abbreviations in Table 2 are as follows: BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride TAHQ: bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)1,4-phenylene DDA: dimeramine mTB: 4,4'-diamino-2,2'-dimethylbiphenyl

[0209]

[0210] (Number-average molecular weight, weight-average molecular weight) The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by gel permeation chromatography (GPC) and converted using a calibration curve for standard polystyrene. The calibration curve was approximated by a cubic equation using a set of five standard polystyrene samples ("TSK standard POLYSTYRENE", manufactured by Tosoh Corporation). The GPC conditions are as follows: GPC instrument: High-speed GPC instrument HLC-8320GPC (manufactured by Tosoh Corporation) Detector: UV-8320 ultraviolet absorption detector (manufactured by Tosoh Corporation) Column: Gelpack GL-S300MDT-5 (2 in total) (manufactured by Resonac Corporation) Eluent: THF / DMF = 1 / 1 (volume ratio) + LiBr (0.06 mol / L) + H ３ PO ４(0.06 mol / L) Flow rate: 1 mL / min Column size: 8 mm I.D. × 300 mm Sample concentration: 5 mg / mL Injection volume: 5 μL Measurement temperature: 40°C

[0211] <Film Preparation> A film was prepared using the obtained varnish (composition) according to the following procedure. [Example 1] The surface of a commercially available glass substrate was degreased with acetone, and the block polyamide acid imide varnish of Example 1 was applied using a film applicator with a film thickness adjustment function so that the film thickness after imidization was 25 μm. The applied varnish was pre-dried at 80°C for 60 minutes using a hot plate to form a block polyamide acid imide layer. Next, the block polyamide acid imide layer was heated in an inert gas oven in a nitrogen atmosphere at 350°C for 1 hour to obtain a block polyimide film. After immersing the glass substrate on which the film was formed in warm water for about 15 minutes, the film was peeled off the glass substrate.

[0212] [Examples 2-8 and Comparative Example 1] Films were obtained in the same manner as above, except that the varnish of the blocked polyamide acid imide in Example 1 was replaced with the varnish of Examples 2-8 and Comparative Example 1.

[0213] <Evaluation of the Films> The properties of the films prepared using the varnishes of Examples 1 to 8 and Comparative Example 1 were evaluated according to the following method. The evaluation results are shown in Table 2.

[0214] (Relative permittivity and dielectric loss tangent) The film was cut to a size of 60 mm x 60 mm and dried at 110°C for 30 minutes. Immediately after drying, the dielectric properties of the film (relative permittivity Dk and dielectric loss tangent Df) were measured using the cavity resonator method (TE mode). Subsequently, the film was immersed in water for 24 hours in an atmosphere of 25°C. After removing the film from the water, the dielectric properties of the film (relative permittivity Dk and dielectric loss tangent Df) were promptly measured using the cavity resonator method (TE mode). A network analyzer (product name "P5003A", manufactured by KEYSIGHT Technologies) and a split cylinder resonator (manufactured by KEYSIGHT Technologies) were used for the measurements. The conditions were a frequency of 10 GHz and a measurement temperature of 25°C.

[0215] (Tensile strength, tensile modulus, and elongation at break) A film was cut to a size of 10 mm in width and 60 mm in length to prepare test specimens. Tensile tests were performed under the following measurement conditions, and the maximum tensile stress applied during the tensile test was defined as the tensile strength (MPa). The elongation at break (%) was calculated by dividing the amount of elongation of the test specimen until break by the distance between the chucks, which was 20 mm. In addition, Young's modulus (MPa) was calculated from the slope of the elastic deformation region at the beginning of stress rise, and the obtained value was defined as the tensile modulus (MPa). Other detailed conditions and calculation methods were carried out in accordance with the international standard ISO 5271 (1993). Equipment name: Shimadzu Corporation "Autograph AGS-100NG" (product name) Test speed: 5 mm / min Distance between chucks: 20 mm Test specimen size: 10 mm in width, 60 mm in length Set temperature: Room temperature (25°C)

[0216] (Thermal expansion coefficient (linear thermal expansion coefficient) and glass transition temperature) A film was cut to a width of 4 mm and a length of 25 mm to prepare a test specimen. A thermomechanical analyzer (TMA7100, manufactured by Hitachi High-Tech Science Co., Ltd.) was used for the measurement. The test specimen was heated from room temperature to 350°C at a rate of 10°C / min using the tensile method with a chuck distance of 10 mm and a load of 10 g, and then cooled to 30°C at a rate of 10°C / min. The temperature was then raised again at a rate of 10°C / min, and the average linear thermal expansion coefficient (ppm / °C) from 30°C to 200°C was calculated and the obtained value was taken as the linear thermal expansion coefficient (ppm / K). The temperature corresponding to the inflection point of the linear thermal expansion coefficient curve was taken as the glass transition temperature (°C).

[0217] <Evaluation of FCCL> The warping and adhesive properties of FCCL prepared using the varnishes of Examples 1 to 8 and Comparative Example 1 were evaluated according to the following method. The evaluation results are shown in Table 2.

[0218] (Preparation of FCCL) Flexible copper-clad laminates (FCCL) were prepared using the obtained varnish (composition) according to the following method. Surface roughness (Rz ＪＩＳA varnish was applied to the matte surface of a low-roughness copper foil (25 μm thick) with a surface roughness of 1.2 μm using a film applicator with a film thickness adjustment function, so that the film thickness after imidization was 25 μm. The applied varnish was pre-dried using a hot plate at 80°C for 30 minutes to form a layer of polyamido-imide or polyamido acid. Next, the copper foil with the polyamido-imide or polyamido acid layer was heated in an inert gas oven in a nitrogen atmosphere at 350°C for 30 minutes to obtain a flexible copper-clad laminate (FCCL) having a polyimide layer.

[0219] (Warping) A 5cm x 5cm piece of FCCL was cut and placed on a surface plate with the polyimide layer facing upwards. The height of the four corners of the FCCL was measured using a ruler. The average value of the four corner heights was calculated and used as the warping value when the polyimide layer was facing upwards. Next, the FCCL was placed on a surface plate with the copper foil side facing upwards, and the height of the four corners of the FCCL was measured using a ruler. The average value of the four corner heights was calculated and used as the warping value when the copper foil side was facing upwards. The evaluation criteria were as follows: A: Both the warping value when the polyimide layer was facing upwards and the warping value when the copper foil was facing upwards were 10mm or less. B: Either the warping value when the polyimide layer was facing upwards or the warping value when the copper foil was facing upwards was greater than 10mm.

[0220] (Adhesion) FCCL copper foil was processed into 5 mm wide straight lines by etching. Using a material testing machine (Shimadzu Corporation's "Small Benchtop Testing Machine EZ-S50N"), the peel strength was measured when the copper foil processed into straight lines was peeled off at a 90° angle to the plane direction of the block polyimide layer. The tensile speed was 50 mm / min.

Claims

1. A polyamic acid comprising diamine units and tetracarboxylic acid units, wherein at least one selected from the group consisting of the diamine units and the tetracarboxylic acid units comprises a unit (X) having a group (X) which comprises at least one non-aromatic hydrocarbon group and the total number of carbon atoms of the at least one non-aromatic hydrocarbon group is 9 or more, and the content of the unit (X) is 12.0 mol% or more based on the total amount of the diamine units and the tetracarboxylic acid units.

2. The polyamic acid according to claim 1, which is a block copolymer having a polyamic acid block and a polyimide block.

3. The polyamic acid according to claim 1 or 2, wherein the tensile modulus is 4.0 GPa or less.

4. The polyamic acid according to any one of claims 1 to 3, wherein the unit (X) comprises a unit (X) having a group (X) with 28 or more carbon atoms.

5. The polyamic acid according to any one of claims 1 to 4, wherein the unit (X) includes a dimer amine unit.

6. The polyamic acid according to any one of claims 1 to 5, wherein the diamine unit and the tetracarboxylic acid unit further include a unit (Y) having an organic group (Y) and not having the group (X).

7. The polyamic acid according to any one of claims 1 to 6, wherein the unit (Y) comprises a 3,3',4,4'-biphenyltetracarboxylic acid unit.

8. The polyamic acid according to any one of claims 1 to 7, wherein the content of the unit (X) is 20.0 mol% or more based on the total amount of the diamine unit and the tetracarboxylic acid unit.

9. The polyamic acid according to any one of claims 1 to 8, wherein the tensile modulus is 1.0 GPa or higher.

10. The diamine unit is a unit represented by the following formula (N): (In the formula, R Ｎ represents an organic group, and P represents the bonding position with the tetracarboxylic acid unit or a hydrogen atom. * represents the bonding position with another atom.) The tetracarboxylic acid unit is a unit represented by the following formula (C), (In the formula, R Ｃ The symbol (*) represents an organic group, and Q represents the bond position with a diamine unit or a hydroxyl group. The asterisk (*) indicates the bond position with another atom. ） 　 The polyamic acid according to any one of claims 1 to 9.

11. The polyamic acid according to any one of claims 1 to 10, wherein the diamine unit is a unit derived from at least one compound selected from the group consisting of diamines and diisocyanates, and the tetracarboxylic acid unit is a unit derived from a tetracarboxylic dianhydride.

12. A printed circuit board material comprising the polyamic acid described in any one of claims 1 to 11.

13. An antenna substrate material comprising the polyamic acid described in any one of claims 1 to 11.

14. A transmission line cable material comprising the polyamic acid described in any one of claims 1 to 11.

15. A composition comprising a polyamic acid according to any one of claims 1 to 11 and a solvent.

16. A polyimide obtained using a polyamic acid according to any one of claims 1 to 11, or the composition according to claim 15.

17. A printed circuit board obtained using a polyamic acid according to any one of claims 1 to 11, a printed circuit board material according to claim 12, or a composition according to claim 15.

18. An antenna substrate obtained using a polyamic acid according to any one of claims 1 to 11, an antenna substrate material according to claim 13, or a composition according to claim 15.

19. A transmission line cable obtained using a polyamic acid according to any one of claims 1 to 11, a transmission line cable material according to claim 14, or a composition according to claim 15.

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