Polyamide, polyimide, non-thermoplastic polyimide film, multilayer polyimide film and metal laminate

Abstract

The polyamide of the present invention has tetracarboxylic dianhydride residues and diamine residues. The tetracarboxylic dianhydride residues include 3,3',4,4'-biphenyltetracarboxylic dianhydride residues and 3,3',4,4'-benzophenonetetracarboxylic dianhydride residues. The diamine residues include p-phenylenediamine residues and 1,3-bis(4-aminophenoxy)benzene residues. The multilayer polyimide film (10) has a non-thermoplastic polyimide film (11) and an adhesive layer (12) comprising thermoplastic polyimide disposed on at least one side of the non-thermoplastic polyimide film (11).

Description

Polyamide, polyimide, non-thermoplastic polyimide film, multilayer polyimide film and metal laminate This invention relates to a polyamide, polyimide, non-thermoplastic polyimide film, multilayer polyimide film, and metal laminate. In recent years, with the expanding demand for electronic products, primarily smartphones, tablets, and laptops, the demand for flexible printed circuit boards (FPCs) has been continuously increasing. Among these, FPCs using multilayer polyimide films with a non-thermoplastic polyimide layer (core layer) and a thermoplastic polyimide layer (adhesive layer) are expected to see further demand growth due to their excellent heat resistance and flexibility. Furthermore, polyimide possesses sufficient heat resistance to withstand high-temperature processes and has a relatively small coefficient of linear expansion, making it less prone to internal stress, thus making it a suitable material for FPCs. Furthermore, in recent years, with the high-speed signal transmission of electronic devices, the requirements for low dielectric constant and low dielectric loss factor of electronic substrate materials have been continuously increasing to achieve high-frequency transmission of electrical signals in circuits. To suppress transmission losses of electrical signals, it is effective to reduce the dielectric constant and dielectric loss factor of electronic substrate materials. In recent years, with the dawn of the IoT (Internet of Things) society, the trend towards higher frequencies has become increasingly apparent, necessitating substrate materials that can suppress transmission losses even in regions above, for example, 10 GHz. Here, transmission loss is expressed using the proportionality constant (k), frequency (f), dielectric loss factor (Df), and relative permittivity (Dk), and is given by the following formula: The dielectric loss factor contributes more to the transmission loss than the relative permittivity. Therefore, to reduce transmission loss, it is important to lower the dielectric loss factor. Transmission Loss = k × f × Df × (Dk) 1 / 2 As a material used in circuit boards capable of adapting to high-frequency applications, a polyimide film (polyimide layer) exhibiting a low dielectric loss factor is known (see, for example, Patent Documents 1-4). [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Publication No. 2014-526399 [Patent Document 2] Japanese Patent Application Publication No. 2009-246201 [Patent Document 3] International Publication No. 2018 / 079710 [Patent Document 4] International Publication No. 2016 / 159060 [The problem the invention aims to solve] However, the techniques described in Patent Documents 1 to 4 still have room for improvement in reducing the dielectric loss factor. This invention addresses the aforementioned problems and aims to provide a polyimide capable of reducing the dielectric loss factor and polyamide as a precursor thereto. Furthermore, this invention also aims to provide a non-thermoplastic polyimide film, a multilayer polyimide film, and a metal-laminated laminate manufactured using this polyimide and polyamide. [Technical Means for Solving the Problem] <Forms of the Invention> The present invention includes the following forms. [1] A polyamide having a tetracarboxylic dianhydride residue and a diamine residue, wherein the tetracarboxylic dianhydride residue comprises a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue and a 3,3',4,4'-benzophenonetetracarboxylic dianhydride residue, and the diamine residue comprises a p-phenylenediamine residue and a 1,3-bis(4-aminophenoxy)benzene residue. [2] As described in [1] above, the content of the above-mentioned p-phenylenediamine residues is 75 mol% to 95 mol% relative to the total amount of the above-mentioned diamine residues. [3] As described in [1] or [2] above, the content of the 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residue is 55 mol% or more and 85 mol% or less relative to the total amount of the tetracarboxylic acid dianhydride residue, and the content of the 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride residue is 10 mol% or more and 30 mol% or less relative to the total amount of the tetracarboxylic acid dianhydride residue. [4] As described in [3] above, the polyamide contains pyromellitic dianhydride residues, wherein the pyromellitic dianhydride residues contain 3 mol% to 15 mol% relative to the total amount of the pyromellitic dianhydride residues. [5] A polyimide, which is an imide of a polyamide as described in any of [1] to [4] above. [6] A non-thermoplastic polyimide film comprising the polyimide described above [5]. [7] A multilayer polyimide film having a non-thermoplastic polyimide film as described above [6] and an adhesive layer comprising thermoplastic polyimide disposed on at least one side of the non-thermoplastic polyimide film. [8] The multilayer polyimide film as described in [7] above, wherein the above-mentioned adhesive layer system is disposed on both sides of the above-mentioned non-thermoplastic polyimide film. [9] A metal-laminated laminate comprising a multilayer polyimide film as described in [7] or [8] above, and a metal layer disposed on the main surface of at least one of the adhesive layers of the multilayer polyimide film. [Effects of the Invention] According to the present invention, a polyimide capable of reducing the dielectric loss factor and polyamide as a precursor thereof can be provided. Furthermore, according to the present invention, a non-thermoplastic polyimide film, a multilayer polyimide film, and a metal laminate manufactured using the polyimide and polyamide can also be provided. The preferred embodiments of the present invention will now be described in detail, but the present invention is not limited thereto. Furthermore, all academic and patent documents described in this specification are incorporated herein by reference. First, the terms used in this specification will be explained. "Structural unit" refers to the repeating unit that constitutes the polymer. "Polyamide" is a polymer that contains the structural unit represented by the following general formula (1) (hereinafter sometimes referred to as "structural unit (1)"). [Chemistry 1] In general formula (1), A 1 Indicates a tetracarboxylic dianhydride residue (derived from the tetravalent organic group of tetracarboxylic dianhydride), A 2 It represents a diamine residue (derived from the divalent organic group of a diamine). The content of structural unit (1) relative to the total structural units constituting polyamide is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, further preferably 80 mol% or more and 100 mol% or less, further preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%. Unless otherwise stated, the "coefficient of linear expansion" refers to the coefficient of linear expansion as the temperature increases from 50°C to 250°C. The method for determining the coefficient of linear expansion is the same as or based on the method described in the examples below. The "relative permittivity" is the relative permittivity at a frequency of 10 GHz, a temperature of 23°C, and a relative humidity of 50%. The "dielectric loss factor" is the dielectric loss factor at a frequency of 10 GHz, a temperature of 23°C, and a relative humidity of 50%. The methods for determining the relative permittivity and dielectric loss factor are the same as those used in the examples below, or are methods that are used as standards thereon. The term "non-thermoplastic polyimide" refers to polyimide that, when fixed in film form to a metal frame and heated at 380°C for 1 minute, maintains its film shape (a flat film shape). The term "thermoplastic polyimide" refers to polyimide that, when fixed in film form to a metal frame and heated at 380°C for 1 minute, does not maintain its film shape. The "main surface" of a layered material (more specifically, non-thermoplastic polyimide film, adhesive layer, multilayer polyimide film, metal layer, etc.) refers to the surface orthogonal to the thickness direction of the layered material. Hereinafter, sometimes "system" is added after the compound name to refer to the compound and its derivatives in a general sense. Also, sometimes tetracarboxylic dianhydride is referred to as "acid dianhydride". Also, sometimes the non-thermoplastic polyimide contained in a non-thermoplastic polyimide film is simply referred to as "non-thermoplastic polyimide". Also, sometimes the thermoplastic polyimide contained in an adhesive layer is simply referred to as "thermoplastic polyimide". Unless otherwise stated, the ingredients or functional groups exemplified in this specification may be used alone or in combination of two or more. For ease of understanding, the diagrams referenced in the following explanations are represented in a patterned manner based on each constituent element. To facilitate the creation of the diagrams, the size, number, shape, etc., of each constituent element in the diagrams may sometimes differ from the actual form. Furthermore, for ease of explanation, in the diagrams described later, the same symbols are used to label the constituent parts that are the same as those in the diagrams described earlier, and sometimes their descriptions are omitted. <First Embodiment: Polyamide> The polyamide of the first embodiment of the present invention (hereinafter, sometimes referred to as "polyamide (1)") has a tetracarboxylic dianhydride residue and a diamine residue. The tetracarboxylic dianhydride residue includes a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue and a 3,3',4,4'-benzophenonetetracarboxylic dianhydride residue. That is, polyamide (1) includes a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue and a 3,3',4,4'-benzophenonetetracarboxylic dianhydride residue as tetracarboxylic dianhydride residues. Furthermore, the diamine residue includes a p-phenylenediamine residue and a 1,3-bis(4-aminophenoxy)benzene residue. That is, polyamide (1) includes a p-phenylenediamine residue and a 1,3-bis(4-aminophenoxy)benzene residue as diamine residues. Hereinafter, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is sometimes referred to as "BPDA". Also, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride is sometimes referred to as "BTDA". Also, p-phenylenediamine is sometimes referred to as "PDA". Also, 1,3-bis(4-aminophenoxy)benzene is sometimes referred to as "TPE-R". Also, pyromellitic dianhydride is sometimes referred to as "PMDA". Also, 4,4'-oxophthalic anhydride is sometimes referred to as "ODPA". Polyimide obtained from polyamide (1) can reduce the dielectric loss factor. The reason is speculated as follows. Polyamide (1) contains BPDA and BTDA residues as tetracarboxylic dianhydride residues, and PDA and TPE-R residues as diamine residues. As described above, polyamide (1) contains residues with rigid structures and residues with curved structures, thus the polyimide obtained from polyamide (1) has a stable high-order structure. Therefore, the dielectric loss factor can be reduced based on the polyimide obtained from polyamide (1). In addition to BPDA and BTDA residues, polyamides (1) may also contain other acid dianhydride residues. Examples of dianhydrides (monomers) used to form other dianhydride residues (excluding BPDA and BTDA residues) include: PMDA, ODPA, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 2,2',3,3'-benzophenonetetracarboxylic acid dianhydride, 3,4'-oxophthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9,10-dinaphthalenetetracarboxylic acid dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, ethylbis(triphthalic acid monoester anhydride), bisphenol Abis(triphthalic acid monoester anhydride), and their derivatives. To obtain polyimide that can improve heat resistance and further reduce dielectric loss factor, PMDA residues are preferred as other acid dianhydride residues. In order to obtain polyimide that can further reduce dielectric loss factor, the total content of BPDA residue and BTDA residue relative to all the dianhydride residues constituting polyimide (1) is preferably 80 mol% or more, and may be 85 mol% or more, 88 mol% or more, 90 mol% or more, or 92 mol% or more, or may be 100 mol. When PMDA residues are used as other acid dianhydride residues, in order to obtain polyimide that can improve heat resistance and further reduce dielectric loss factor, the total content of BPDA residues, BTDA residues and PMDA residues relative to all acid dianhydride residues constituting polyimide (1) is preferably 85 mol% or more, more preferably 90 mol% or more, and may also be 100 mol%. In order to obtain polyimide that can further reduce dielectric loss factor, the content of BPDA residues is preferably 55 mol% to 85 mol% relative to all the dianhydride residues constituting polyimide (1), more preferably 60 mol% to 80 mol%, and even more preferably 65 mol% to 78 mol%. In order to obtain polyimide that can further reduce dielectric loss factor, the content of BTDA residues is preferably 10 mol% to 30 mol% relative to all the dianhydride residues constituting polyimide (1), and more preferably 15 mol% to 25 mol%. In order to obtain polyimide that can improve heat resistance and further reduce dielectric loss factor, the content of PMDA residues is preferably 3 mol% to 15 mol% relative to all the dianhydride residues constituting polyimide (1), and more preferably 5 mol% to 12 mol%. Polyamide (1) may contain other diamine residues in addition to PDA and TPE-R residues. Examples of diamines (monomers) used to form other diamine residues (diamine residues other than PDA and TPE-R residues) include: 1,4-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'- Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenylN-methylamine, 4,4'-diaminodiphenylN-aniline, 1,3-diaminobenzene, 1,2-diaminobenzene, and their derivatives. In order to obtain polyimide that can further reduce dielectric loss factor, the total content of PDA residue and TPE-R residue relative to all diamine residues constituting polyimide (1) is preferably 85 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, and can also be 100 mol%. In order to obtain polyimide that can further reduce dielectric loss factor, the content of PDA residues is preferably 75 mol% to 95 mol% relative to all diamine residues constituting polyimide (1), more preferably 80 mol% to 95 mol%, and even more preferably 80 mol% to 90 mol%. In order to obtain polyimide that can further reduce dielectric loss factor, the content of TPE-R residues is preferably 2 mol% to 20 mol% relative to all diamine residues constituting polyamide (1), more preferably 5 mol% to 18 mol%, and even more preferably 10 mol% to 18 mol%. To obtain a polyimide that can further reduce the dielectric loss factor, the mass ratio obtained by dividing the total mass of the dianhydride residues constituting polyimide (1) by the total mass of the diamine residues constituting polyimide (1) is preferably 0.95 to 1.05, more preferably 0.97 to 1.03, and even more preferably 0.99 to 1.01. By adjusting the above mass ratio to 0.95 to 1.05, the mass ratio obtained by dividing the total mass of the dianhydride residues constituting polyimide by the total mass of the diamine residues constituting polyimide becomes 0.95 to 1.05. An example of a method for synthesizing polyimide (1) will be described below. To obtain a polyimide with a further reduced dielectric loss factor and a small coefficient of linear expansion, the polyamide (1) preferably satisfies condition 1 below, more preferably condition 2 below, further preferably condition 3 below, and especially preferably condition 4 below. Condition 1: The content of BPDA residues relative to all dianhydride residues constituting polyamide (1) is 55 mol% to 85 mol% and the content of BTDA residues relative to all dianhydride residues constituting polyamide (1) is 10 mol% to 30 mol%. Condition 2: Condition 1 above is satisfied, and the polyamide (1) further has PMDA residues as dianhydride residues. Condition 3: Condition 2 above is satisfied, and the content of PMDA residues relative to all dianhydride residues constituting polyamide (1) is 3 mol% to 15 mol%. Condition 4: The above condition 3 is satisfied, and the content of PDA residues relative to all diamine residues constituting polyamide (1) is more than 75 mol% and less than 95 mol%. <Second Embodiment: Polyimide> Next, the polyimide of the second embodiment of the present invention will be described. The polyimide of the second embodiment is a amide of the above-mentioned polyamide (1). The polyimide of the second embodiment can be obtained by known methods, and its manufacturing method is not particularly limited. An example of a method for amide-imidizing polyamide (1) will be described below. <Third Embodiment: Non-Thermoplastic Polyimide Film> Next, the non-thermoplastic polyimide film of the third embodiment of the present invention will be described. The non-thermoplastic polyimide film of the third embodiment is a non-thermoplastic polyimide film containing the polyimide of the second embodiment (more specifically, polyamide (1) autoimide is non-thermoplastic polyimide). The non-thermoplastic polyimide film of the third embodiment may contain components (additives) other than non-thermoplastic polyimide. Examples of additives include dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers. The content of non-thermoplastic polyimide in the non-thermoplastic polyimide film relative to the total amount of the non-thermoplastic polyimide film is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may also be 100% by weight. [Method for manufacturing non-thermoplastic polyimide film] The non-thermoplastic polyimide contained in the non-thermoplastic polyimide film is obtained by amide-imidizing polyamide acid (1) as its precursor. As a method for manufacturing polyamide (1) (synthetic method), all known methods and combinations thereof can be used. In manufacturing polyamide (1), a diamine and a tetracarboxylic dianhydride are usually reacted in an organic solvent. The mass of the diamine and the mass of the tetracarboxylic dianhydride during the reaction are preferably substantially the same. In the case of synthesizing polyamide (1) using diamine and tetracarboxylic dianhydride, the desired polyamide (1) (polymer of diamine and tetracarboxylic dianhydride) can be obtained by adjusting the mass of each diamine and the mass of each tetracarboxylic dianhydride. The molar fraction of each residue in polyamide (1) is, for example, consistent with the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of polyamide (1). The temperature conditions for the reaction of diamine with tetracarboxylic dianhydride, i.e., the synthesis reaction of polyamide (1), are not particularly limited, but are, for example, in the range of 10°C to 150°C. The reaction time for the synthesis reaction of polyamide (1) is, for example, in the range of 10 minutes to 30 hours. In this embodiment, any monomer addition method can be used in the manufacture of polyamide (1). A representative method for manufacturing polyamide (1) is illustrated below. As a method for manufacturing polyamide (1), an example of a polymerization method (hereinafter sometimes referred to as "polymerization method A") can be exemplified by the following steps (Aa) and (Ab). (Aa): The following step involves reacting a diamine and an acid dianhydride in an organic solvent in a state of excess diamine to obtain a prepolymer with amino groups at both ends. (Ab): The following step involves adding a diamine with a structure different from that used in step (Aa), and then adding an acid dianhydride with a structure different from that used in step (Aa), so that the diamine and acid dianhydride in all steps are substantially equal in molar, thereby carrying out polymerization. Furthermore, as a method for manufacturing polyamide (1), a polymerization method can also be exemplified by the following steps (Ba) and (Bb) (hereinafter sometimes referred to as "B polymerization method"). (Ba): The following step involves reacting a diamine and an acid dianhydride in an organic solvent in an excess of acid dianhydride to obtain a prepolymer with anhydride groups at both ends. (Bb): The following step involves adding an acid dianhydride with a structure different from that used in step (Ba), and then adding a diamine with a structure different from that used in step (Ba), so that the diamine and acid dianhydride in all steps are substantially equal in molar, thereby carrying out polymerization. In this specification, polymerization methods in which a specific diamine or a specific acid dianhydride is selectively reacted with any or a specific diamine or any or a specific acid dianhydride in a predetermined order (such as polymerization method A, polymerization method B, etc.) are described as sequential polymerization. Conversely, in this specification, polymerization methods in which the order of addition of the diamine and acid dianhydride is not predetermined (polymerization methods in which monomers react with each other arbitrarily) are described as random polymerization. Furthermore, in cases where sequential polymerization is carried out in two stages as in polymerization method A or polymerization method B, in this specification, the first half of the steps (step (Aa), step (Ba), etc.) are described as "1st sequential polymerization step," and the second half of the steps (step (Ab), step (Bb), etc.) are described as "2nd sequential polymerization step." In this embodiment, in order to obtain a non-thermoplastic polyimide film that can further reduce the dielectric loss factor, the polymerization method of polyimide (1) is preferably sequential polymerization. When obtaining non-thermoplastic polyimide, a method can be used to obtain non-thermoplastic polyimide from a polyamide solution containing polyamide (1) and an organic solvent. Examples of organic solvents that can be used in the polyamide solution include: urea solvents such as tetramethylurea and N,N-dimethylethylurea; urethane solvents such as dimethyl urethane; urethane solvents such as diphenyl urethane and tetramethyl urethane; N,N-dimethylacetamide, N,N-dimethylformamide (hereinafter sometimes referred to as "DMF"), N,N-diethylacetamide, and N-methyl-2-pyrrolidone. Solvents such as trimethylammonium hexamethylphosphate and acetamide; ester solvents such as γ-butyrolactone; haloalkanes such as chloroform and dichloromethane; aromatic hydrocarbon solvents such as benzene and toluene; phenol solvents such as phenol and cresol; ketone solvents such as cyclopentanone; and ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dimethyl ether, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents are usually used alone, but two or more may be used in combination as needed. When polyacrylic acid (1) is obtained using the above polymerization method, the reaction solution (the solution after the reaction) itself can be used as the polyacrylic acid solution for obtaining non-thermoplastic polyimide. In this case, the organic solvent in the polyacrylic acid solution is the organic solvent used in the reaction of the above polymerization method. Furthermore, a polyamide solution can be prepared by dissolving solid polyamide (1) obtained by removing the solvent from the self-reaction solution in an organic solvent. Additives such as dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers can be added to the polyacrylic acid solution. The concentration of polyacrylic acid (1) in the polyacrylic acid solution is not particularly limited, but relative to the total amount of polyacrylic acid solution, it is preferably 5% to 35% by weight, and more preferably 8% to 30% by weight. When the concentration of polyacrylic acid (1) is 5% to 35% by weight, appropriate molecular weight and solution viscosity can be obtained. There are no particular limitations on the method for obtaining a non-thermoplastic polyimide film using a polyamide solution, and various known methods can be applied. For example, a method for obtaining a non-thermoplastic polyimide film via the following steps i) to iii) can be exemplified. Step i): The following step is to coat a dopant solution containing a polyamide solution onto a support to form a coated film. Step ii): The following step is to dry the coated film on the support to form a self-sustaining polyamide film (hereinafter, sometimes referred to as a "gel film"), and then peel the gel film off from the support. Step iii): The following step is to heat the gel film to amide-imide the polyamide (1) in the gel film to obtain a non-thermoplastic polyimide film containing non-thermoplastic polyimide. The methods for obtaining non-thermoplastic polyimide films via steps i) to iii) are broadly classified into thermo-imidization and chemical imidization. Thermo-imidization involves coating a polyamide solution as a dopant onto a support without using dehydrating or ring-closing agents, followed by heating to promote imidization. Chemical imidization, on the other hand, uses a solution of at least one of a dehydrating or ring-closing agent and a catalyst added to a polyamide solution as a dopant to promote imidization. Both methods can be used, but chemical imidization offers superior productivity. As a dehydrating ring-closing agent, acid anhydrides, represented by acetic anhydride, are suitable. As a catalyst, aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines (more specifically, isoquinoline, etc.) are suitable. When adding at least one of the dehydrating ring-closing agent and catalyst to the polyacrylic acid solution, it can be added directly without dissolving in the organic solvent, or it can be added after being dissolved in an organic solvent. In the method of adding directly without dissolving in the organic solvent, sometimes the reaction proceeds rapidly before at least one of the dehydrating ring-closing agent and catalyst diffuses, forming a gel. Therefore, it is preferable to add a solution (acetylation accelerator) obtained by dissolving at least one of the dehydrating ring-closing agent and catalyst in an organic solvent to the polyacrylic acid solution. In step i), there are no particular limitations on the method of coating the dopant onto the support. Methods using previously known coating devices such as die coating machines, corner wheel coating machines (registered trademarks), reverse coating machines, and blade coating machines can be adopted. As the support for coating the dopant solution in step i), a glass plate, aluminum foil, annular stainless steel strip, stainless steel drum, etc., are suitable. In step ii), the drying conditions (heating conditions) of the coated film are set according to the final film thickness and production speed, and the dried polyacrylic acid film (gel film) is peeled off from the support. The drying temperature of the coated film is, for example, 50°C to 200°C. Furthermore, the drying time for drying the coated film is, for example, 1 minute to 100 minutes. Subsequently, in step iii), for example, by fixing the ends of the gel film to prevent shrinkage during hardening and by performing a heat treatment, water, residual solvent, amide accelerator, etc., are removed from the gel film, and the remaining polyamide (1) is completely amide-iminated to obtain a non-thermoplastic polyamide film containing non-thermoplastic polyamide. The heating conditions are appropriately set according to the thickness of the final film and the production speed. For example, the maximum temperature in step iii) is 370°C to 420°C, and the heating time at the maximum temperature is 10 seconds to 180 seconds. Furthermore, the temperature can be maintained at any temperature for any time before reaching the maximum temperature. Step iii) can be performed in air, under reduced pressure, or in an inert gas such as nitrogen. There are no particular limitations on the heating device that can be used in step iii), for example, a hot air circulating oven or a far-infrared oven. Non-thermoplastic polyimide films obtained in this way are suitable for materials such as high-frequency circuit boards (more specifically, the core layer of multilayer polyimide films, the insulating layer of metal laminates, etc.) because they can reduce the dielectric loss factor. [Physical Properties of Non-Thermoplastic Polyimide Films] To reduce transmission losses, the relative permittivity of the non-thermoplastic polyimide film is preferably 3.70 or less. Furthermore, to reduce transmission losses, the dielectric loss factor of the non-thermoplastic polyimide film is preferably 0.0050 or less, more preferably 0.0040 or less, and even more preferably 0.0030 or less. In order to suppress the generation of internal stress when used in FPC, the coefficient of linear expansion of the non-thermoplastic polyimide film is preferably below 25 ppm / K, more preferably below 18 ppm / K, and even more preferably below 16 ppm / K. There is no particular limitation on the thickness of non-thermoplastic polyimide films, for example, it can be between 5 μm and 50 μm. The thickness of non-thermoplastic polyimide films can be measured using a laser hologram. <Fourth Embodiment: Multilayer Polyimide Film> Next, the multilayer polyimide film according to the fourth embodiment of the present invention will be described. The multilayer polyimide film of the fourth embodiment has a non-thermoplastic polyimide film of the third embodiment and an adhesive layer comprising thermoplastic polyimide. Furthermore, in the following description, content that is repeated with the first to third embodiments will sometimes be omitted. Figure 1 is a cross-sectional view showing an example of a multilayer polyimide film according to the fourth embodiment. As shown in Figure 1, the multilayer polyimide film 10 has a non-thermoplastic polyimide film 11 and an adhesive layer 12 containing thermoplastic polyimide disposed on at least one side (one main side) of the non-thermoplastic polyimide film 11. Furthermore, in the multilayer polyimide film 10 shown in Figure 1, an adhesive layer 12 is provided only on one side of the non-thermoplastic polyimide film 11, but adhesive layers 12 may also be provided on both sides (two main sides) of the non-thermoplastic polyimide film 11. When adhesive layers 12 are provided on both sides of the non-thermoplastic polyimide film 11, the two adhesive layers 12 may contain the same type of polyimide or may contain different types of polyimide. Also, the thicknesses of the two adhesive layers 12 may be the same or different. In the following description, "multilayer polyimide film 10" includes films with adhesive layers 12 provided only on one side of the non-thermoplastic polyimide film 11 and films with adhesive layers 12 provided on both sides of the non-thermoplastic polyimide film 11. The thickness of the multilayer polyimide film 10 (the total thickness of all layers) is, for example, 6 μm to 60 μm. The thinner the multilayer polyimide film 10, the easier it is to achieve lightweighting of the resulting FPC, and the improved flexibility of the resulting FPC. To ensure mechanical strength, facilitate lightweighting of the FPC, and improve the flexibility of the FPC, the thickness of the multilayer polyimide film 10 is preferably 7 μm to 60 μm, more preferably 10 μm to 60 μm. The thickness of the multilayer polyimide film 10 can be measured using a laser hologram. In order to ensure good adhesion to the metal foil and to easily achieve the thinning of the FPC, the thickness of the adhesive layer 12 (in the case of two adhesive layers 12, the thickness of each adhesive layer 12) is preferably more than 1 μm and less than 15 μm. Furthermore, to facilitate the adjustment of the linear expansion coefficient of the multilayer polyimide film 10, the thickness ratio of the non-thermoplastic polyimide film 11 to the adhesive layer 12 (thickness of non-thermoplastic polyimide film 11 / thickness of adhesive layer 12) is preferably 55 / 45 or more and 95 / 5 or less. In the case where two adhesive layers 12 are provided, the thickness of the adhesive layer 12 used to calculate the thickness ratio is the total thickness of the adhesive layer 12. To suppress warping of the multilayer polyimide film 10, it is preferable that adhesive layers 12 are provided on both sides of the non-thermoplastic polyimide film 11, and more preferably that adhesive layers 12 comprising the same type of polyimide are provided on both sides of the non-thermoplastic polyimide film 11. When adhesive layers 12 are provided on both sides of the non-thermoplastic polyimide film 11, the thickness of the two adhesive layers 12 is preferably the same to suppress warping of the multilayer polyimide film 10. Furthermore, even if the thicknesses of the two adhesive layers 12 are different, when using the thickness of the thicker adhesive layer 12 as a reference, as long as the thickness of the other adhesive layer 12 is 40% or more but not 100%, warping of the multilayer polyimide film 10 can also be suppressed. [Adhesive Layer 12] The thermoplastic polyimide contained in adhesive layer 12 has dianhydride residues and diamine residues. Examples of compounds that are the same as those used to form the dianhydride residues in the thermoplastic polyimide are those used to form the dianhydride residues in the aforementioned non-thermoplastic polyimide. The dianhydride residues in the thermoplastic polyimide and the dianhydride residues in the non-thermoplastic polyimide may be of the same type or different types. To ensure thermoplasticity, the diamine residues in the thermoplastic polyimide are preferably diamine residues with a curved structure. To more easily ensure thermoplasticity, the content of diamine residues with a curved structure relative to all diamine residues constituting the thermoplastic polyimide is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, and can also be 100 mol%. Examples of diamines (monomers) used to form diamine residues with curved structures include: 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 1,3-bis(3-aminophenoxy)benzene, TPE-R, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes referred to as "BAPP"), etc. To more easily ensure thermoplasticity, the diamine residues in thermoplastic polyimides are preferably BAPP residues. In order to obtain an adhesive layer 12 with excellent adhesion to the metal foil, the thermoplastic polyimide is preferably composed of one or more residues selected from the group consisting of BPDA residues and PMDA residues, and BAPP residues. The next layer 12 may also contain components (additives) other than thermoplastic polyimide. Examples of additives include dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers. The content of thermoplastic polyimide in the next layer 12 relative to the total amount of the next layer 12 is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may also be 100% by weight. (Method for forming adhesive layer 12) Adhesive layer 12 is formed, for example, by coating at least one side of a non-thermoplastic polyimide film 11 with a polyamide solution (hereinafter sometimes referred to as "thermoplastic polyamide solution") containing polyamide as a precursor of thermoplastic polyimide, followed by heating (drying and amide formation of polyamide). By this method, a multilayer polyimide film 10 having a non-thermoplastic polyimide film 11 and an adhesive layer 12 disposed on at least one side of the non-thermoplastic polyimide film 11 can be obtained. Alternatively, a solution containing thermoplastic polyimide (thermoplastic polyimide solution) can be used instead of thermoplastic polyamide solution to form a coating film containing thermoplastic polyimide solution on at least one side of non-thermoplastic polyimide film 11, and the coating film is dried to form adhesive layer 12. Alternatively, a co-extrusion die can be used to form a laminate on a support, comprising a layer of polyamide containing a precursor of non-thermoplastic polyimide as a non-thermoplastic polyimide film 11 and a layer of polyamide containing a precursor of thermoplastic polyimide. The resulting laminate is then heated to simultaneously form the non-thermoplastic polyimide film 11 and the adhesive layer 12. In this method, by using a metal foil as a support, a metal-bonded laminate (a laminate of multiple polyimide films 10 and metal foil) can be obtained simultaneously with the completion of amide formation. When manufacturing a multilayer polyimide film 10 comprising three polyimide layers, it is suitable to repeat the above-described coating and heating steps multiple times, or to form multiple coated films by co-extrusion or continuous coating (continuous casting) while simultaneously heating. Various surface treatments, such as corona treatment or plasma treatment, can also be performed on the outermost surface of the multilayer polyimide film 10. <Fifth Embodiment: Metal-Laminated Laminate> Next, the metal-laminated laminate according to the fifth embodiment of the present invention will be described. The metal-laminated laminate of the fifth embodiment has a multilayer polyimide film as in the fourth embodiment, and a metal layer disposed on the main surface of at least one adhesive layer of the multilayer polyimide film. In the following description, content that is repeated with the first to fourth embodiments will sometimes be omitted. Figure 2 is a cross-sectional view showing an example of a metal laminate according to the fifth embodiment. As shown in Figure 2, the metal laminate 20 has a multilayer polyimide film 10 and a metal layer 13 (metal foil) disposed on the main surface 12a of the adhesive layer 12 of the multilayer polyimide film 10. [Manufacturing Method of Metal-Laminated Laminate 20] When manufacturing a metal-laminate laminate 20 using a multilayer polyimide film 10, a metal foil forming a metal layer 13 is laminated onto at least one side of the multilayer polyimide film 10 (for example, in the case of FIG. 2, the main surface 12a of the adhesive layer 12 opposite to the non-thermoplastic polyimide film 11). This yields the metal-laminate laminate 20 shown in FIG. 2. There are no particular limitations on the method for laminating the metal foil onto the main surface 12a of the adhesive layer 12, and various known methods can be used. For example, a continuous processing method using a hot roller laminating apparatus with one or more metal rollers or a dual-belt press (DBP) can be employed. The specific configuration of the hot roller laminating apparatus is not particularly limited; however, to ensure a good appearance of the obtained metal-laminate laminate 20, it is preferable to place a protective material between the pressure surface and the metal foil. When an adhesive layer 12 is provided on both sides of a non-thermoplastic polyimide film 11, a double-sided metal laminate (not shown) can be obtained by laminating metal foil on both sides (two main sides) of a multilayer polyimide film 10. There are no particular limitations on the metal foil used as the metal layer 13; any metal foil can be used. For example, metal foils made of copper, stainless steel, nickel, aluminum, and alloys of these metals are suitable. Furthermore, while rolled copper foil and electrolytic copper foil are commonly used in conventional metal laminates, copper foil is also preferred in this fifth embodiment. Additionally, the metal foil can be one whose surface roughness is adjusted by surface treatment as needed. Furthermore, a rust-preventive layer, a heat-resistant layer, an adhesive layer, etc., can be formed on the surface of the metal foil. There are no particular limitations on the thickness of the metal foil, as long as it is thick enough to perform its intended function. To suppress wrinkles when laminating with the multilayer polyimide film 10 and to easily achieve thinner FPCs, the thickness of the metal foil is preferably 5 μm to 50 μm. [Example] The present invention will be specifically described below using examples, but the present invention is not limited to these examples. <Methods for Determining Physical Properties> First, the methods for determining the relative permittivity, dielectric loss factor, and coefficient of linear expansion of polyimide films will be explained. [Relative Permittivity and Dielectric Loss Factor] The relative permittivity and dielectric loss factor of the polyimide film were measured using a network analyzer (HP's "8719C") and a resonant cavity perturbation dielectric constant measuring device (EM LAB's "CP531"). Specifically, firstly, the polyimide film was cut into 2 mm × 100 mm pieces to prepare samples for measuring the relative permittivity and dielectric loss factor. Then, the samples were placed in an environment of 23°C and 50% relative humidity for 24 hours. The relative permittivity and dielectric loss factor were then measured using the aforementioned network analyzer and resonant cavity perturbation dielectric constant measuring device at 23°C, 50% relative humidity, and a measurement frequency of 10 GHz. When the dielectric loss factor was below 0.0030, it was evaluated as "capable of reducing the dielectric loss factor." On the other hand, when the dielectric loss factor exceeds 0.0030, it is evaluated as "unable to reduce the dielectric loss factor". [Coefficient of Linear Expansion (CTE)] Using a thermal analysis apparatus (TMA / SS6100 manufactured by Hitachi High-Tech Science), the polyimide film (sample) was heated from -10°C to 300°C at a heating rate of 10°C / min, and then cooled back to -10°C at a cooling rate of 40°C / min. Subsequently, the sample was heated again to 300°C at a heating rate of 10°C / min, and the coefficient of linear expansion was determined based on the strain from 50°C to 250°C during the second heating. The measurement conditions are shown below. Sample (polyimide film) dimensions: width 3 mm, length 10 mm; Load: 1 g; Measurement environment: air. <Preparation of Polyimide Film> The preparation methods of the polyimide films of the Examples and Comparative Examples will be described below. Furthermore, the compounds and reagents will be referred to by the following abbreviations. Also, the preparation of the polyamide solutions used in the preparation of the polyimide films was carried out under a nitrogen atmosphere at 20°C. DMF: N,N-Dimethylformamide; PDA: p-phenylenediamine; TPE-R: 1,3-bis(4-aminophenoxy)phenyl; BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane; BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride; PMDA: pyromellitic dianhydride; BTDA: 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride; ODPA: 4,4'-oxophthalic anhydride; AA: acetic anhydride; IQ: isoquinoline. [Example 1] (1st sequential polymerization step) 314.58 g of DMF and 10.11 g of PDA were added to a 2000 mL glass flask. While stirring the contents of the flask, 16.25 g of BPDA, 1.54 g of PMDA, and 8.67 g of BTDA were added. The contents of the flask were then stirred for 30 minutes. (2nd Sequential Polymerization Step) Next, while stirring the contents of the flask, 16.85 g of a pre-prepared PDA solution (solvent: DMF, PDA concentration: 20 wt%) and 4.97 g of TPE-R were slowly added. After visually confirming that the TPE-R had dissolved, 14.17 g of BPDA was added to the flask while stirring, and the contents were stirred for 30 minutes. Then, a pre-prepared PMDA solution (solvent: DMF, PMDA concentration: 7.2 wt%) was continuously added to the flask at a rate that prevented a rapid increase in the viscosity of the contents for a specified time. Then, when the viscosity of the contents reached 1500 poise at 23°C, the addition of PMDA solution was stopped, and the contents were stirred for 1 hour to obtain a polyacrylic acid solution. The solids content of the obtained polyacrylic acid solution was 15 wt%. Furthermore, the viscosity of the obtained polyacrylic acid solution at a temperature of 23°C is 1500–2000 poise. (Film Forming Steps) Next, 27.5 g of a amide imidization accelerator (weight ratio: AA / IQ / DMF = 42 / 21 / 37) containing a mixture of AA, IQ, and DMF was added to 55 g of polyamide solution (polyamide solution obtained according to the above preparation method) to prepare a dopant solution. Then, under an environment below 0°C, the dopant solution was degassed while being stirred, and then coated onto an aluminum foil using a corner-shaped coating machine to form a coated film. Next, the coated film was heated at 110°C for 160 seconds to obtain a self-sustaining gel film. The obtained gel film was peeled off from the aluminum foil, fixed to a metal frame, and placed in a hot air circulating oven preheated to 300°C for 56 seconds. Subsequently, the heated film was placed in a far-infrared (IR) oven preheated to 380°C and heated at 380°C for 49 seconds to amide the polyamide in the gel film. Then, it was cut off from the metal frame to obtain the polyamide film of Example 1 (thickness: 17 μm). Furthermore, the polyimide film obtained through the same procedure as described above was fixed to a metal frame and heated in an IR oven at 380°C for 1 minute. The result showed that the shape of the polyimide film was maintained. Therefore, the polyimide contained in the polyimide film of Example 1 is a non-thermoplastic polyimide. In other words, the polyimide film of Example 1 is a non-thermoplastic polyimide film. Regarding the polyimide films of Examples 2 to 12 described below, the polyimide films obtained through the same procedure as described below were also fixed to metal frames and heated in an IR oven at 380°C for 1 minute. The result showed that the shape of the polyimide film was maintained. Therefore, the polyimide contained in the polyimide films of Examples 2 to 12 are all non-thermoplastic polyimides. In other words, the polyimide films in Examples 2 to 12 are all non-thermoplastic polyimide films. [Examples 2-12] The types and ratios (feed ratios) of monomers used in the 1st sequential polymerization step and the types and ratios (feed ratios) of monomers used in the 2nd sequential polymerization step are shown in Tables 1 and 2 below. Except for this, polyimide films (thickness: 17 μm for all) of Examples 2-12 were obtained using the same method as in Example 1. Furthermore, the total mass of dianhydride and diamine in any of Examples 2-12 was the same as in Example 1. [Comparative Example 1] The 1st sequential polymerization step and the 2nd sequential polymerization step were modified as shown below. Otherwise, the polyimide film (thickness: 17 μm) of Comparative Example 1 was obtained by the same method as in Example 1. (Comparative Example 1, 1st sequential polymerization step) 315.40 g of DMF and 9.78 g of PDA were added to a 2000 mL glass flask. While stirring the contents of the flask, 15.72 g of BPDA, 1.49 g of PMDA, and 8.39 g of BTDA were added. The contents of the flask were then stirred for 30 minutes. (Comparative Example 1, 2nd Sequential Polymerization Step) Next, while stirring the contents of the flask, 16.30 g of a pre-prepared PDA solution (solvent: DMF, PDA concentration: 20 wt%) and 6.75 g of BAPP were slowly added to the flask. After visually confirming that the BAPP had dissolved, 13.71 g of BPDA was added to the flask while stirring the contents, and the flask contents were stirred for 30 minutes. Then, a pre-prepared PMDA solution (solvent: DMF, PMDA concentration: 7.2 wt%) was continuously added to the flask at a rate that prevented a rapid increase in the viscosity of the flask contents for a specified time. Then, when the viscosity of the flask contents reached 1500 poise at a temperature of 23°C, the addition of PMDA solution was stopped, and the flask contents were stirred for 1 hour to obtain a polyacrylic acid solution. The solids content of the obtained polyacrylic acid solution was 15 wt%. Furthermore, the viscosity of the obtained polyacrylic acid solution at a temperature of 23°C is 1500–2000 poise. [Comparative Example 2] A polyamide solution was prepared using the method (random polymerization) shown below. Otherwise, a polyimide film (thickness: 17 μm) of Comparative Example 2 was obtained using the same method as in Example 1. (Preparation method of polyacrylic acid solution in Comparative Example 2) 165.61 g of DMF, 2.08 g of TPE-R, and 6.71 g of PDA were added to a 500 mL glass flask. While stirring the contents of the flask, 20.98 g of BPDA was added. The contents of the flask were then stirred for 60 minutes to obtain a polyacrylic acid solution. The solid content concentration of the obtained polyacrylic acid solution was 15% by weight. Furthermore, the viscosity of the obtained polyacrylic acid solution at 23°C was 1500 poise. [Comparative Example 3] A polyamide solution was prepared using the method (random polymerization) shown below. Otherwise, a polyimide film (thickness: 17 μm) of Comparative Example 3 was obtained using the same method as in Example 1. (Preparation method of polyacrylic acid solution in Comparative Example 3) 160.84 g of DMF and 7.95 g of PDA were added to a 500 mL glass flask. While stirring the contents of the flask, 17.31 g of BPDA and 4.03 g of BTDA were added. The contents of the flask were then stirred for 30 minutes. Next, a pre-prepared BTDA solution (solvent: DMF, BTDA concentration: 0.71 g, BTDA concentration: 7.2 wt%) was continuously added to the flask at a rate that prevented a rapid increase in the viscosity of the contents for a specified time. Then, the addition of BTDA solution was stopped when the viscosity of the contents reached 1500 poise at a temperature of 23°C. The contents of the flask were then stirred for 1 hour to obtain a polyacrylic acid solution. The solid content concentration of the obtained polyacrylic acid solution was 15 wt%. Furthermore, the viscosity of the obtained polyacrylic acid solution at a temperature of 23°C is 1500–2000 poise. [Comparative Example 4] A polyamide solution was prepared using the method (random polymerization) shown below. Otherwise, a polyimide film (thickness: 17 μm) of Comparative Example 4 was obtained using the same method as in Example 1. (Preparation method of polyacrylic acid solution in Comparative Example 4) 163.95 g of DMF, 6.59 g of PDA, and 3.14 g of TPE-R were added to a 500 mL glass flask. While stirring the contents of the flask, 15.57 g of ODPA and 4.22 g of PMDA were added. The contents of the flask were then stirred for 30 minutes. Next, a pre-prepared PMDA solution (solvent: DMF, PMDA concentration: 0.47 g, PMDA concentration: 7.2 wt%) was continuously added to the flask at a rate that prevented a rapid increase in the viscosity of the contents for a specified time. Then, the addition of PMDA solution was stopped when the viscosity of the contents reached 1500 poise at a temperature of 23°C. The contents of the flask were then stirred for 1 hour to obtain a polyacrylic acid solution. The solid content concentration of the obtained polyacrylic acid solution was 15 wt%. Furthermore, the viscosity of the obtained polyacrylic acid solution at a temperature of 23°C is 1500–2000 poise. [Comparative Example 5] A polyamide solution was prepared using the method (random polymerization) shown below. Otherwise, a polyimide film (thickness: 17 μm) of Comparative Example 5 was obtained using the same method as in Example 1. (Preparation method of polyacrylic acid solution in Comparative Example 5) 163.88 g of DMF, 7.07 g of PDA, and 2.12 g of TPE-R were added to a 500 mL glass flask. While stirring the contents of the flask, 19.23 g of BPDA and 1.11 g of PMDA were added. The contents of the flask were then stirred for 30 minutes. Next, a pre-prepared PMDA solution (solvent: DMF, PMDA concentration: 0.48 g, PMDA concentration: 7.2 wt%) was continuously added to the flask at a rate that prevented a rapid increase in the viscosity of the contents for a specified time. Then, the addition of PMDA solution was stopped when the viscosity of the contents reached 1500 poise at a temperature of 23°C. The contents of the flask were then stirred for 1 hour to obtain a polyacrylic acid solution. The solid content concentration of the obtained polyacrylic acid solution was 15 wt%. Furthermore, the viscosity of the obtained polyacrylic acid solution at a temperature of 23°C is 1500–2000 poise. <Results> For Examples 1-12 and Comparative Examples 1-5, the types and ratios (feed ratios) of monomers used in the 1st sequential polymerization step, the types and ratios (feed ratios) of monomers used in the 2nd sequential polymerization step, the relative permittivity, the dielectric loss factor, and the CTE are shown in Tables 1 and 2. Furthermore, in Tables 1 and 2, "1st" and "2nd" refer to "1st sequential polymerization step" and "2nd sequential polymerization step," respectively. Regarding Comparative Examples 2-5, since they are random polymerizations, the types of monomers used and their ratios (feed ratios) are recorded in the "1st" column. Furthermore, in Tables 1 and 2, the values ​​in the "Diamine" column represent the content (in moles) of each diamine relative to the total amount of diamine used (in the case of sequential polymerization, the sum of the total amount of diamine used in the 1st sequential polymerization step and the total amount of diamine used in the 2nd sequential polymerization step). In Tables 1 and 2, the values ​​in the "Acid Dihydric Anhydride" column represent the content (in moles) of each acid dianhydride relative to the total amount of acid dianhydride used (in the case of sequential polymerization, the sum of the total amount of acid dianhydride used in the 1st sequential polymerization step and the total amount of acid dianhydride used in the 2nd sequential polymerization step). Furthermore, for any of Examples 1-12 and Comparative Examples 1-5, the molar fraction of each residue in the polyamide solution prepared was consistent with the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used. Also, for any of Examples 1-12 and Comparative Examples 1-5, the mass ratio obtained by dividing the total mass of tetracarboxylic dianhydride residues constituting the polyimide in the obtained polyimide film by the total mass of the diamine residues constituting the polyimide was 0.99 or more and 1.01 or less. Furthermore, in Table 2, "-" in the CTE column indicates that no measurement was performed. [Table 1] [Table 2] The polyamide solutions prepared in Examples 1-12 contain polyamide residues including BPDA residues, BTDA residues, PDA residues and TPE-R residues. In Examples 1-12, the dielectric loss factor was 0.0030 or less. Therefore, the polyimide films of Examples 1-12 can reduce the dielectric loss factor. The polyacrylic acid contained in the polyacrylic acid solutions prepared in Comparative Examples 1 and 3 did not contain TPE-R residues. The polyacrylic acid contained in the polyacrylic acid solutions prepared in Comparative Examples 2, 4, and 5 did not contain BTDA residues. The polyacrylic acid contained in the polyacrylic acid solution prepared in Comparative Example 4 did not contain BPDA residues. In Comparative Examples 1-5, the dielectric loss factor exceeded 0.0030. Therefore, the polyimide films of Comparative Examples 1-5 failed to reduce the dielectric loss factor. The above results indicate that, according to the present invention, a non-thermoplastic polyimide film capable of reducing the dielectric loss factor can be provided. 10: Multilayer polyimide film; 11: Non-thermoplastic polyimide film; 12: Adhesive layer; 12a: Main surface; 13: Metal layer; 20: Metal laminated laminate. Figure 1 is a cross-sectional view showing an example of the multilayer polyimide film of the present invention. Figure 2 is a cross-sectional view showing an example of the metal-laminated laminate of the present invention. 10: Multilayer polyimide film 11: Non-thermoplastic polyimide film 12: Next layer

Claims

1. A polyamide having tetracarboxylic dianhydride residues and diamine residues, wherein the tetracarboxylic dianhydride residues comprise 3,3',4,4'-biphenyltetracarboxylic dianhydride residues and 3,3',4,4'-benzophenone tetracarboxylic dianhydride residues, and the diamine residues comprise p-phenylenediamine residues and 1,3-bis(4-aminophenoxy)benzene residues; wherein the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residues is 55 mol% to 85 mol% relative to the total amount of the tetracarboxylic dianhydride residues; wherein the content of the 3,3',4,4'-benzophenone tetracarboxylic dianhydride residues is 10 mol% to 30 mol% relative to the total amount of the tetracarboxylic dianhydride residues; and wherein the content of the p-phenylenediamine residues is 75 mol% to 95 mol% relative to the total amount of the diamine residues. The content of the above-mentioned 1,3-bis(4-aminophenoxy)benzene residues is more than 2 mol% and less than 20 mol% relative to the total amount of the above-mentioned diamine residues.

2. The polyamide of claim 1, wherein the aforementioned tetracarboxylic dianhydride residues further include pyromellitic dianhydride residues, and the content of the aforementioned pyromellitic dianhydride residues is 3 mol% to 15 mol% relative to the total amount of the aforementioned tetracarboxylic dianhydride residues.

3. A polyimide, which is a polyimide of the polyamide as claimed in claim 1.

4. A non-thermoplastic polyimide film comprising the polyimide of claim 3.

5. A multilayer polyimide film having a non-thermoplastic polyimide film as claimed in claim 4, and an adhesive layer comprising thermoplastic polyimide disposed on at least one side of the non-thermoplastic polyimide film.

6. The multilayer polyimide film of claim 5, wherein the aforementioned adhesive layer system is disposed on both sides of the aforementioned non-thermoplastic polyimide film.

7. A metal laminate having a multilayer polyimide film as claimed in claim 5, and a metal layer disposed on the main surface of at least one of the adhesive layers of the multilayer polyimide film.

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