Non-thermoplastic polyimide film, multi-layer polyimide film, and metal-clad laminate

Abstract

This non-thermoplastic polyimide film (11) contains a non-thermoplastic polyimide. The non-thermoplastic polyimide includes a 3,3',4,4'-biphenyl-tetracarboxylic acid dianhydride residue, a 4,4'-oxydiphthalic acid anhydride residue, a p-phenylenediamine residue, and a 1,3-bis(4-aminophenoxy)benzene residue. The relationships A1 + A2 ≥ 80, B1 + B2 ≥ 80, and (A1 + B1) / (A2 + B2) ≤ 3.50 are satisfied, where A1 mol% is the 3,3',4,4'-biphenyl-tetracarboxylic acid dianhydride residue content, A2 mol% is the 4,4'-oxydiphthalic acid anhydride residue content, B1 mol% is the p-phenylenediamine residue content, and B2 mol% is the 1,3-bis(4-aminophenoxy)benzene residue content.

Description

[Technical Field]

[0001] The present invention relates to a non-thermoplastic polyimide film, a multilayer polyimide film, and a metal-clad laminate. [Background technology]

[0002] In recent years, demand for flexible printed circuit boards (hereinafter sometimes referred to as "FPCs") has grown in line with the expansion of electronic products, particularly smartphones, tablet PCs, and laptops. In particular, demand for FPCs made from multilayer polyimide film with a non-thermoplastic polyimide layer (core layer) and a thermoplastic polyimide layer (adhesive layer) is expected to grow further due to its excellent heat resistance and flexibility. Furthermore, polyimide has sufficient heat resistance to be suitable for high-temperature processes, and its relatively low linear expansion coefficient makes it less susceptible to internal stress, making it an ideal material for FPCs.

[0003] Furthermore, with the recent trend toward high-speed signal transmission in electronic devices, there is an increasing demand for electronic circuit board materials with low dielectric constants and low dielectric loss tangents to enable higher frequencies of electrical signals propagating through circuits. Reducing the dielectric constant and dielectric loss tangent of electronic circuit board materials is effective in suppressing electrical signal transmission loss. In recent years, as we enter the dawn of the IoT society, the trend toward higher frequencies is accelerating, and there is a demand for circuit board materials that can suppress transmission loss, even in the 10 GHz and higher frequency range.

[0004] Transmission loss is expressed by the following formula using a proportionality constant (k), frequency (f), dielectric loss tangent (Df), and relative permittivity (Dk). The dielectric loss tangent contributes more to transmission loss than the relative permittivity. Therefore, in order to reduce transmission loss, it is particularly important to reduce the dielectric loss tangent. Transmission loss = k × f × Df × (Dk) 1 / 2

[0005] BACKGROUND ART Polyimide films (polyimide layers) that exhibit a low dielectric loss tangent are known as materials used in circuit boards that are adaptable to higher frequencies (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2014-526399 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-246201 [Patent Document 3] International Publication No. 2018 / 079710 [Patent Document 4] International Publication No. 2016 / 159060 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the techniques described in Patent Documents 1 to 4 still have room for improvement in terms of reducing the dielectric loss tangent.

[0008] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a non-thermoplastic polyimide film capable of reducing the dielectric loss tangent, and a multilayer polyimide film and a metal-clad laminate using the non-thermoplastic polyimide film. [Means for solving the problem]

[0009] A first non-thermoplastic polyimide film according to the present invention comprises a non-thermoplastic polyimide having, as tetracarboxylic dianhydride residues, 3,3',4,4'-biphenyltetracarboxylic dianhydride residues and 4,4'-oxydiphthalic anhydride residues, and, as diamine residues, p-phenylenediamine residues and 1,3-bis(4-aminophenoxy)benzene residues. When the content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A1 mol %, the content of the 4,4'-oxydiphthalic anhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A2 mol %, the content of the p-phenylenediamine residues relative to all diamine residues constituting the non-thermoplastic polyimide is B1 mol %, and the content of the 1,3-bis(4-aminophenoxy)benzene residues relative to all diamine residues constituting the non-thermoplastic polyimide is B2 mol %, the relationships A1+A2≧80, B1+B2≧80, and (A1+B1) / (A2+B2)≦3.50 are satisfied.

[0010] In one embodiment of the first non-thermoplastic polyimide film according to the present invention, the A1, the A2, the B1, and the B2 satisfy the relationship 1.60≦(A1+B1) / (A2+B2)≦3.50.

[0011] In one embodiment of the first non-thermoplastic polyimide film according to the present invention, the non-thermoplastic polyimide further has a pyromellitic dianhydride residue as the tetracarboxylic dianhydride residue.

[0012] In one embodiment of the first non-thermoplastic polyimide film according to the present invention, the content of the pyromellitic dianhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is 3 mol % or more and 12 mol % or less.

[0013] In one embodiment of the first non-thermoplastic polyimide film according to the present invention, the ratio of the total amount of tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide divided by the total amount of diamine residues constituting the non-thermoplastic polyimide is 0.95 or more and 1.05 or less.

[0014] In one embodiment of the first non-thermoplastic polyimide film according to the present invention, the non-thermoplastic polyimide film contains crystalline portions having a lamellar structure and amorphous portions sandwiched between the crystalline portions, and has a lamellar period determined by X-ray scattering of 15 nm or more.

[0015] The second non-thermoplastic polyimide film of the present invention contains a non-thermoplastic polyimide and contains crystalline portions having a lamellar structure and amorphous portions sandwiched between the crystalline portions, and has a lamellar periodicity of 15 nm or more as determined by X-ray scattering.

[0016] The multilayer polyimide film of the present invention comprises the first or second non-thermoplastic polyimide film of the present invention and an adhesive layer containing a thermoplastic polyimide disposed on at least one side of the non-thermoplastic polyimide film.

[0017] In the multilayer polyimide film according to one embodiment of the present invention, the adhesive layers are disposed on both sides of the non-thermoplastic polyimide film.

[0018] A first metal-clad laminate according to the present invention comprises the first or second non-thermoplastic polyimide film according to the present invention and a metal layer disposed on at least one side of the non-thermoplastic polyimide film.

[0019] The second metal-clad laminate according to the present invention comprises the multilayer polyimide film according to the present invention and a metal layer disposed on a main surface of at least one of the adhesive layers of the multilayer polyimide film. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a non-thermoplastic polyimide film capable of reducing the dielectric loss tangent, and a multilayer polyimide film and a metal-clad laminate using the non-thermoplastic polyimide film. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing an example of a multilayer polyimide film according to the present invention. [Figure 2] 1 is a cross-sectional view showing an example of a metal-clad laminate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0023] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. A "polyimide" is a polymer containing a structural unit represented by the following general formula (1) (hereinafter, sometimes referred to as "structural unit (1)").

[0024] [ka]

[0025] In general formula (1), X 1 represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from tetracarboxylic dianhydride), and X 2 represents a diamine residue (a divalent organic group derived from a diamine).

[0026] The content of the structural unit (1) relative to all structural units constituting the polyimide 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, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0027] Unless otherwise specified, the "linear expansion coefficient" refers to the linear expansion coefficient at elevated temperatures from 50° C. to 250° C. The linear expansion coefficient is measured by the same method as in the examples described below or a method equivalent thereto.

[0028] The "dielectric constant" is the dielectric constant at a frequency of 10 GHz, a temperature of 23°C, and a relative humidity of 50%. The "dielectric loss tangent" is the dielectric loss tangent at a frequency of 10 GHz, a temperature of 23°C, and a relative humidity of 50%. The methods for measuring the dielectric constant and the dielectric loss tangent are the same as or similar to those in the examples described below.

[0029] "Non-thermoplastic polyimide" refers to polyimide that retains its film shape (flat membrane shape) when fixed in film form on a metal frame and heated at 380°C for 1 minute. "Thermoplastic polyimide" refers to polyimide that does not retain its film shape when fixed in film form on a metal frame and heated at 380°C for 1 minute.

[0030] The "principal surface" of a layered material (more specifically, a non-thermoplastic polyimide film, an adhesive layer, a multilayer polyimide film, a metal layer, etc.) refers to a surface perpendicular to the thickness direction of the layered material.

[0031] "Lamellar period" refers to the distance between the centers of gravity of adjacent crystalline portions (crystalline portions having a lamellar structure) in a film containing crystalline portions having a lamellar structure and amorphous portions sandwiched between the crystalline portions. Amorphous portions (intermediate layers) that could not crystallize exist between adjacent crystalline portions, and a higher-order structure is formed in the film in which some of the amorphous portions are confined within the laminated lamellar structure. The lamellar period can be determined by analyzing the higher-order structure of the film using X-ray scattering (more specifically, ultra-small-angle X-ray scattering). The lamellar period can be measured by the same method as in the examples described below or a method equivalent thereto.

[0032] Hereinafter, the compound name may be followed by "system" to refer to the compound and its derivatives collectively. Tetracarboxylic acid dianhydride may be referred to as "acid dianhydride." Non-thermoplastic polyimide contained in a non-thermoplastic polyimide film may be referred to simply as "non-thermoplastic polyimide." Thermoplastic polyimide contained in an adhesive layer may be referred to simply as "thermoplastic polyimide."

[0033] The drawings referred to in the following description mainly show each component in a schematic manner for ease of understanding, and the size, number, shape, etc. of each component shown may differ from the actual size, number, shape, etc. of each component due to the convenience of creating the drawings. Furthermore, for convenience of explanation, in drawings described later, the same components as those in previously described drawings may be assigned the same reference numerals, and their explanation may be omitted.

[0034] <First embodiment: non-thermoplastic polyimide film> The non-thermoplastic polyimide film according to the first embodiment of the present invention (hereinafter sometimes referred to as "non-thermoplastic polyimide film F1") contains a non-thermoplastic polyimide. The non-thermoplastic polyimide has, as tetracarboxylic dianhydride residues, 3,3',4,4'-biphenyltetracarboxylic dianhydride residues and 4,4'-oxydiphthalic anhydride residues, and has, as diamine residues, p-phenylenediamine residues and 1,3-bis(4-aminophenoxy)benzene residues. When the content of 3,3',4,4'-biphenyltetracarboxylic dianhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A1 mol %, the content of 4,4'-oxydiphthalic anhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A2 mol %, the content of p-phenylenediamine residues relative to all diamine residues constituting the non-thermoplastic polyimide is B1 mol %, and the content of 1,3-bis(4-aminophenoxy)benzene residues relative to all diamine residues constituting the non-thermoplastic polyimide is B2 mol %, the relationships A1+A2≧80, B1+B2≧80, and (A1+B1) / (A2+B2)≦3.50 are satisfied.

[0035] Hereinafter, 3,3',4,4'-biphenyltetracarboxylic dianhydride may be referred to as "BPDA." 4,4'-oxydiphthalic anhydride may be referred to as "ODPA." p-Phenylenediamine may be referred to as "PDA." 1,3-bis(4-aminophenoxy)benzene may be referred to as "TPE-R." Pyromellitic dianhydride may be referred to as "PMDA." 3,3',4,4'-benzophenonetetracarboxylic dianhydride may be referred to as "BTDA." p-Phenylenebis(trimellitic acid monoester acid anhydride) may be referred to as "TMHQ."

[0036] In the first embodiment, "A1+A2≧80" means that the total content of BPDA residues and ODPA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is 80 mol % or more. In the first embodiment, "B1+B2≧80" means that the total content of PDA residues and TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimide is 80 mol % or more.

[0037] Both BPDA residues and PDA residues have a rigid structure. On the other hand, both ODPA residues and TPE-R residues have a bent structure. In the first embodiment, "(A1+B1) / (A2+B2)" is the abundance ratio of residues having a rigid structure to residues having a bent structure. Hereinafter, "(A1+B1) / (A2+B2)" may be referred to as the "rigid / flexible ratio."

[0038] The non-thermoplastic polyimide film F1 can reduce the dielectric loss tangent, and the reason for this is presumed to be as follows.

[0039] Generally, when preparing a polyimide film, it is necessary to use a monomer with a linear rigid structure to obtain a stable lamellar structure. On the other hand, if an excessive amount of a monomer with a rigid structure is used, it tends to be difficult to form a lamellar structure in which the molecular chains are folded at bends.

[0040] In the non-thermoplastic polyimide film F1, the total content of BPDA residues and ODPA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is 80 mol % or more, and the total content of PDA residues and TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimide is 80 mol % or more. Furthermore, the non-thermoplastic polyimide film F1 has a rigid / flexible ratio of 3.50 or less. Therefore, in the non-thermoplastic polyimide film F1, residues having a rigid structure and residues having a flexible structure are present in a balance suitable for obtaining a stable lamellar structure, and therefore the packing of the crystalline portion having the lamellar structure tends to be high.

[0041] On the other hand, the amorphous portions confined within the laminated lamellar structure are more highly oriented due to the adjacent lamellar structures, resulting in a higher density than the amorphous portions outside the laminated lamellar structure. Therefore, the amorphous portions confined within the laminated lamellar structure are thought to contribute less to dielectric relaxation than the amorphous portions outside the laminated lamellar structure. "Dielectric relaxation" refers to the phenomenon in which molecular dipoles fluctuate and energy is released when an external field such as an electric field is applied to a resin. To reduce the dielectric loss tangent, it is necessary to form a high-order structure that is less susceptible to dielectric relaxation. The inventors believed that by increasing the lamellar period and increasing the proportion of amorphous portions confined within the laminated lamellar structure, a high-order structure that is less susceptible to dielectric relaxation could be formed, thereby reducing the dielectric loss tangent. In the non-thermoplastic polyimide film F1, the crystalline portions having a lamellar structure tend to have a higher packing property, which increases the distance between adjacent crystalline portions and increases the lamellar period. Therefore, the non-thermoplastic polyimide film F1 can reduce the dielectric loss tangent.

[0042] In the first embodiment, in order to reduce the linear expansion coefficient, the stiffness / flexibility ratio is preferably 1.60 or more, and more preferably 1.70 or more.

[0043] The non-thermoplastic polyimide film F1 will be described in detail below.

[0044] [Non-thermoplastic polyimide] The non-thermoplastic polyimide contained in the non-thermoplastic polyimide film F1 may have other acid dianhydride residues in addition to the BPDA residue and the ODPA residue. Examples of acid dianhydrides (monomers) for forming other acid dianhydride residues (acid dianhydride residues other than BPDA residues and ODPA residues) include PMDA, BTDA, TMHQ, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,4'-oxydiphthalic anhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, ethylene bis(trimellitic acid monoester acid anhydride), bisphenol A bis(trimellitic acid monoester acid anhydride), and derivatives thereof.

[0045] In order to obtain a non-thermoplastic polyimide film F1 capable of further reducing the dielectric loss tangent, the other acid dianhydride residue is preferably one or more selected from the group consisting of PMDA residue, BTDA residue, and TMHQ residue. In addition, in order to obtain a non-thermoplastic polyimide film F1 capable of further reducing the dielectric loss tangent while improving heat resistance, the other acid dianhydride residue is preferably PMDA residue.

[0046] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the total content of BPDA residues and ODPA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 83 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%.

[0047] When a PMDA residue is used as the other acid dianhydride residue, in order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent while improving heat resistance, the total content of BPDA residues, ODPA residues, and PMDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 85 mol % or more, more preferably 90 mol % or more, and may be 100 mol %.

[0048] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of BPDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 20 mol % or more and 70 mol % or less, and more preferably 25 mol % or more and 65 mol % or less.

[0049] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of ODPA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 20 mol % or more and 70 mol % or less, and more preferably 30 mol % or more and 60 mol % or less.

[0050] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent while improving the heat resistance, the content of PMDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 1 mol % or more and 15 mol % or less, and more preferably 3 mol % or more and 12 mol % or less.

[0051] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of BTDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 1 mol % or more and 5 mol % or less, and more preferably 2 mol % or more and 4 mol % or less.

[0052] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of TMHQ residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is preferably 4 mol % or more and 8 mol % or less, and more preferably 5 mol % or more and 7 mol % or less.

[0053] The non-thermoplastic polyimide contained in the non-thermoplastic polyimide film F1 may have other diamine residues in addition to the PDA residue and the TPE-R residue. Examples of diamines (monomers) for forming other diamine residues (diamine residues other than PDA residues and TPE-R residues) include 1,4-bis(4-aminophenoxy)benzene, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,3-diaminobenzene, 1,2-diaminobenzene, and derivatives thereof.

[0054] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the total content of PDA residues and TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimide is preferably 85 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more, and may be 100 mol %.

[0055] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of PDA residues relative to all diamine residues constituting the non-thermoplastic polyimide is preferably 70 mol % or more and 98 mol % or less, and more preferably 80 mol % or more and 95 mol % or less.

[0056] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the content of TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimide is preferably 2 mol % or more and 30 mol % or less, and more preferably 5 mol % or more and 20 mol % or less.

[0057] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric tangent, the ratio of the total amount of acid dianhydride residues constituting the non-thermoplastic polyimide divided by the total amount of diamine residues constituting the non-thermoplastic polyimide is preferably 0.95 or more and 1.05 or less, more preferably 0.97 or more and 1.03 or less, and even more preferably 0.99 or more and 1.01 or less.

[0058] The non-thermoplastic polyimide film F1 may contain components (additives) other than the non-thermoplastic polyimide. Examples of additives that can be used include dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers. The content of the non-thermoplastic polyimide in the non-thermoplastic polyimide film F1 is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may be 100% by weight, based on the total weight of the non-thermoplastic polyimide film F1.

[0059] In order to obtain a non-thermoplastic polyimide film F1 that can further reduce the dielectric loss tangent and has a small linear expansion coefficient, it is preferable to satisfy the following condition 1, more preferably to satisfy the following condition 2, even more preferably to satisfy the following condition 3, and particularly preferably to satisfy the following condition 4. Condition 1: The non-thermoplastic polyimide has only PDA residues and TPE-R residues as diamine residues, and the stiffness / flexibility ratio is 1.60 or more and 3.50 or less. Requirement 2: The above requirement 1 is satisfied, and the non-thermoplastic polyimide further has a PMDA residue as an acid dianhydride residue. Requirement 3: The above requirement 2 is satisfied, and the total content of BPDA residues, ODPA residues, and PMDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is 90 mol % or more and 100 mol % or less. Requirement 4: The above requirement 3 is satisfied, and the content of PMDA residues relative to all acid dianhydride residues constituting the non-thermoplastic polyimide is 3 mol % or more and 12 mol % or less.

[0060] [Method of manufacturing non-thermoplastic polyimide film F1] The non-thermoplastic polyimide contained in the non-thermoplastic polyimide film F1 is obtained by imidizing its precursor, polyamic acid.

[0061] Any known method or a combination thereof can be used for producing (synthesizing) polyamic acid. Polyamic acid is typically produced by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. It is preferable that the amounts of diamine and tetracarboxylic dianhydride used during the reaction are substantially equal. When synthesizing polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the amounts of each diamine and each tetracarboxylic dianhydride. The molar fraction of each residue in the polyimide formed from the polyamic acid corresponds, for example, to the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of the polyamic acid. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the polyamic acid synthesis reaction, are not particularly limited, but are, for example, in the range of 10°C to 150°C. The reaction time for the polyamic acid synthesis reaction is, for example, in the range of 10 minutes to 30 hours. In the present embodiment, any method for adding a monomer may be used to produce the polyamic acid. Typical methods for producing the polyamic acid include the following.

[0062] An example of a method for producing polyamic acid is a polymerization method (hereinafter sometimes referred to as "polymerization method A") that involves the following steps (Aa) and (Ab). (Aa): A step of reacting a diamine with an acid dianhydride in an organic solvent with an excess of diamine to obtain a prepolymer having amino groups at both ends. (Ab): A step of polymerizing by adding a diamine having a different structure from that used in step (Aa) and then adding an acid dianhydride having a different structure from that used in step (Aa) so that the diamine and the acid dianhydride are substantially equimolar in all steps.

[0063] Another example of a method for producing polyamic acid is a method of polymerization through the following steps (Ba) and (Bb) (hereinafter, sometimes referred to as "polymerization method B"). (Ba): A step of reacting a diamine with an acid dianhydride in an organic solvent with an excess of the acid dianhydride to obtain a prepolymer having acid anhydride groups at both ends. (Bb): A step of polymerizing by adding an acid dianhydride having a structure different from that used in step (Ba) and then adding a diamine having a structure different from that used in step (Ba) so that the diamine and the acid dianhydride are substantially equimolar in all steps.

[0064] A polymerization method in which the addition order of diamines and dianhydrides is set so that a specific diamine or dianhydride selectively reacts with any or specific diamines or any or specific dianhydrides (e.g., the above-mentioned polymerization method A and polymerization method B) is referred to herein as sequence polymerization. In contrast, a polymerization method in which the addition order of diamines and dianhydrides is not set (a polymerization method in which monomers react with each other randomly) is referred to herein as random polymerization. Furthermore, when sequence polymerization is performed in two steps, such as polymerization method A and polymerization method B, the first step (step (Aa), step (Ba), etc.) is referred to herein as the "first sequence polymerization step," and the second step (step (Ab), step (Bb), etc.) is referred to herein as the "second sequence polymerization step."

[0065] In this embodiment, in order to obtain a non-thermoplastic polyimide film F1 capable of further reducing the dielectric loss tangent, sequence polymerization is preferred as the method for polymerizing polyamic acid.

[0066] When obtaining a non-thermoplastic polyimide, a method of obtaining the non-thermoplastic polyimide from a polyamic acid solution containing a polyamic acid and an organic solvent may be employed. Examples of organic solvents that can be used in polyamic acid solutions include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide-based solvents such as dimethyl sulfoxide; sulfone-based solvents such as diphenyl sulfone and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide, N,N-dimethylformamide (hereinafter sometimes referred to as "DMF"), N,N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphoric triamide; ester-based solvents such as γ-butyrolactone; alkyl halide solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents are typically used alone, but two or more may be used in combination as needed. When polyamic acid is obtained by the above-mentioned polymerization method, the reaction solution (the solution after the reaction) itself may be used as a polyamic acid solution for obtaining a non-thermoplastic polyimide. In this case, the organic solvent in the polyamic acid solution is the organic solvent used in the reaction in the above-mentioned polymerization method. Alternatively, the solid polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare a polyamic acid solution.

[0067] The polyamic acid solution may contain additives such as dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers. The concentration of polyamic acid in the polyamic acid solution is not particularly limited and is, for example, 5% by weight to 35% by weight, and preferably 8% by weight to 30% by weight, based on the total amount of the polyamic acid solution. When the polyamic acid concentration is 5% by weight to 35% by weight, an appropriate molecular weight and solution viscosity can be obtained.

[0068] The method for obtaining the non-thermoplastic polyimide film F1 using the polyamic acid solution is not particularly limited, and various known methods can be applied, for example, a method for obtaining the non-thermoplastic polyimide film F1 through the following steps i) to iii): Step i): A step of applying a dope solution containing a polyamic acid solution onto a support to form a coating film. Step ii): A step of drying the coating film on the support to form a self-supporting polyamic acid film (hereinafter, sometimes referred to as a "gel film"), and then peeling the gel film from the support. Step iii) A step of heating the gel film to imidize the polyamic acid in the gel film to obtain a non-thermoplastic polyimide film F1 containing a non-thermoplastic polyimide.

[0069] Methods for obtaining the non-thermoplastic polyimide film F1 through steps i) to iii) are roughly divided into thermal imidization and chemical imidization. The thermal imidization method is a method in which a polyamic acid solution is applied as a dope onto a support without using a dehydrating ring-closing agent or the like, and the dope is heated to promote imidization. On the other hand, the chemical imidization method is a method in which a polyamic acid solution to which at least one of a dehydrating ring-closing agent and a catalyst has been added is used as a dope to promote imidization. Either method may be used, but the chemical imidization method is superior in productivity.

[0070] As the dehydrating ring-closing agent, an acid anhydride, such as acetic anhydride, is preferably used. As the catalyst, a tertiary amine such as an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine (more specifically, isoquinoline, etc.) is preferably used. When adding at least one of the dehydrating ring-closing agent and the catalyst to the polyamic acid solution, they may be added directly without being dissolved in an organic solvent, or they may be added dissolved in an organic solvent. When adding them directly without being dissolved in an organic solvent, the reaction may proceed too quickly before at least one of the dehydrating ring-closing agent and the catalyst diffuses, resulting in the formation of a gel. Therefore, it is preferable to add a solution (imidization accelerator) obtained by dissolving at least one of the dehydrating ring-closing agent and the catalyst in an organic solvent to the polyamic acid solution.

[0071] In step i), the method for applying the dope solution onto the support is not particularly limited, and a method using a conventionally known coating device such as a die coater, a comma coater (registered trademark), a reverse coater, or a knife coater can be used.

[0072] In step i), the support on which the dope solution is applied is preferably a glass plate, aluminum foil, an endless stainless steel belt, a stainless steel drum, or the like. In step ii), the drying conditions (heating conditions) for the coating film are set according to the thickness of the final film to be obtained and the production rate, and the dried polyamic acid film (gel film) is peeled off from the support. The drying temperature for the coating film is, for example, 50°C or higher and 200°C or lower. The drying time for drying the coating film is, for example, 1 minute or higher and 100 minutes or lower.

[0073] Next, in step iii), for example, the gel film is heated while the edges are fixed to prevent shrinkage during curing. This removes water, residual solvent, imidization accelerator, etc. from the gel film, completely imidizing the remaining polyamic acid, and obtaining a non-thermoplastic polyimide film F1 containing a non-thermoplastic polyimide. Heating conditions are appropriately set depending on the thickness of the final film and the production rate. Heating conditions for step iii) include a maximum temperature of, for example, 370°C to 420°C, and a heating time at the maximum temperature of, for example, 10 seconds to 180 seconds. The temperature may be maintained for any period of time before reaching the maximum temperature. Step iii) can be performed in air, under reduced pressure, or in an inert gas such as nitrogen. Heating devices that can be used in step iii) are not particularly limited, and examples include a hot air circulation oven and a far-infrared oven.

[0074] The non-thermoplastic polyimide film F1 obtained in this manner can reduce the dielectric tangent, and is therefore suitable, for example, as a material for high-frequency circuit boards (more specifically, the core layer of a multi-layer polyimide film, the insulating layer of a metal-clad laminate, etc.).

[0075] [Physical properties of non-thermoplastic polyimide film F1] To obtain a non-thermoplastic polyimide film F1 capable of further reducing the dielectric loss tangent, the lamellar period of the non-thermoplastic polyimide film F1 is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 23 nm or more, and may be 24 nm or more, 25 nm or more, 26 nm or more, 27 nm or more, 28 nm or more, 29 nm or more, 30 nm or more, 31 nm or more, 32 nm or more, 33 nm or more, 34 nm or more, 35 nm or more, 36 nm or more, 37 nm or more, 38 nm or more, 39 nm or more, or 40 nm or more. The upper limit of the lamellar period of the non-thermoplastic polyimide film F1 is not particularly limited, but is, for example, 60 nm.

[0076] The lamellar period of the non-thermoplastic polyimide film F1 can be adjusted, for example, by changing at least one of the content of each residue constituting the non-thermoplastic polyimide and the heating conditions in the above step iii) (more specifically, the maximum temperature, the heating time at the maximum temperature, etc.).

[0077] In order to reduce transmission loss, the non-thermoplastic polyimide film F1 preferably has a relative dielectric constant of 3.60 or less, and a dielectric loss tangent of 0.0050 or less, more preferably 0.0040 or less, and even more preferably less than 0.0030.

[0078] In order to suppress the generation of internal stress when used in an FPC, the linear expansion coefficient of the non-thermoplastic polyimide film F1 is preferably 25 ppm / K or less, more preferably 18 ppm / K or less, and even more preferably 16 ppm / K or less.

[0079] The thickness of the non-thermoplastic polyimide film F1 is not particularly limited, but is, for example, 5 μm to 50 μm The thickness of the non-thermoplastic polyimide film F1 can be measured using a laser hologram.

[0080] <Second embodiment: non-thermoplastic polyimide film> Next, a non-thermoplastic polyimide film according to a second embodiment of the present invention (hereinafter, sometimes referred to as "non-thermoplastic polyimide film F2") will be described. In the following description, the same content as in the first embodiment may be omitted. The following description will focus on the differences from the first embodiment (non-thermoplastic polyimide film F1).

[0081] The non-thermoplastic polyimide film F2 contains a non-thermoplastic polyimide, and has a crystalline portion having a lamellar structure and an amorphous portion sandwiched between the crystalline portions, and has a lamellar period of 15 nm or more as determined by X-ray scattering. The non-thermoplastic polyimide film F2 has the above-mentioned configuration, thereby being able to reduce the dielectric loss tangent.

[0082] The non-thermoplastic polyimide film F2 is not particularly limited as long as it satisfies the above-mentioned constitution. However, in the second embodiment, in order to easily adjust the lamellar period to 15 nm or more, it is preferable that the following condition A is satisfied, and it is more preferable that the following conditions A and B are satisfied. Condition A: The non-thermoplastic polyimide has, as the tetracarboxylic dianhydride residues, BPDA residues and ODPA residues, and, as the diamine residues, PDA residues and TPE-R residues. Condition B: When the content of BPDA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A1 mol %, the content of ODPA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A2 mol %, the content of PDA residues relative to all diamine residues constituting the non-thermoplastic polyimide is B1 mol %, and the content of TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimide is B2 mol %, the relationships A1+A2≧80, B1+B2≧80, and (A1+B1) / (A2+B2)≦3.50 are satisfied.

[0083] Other aspects of the second embodiment are the same as those described in the above-mentioned section <First embodiment: Non-thermoplastic polyimide film> (including the sections [Non-thermoplastic polyimide], [Manufacturing method for non-thermoplastic polyimide film F1], and [Physical properties of non-thermoplastic polyimide film F1]).

[0084] <Third embodiment: multilayer polyimide film> Next, a multilayer polyimide film according to a third embodiment of the present invention will be described. The multilayer polyimide film according to the third embodiment has a non-thermoplastic polyimide film F1 or a non-thermoplastic polyimide film F2 and an adhesive layer containing a thermoplastic polyimide. Hereinafter, the "non-thermoplastic polyimide film F1 or a non-thermoplastic polyimide film F2" may be referred to as a "specific non-thermoplastic polyimide film." In addition, in the following description, description of content that overlaps with the first and second embodiments may be omitted.

[0085] Fig. 1 is a cross-sectional view showing an example of a multilayer polyimide film according to embodiment 3. As shown in Fig. 1, a multilayer polyimide film 10 has a specific non-thermoplastic polyimide film 11 and an adhesive layer 12 containing a thermoplastic polyimide disposed on at least one surface (one main surface) of the specific non-thermoplastic polyimide film 11.

[0086] In the multilayer polyimide film 10 shown in FIG. 1, the adhesive layer 12 is provided on only one side of the specific non-thermoplastic polyimide film 11, but the adhesive layer 12 may be provided on both sides (both main sides) of the specific non-thermoplastic polyimide film 11. When the adhesive layer 12 is provided on both sides of the specific non-thermoplastic polyimide film 11, the two adhesive layers 12 may contain the same type of polyimide or different types of polyimide. Furthermore, the thicknesses of the two adhesive layers 12 may be the same or different. In the following description, the "multilayer polyimide film 10" includes a film in which the adhesive layer 12 is provided on only one side of the specific non-thermoplastic polyimide film 11 and a film in which the adhesive layer 12 is provided on both sides of the specific non-thermoplastic polyimide film 11.

[0087] The thickness of the multilayer polyimide film 10 (total thickness of each layer) is, for example, 6 μm or more and 60 μm or less. The thinner the multilayer polyimide film 10, the easier it is to reduce the weight of the resulting FPC and improve the foldability of the resulting FPC. In order to facilitate weight reduction of the FPC while ensuring mechanical strength and improve the foldability of the FPC, the thickness of the multilayer polyimide film 10 is preferably 7 μm or more and 60 μm or less, and more preferably 10 μm or more and 60 μm or less. The thickness of the multilayer polyimide film 10 can be measured using a laser hologram.

[0088] To easily achieve a thinner FPC while ensuring adhesion to the metal foil, the thickness of the adhesive layer 12 (when two adhesive layers 12 are provided, the thickness of each adhesive layer 12) is preferably 1 μm or more and 15 μm or less. Furthermore, to easily adjust the linear expansion coefficient of the multilayer polyimide film 10, the thickness ratio of the specific non-thermoplastic polyimide film 11 to the adhesive layer 12 (thickness of the specific non-thermoplastic polyimide film 11 / thickness of the adhesive layer 12) is preferably 55 / 45 or more and 95 / 5 or less. When two adhesive layers 12 are provided, the thickness of the adhesive layer 12 is the total thickness of the adhesive layers 12.

[0089] In order to suppress warping of the multilayer polyimide film 10, it is preferable that adhesive layers 12 are provided on both sides of the specific non-thermoplastic polyimide film 11, and it is more preferable that adhesive layers 12 containing the same type of polyimide are provided on both sides of the specific non-thermoplastic polyimide film 11. When adhesive layers 12 are provided on both sides of the specific non-thermoplastic polyimide film 11, it is preferable that the thicknesses of the two adhesive layers 12 be the same in order to suppress warping of the multilayer polyimide film 10. Even if the thicknesses of the two adhesive layers 12 are different from each other, warping of the multilayer polyimide film 10 can be suppressed as long as the thickness of the other adhesive layer 12 is in the range of 40% or more and less than 100% of the thickness of the thicker adhesive layer 12.

[0090] [Adhesive layer 12] The thermoplastic polyimide contained in the adhesive layer 12 has an acid dianhydride residue and a diamine residue. Examples of the acid dianhydride (monomer) for forming the acid dianhydride residue in the thermoplastic polyimide include the same compounds as the acid dianhydride (monomer) for forming the acid dianhydride residue in the non-thermoplastic polyimide described above. The acid dianhydride residue in the thermoplastic polyimide and the acid dianhydride residue in the non-thermoplastic polyimide may be the same or different.

[0091] To ensure thermoplasticity, the diamine residues contained in the thermoplastic polyimide are preferably diamine residues having a bent structure. To more easily ensure thermoplasticity, the content of the diamine residues having a bent structure is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, based on the total diamine residues constituting the thermoplastic polyimide. Examples of diamines (monomers) for forming the diamine residues having a bent structure include 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 1,3-bis(3-aminophenoxy)benzene, TPE-R, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes referred to as "BAPP"). To more easily ensure thermoplasticity, the diamine residues contained in the thermoplastic polyimide are preferably BAPP residues.

[0092] In order to obtain an adhesive layer 12 that has excellent adhesion to the metal foil, the thermoplastic polyimide preferably contains one or more residues selected from the group consisting of BPDA residues and PMDA residues, and a BAPP residue.

[0093] The adhesive layer 12 may contain components (additives) other than the thermoplastic polyimide. Examples of additives that can be used include dyes, surfactants, leveling agents, plasticizers, silicones, fillers, and sensitizers. The content of the thermoplastic polyimide in the adhesive 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 be 100% by weight, based on the total weight of the adhesive layer 12.

[0094] (Method of forming adhesive layer 12) The adhesive layer 12 is formed, for example, by applying a polyamic acid solution containing polyamic acid, a precursor of thermoplastic polyimide, (hereinafter sometimes referred to as a "thermoplastic polyamic acid solution") to at least one surface of the specific non-thermoplastic polyimide film 11, followed by heating (drying and imidization of the polyamic acid). This method results in a multilayer polyimide film 10 having the specific non-thermoplastic polyimide film 11 and an adhesive layer 12 disposed on at least one surface of the specific non-thermoplastic polyimide film 11. Alternatively, a solution containing a thermoplastic polyimide (thermoplastic polyimide solution) may be used instead of the thermoplastic polyamic acid solution to form a coating film of the thermoplastic polyimide solution on at least one surface of the specific non-thermoplastic polyimide film 11, and the coating film may be dried to form the adhesive layer 12.

[0095] Alternatively, for example, a co-extrusion die may be used to form a laminate on a support, the laminate comprising a layer containing polyamic acid, which is a precursor of the non-thermoplastic polyimide contained in the specific non-thermoplastic polyimide film 11, and a layer containing polyamic acid, which is a precursor of the thermoplastic polyimide, and then the resulting laminate may be heated to simultaneously form the specific non-thermoplastic polyimide film 11 and the adhesive layer 12. In this method, by using a metal foil as the support, a metal-clad laminate (a laminate of a multilayer polyimide film 10 and a metal foil) is obtained at the same time as imidization is completed.

[0096] When producing a multilayer polyimide film 10 containing three polyimide layers, the above-mentioned coating and heating steps are preferably repeated multiple times, or multiple coating layers are formed by coextrusion or continuous coating (continuous casting) and then heated at the same time. The outermost surface of the multilayer polyimide film 10 can also be subjected to various surface treatments such as corona treatment and plasma treatment.

[0097] <Fourth embodiment: metal-clad laminate> Next, a metal-clad laminate according to a fourth embodiment of the present invention (hereinafter, sometimes referred to as "metal-clad laminate M1") will be described. The metal-clad laminate M1 has a specific non-thermoplastic polyimide film and a metal layer disposed on at least one side (one main surface) of the specific non-thermoplastic polyimide film. In the following description, the description of the same content as in the first and second embodiments may be omitted.

[0098] The metal-clad laminate M1 can be obtained, for example, by forming a first plating layer on one or both sides of a specific non-thermoplastic polyimide film by a dry plating method, and then forming a second plating layer on the first plating layer by a wet plating method (electroless plating, electrolytic plating, etc.). Dry plating methods include PVD (more specifically, vacuum deposition, sputtering, ion plating, etc.) and CVD. The thickness (total thickness) of the metal layer consisting of the first plating layer and the second plating layer is, for example, 1 μm or more and 50 μm or less.

[0099] In addition to the above-mentioned methods, the metal-clad laminate M1 can also be obtained by, for example, applying a solution containing a polyamic acid, which is a precursor of a non-thermoplastic polyimide (more specifically, the non-thermoplastic polyimide contained in the specific non-thermoplastic polyimide film), to a metal foil, and then heating the coating film formed on the metal foil (hereinafter, this may be referred to as the "coating method"). By heating the coating film, the solvent is removed and imidization is carried out on the metal foil, and the metal-clad laminate M1, which is a laminate of the specific non-thermoplastic polyimide film and a metal layer made of metal foil, is obtained.

[0100] In the coating method, the coating device for coating the metal foil with the solution containing polyamic acid is not particularly limited, and examples thereof include a die coater, a comma coater (registered trademark), a reverse coater, a knife coater, etc. The heating device for heating the coating film is also not particularly limited, and examples thereof include a hot air circulation oven, a far-infrared oven, etc.

[0101] The metal foil usable in the coating method is not particularly limited. Metal foils usable in the coating method include, for example, metal foils made of copper, stainless steel, nickel, aluminum, and alloys of these metals. While rolled copper foil, electrolytic copper foil, and other copper foils are commonly used in general metal-clad laminates, copper foil is also preferably used in the fourth embodiment. The metal foil may be subjected to a surface treatment or the like depending on the purpose, thereby adjusting the surface roughness, etc. Furthermore, an anti-corrosion layer, a heat-resistant layer, an adhesive layer, etc. may be formed on the surface of the metal foil. The thickness of the metal foil is not particularly limited, and may be any thickness that can exhibit sufficient functionality depending on the application. To easily achieve a thinner FPC while ensuring ease of handling, the thickness of the metal foil is preferably 5 μm or more and 50 μm or less.

[0102] <Fifth embodiment: metal-clad laminate> Next, a metal-clad laminate according to a fifth embodiment of the present invention (hereinafter, sometimes referred to as "metal-clad laminate M2") will be described. The metal-clad laminate M2 has the multilayer polyimide film according to the third 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, the description of the same content as in the first, second, and third embodiments may be omitted.

[0103] 2 is a cross-sectional view showing an example of a metal-clad laminate M2. As shown in FIG. 2, a metal-clad laminate 20 includes a multilayer polyimide film 10 and a metal layer 13 (metal foil) disposed on a main surface 12a of an adhesive layer 12 of the multilayer polyimide film 10.

[0104] [Method of manufacturing metal-clad laminate 20] When manufacturing a metal-clad laminate 20 using a multilayer polyimide film 10, a metal foil that will become the metal layer 13 is laminated to 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 the specific non-thermoplastic polyimide film 11 side). This results in the metal-clad laminate 20 shown in FIG. 2. The method for laminating the metal foil to the main surface 12a of the adhesive layer 12 is not particularly limited, and various known methods can be used. For example, a continuous processing method using a hot roll laminating device having one or more pairs of metal rolls or a double belt press (DBP) can be used. The specific configuration of the means for performing hot roll lamination is not particularly limited, but it is preferable to place a protective material between the pressure surface and the metal foil to improve the appearance of the resulting metal-clad laminate 20.

[0105] When adhesive layers 12 are provided on both sides of the specific non-thermoplastic polyimide film 11, a double-sided metal-clad laminate (not shown) can be obtained by laminating metal foil to both sides (both main surfaces) of the multilayer polyimide film 10.

[0106] The metal foil for the metal layer 13 is not particularly limited, and any metal foil can be used. For example, metal foils made of copper, stainless steel, nickel, aluminum, and alloys of these metals are suitable. While rolled copper foil, electrolytic copper foil, and other copper foils are commonly used in general metal-clad laminates, copper foil is also preferably used in the fifth embodiment. The metal foil may be subjected to a surface treatment or the like to adjust the surface roughness, etc., depending on the purpose. Furthermore, an anti-corrosion layer, a heat-resistant layer, an adhesive layer, etc. may be formed on the surface of the metal foil. The thickness of the metal foil is not particularly limited, and may be any thickness that can sufficiently perform its functions depending on the application. To easily achieve a thin FPC while suppressing the occurrence of wrinkles when bonded to the multilayer polyimide film 10, the thickness of the metal foil is preferably 5 μm or more and 50 μm or less. [Example]

[0107] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0108] <Methods for measuring physical properties> First, methods for measuring the lamellar period, relative dielectric constant, dielectric loss tangent, and linear expansion coefficient of a polyimide film will be described.

[0109] [Lamellar period] First, ten measurement samples were prepared by cutting polyimide film into 1.5 cm x 1.0 cm pieces. The ten polyimide films were then stacked in the same direction and placed in a sample holder. The sample holder was then inserted into the sample stage of an X-ray scattering measurement device (Rigaku Corporation's "NANOPIX"®) and optically adjusted so that the X-rays passed through the center of the crosshairs on the sample holder. Two-dimensional SAXS images were then obtained by ultra-small-angle X-ray scattering (USAXS) under the following conditions:

[0110] (Measurement conditions) X-ray source: Cu (λ=1.5418Å) Detector: Rigaku "HyPix (registered trademark)-6000" X-ray beam diameter: 0.4 nm Standard sample: Silver behenate Camera length: 1349.20mm Temperature: Room temperature (20℃) Irradiation time: 60 minutes Measurement range (2θ): 0 to 3.5° (= 0 to 2.5 nm) -1 )

[0111] Next, the lamellar period was calculated using the following method using Rigaku's "SmartLab Studio II (Powder XRD)" and "2DP" software. First, the 2D SAXS image and its blank obtained by the above procedure were circularly averaged using Rigaku's "2DP" software to obtain a 1D SAXS pattern and a blank SAXS pattern, respectively. Next, the background of the 1D SAXS pattern was removed using the blank SAXS pattern as background data. When removing the background, the X-ray scattering intensity ratio was calculated from the direct beam intensities of both images and intensity correction was performed. Next, the peaks appearing at 2θ<1° were separated from the 1D SAXS pattern after background removal using Rigaku's "SmartLab Studio II (Powder XRD)" software. During separation, waveform optimization was performed by peak profile fitting of the initial structure.

[0112] The separated peaks at 2θ<1° were identified as peaks derived from the lamellar periodicity, and the lamellar periodicity d was calculated from the scattering vector q of the peak derived from the lamellar periodicity. The scattering vector q was calculated using the formula "q = (4π sinθ) / λ (where θ is the scattering angle and λ is the wavelength of the X-rays used in the measurement)", and the lamellar periodicity d was calculated using the formula "d = 2π / q".

[0113] [Dielectric constant and dielectric loss tangent] The dielectric constant and dielectric loss tangent of the polyimide film were measured using a network analyzer (Hewlett-Packard "8719C") and a cavity resonator perturbation dielectric constant analyzer (EM Lab "CP531"). Specifically, the polyimide film was first cut into 2 mm x 100 mm pieces to prepare samples for measuring the dielectric constant and dielectric loss tangent. The measurement samples were then left for 24 hours in an atmosphere at 23°C and 50% relative humidity. The dielectric constant and dielectric loss tangent were then measured using the network analyzer and the cavity resonator perturbation dielectric constant analyzer at 23°C, 50% relative humidity, and a measurement frequency of 10 GHz. A dielectric loss tangent of less than 0.0030 was evaluated as "reduced." On the other hand, a dielectric loss tangent of 0.0030 or greater was evaluated as "not reduced."

[0114] Coefficient of Linear Expansion (CTE) Using a thermal analyzer (Hitachi High-Tech Science Corporation, "TMA / SS6100"), a polyimide film (sample) was heated from -10°C to 300°C at a heating rate of 10°C / min, and then cooled to -10°C at a heating rate of 40°C / min. The sample was then heated again to 300°C at a heating rate of 10°C / min, and the linear expansion coefficient was determined from the amount of strain during the second heating from 50°C to 250°C. The measurement conditions are shown below. Sample (polyimide film) size: width 3 mm, length 10 mm Load: 1g Measurement atmosphere: Air atmosphere

[0115] <Preparation of polyimide film> The methods for producing polyimide films in Examples and Comparative Examples are described below. In the following, compounds and reagents are abbreviated as follows. The polyamic acid solutions used for producing the polyimide films were all prepared in a nitrogen atmosphere at 20°C. DMF: N,N-dimethylformamide PDA: p-phenylenediamine TPE-R: 1,3-bis(4-aminophenoxy)benzene ODA: 4,4'-oxydianiline BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane TPE-Q: 1,4-bis(4-aminophenoxy)benzene m-TB: 4,4'-diamino-2,2'-dimethylbiphenyl BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride TMHQ: p-phenylenebis(trimellitic acid monoester acid anhydride) BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride BISDA: 5,5'-[1-methyl-1,1-ethanediylbis(1,4-phenylene)bisoxy]bis(isobenzofuran-1,3-dione) AA: acetic anhydride IQ: Isoquinoline

[0116] [Example 1] A 500 mL glass flask was charged with 164.2 g of DMF, 3.0 g of TPE-R, and 6.4 g of PDA. Then, while stirring the contents of the flask, 12.2 g of BPDA and 7.9 g of ODPA were added. The contents of the flask were then stirred for 30 minutes. Next, while stirring the contents of the flask, a pre-prepared PMDA solution (solvent: DMF, dissolved amount of PMDA: 0.5 g, PMDA concentration: 7.9 wt%) was added to the flask for a predetermined period of time at a rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents reached 1500 poise at 23°C, the addition of the PMDA solution was stopped, and the flask contents were further stirred for 1 hour to obtain polyamic acid solution P1. The resulting polyamic acid solution P1 had a solids concentration of 15 wt%. The resulting polyamic acid solution P1 had a viscosity at a temperature of 23°C of 1500 to 2000 poise.

[0117] Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 42 / 21 / 37) was added to 55 g of polyamic acid solution P1 (polyamic acid solution P1 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while stirring in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 110°C for 180 seconds to obtain a self-supporting gel film. The resulting 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 and heated at 300°C for 56 seconds. The heated film was then placed in a far-infrared (IR) oven preheated to 380°C and heated at 380°C for 49 seconds to imidize the polyamic acid in the gel film. The film was then cut from the metal frame to obtain the polyimide film of Example 1 (thickness: 17 μm).

[0118] In addition, when a polyimide film obtained by the same procedure as above was fixed to a metal frame and heated in an IR oven at a heating temperature of 380°C for 1 minute, the shape of the polyimide film (film shape) was maintained. Therefore, the polyimide contained in the polyimide film of Example 1 was a non-thermoplastic polyimide. In other words, the polyimide film of Example 1 was a non-thermoplastic polyimide film. Regarding the polyimide films of Examples 2 to 37 and Comparative Examples 1 to 8 described below, polyimide films obtained by the same procedure as below were fixed to a metal frame and heated in an IR oven at a heating temperature of 380°C for 1 minute, the shape of the polyimide film (film shape) was maintained. Therefore, the polyimide contained in the polyimide films of Examples 2 to 37 and Comparative Examples 1 to 8 was all non-thermoplastic polyimide. In other words, the polyimide films of Examples 2 to 37 and Comparative Examples 1 to 8 were all non-thermoplastic polyimide films.

[0119] [Example 2] A 500 mL glass flask was charged with 164.1 g of DMF, 2.5 g of TPE-R, and 6.7 g of PDA. Then, while stirring the contents of the flask, 12.4 g of BPDA and 8.0 g of ODPA were added. The contents of the flask were then stirred for 30 minutes. Next, while stirring the contents of the flask, a pre-prepared PMDA solution (solvent: DMF, dissolved amount of PMDA: 0.5 g, PMDA concentration: 7.8 wt%) was added to the flask for a predetermined period of time at a rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents reached 1500 poise at 23°C, the addition of the PMDA solution was stopped, and the contents of the flask were further stirred for 1 hour to obtain polyamic acid solution P2. The resulting polyamic acid solution P2 had a solids concentration of 15 wt%. The resulting polyamic acid solution P2 had a viscosity at a temperature of 23°C of 1500 to 2000 poise.

[0120] Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 42 / 21 / 37) was added to 55 g of polyamic acid solution P2 (polyamic acid solution P2 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while stirring in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 110°C for 180 seconds to obtain a self-supporting gel film. The resulting 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 and heated at 300°C for 56 seconds. Next, the heated film was placed in an IR oven preheated to 380°C and heated at 380°C for 49 seconds to imidize the polyamic acid in the gel film. Thereafter, the film was cut from the metal frame to obtain the polyimide film of Example 2 (thickness: 17 μm).

[0121] [Example 3] A 500 mL glass flask was charged with 164.1 g of DMF, 2.5 g of TPE-R, and 6.7 g of PDA. Then, while stirring the contents of the flask, 12.5 g of BPDA, 7.4 g of ODPA, and 0.5 g of PMDA were added. The contents of the flask were then stirred for 30 minutes. Next, while stirring the contents of the flask, a pre-prepared PMDA solution (solvent: DMF, dissolved amount of PMDA: 0.5 g, PMDA concentration: 7.8 wt%) was added to the flask for a predetermined period of time at a rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents reached 1500 poise at 23°C, the addition of the PMDA solution was stopped, and the flask contents were further stirred for 1 hour to obtain polyamic acid solution P3. The resulting polyamic acid solution P3 had a solids concentration of 15 wt%. The resulting polyamic acid solution P3 had a viscosity at a temperature of 23°C of 1500 to 2000 poise.

[0122] Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 42 / 21 / 37) was added to 55 g of polyamic acid solution P3 (polyamic acid solution P3 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while stirring in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 110°C for 180 seconds to obtain a self-supporting gel film. The resulting 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 and heated at 300°C for 56 seconds. The heated film was then placed in an IR oven preheated to 380°C and heated at 380°C for 49 seconds to imidize the polyamic acid in the gel film. The film was then cut from the metal frame to obtain the polyimide film of Example 3 (thickness: 17 μm).

[0123] [Example 4] A 500 mL glass flask was charged with 164.1 g of DMF, 2.5 g of TPE-R, and 6.7 g of PDA. Then, while stirring the contents of the flask, 12.4 g of BPDA, 7.4 g of ODPA, and 0.7 g of BTDA were added. The contents of the flask were then stirred for 30 minutes. Next, while stirring the contents of the flask, a pre-prepared PMDA solution (solvent: DMF, dissolved amount of PMDA: 0.5 g, PMDA concentration: 7.8 wt%) was added to the flask for a predetermined period of time at a rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents reached 1500 poise at 23°C, the addition of the PMDA solution was stopped, and the flask contents were further stirred for 1 hour to obtain polyamic acid solution P4. The resulting polyamic acid solution P4 had a solids concentration of 15 wt%. The resulting polyamic acid solution P4 had a viscosity at a temperature of 23°C of 1500 to 2000 poise.

[0124] Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 42 / 21 / 37) was added to 55 g of polyamic acid solution P4 (polyamic acid solution P4 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while stirring in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 110°C for 180 seconds to obtain a self-supporting gel film. The resulting 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 and heated at 300°C for 56 seconds. Next, the heated film was placed in an IR oven preheated to 380°C and heated at 380°C for 49 seconds to imidize the polyamic acid in the gel film. Thereafter, the film was cut from the metal frame to obtain the polyimide film of Example 4 (thickness: 17 μm).

[0125] [Example 5] (1st sequence polymerization process) A 500 mL glass flask was charged with 164.0 g of DMF and 6.9 g of PDA, and then 12.5 g of BPDA and 5.5 g of ODPA were added to the flask while stirring the contents of the flask, followed by stirring for 30 minutes.

[0126] (2nd sequence polymerization process) Next, 2.1 g of TPE-R was gradually added to the flask while stirring the contents. After visually confirming that the TPE-R had dissolved, 2.6 g of ODPA was added to the flask while stirring the contents, and the contents were stirred for 30 minutes. Next, a previously prepared PMDA solution (solvent: DMF, dissolved amount of PMDA: 0.5 g, PMDA concentration: 7.7 wt%) was added to the flask for a predetermined time at an addition rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents at 23°C reached 1500 poise, the addition of the PMDA solution was stopped, and the flask contents were further stirred for 1 hour to obtain polyamic acid solution P5. The resulting polyamic acid solution P5 had a solids concentration of 15 wt%. The resulting polyamic acid solution P5 also had a viscosity of 1500 to 2000 poise at 23°C.

[0127] (Film forming process) Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 42 / 21 / 37) was added to 55 g of polyamic acid solution P5 (polyamic acid solution P5 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while being stirred in an atmosphere at a temperature of 0°C or below, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at a heating temperature of 110°C for 180 seconds to obtain a self-supporting gel film. The resulting gel film was peeled off from the aluminum foil, fixed to a metal frame, and placed in a hot air circulating oven preheated to 350°C. The film was heated at 350°C for 19 seconds, then at 380°C for 16 seconds, and then at 400°C for 49 seconds to imidize the polyamic acid in the gel film. The film was then cut from the metal frame to obtain the polyimide film of Example 5 (thickness: 17 μm).

[0128] [Example 6, Examples 8 to 37, Comparative Examples 1 to 3, Comparative Example 5, and Comparative Example 6] Polyimide films (thickness: 17 μm each) of Examples 6, 8 to 37, Comparative Examples 1 to 3, 5, and 6 were obtained in the same manner as in Example 5, except that the types and ratios (feed ratios) of monomers used in the first sequence polymerization step, the types and ratios (feed ratios) of monomers used in the second sequence polymerization step, the heating conditions in the film-forming step, and the weight ratios of the imidization accelerators were as shown in Tables 1 to 10 described below. Note that in all of Examples 6, 8 to 37, Comparative Examples 1 to 3, 5, and 6, the total amount of acid dianhydride and diamine was the same as in Example 5.

[0129] [Example 7] (1st sequence polymerization process) A 500 mL glass flask was charged with 161.4 g of DMF and 7.4 g of PDA, and then 12.7 g of BPDA and 6.7 g of ODPA were added to the flask while stirring the contents of the flask, followed by stirring for 30 minutes.

[0130] (2nd sequence polymerization process) Next, 1.0 g of TPE-R was gradually added to the flask while stirring the contents. After visually confirming that the TPE-R had dissolved, 1.5 g of ODPA was added to the flask while stirring the contents, and the contents were stirred for 30 minutes. Next, a previously prepared ODPA solution (solvent: DMF, dissolved amount of ODPA: 0.7 g, ODPA concentration: 7.5 wt%) was added to the flask for a predetermined time at an addition rate that prevented a sudden increase in the viscosity of the flask contents. When the viscosity of the flask contents at 23°C reached 1500 poise, the addition of the ODPA solution was stopped, and the flask contents were further stirred for 1 hour to obtain polyamic acid solution P7. The resulting polyamic acid solution P7 had a solids concentration of 15 wt%. The resulting polyamic acid solution P7 had a viscosity of 1500 to 2000 poise at 23°C.

[0131] (Film forming process) Next, 27.5 g of an imidization accelerator consisting of a mixture of AA, IQ, and DMF (weight ratio: AA / IQ / DMF = 44 / 22 / 34) was added to 55 g of polyamic acid solution P7 (polyamic acid solution P7 obtained by the above preparation method) to prepare a dope solution. The dope solution was then degassed while being stirred in an atmosphere below 0°C, and then coated onto aluminum foil using a comma coater to form a coating film. The coating film was then heated at 110°C for 180 seconds to obtain a self-supporting gel film. The resulting gel film was peeled off from the aluminum foil, fixed to a metal frame, and placed in a hot air circulating oven preheated to 350°C. The gel film was heated at 350°C for 19 seconds, then at 380°C for 16 seconds, and then at 400°C for 49 seconds to imidize the polyamic acid in the gel film. The gel film was then cut from the metal frame to obtain the polyimide film of Example 7 (thickness: 17 μm).

[0132] [Comparative Examples 4, 7, and 8] Polyimide films (thickness: 17 μm in each case) of Comparative Examples 4, 7, and 8 were obtained in the same manner as in Example 7, except that the types and ratios (feed ratios) of monomers used in the first sequence polymerization step, the types and ratios (feed ratios) of monomers used in the second sequence polymerization step, the heating conditions in the film-forming step, and the weight ratio of the imidization accelerator were as shown in Tables 5 and 10 described below. Note that in all of Comparative Examples 4, 7, and 8, the total amount of acid dianhydride and diamine was the same as in Example 7.

[0133] <Result> For Examples 1 to 37 and Comparative Examples 1 to 8, the types and ratios (feed ratios) of monomers used in the first sequence polymerization step, the types and ratios (feed ratios) of monomers used in the second sequence polymerization step, and the rigidity / flexibility ratio are shown in Tables 1 to 5. Furthermore, for Examples 1 to 37 and Comparative Examples 1 to 8, the weight ratios of the imidization accelerators, heating conditions in the film-forming step, relative dielectric constants, dielectric loss tangents, lamellar periods, and CTEs are shown in Tables 6 to 10.

[0134] In Tables 1 to 5, "1st" and "2nd" mean "1st sequence polymerization step" and "2nd sequence polymerization step," respectively. Since Examples 1 to 4 were random polymerizations, the types of monomers used and their ratios (feed ratios) are listed in the "1st" column.

[0135] In Tables 1 to 5, the values ​​in the "Diamine" column indicate the content (unit: mol%) of each diamine relative to the total amount of diamine used (in the case of sequence polymerization, the total amount of diamine used in the first sequence polymerization step and the total amount of diamine used in the second sequence polymerization step). In Tables 1 to 5, the values ​​in the "Acid Dianhydride" column indicate the content (unit: mol%) of each acid dianhydride relative to the total amount of acid dianhydride used (in the case of sequence polymerization, the total amount of acid dianhydride used in the first sequence polymerization step and the total amount of acid dianhydride used in the second sequence polymerization step). In the "Diamine" and "Acid Dianhydride" columns of Tables 1 to 5, "-" indicates that the component (PDA, TPE-R, m-TB, ODA, TPE-Q, BAPP, BPDA, PMDA, TMHQ, BTDA, ODPA, or BISDA) was not used. In all of Examples 1 to 37 and Comparative Examples 1 to 8, the molar fraction of each residue in the polyimide contained in the obtained polyimide film was consistent with the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used. Furthermore, in all of Examples 1 to 37 and Comparative Examples 1 to 8, the ratio of the total amount of tetracarboxylic dianhydride residues constituting the polyimide contained in the obtained polyimide film divided by the total amount of diamine residues constituting the polyimide was 0.99 or more and 1.01 or less.

[0136] In addition, in Tables 6 to 10, "-" means that no measurement was performed.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] [Table 4]

[0141] [Table 5]

[0142] [Table 6]

[0143] [Table 7]

[0144] [Table 8]

[0145] [Table 9]

[0146] [Table 10]

[0147] The non-thermoplastic polyimides contained in the polyimide films of Examples 1 to 37 had BPDA residues, ODPA residues, PDA residues, and TPE-R residues. In Examples 1 to 37, the total content of BPDA residues and ODPA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimides was 80 mol % or more. In Examples 1 to 37, the total content of PDA residues and TPE-R residues relative to all diamine residues constituting the non-thermoplastic polyimides was 80 mol % or more. In Examples 1 to 37, the rigid / flex ratio was 3.50 or less. In Examples 1 to 37, the lamellar period was 15 nm or more.

[0148] The dielectric loss tangent was less than 0.0030 in Examples 1 to 37. Therefore, the polyimide films of Examples 1 to 37 were able to reduce the dielectric loss tangent.

[0149] The non-thermoplastic polyimides contained in the polyimide films of Comparative Examples 1, 3, 4, and 6 did not have a TPE-R residue. The non-thermoplastic polyimide contained in the polyimide film of Comparative Example 1 did not have a BPDA residue or an ODPA residue. In Comparative Examples 2 and 3, the total content of BPDA residues and ODPA residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide was less than 80 mol%. In Comparative Examples 2 to 8, the stiffness / flexibility ratio exceeded 3.50. In Comparative Example 1, the lamellar period was less than 15 nm.

[0150] The dielectric loss tangent was 0.0030 or more in Comparative Examples 1 to 8. Therefore, the polyimide films of Comparative Examples 1 to 8 could not reduce the dielectric loss tangent.

[0151] The above results demonstrate that the present invention can provide a non-thermoplastic polyimide film capable of reducing the dielectric loss tangent. [Explanation of symbols]

[0152] 10: Multi-layer polyimide film 11: Specific non-thermoplastic polyimide film (non-thermoplastic polyimide film) 12: Adhesive layer 13: Metal layer 20:Metal clad laminate

Claims

1. A non-thermoplastic polyimide film comprising a non-thermoplastic polyimide, the non-thermoplastic polyimide has, as tetracarboxylic dianhydride residues, a 3,3',4,4'-biphenyltetracarboxylic dianhydride residue and a 4,4'-oxydiphthalic anhydride residue, and, as diamine residues, a p-phenylenediamine residue and a 1,3-bis(4-aminophenoxy)benzene residue; The content of the 3,3',4,4'-biphenyltetracarboxylic dianhydride residue relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is represented by A １ % by mole, and the content of the 4,4'-oxydiphthalic anhydride residue relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is A ２ % by mole, and the content of the p-phenylenediamine residue relative to all diamine residues constituting the non-thermoplastic polyimide is B １ % by mole, and the content of the 1,3-bis(4-aminophenoxy)benzene residue relative to all diamine residues constituting the non-thermoplastic polyimide is B ２ When expressed as mole %, A １ +A ２ ≧80, B １ +B ２ ≧80, and (A １ +B １ ) / (A ２ +B ２ ) ≦3.

50.

2. The above A １ , the above-mentioned A ２ , the above B １ and B ２ is 1.60≦(A １ +B １ ) / (A ２ +B ２ 2. The non-thermoplastic polyimide film according to claim 1, wherein the relationship of (R) is 0.01 to 0.25, and (R) is 0.01 to 0.

25.

3. 3. The non-thermoplastic polyimide film according to claim 1, wherein the non-thermoplastic polyimide further contains a pyromellitic dianhydride residue as the tetracarboxylic dianhydride residue.

4. 4. The non-thermoplastic polyimide film according to claim 3, wherein the content of the pyromellitic dianhydride residues relative to all tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide is 3 mol % or more and 12 mol % or less.

5. 5. The non-thermoplastic polyimide film according to claim 1, wherein a ratio of the total amount of substance of tetracarboxylic dianhydride residues constituting the non-thermoplastic polyimide divided by the total amount of substance of diamine residues constituting the non-thermoplastic polyimide is 0.95 or more and 1.05 or less.

6. the non-thermoplastic polyimide film contains crystalline portions having a lamellar structure and amorphous portions sandwiched between the crystalline portions, The non-thermoplastic polyimide film according to any one of claims 1 to 5, wherein the lamellar period obtained by X-ray scattering is 15 nm or more.

7. A multilayer polyimide film comprising the non-thermoplastic polyimide film according to any one of claims 1 to 6 and an adhesive layer containing a thermoplastic polyimide arranged on at least one surface of the non-thermoplastic polyimide film.

8. The multilayer polyimide film according to claim 7 , wherein the adhesive layer is disposed on both sides of the non-thermoplastic polyimide film.

9. A metal-clad laminate comprising the non-thermoplastic polyimide film according to any one of claims 1 to 6 and a metal layer disposed on at least one surface of the non-thermoplastic polyimide film.

10. A metal-clad laminate comprising the multilayer polyimide film according to claim 7 or 8 and a metal layer disposed on a main surface of at least one of the adhesive layers of the multilayer polyimide film.

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