Polyamic acid, polyimide, polyimide film, metal-coated laminate, and circuit board

Abstract

To provide a polyimide film having low thermal expansion properties, low hygroscopicity and good film-forming properties required as an FPC material and having a sufficiently low dielectric loss tangent.SOLUTION: Provided is a polyamic acid or polyimide which contains an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, and which satisfies the following conditions: condition (i): contains at least 25 mol% of acid dianhydride residues derived from the acid dianhydride represented by the following formula (1) relative to all acid dianhydride residues; condition (ii): contains at least 50 mol% of diamine residues derived from 4,4'-biphenyldiamine compounds relative to all diamine residues; and condition (iii): the proportion of monomer residues possessing a biphenyl skeleton is 65 mol% or higher relative to all monomer residues derived from all monomer components.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid, a polyimide, a polyimide film, a metal-clad laminate, and a circuit board. [Background technology]

[0002] In recent years, the increasing performance and functionality of electrical and electronic devices has led to demands for faster information transmission, and the components and materials used in these devices are also being required to support this high-speed transmission. Because transmitting high-frequency signals can easily result in problems such as electrical signal loss and long signal delay times, efforts are underway to improve the electrical properties of circuit boards, such as flexible printed circuits (FPCs), used in high-frequency devices, so that they can handle high-speed transmission. Therefore, efforts are being made to lower the dielectric dissipation factor of polymers used as FPC materials in order to reduce transmission loss.

[0003] Typical examples of polymers with low dielectric loss tangent include fluororesins, liquid crystal polymers (LCPs), and modified polyimides (MPIs). However, fluororesins have issues with adhesion to low-roughening copper foil, laser processability, and copper plating, while LCPs have issues with poor adhesion to low-roughening copper foil and difficulty in multilayering. Furthermore, while MPIs do not have the same issues as fluororesins and LCPs, they generally have issues with high moisture absorption and dielectric loss tangent.

[0004] It has been proposed to introduce an ester structure into the polyimide chain in order to reduce the dielectric loss tangent of polyimide (for example, Patent Document 1). It has also been proposed to introduce an ester structure into the polyimide chain for the purposes of low thermal expansion and low moisture absorption (for example, Patent Documents 2 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-074894 [Patent Document 2] Retable No. 2010-093021 [Patent Document 3] Japanese Patent Application Publication No. 10-36506 [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-336011 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, the dielectric loss tangent is reduced by introducing an ester structure into the polyimide chain, but in the examples, the dielectric loss tangent at 10 GHz exceeds 0.003, which is not satisfactory in terms of reducing the transmission loss of high-frequency signals. Also, in Patent Document 1, the imidization of polyimide is carried out using a cyclization agent, so the dielectric loss tangent tends to be difficult to reduce by increasing the polar group. On the other hand, when 1,4-diaminobenzene (p-PDA; paraphenylenediamine) is used as the diamine component as in Patent Documents 3 and 4, there is a problem that the polyimide film tends to become brittle and film formability is reduced.

[0007] Therefore, an object of the present invention is to provide a polyimide film that has the low thermal expansion and good film-forming properties required for an FPC material, and also has a sufficiently low dielectric loss tangent. [Means for solving the problem]

[0008] As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by using an acid dianhydride having a specific structure and a diamine compound in a predetermined ratio as monomers for forming polyimide, and have thus completed the present invention.

[0009] That is, the polyamic acid according to the first aspect of the present invention is a polyamic acid containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, and satisfies the following conditions (i) to (iii):

[0010] Condition (i): The acid dianhydride residues derived from the acid dianhydride represented by the following formula (1) account for 25 mol% or more of the total acid dianhydride residues.

[0011] [ka]

[0012] Condition (ii): The diamine residues derived from the diamine compound represented by the following general formula (2) constitute 50 mol % or more of the total diamine residues.

[0013] [ka]

[0014] In formula (2), Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group; p and q independently represent an integer of 0 to 4;

[0015] Condition (iii): The ratio of monomer residues having a biphenyl skeleton to all monomer residues derived from all monomer components is 65 mo1% or more.

[0016] The polyamic acid according to the first aspect of the present invention may contain diamine residues derived from diamine compounds represented by the following general formulas (3) to (6) in an amount of 1 to 50 mol % relative to the total diamine residues:

[0017] [ka]

[0018] In formulas (3) to (6), R independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group, or an alkylthio group; linking group A independently represents a divalent group selected from -O-, -SO2-, -CH2-, or -C(CH3)2-; linking group X independently represents -CH2-, -O-CH2-O-, -O-C2H4-O-, -O-C3H6-O-, -O-C4H8-O-, or -O-C5H 10 represents -O-, -O-CH2-C(CH3)2-CH2-O-, -C(CH3)2-, -C(CF3)2- or -SO2-, m independently represents an integer of 1 to 4, and n independently represents an integer of 0 to 4, provided that in formula (5), when linking group A does not include -CH2-, -C(CH3)2-, -C(CF3)2- or -SO2-, any of n's is 1 or greater.

[0019] A polyimide according to a second aspect of the present invention is obtained by imidizing the polyamic acid according to the first aspect.

[0020] A polyimide film according to a third aspect of the present invention is a polyimide film comprising a single or multiple polyimide layers, At least one of the polyimide layers contains the polyimide of the second aspect as a main resin component.

[0021] A polyimide film according to a fourth aspect of the present invention may be a polyimide film comprising: a polyimide layer (A) containing a first polyimide as a primary resin component; and a polyimide layer (B) laminated on the polyimide layer (A) and containing a second polyimide different from the first polyimide as a primary resin component. In the polyimide film according to the fourth aspect, the first polyimide may be a polyimide containing acid dianhydride residues derived from an acid dianhydride component and diamine residues derived from a diamine component, wherein the total acid dianhydride residues contain 5 mol % to 90 mol % of residues derived from pyromellitic dianhydride and 10 mol % to 95 mol % of residues derived from an acid dianhydride having a ketone group (—CO—) in the molecule, and the residues derived from pyromellitic dianhydride and the residues derived from an acid dianhydride having a ketone group (—CO—) in the molecule account for a total of 80 mol % or more. The polyimide film of the fourth aspect may contain, among all diamine residues, residues derived from a diamine compound represented by the following general formula (A1) in a proportion of 5 mol % to 90 mol %: Furthermore, the polyimide film of the fourth aspect may have a storage modulus E' at 300°C of 1.0 x 10 as measured using a dynamic viscoelasticity measuring apparatus (DMA). 8 Pa or more and the storage modulus E' at 350°C is 1.0 × 10 7 It may also be a polyimide having a viscosity of 100 Pa or more. Furthermore, in a polyimide film according to a fourth aspect, the second polyimide is the polyimide according to the second aspect.

[0022] [ka] In formula (A1), the linking group X1 represents a single bond or a divalent group selected from -CONH-; Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group; n1 represents an integer of 0 to 2; and p and q independently represent integers of 0 to 4.

[0023] The polyimide film according to the third or fourth aspect of the present invention may have a dielectric loss tangent (Tanδ) of less than 0.003 at 10 GHz when measured with a split post dielectric resonator (SPDR) in an environment of a temperature of 24 to 26°C and a humidity of 45 to 55%, and may have a coefficient of thermal expansion (CTE) of less than 25 ppm / K.

[0024] A metal-clad laminate according to a fifth aspect of the present invention is a metal-clad laminate comprising an insulating resin layer and a metal layer provided on at least one surface of the insulating resin layer, wherein the insulating resin layer comprises the polyimide film according to the third or fourth aspect.

[0025] A circuit board according to a sixth aspect of the present invention is a circuit board comprising an insulating resin layer and a wiring layer provided on at least one surface of the insulating resin layer, wherein the insulating resin layer contains the polyimide film according to the third or fourth aspect. [Effects of the Invention]

[0026] The polyamic acid and polyimide of the present invention satisfy the conditions (i) to (iii), and thus can form a polyimide film having an extremely low dielectric loss tangent without impairing the low thermal expansion and favorable film-forming properties. Therefore, by using the polyimide film of the present invention as a circuit board material, a circuit board capable of supporting high-speed transmission can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0027] Next, an embodiment of the present invention will be described.

[0028] <Polyamic acid / polyimide> The polyamic acid of one embodiment of the present invention is a precursor of polyimide, and is a polyamic acid obtained by reacting a specific acid dianhydride component with a specific diamine component, and contains an acid dianhydride residue derived from the acid dianhydride component and a diamine residue derived from the diamine component. The polyimide of the present embodiment is obtained by imidizing the polyamic acid, and contains a specific acid anhydride residue and a specific diamine residue. In the present invention, the acid anhydride residue refers to a tetravalent group derived from an acid dianhydride, and the diamine residue refers to a divalent group derived from a diamine compound. When the raw materials, acid dianhydride and diamine compound, are reacted in approximately equimolar amounts, the types and molar ratios of the acid dianhydride residue and diamine residue contained in the polyimide can be made to correspond approximately to the types and molar ratios of the raw materials. In the present invention, the term "polyimide" refers to a resin made of a polymer having an imide group in the molecular structure, such as polyimide, polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, or polybenzimidazoleimide.

[0029] The acid anhydride residues and diamine residues contained in the polyamic acid and polyimide of the present embodiment will be described below together with their raw materials.

[0030] The polyamic acid and polyimide of the present embodiment satisfy the following conditions (i) to (iii).

[0031] Condition (i): The acid dianhydride residue derived from the acid dianhydride represented by the following formula (1) is contained in an amount of 25 mol % or more relative to the total acid dianhydride residues. Hereinafter, the acid dianhydride residue derived from the acid dianhydride represented by formula (1) may be referred to as "acid dianhydride residue (1)."

[0032] [ka]

[0033] The acid dianhydride represented by formula (1) is known as p-biphenylene bis(trimellitic acid monoester dihydrate) (BP-TME), and has a biphenyl skeleton and two ester structures (-CO-O-) bonded to the biphenyl skeleton within the molecule. The biphenyl skeleton is rigid, and the ester structures have the effect of imparting an ordered structure to the entire polymer. Therefore, by containing the acid dianhydride residue (1), it is possible to reduce the coefficient of thermal expansion (low CTE) and effectively reduce the dielectric loss tangent (low dielectric loss tangent) by improving the ordered structure of the molecules and suppressing their movement.

[0034] The content of the acid dianhydride residue (1) in the polyamic acid and polyimide of the present embodiment is 25 mol % or more, preferably 25 to 100 mol %, and more preferably 40 to 80 mol %, based on the total amount of acid dianhydride residues. If the content of the acid dianhydride residue (1) is less than 25 mol %, the effects of improving the molecular order structure and suppressing movement, thereby lowering the dielectric tangent and CTE, are not fully achieved. The upper limit of the content of the acid dianhydride residue (1) may be 100 mol %, but when other acid dianhydrides are used in combination for the purpose of imparting desired functionality, the amount of the acid dianhydride represented by formula (1) used can be adjusted depending on the amount of the other acid dianhydride used.

[0035] Here, as an analogous compound of the acid dianhydride represented by formula (1), compounds in which the biphenyl skeleton in formula (1) has a substituent such as a phenyl group are known (for example, Patent Document 2). However, the presence of the substituent bonded to the biphenyl skeleton reduces the effect of suppressing the molecular motion of the polyimide, which is a disadvantage in that the dielectric loss tangent cannot be sufficiently reduced. Another known acid dianhydride, 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), has two ester structures similar to those of the acid dianhydride represented by formula (1). Because TAHQ has two ester structures bonded to a phenylene group, it has rigidity, but does not sufficiently reduce the dielectric loss tangent. Furthermore, compared to the acid dianhydride represented by formula (1), TAHQ does not have a biphenyl skeleton, which reduces its ability to inhibit molecular motion, making it less effective at lowering the dielectric loss tangent. Furthermore, because TAHQ has a smaller molecular weight, polyimides using TAHQ have a relatively higher imide group concentration in the polyimide, which results in increased hygroscopicity. Another known acid dianhydride that has two ester structures similar to the acid dianhydride represented by formula (1) is 2,6-naphthalenebis(trimellitic acid monoester acid anhydride) (26DHN-TME), in which the biphenyl structure in formula (1) is replaced with a naphthalene structure. 26DHN-TME has the disadvantages of being prone to foaming due to the presence of the naphthalene ester structure, and of being unable to sufficiently reduce the coefficient of thermal expansion (CTE) due to the reduced linearity of the polyimide.

[0036] Condition (ii): The diamine residue derived from the diamine compound represented by the following general formula (2) is contained in an amount of 50 mol % or more relative to the total diamine residues. Hereinafter, the diamine residue derived from the diamine compound represented by formula (2) may be referred to as "diamine residue (2)."

[0037] [ka]

[0038] In the general formula (2), Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group, and p and q independently represent an integer of 0 to 4. In the formula (2), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR x R y (where Rx ,R y may be independently any substituent such as an alkyl group.

[0039] The diamine residue (2) has a rigid structure and therefore has the effect of imparting an ordered structure to the entire polymer. The inclusion of the diamine residue (2) results in a polyimide with low moisture absorption and reduces the moisture content inside the molecular chain, thereby lowering the dielectric loss tangent. Furthermore, the diamine residue (2) contains a biphenyl skeleton, which is a common structure with the acid dianhydride residue (1), and therefore has a greater effect of imparting an ordered structure to the entire polymer. Furthermore, the molecular weight of the monomer-derived units can be increased, thereby reducing the imide group concentration.

[0040] Representative examples of the diamine compound represented by general formula (2) include 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-di-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), and 4,4'-diaminobiphenyl.

[0041] The content of the diamine residue (2) in the polyamic acid and polyimide of the present embodiment is 50 mol % or more, preferably 60 to 100 mol %, and more preferably 60 to 95 mol %, based on the total diamine residues. If the content of the diamine residue (2) is less than 50 mol %, the effect of reducing the dielectric loss tangent is not sufficiently exhibited. From the viewpoint of reducing the dielectric loss tangent, it is preferable to make the proportion of the diamine residue (2) in all diamine residues as large as possible, and the content of the diamine residue (2) may be 100 mol %. On the other hand, when taking into consideration the suppression of foaming and the shortening of the heat treatment time for thermal imidization, which will be described later, it is preferable to set the upper limit of the content of the diamine residue (2) in the range of 60 to 95 mol % of all diamine residues.

[0042] Condition (iii): The ratio of monomer residues having a biphenyl skeleton (biphenyl skeleton-containing residues) to all monomer residues derived from all monomer components is 65 mo1% or more. Here, the biphenyl skeleton is a skeleton formed by two single-bonded phenyl groups. Therefore, examples of biphenyl skeleton-containing residues include biphenyldiyl and biphenyltetrayl groups. When the proportion of biphenyl skeleton-containing residues relative to all monomer residues derived from all monomer components is 65 mo1% or more, the rigid structure derived from the monomers facilitates the formation of an ordered structure throughout the polymer, thereby suppressing molecular motion and reducing the dielectric loss tangent. When the proportion of biphenyl skeleton-containing residues is less than 65 mo1%, the dielectric loss tangent is not sufficiently reduced. Therefore, when used in, for example, a circuit board, it becomes difficult to apply to high-speed transmission. From this perspective, the proportion of biphenyl skeleton-containing residues is preferably 70 mo1% or more, and more preferably 80 mo1% or more.

[0043] Furthermore, the polyamic acid and polyimide of the present embodiment are characterized by a relatively high ester group concentration because they contain, as a main structural unit, an acid dianhydride residue (1) derived from an acid dianhydride represented by formula (1) having two ester structures (-CO-O-) in the molecule. From the viewpoint of imparting an ordered structure to the entire polymer and reducing the dielectric loss tangent, the ester group concentration in the polyamic acid and polyimide of the present embodiment is, for example, preferably in the range of 3 to 15 wt%, more preferably in the range of 7 to 15 wt%. Here, the ester group concentration can be calculated from the proportion of ester groups (-COO-) in the molecular weight of the entire polyimide-imide structure.

[0044] (Other acid dianhydride residues) The polyamic acid and polyimide of the present embodiment may contain, in addition to the residue derived from the acid dianhydride represented by the above formula (1), residues of acid dianhydrides generally used as raw materials for polyimides, within the scope of not impairing the effects of the present invention. Examples of such acid dianhydride residues include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,3',3,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3,6,7-naphthalenetetracarboxylic dian ... ,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3''-p-terphenyltetracarboxylic acid dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3.4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic acid Dianhydrides, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol Examples include acid dianhydride residues derived from aromatic tetracarboxylic dianhydrides such as bisanhydrotrimellitate. Among these, acid dianhydride residues derived from BPDA (hereinafter also referred to as "BPDA residues") are particularly preferred because they have rigidity, making it easy to form an ordered polymer structure and reducing the dielectric loss tangent by suppressing molecular motion, while acid dianhydride residues derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residues") are preferred from the perspective of lowering the CTE.

[0045] (Other diamine residues) The polyamic acid and polyimide of the present embodiment preferably contain, in addition to the residue derived from the diamine compound represented by the above formula (2), a diamine residue derived from a diamine compound represented by the following general formulas (3) to (6):

[0046] [ka]

[0047] In formulas (3) to (6), R independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms, an alkoxy group, or an alkylthio group; linking group A independently represents a divalent group selected from -O-, -SO2-, -CH2-, or -C(CH3)2-; linking group X independently represents -CH2-, -O-CH2-O-, -O-C2H4-O-, -O-C3H6-O-, -O-C4H8-O-, or -O-C5H 10 represents -O-, -O-CH2-C(CH3)2-CH2-O-, -C(CH3)2-, -C(CF3)2-, or -SO2-, m independently represents an integer of 1 to 4, and n independently represents an integer of 0 to 4. However, in formula (5), when linking group A does not contain -CH2-, -C(CH3)2-, -C(CF3)2-, or -SO2-, any one of n's is 1 or more. Here, "independently" means that in one or more of the above formulas (3) to (6), multiple linking groups A, multiple linking groups X, multiple substituents R, or multiple m's and n's may be the same or different. In the above formulas (3) to (6), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR x R y (where R x ,R y may be independently any substituent such as an alkyl group.

[0048] Examples of the aromatic diamine represented by the general formula (3) include 2,6-diamino-3,5-diethyltoluene and 2,4-diamino-3,5-diethyltoluene.

[0049] Examples of the aromatic diamine represented by the general formula (4) include 2,4-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane and bis(4-amino-3-ethyl-5-methylphenyl)methane.

[0050] Examples of aromatic diamines represented by general formula (5) include 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, and 1,4-bis(4-aminophenoxy)-2,5-di-tert-butylbenzene.

[0051] An example of the aromatic diamine represented by the general formula (6) is 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[0052] Because the diamine compounds represented by general formulas (3) to (6) have bulky molecular structures, the use of one or more of these diamine compounds in combination with the diamine compound represented by general formula (2) can improve the diffusion efficiency of organic solvents from the polyimide film, suppress foaming, and shorten the heat treatment time for thermal imidization when forming a polyimide film by a casting method. From this perspective and from the perspective of achieving a low CTE, the polyimide film of the present embodiment preferably contains 1 to 50 mol %, more preferably 5 to 50 mol %, and most preferably 5 to 40 mol % of diamine residues derived from the diamine compounds represented by general formulas (3) to (6) in total, based on all diamine residues.

[0053] The polyamic acid and polyimide of the present embodiment may contain residues of diamine compounds generally used as raw materials for polyimides, in addition to residues derived from the diamine compounds represented by the above general formula (2) and general formulas (3) to (6), within the scope of the invention. Examples of such diamine residues include 1,4-diaminobenzene (p-PDA), 4-aminophenyl-4'-aminobenzoate (APAB), 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, and 3,4'-diaminodiphenyl. Propane, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, (3,3'-bisamino)diphenylamine, 1,4-bis(3-aminophenoxy)benzene , 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy]benzenamine, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene) 4,4'-[4-(4-aminophenoxy)phenyl]bisaniline, bis[4,4'-(3-aminophenoxy)]benzanilide, 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), 2,2- Bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3 ,3''-Diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene (butyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,Examples include diamine residues derived from aromatic diamine compounds such as 4'-diaminobenzanilide and 6-amino-2-(4-aminophenoxy)benzoxazole, and diamine residues derived from aliphatic diamine compounds such as dimer acid-type diamines in which the two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups. Although 1,4-diaminobenzene (p-PDA) has rigidity, its molecular weight is smaller than that of the diamine compound represented by general formula (2). Therefore, polyimides using p-PDA may produce brittle films, resulting in poor film-forming properties, or may have a relatively high imide group concentration in the polyimide, resulting in increased moisture absorption. Therefore, it is preferable not to use p-PDA, and even if it is used, it is preferable to limit its amount to 50 mol% or less of the total diamine residues.

[0054] In the polyamic acid and polyimide of the present embodiment, by selecting the types of the acid dianhydride residues and diamine residues, or by selecting the respective molar ratios when two or more types of acid dianhydride residues or diamine residues are contained, it is possible to control the moisture absorption, dielectric properties, thermal expansion coefficient, storage modulus, tensile modulus, etc. Furthermore, in the polyamic acid and polyimide of the present embodiment, when a plurality of structural units are contained, they may be present as blocks or randomly, but are preferably present randomly.

[0055] In addition, the polyamic acid and polyimide of the present embodiment preferably contain an aromatic dianhydride residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine. By containing only aromatic dianhydride residues and diamine residues contained in the polyamic acid and polyimide, the dimensional accuracy of the polyimide film can be improved in a high-temperature environment.

[0056] (Synthesis of Polyamic Acid and Polyimide) Generally, polyimides can be produced by reacting an acid dianhydride with a diamine compound in a solvent to produce a polyamic acid, which is a precursor of the polyimide, followed by heating to close the ring (imidization). For example, polyamic acid can be obtained by dissolving approximately equimolar amounts of an acid dianhydride and a diamine compound in an organic solvent and stirring the mixture at a temperature ranging from 0 to 100°C for 30 minutes to 24 hours to cause a polymerization reaction. During the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is in the range of 5 to 30 wt %, preferably 10 to 20 wt %, of the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and cresol. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such organic solvents used is not particularly limited, but it is preferable to adjust the amount so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight.

[0057] The synthesized polyamic acid is usually advantageously used as a solution in a reaction solvent, but it can be concentrated, diluted, or replaced with another organic solvent as necessary. Polyamic acid is advantageously used because it generally has excellent solvent solubility. The viscosity of the polyamic acid solution is preferably within the range of 500 cps to 100,000 cps. If the viscosity is outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating using a coater or the like.

[0058] The polyamic acid of the present embodiment can be in the form of a resin composition. The resin composition can contain optional components such as an organic solvent, an organic filler, an inorganic filler, a cyclization agent, an imidization catalyst, a curing agent, a plasticizer, an elastomer, a coupling agent, a pigment, a flame retardant, and a heat dissipation agent. The organic solvent can be the same as the organic solvent used in the polymerization reaction. The content of the organic solvent is not particularly limited, but it is preferable that the concentration of the polyamic acid be about 5 to 30 wt %.

[0059] The method for imidizing the polyamic acid is not particularly limited, and a suitable example is a heat treatment in which the polyamic acid is heated in the solvent at a temperature in the range of 80 to 400°C for 1 to 24 hours. When the polyamic acid is imidized by heating, the resin composition preferably contains substantially no cyclization agent or imidization catalyst. Here, "substantially no cyclization agent or imidization catalyst" means that the content of the cyclization agent and imidization catalyst is sufficiently less than the amount that would allow imidization to proceed, for example, 0.1 wt% or less.

[0060] (imide group concentration) The imide group concentration of the polyimide of this embodiment is preferably, for example, 30% by weight or less, and more preferably 25% by weight or less. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO)2-N-) in the polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 30% by weight, the hygroscopicity increases due to the increase in polar groups. By selecting the combination of the acid dianhydride and diamine compound, the molecular orientation in the polyimide can be controlled, thereby suppressing the increase in CTE associated with a decrease in the imide group concentration and ensuring low hygroscopicity.

[0061] (Weight average molecular weight) The weight-average molecular weight of the polyimide of this embodiment is, for example, preferably in the range of 10,000 to 400,000, more preferably in the range of 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the film tends to have reduced strength and become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during coating.

[0062] [Polyimide film] A polyimide film according to one embodiment of the present invention is a polyimide film comprising a single or multiple polyimide layers, at least one of which contains a polyimide satisfying the above conditions (i) to (iii) as the main resin component. Preferably, the main polyimide layer contains a polyimide satisfying the above conditions (i) to (iii) as the main resin component. Here, "main resin component" refers to a component that accounts for more than 50% by weight of the total resin component. Furthermore, "main polyimide layer" refers to a layer that accounts for more than 50%, preferably 60 to 100%, of the total thickness of the polyimide film. The main polyimide layer preferably contains 70% by weight or more, more preferably 80% by weight or more, of the polyimide satisfying the above conditions (i) to (iii) as the main resin component. Most preferably, the entire resin component is composed of the polyimide. By containing a polyimide that satisfies the above conditions (i) to (iii) as the main resin component of the main layer, it is possible to reduce the dielectric loss tangent of the entire polyimide film.

[0063] The polyimide film of this embodiment may be a multilayer polyimide film comprising a polyimide layer (A) containing a first polyimide as a primary resin component, and a polyimide layer (B) laminated on the polyimide layer (A) and containing a second polyimide different from the first polyimide as a primary resin component. In this case, the polyimide layer (B) is preferably a non-thermoplastic polyimide layer containing a non-thermoplastic polyimide, and is preferably a polyimide layer containing a polyimide as a primary resin component that satisfies the above conditions (i) to (iii). Here, the "non-thermoplastic polyimide" refers to a polyimide having a storage modulus of 1.0 × 10 at 30°C as measured using a dynamic mechanical analyzer (DMA). 9 Pa or more, and the storage modulus in the temperature range within the glass transition temperature + 30°C is 1.0 × 10 8 "Thermoplastic polyimide" means a polyimide having a storage modulus of 1.0 x 10 Pa or more at 30°C as measured using a dynamic viscoelasticity measuring device (DMA). 9 Pa or more, and the storage modulus in the temperature range within the glass transition temperature + 30°C is 1.0 × 10 8 This means that it indicates less than Pa.

[0064] The multilayer polyimide film of this embodiment may have a two-layer structure of polyimide layer (A) / polyimide layer (B), or a three-layer structure of polyimide layer (A) / polyimide layer (B) / polyimide layer (A), or may further include any additional polyimide layer. A polyimide layer (B) made of a polyimide satisfying the above (i) to (iii) has a relatively low gas permeability, and tends to be prone to foaming due to the presence of solvent or imidized water between the polyimide layer (B) and the polyimide layer (A). Therefore, by configuring the main component of the resin component in the polyimide layer (A) as described below, the occurrence of foaming can be effectively suppressed even if the gas permeability of the polyimide layer (B) is low.

[0065] <Configuration of Polyimide Layer (A)> The polyimide constituting the polyimide layer (A) is preferably a non-thermoplastic polyimide obtained by reacting a diamine component with a tetracarboxylic dianhydride component, and contains an acid dianhydride residue derived from an acid dianhydride and a diamine residue derived from a diamine compound.

[0066] (Acid dianhydride residue) The polyimide constituting the polyimide layer (A) contains, among all the acid dianhydride residues, an acid dianhydride residue derived from pyromellitic dianhydride (PMDA residue) and an acid dianhydride residue derived from a tetracarboxylic dianhydride having a ketone group (-CO-) in the molecule (hereinafter, sometimes referred to as a "ketone group-containing residue").

[0067] PMDA residues, which possess excellent structural planarity and rigidity, can enhance stacking between molecular chains and lower the dielectric loss tangent of polyimides. They also maintain a relatively high modulus of elasticity at high temperatures, which is expected to suppress foaming. However, PMDA residues alone result in poor entanglement of molecular chains, which can lead to reduced peel strength with metal layers and reduced interlayer adhesion with other polyimide layers, making them prone to foaming. On the other hand, ketone group-containing residues, due to their ketone groups, can improve adhesion between polyimide layers and suppress foaming through interactions and chemical reactions with functional groups in adjacent polyimide layers. Furthermore, the combined use of two or more acid dianhydride residues can improve molecular chain entanglement and increase peel strength. Furthermore, the reduced regularity of the molecular arrangement can suppress mobility in an electric field, potentially resulting in a lower dielectric loss tangent. Therefore, in the polyimide constituting the polyimide layer (A), in order to achieve a good balance between a low dielectric tangent, suppression of the foaming phenomenon, and improvement of peel strength, a PMDA residue and a ketone group-containing residue are used in combination as the acid dianhydride residue.

[0068] The content of such PMDA residues in the total acid dianhydride residues is preferably 5 mol % to 90 mol % and more preferably 20 mol % to 80 mol %. If the content of PMDA residues in the total acid dianhydride residues is below this range, there is a concern that the dielectric properties and storage modulus at 300°C and 350°C may be reduced. If the content exceeds this range, foaming may occur more easily and the peel strength may be reduced.

[0069] The ketone group-containing residues are preferably contained in an amount of 10 mol % to 95 mol % of the total acid dianhydride residues, more preferably 20 mol % to 80 mol % of the total acid dianhydride residues. If the content of the ketone group-containing residues in the total acid dianhydride residues is below this range, it becomes difficult to suppress the foaming phenomenon and improve the peel strength, while if it exceeds this range, the dielectric properties tend to deteriorate.

[0070] Examples of the ketone group-containing residue include acid dianhydride residues derived from 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 2,3',3,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 4,4'-(paraphenylenedicarbonyl)diphthalic dianhydride, 4,4'-(metaphenylenedicarbonyl)diphthalic dianhydride, and the like. Among these, the acid dianhydride residue derived from 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) is preferred. Furthermore, the functional group capable of interacting with the ketone group is not particularly limited as long as it is a functional group capable of generating, for example, physical interaction through intermolecular forces or chemical interaction through covalent bonds with the ketone group. A representative example is the amino group (-NH).

[0071] In the polyimide constituting the polyimide layer (A), the total content of PMDA residues and ketone group-containing residues in all acid dianhydride residues is preferably 80 mol % or more, more preferably 90 mol % or more, in order to achieve a good balance between a low dielectric tangent, suppression of the foaming phenomenon, and improvement of peel strength.

[0072] (Other acid dianhydride residues) The polyimide constituting the polyimide layer (A) may contain, in addition to the PMDA residue and the ketone group-containing residue, an acid dianhydride residue derived from an acid dianhydride generally used as a raw material for polyimides.

[0073] (diamine residue) The diamine residues constituting the polyimide layer (A) preferably contain, among all diamine residues, a diamine residue derived from a diamine compound represented by the following general formula (A1).

[0074] [ka]

[0075] In general formula (A1), the linking group X1 represents a single bond or a divalent group selected from -CONH-, Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group, n1 represents an integer of 0 to 2, and p and q independently represent integers of 0 to 4. In general formula (A1), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR x R y (where R x ,R y may be independently any substituent such as an alkyl group.

[0076] Specific examples of diamine residues derived from the diamine compound of general formula (A1) include diamine residues derived from 1,4-diaminobenzene (p-PDA), 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-n-propyl-4,4'-diaminobiphenyl, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, etc. Among these, the diamine residue derived from 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is preferred in terms of dielectric properties.

[0077] The diamine residue derived from the diamine compound represented by general formula (A1) can improve the planarity and rigidity of the polyimide, thereby improving the stacking between molecular chains. This reduces the mobility of the diamine residue. As a result, the dielectric loss tangent of the polyimide can be reduced. Furthermore, the planarity of the molecular skeleton of the polyimide can be improved, thereby reducing the thermal expansion coefficient in the in-plane direction.

[0078] The diamine residues derived from the diamine compound represented by general formula (A1) are preferably contained in an amount of 5 mol % to 90 mol % of the total diamine residues, more preferably 20 mol % to 80 mol %. If the content of diamine residues derived from the diamine compound represented by general formula (A1) in the total diamine residues is below this range, it becomes difficult to reduce the dielectric loss tangent and in-plane thermal expansion coefficient of the polyimide. If the content exceeds this range, the rigidity of the diamine residues becomes too high, reducing the amount of entanglement of the molecular chains, thereby reducing the peel strength with the metal layer. Furthermore, the increased regularity of the arrangement of the diamine residue moieties changes the responsiveness to an electric field, making the dielectric loss tangent more likely to deteriorate.

[0079] The polyimide constituting the polyimide layer (A) preferably contains, among all diamine residues, diamine residues derived from diamine compounds represented by the following general formulas (A2) to (A5), in addition to diamine residues derived from diamine compounds represented by the following general formulas (A1). The diamine residues derived from diamine compounds represented by the following general formulas (A2) to (A5) have, as linking groups to the aromatic rings, divalent groups independently selected from -O-, -S-, -CO-, -SO-, -SO2-, -CH2-, -C(CH3)2-, and -NH-. Furthermore, the aromatic rings to which the amino groups are linked have para-position bonds. This provides a high degree of freedom for rotation and bending of the polyimide molecular chains. By improving the flexibility of the polyimide molecular chains, it is possible to balance the interaction and degree of entanglement between the molecular chains, which facilitates both suppressing a decrease in the storage modulus E' at high temperatures and improving film strength.

[0080] [ka]

[0081] In the general formulae (A2) to (A5), R1 independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, the linking group A' independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO2-, -CH2-, -C(CH3)2-, and -NH-, and n2 independently represents an integer of 0 to 4. The linking position of the aromatic ring not bonded to an amino group is a position other than the ortho position. Here, "independently" means that in one or more of the above formulae (A2) to (A3), the multiple linking groups A', the multiple substituents R1, or the multiple n2 may be the same or different. In the general formulae (A2) to (A5), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR x R y (where R x ,R y may be independently any substituent such as an alkyl group.

[0082] The total content of diamine residues derived from diamine compounds represented by general formulas (A2) to (A5) in all diamine residues is preferably 10 mol % to 95 mol %, more preferably 20 mol % to 80 mol %. If the content is below this range, the flexibility of the molecular chains decreases, resulting in a decrease in the amount of entanglement between the molecular chains and a decrease in peel strength with the metal layer. On the other hand, if the content is above this range, the degree of freedom for rotation and bending of the polyimide molecular chains becomes too high, making it difficult to suppress molecular movement, and the dielectric loss tangent tends to increase.

[0083] Specific examples of the diamine residue derived from the diamine compounds represented by general formulas (A2) to (A5) include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-bisamino)diphenylamine, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis[2-(4-aminophenoxy)phenyl]-2-methyl-2-propanol ... Preferred examples of the diamine residues include those derived from 2,2-bis[4-(4-aminophenoxy)phenyl]benzene, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(4-aminophenoxy)]benzanilide, bis[4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]methane, and 4,4′-bis(4-aminophenoxy)biphenyl. Among these, diamine residues derived from 1,3-bis(4-aminophenoxy)benzene (TPE-R) and 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene are preferred in terms of the number of aromatic groups, linking groups, and linking positions.

[0084] (Other diamine residues) The polyimide constituting the polyimide layer (A) may contain, in addition to the above diamine residues, diamine residues derived from diamine components generally used as raw materials for polyimides.

[0085] (ratio of acid dianhydride residues to diamine residues) In the polyimide constituting the polyimide layer (A), the sum (T1) of the content of diamine residues derived from the diamine compound represented by general formula (A1), which is a rigid monomer, and the content of PMDA residues is preferably 90 mol % or more of the sum of the total content of acid dianhydride residues and the total content of diamine residues. A content of 90 mol % or more improves planarity and stacking between molecular chains, thereby maintaining a high storage modulus at high temperatures. Furthermore, the ratio (T1 / T2) of the sum (T1) of the content of diamine residues derived from the diamine compound represented by general formula (A1), which is a rigid monomer, and the content (T2) of at least one diamine residue derived from the diamine compound represented by general formulas (A2) to (A5), which is a flexible monomer, is preferably greater than 1. A ratio exceeding 1 increases the proportion of rigid monomers compared to flexible monomers, suppressing molecular chain motion and enabling a lower dielectric loss tangent.

[0086] The polyimide constituting the polyimide layer (A) may contain the same optional components as the polyimide constituting the polyimide layer (B).

[0087] The polyimide constituting the polyimide layer (A) preferably has a storage modulus E' at 300°C measured using a dynamic viscoelasticity measuring device (DMA) of 1.0 x 10 8 Pa or more, preferably 5.0 × 10 8 Pa or more, and the storage modulus E' at 350°C is preferably 1.0 × 10 7 The storage modulus E' at 300°C should be 1.0 x 10 8 Pa or more, and the storage modulus E' at 350°C is 1.0 x 10 7 By setting the pressure to be equal to or higher than Pa, it is possible to prevent the occurrence of a foaming phenomenon due to volume expansion caused by evaporation of the solvent or imidized water during heat treatment.

[0088] The weight-average molecular weight of the polyimide constituting the polyimide layer (A) is preferably 10,000 to 400,000, more preferably 50,000 to 350,000. If the weight-average molecular weight is below this range, the polyimide film becomes easily brittle, while if it exceeds this range, the viscosity increases, which may cause defects such as uneven thickness and streaks during coating. The weight-average molecular weight can be measured using a gel permeation chromatography device.

[0089] The polyimide constituting the polyimide layer (A) can be produced by a conventional method, similar to the polyimide constituting the polyimide layer (B) that satisfies the above conditions (i) to (iii).

[0090] The coefficient of thermal expansion (CTE) of the polyimide layer (A) is preferably 60 ppm / K or less, more preferably 30 ppm / K or more and 55 ppm / K or less. By setting the coefficient of thermal expansion to 60 ppm / K or less, it becomes easy to control the dimensional change rate of the polyimide film or metal-clad laminate. The coefficient of thermal expansion (CTE) of the polyimide layer (A) can be adjusted mainly by the types and proportions of acid dianhydride residues and diamine residues in the polyimide constituting the polyimide, and the heat treatment conditions in the imidization step.

[0091] The polyimide constituting the polyimide layer (A) serves as an adhesive layer in contact with, for example, the wiring layer of a circuit board, and therefore preferably has a completely imidized structure in order to suppress copper diffusion. However, a portion of the polyimide may be in the form of an amic acid. The imidization rate can be determined by measuring the infrared absorption spectrum of the polyimide thin film by the single-reflection ATR method using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) at 1015 cm -1 Based on the benzene ring absorber near 1780cm -1 It is calculated from the absorbance of the C=O stretching derived from the imide group.

[0092] <Polyimide film form> The polyimide film of the present embodiment (including a multilayer polyimide film having the above-mentioned polyimide layer (A) and polyimide layer (B); the same applies hereinafter) may be a film (sheet) made of an insulating resin, and may be in a state of being laminated on a substrate such as a metal foil such as a copper foil, a glass plate, or a resin sheet such as a polyimide film, a polyamide film, or a polyester film.

[0093] <Coefficient of thermal expansion (CTE)> When the polyimide film of the present embodiment is used, for example, as an insulating resin layer of a circuit board, in order to prevent warpage and a decrease in dimensional stability, the coefficient of thermal expansion (CTE) is preferably less than 30 ppm / K, more preferably in the range of 1 ppm / K or more and less than 25 ppm / K, and most preferably in the range of 15 ppm / K or more and less than 25 ppm / K. If the coefficient of thermal expansion (CTE) of the polyimide film is 30 ppm / K or more, warpage may occur and dimensional stability may decrease. A polyimide film having a desired CTE can be obtained by appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions.

[0094] <Dielectric loss tangent> When the polyimide film of this embodiment is used as an insulating resin layer of a circuit board, for example, in order to reduce dielectric loss during high-frequency signal transmission, the film as a whole preferably has a dielectric loss tangent (Tan δ) of less than 0.003 at 10 GHz when measured using a split post dielectric resonator (SPDR) at a temperature of 24 to 26°C and a humidity of 45 to 55%. To improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer. A dielectric loss tangent (Tan δ) of less than 0.003 at 10 GHz enhances the effect of reducing transmission loss. Therefore, when the polyimide film is used as an insulating resin layer of a high-frequency circuit board, transmission loss can be efficiently reduced. If the dielectric loss tangent at 10 GHz is 0.003 or more, when the polyimide film is used as an insulating resin layer of a circuit board, problems such as increased electrical signal loss are likely to occur.

[0095] Furthermore, the polyimide film of this embodiment preferably has a dielectric loss tangent (Tanδ) of less than 0.006 at 10 GHz when measured with a split post dielectric resonator (SPDR) in a water-absorbing environment in which the polyimide film is immersed in pure water for 48 hours, and preferably has a water absorption rate of 0.6 weight percent or less. In order to improve the transmission loss of the circuit board and reduce the influence of the environment, it is important to control the dielectric loss tangent of the insulating resin layer even when water is absorbed. A dielectric loss tangent (Tanδ) of less than 0.006 at 10 GHz can reduce changes in transmission loss due to environmental influences. The lower limit of the dielectric loss tangent is not particularly limited.

[0096] <Dielectric constant> When the polyimide film of the present embodiment is used as an insulating resin layer of a circuit board, for example, the dielectric constant at 10 GHz is preferably 4.0 or less when measured using a split post dielectric resonator (SPDR) at a temperature of 24 to 26°C and a humidity of 45 to 55% to ensure impedance consistency. A dielectric constant of more than 4.0 at 10 GHz can lead to increased dielectric loss when used as an insulating resin layer of a circuit board, resulting in problems such as increased electrical signal loss in the transmission path of high-frequency signals. Furthermore, the polyimide film of the present embodiment preferably has a dielectric property index, √Dk×Df (where Dk is the dielectric constant, Df is the dielectric dissipation factor, and √Dk is the square root of the dielectric constant), of 0.006 or less, more preferably 0.005 or less, when measured after leaving the polyimide film for 24 hours at a temperature of 24 to 26°C and a humidity of 45 to 55% (humidity-controlled). Furthermore, the value of √Dk×Df is preferably 0.01 or less, and more preferably 0.009 or less, when measured after immersing the polyimide film in pure water for 48 hours (when water is absorbed).

[0097] <Thickness> The thickness of the polyimide film of the present embodiment is not particularly limited, and is preferably within the range of, for example, 5 to 60 μm, more preferably within the range of 15 to 50 μm. In the case of a multilayer polyimide film, the thickness of the polyimide layer (A) is preferably within the range of, for example, 1 to 15 μm, more preferably within the range of 2 to 10 μm. The thickness of the polyimide layer (B) is preferably more than 50%, more preferably 60% or more of the total thickness of the insulating resin layer.

[0098] [Polyimide film manufacturing method] As preferred aspects of the method for producing a polyimide film according to the present embodiment, for example, the following [1] to [3] can be exemplified. [1] A method for producing a polyimide film by applying a polyamic acid solution to a supporting substrate, drying the solution once or repeatedly, and then imidizing the solution. [2] A method in which a polyamic acid solution is applied to a support substrate and dried once or multiple times, and then the polyamic acid gel film is peeled off from the support substrate and imidized to produce a polyimide film. [3] A method for producing a polyimide film by multilayer extrusion, in which a polyamic acid solution is simultaneously coated and dried in a multilayer laminate, and then imidized (hereinafter referred to as the multilayer extrusion method).

[0099] The method [1] above may include, for example, the following steps 1a to 1c: (1a) applying a polyamic acid solution to a supporting substrate and drying it; (1b) forming a polyimide layer by heat-treating polyamic acid on a supporting substrate to imidize it; (1c) separating the supporting substrate and the polyimide layer to obtain a polyimide film; may include:

[0100] The method [2] above may include, for example, the following steps 2a to 2c: (2a) applying a polyamic acid solution to a supporting substrate and drying; (2b) separating the support substrate from the polyamic acid gel film; (2c) heat-treating the polyamic acid gel film to imidize it, thereby obtaining a polyimide film; may include:

[0101] In the above-mentioned method [1] or [2], by repeating step 1a or step 2a multiple times, a polyamic acid laminate structure can be formed on the support substrate. The method for applying the polyamic acid solution to the support substrate is not particularly limited, and it can be applied using, for example, a coater such as a comma coater, a die coater, a knife coater, or a lip coater.

[0102] The above method [3] can be carried out in the same manner as the above method [1] or [2], except that in step 1a of the above method [1] or step 2a of the above method [2], a polyamic acid laminate structure is simultaneously applied by multilayer extrusion and dried.

[0103] In the polyimide film produced in this embodiment, it is preferable to complete the imidization of the polyamic acid on the support substrate. Since the polyamic acid resin layer is imidized while being fixed to the support substrate, the expansion and contraction changes of the polyimide layer during the imidization process can be suppressed, and the thickness and dimensional accuracy of the polyimide film can be maintained.

[0104] [Metal-clad laminate] A metal-clad laminate according to one embodiment of the present invention is a metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, wherein the insulating resin layer includes a single or multiple polyimide layers, and at least one of the polyimide layers contains a polyimide that satisfies the above conditions (i) to (iii) as the main resin component.

[0105] A preferred embodiment of the metal-clad laminate includes an insulating resin layer having multiple polyimide layers, including a polyimide layer (A) in contact with the metal layer and a polyimide layer (B) laminated on the polyimide layer (A), and the polyimide constituting the main polyimide layer, the polyimide layer (B), satisfies the above conditions (i) to (iii). The configurations of the polyimide layer (A) and the polyimide layer (B) are the same as those described for the multilayer polyimide film. Such a metal-clad laminate includes the polyimide layer (B) with a low coefficient of thermal expansion (CTE) and a low dielectric loss tangent, thereby improving the dimensional stability of the entire insulating resin layer and achieving a low dielectric loss tangent. However, a polyimide layer (B) made of a polyimide satisfying the above conditions (i) to (iii) has relatively low gas permeability, and is prone to foaming due to the retention of solvents or imidized water between the polyimide layer (B) and the polyimide layer (A). Therefore, by configuring the polyimide layer (A) as described above, it is possible to effectively suppress the occurrence of the foaming phenomenon even if the gas permeability of the polyimide layer (B) is low.

[0106] The thickness of the polyimide layer (A) in the metal-clad laminate is not particularly limited, and is preferably within the range of 1 to 15 μm, more preferably 2 to 10 μm. The polyimide layer (B) preferably has a thickness of more than 50%, more preferably 60% or more of the total thickness of the insulating resin layer.

[0107] (metal layer) The metal layer constituting the metal-clad laminate of this embodiment is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or a copper alloy is particularly preferred. The material of the wiring layer in the circuit board described below is also the same as the metal layer.

[0108] The thickness of the metal layer is not particularly limited, but when a metal foil such as copper foil is used, it is preferably 35 μm or less, and more preferably in the range of 5 μm to 25 μm. From the viewpoint of production stability and handling, the lower limit of the thickness of the metal foil is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Furthermore, commercially available copper foil may be used as the copper foil.

[0109] The ten-point average roughness (Rzjis) of the surface of the metal layer in contact with the polyimide layer (A) is preferably 1.2 μm or less, more preferably 1.0 μm or less. When the metal layer is made of metal foil, making the surface roughness Rzjis 1.2 μm or less enables fine wiring processing that supports high-density mounting and reduces transmission loss during high-frequency signal transmission, making it possible to apply the metal layer to circuit boards for high-frequency signal transmission.

[0110] The metal layer may be subjected to a surface treatment using, for example, siding, aluminum alcoholate, aluminum chelate, or a silane coupling agent, for the purpose of, for example, rust prevention or improving adhesive strength.

[0111] The metal-clad laminate of this embodiment can be produced by a conventional method, for example, the following methods [1] and [2].

[0112] [1] A method for producing a metal-clad laminate in which a polyamic acid solution is applied to a metal foil that will become the metal layer, followed by drying, is repeated once or multiple times, and then imidized to form a polyimide insulating layer.

[0113] [2] A method for producing a metal clad laminate in which a polyimide insulating layer is formed by applying a polyamic acid solution to a metal foil that will become the metal layer by multi-layer extrusion, laminating it in multiple layers, drying it, and then imidizing it (hereinafter referred to as the multi-layer extrusion method).

[0114] The method [1] above may include, for example, the following steps (1a) and (1b): (1a) applying a polyamic acid solution to a metal foil and drying it; and (1b) a step of forming a polyimide layer (A) by heat-treating the polyamic acid on the metal foil to imidize it. In this case, by adjusting the heating conditions in the drying step of step (1a) and, in particular, the heating conditions in the imidization step of step (1b), it is possible to control the in-plane orientation of the polyimide, and thereby control the properties of the polyimide, such as the birefringence and CTE.

[0115] In the method [1] above, a polyamic acid laminate structure can be formed on a metal foil by repeatedly performing step (1a) for a polyamic acid solution of a precursor of the polyimide constituting the polyimide layer (A) and a polyamic acid solution of a precursor of the polyimide constituting the polyimide layer (B). The method for applying the polyamic acid solution to the metal foil is not particularly limited, and it can be applied using a coater such as a comma coater, a die coater, a knife coater, or a lip coater.

[0116] The method [2] above can be carried out in the same manner as the method [1] above, except that in step (1a) of the method [1] above, a polyamic acid solution of a precursor of a polyimide constituting the polyimide layer (A) and a polyamic acid solution of a precursor of a polyimide constituting the polyimide layer (B) are simultaneously applied by multilayer extrusion and dried.

[0117] In the metal-clad laminate produced in this manner, the imidization of the polyamic acid is completed on the metal foil, so that the polyamic acid resin layer is imidized while being fixed to the metal foil. This suppresses changes in the expansion and contraction of the polyimide layer during the imidization process, and allows the thickness and dimensional accuracy of the polyimide insulating layer to be maintained.

[0118] [Circuit board] The metal-clad laminate of the present invention is useful mainly as a circuit board material for FPCs and the like. The metal layer of the metal-clad laminate is processed into a pattern by a conventional method to form a wiring layer, thereby producing a circuit board that is an embodiment of the present invention. A circuit board in which the metal layer of the metal-clad laminate of the present invention is processed into wiring is also an aspect of the present invention. That is, the circuit board of this embodiment comprises an insulating resin layer containing a single or multiple polyimide layers, and a wiring layer provided on at least one surface of the insulating resin layer, and the insulating resin layer may contain the polyimide layer (B). In addition, in order to improve adhesion between the insulating resin layer and the wiring layer, the layer of the insulating resin layer that contacts the wiring layer may be a polyimide layer (A). [Example]

[0119] The features of the present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[0120] [Viscosity measurement] The viscosity was measured at 25°C using an E-type viscometer (Brookfield, product name: DV-II+Pro). The rotation speed was set so that the torque was 10% to 90%, and the viscosity was read when the viscosity stabilized 2 minutes after the start of measurement.

[0121] [Glass transition temperature (Tg) and classification of polyimide film as non-thermoplastic or thermoplastic] The glass transition temperature was determined by measuring a 5 mm x 70 mm polyimide film using a dynamic viscoelasticity measuring device (DMA: manufactured by TA Instruments, product name: RSA G2) at a heating rate of 4°C / min from 30°C to 400°C at a frequency of 1 Hz, and the temperature at which the change in elastic modulus (tan δ) reached a maximum was defined as the glass transition temperature. The storage modulus at 30°C measured using DMA was 1.0 x 10 9 The storage modulus is 1.0×10 Pa or more in the temperature range within the glass transition temperature + 30°C. 8Those showing a storage modulus of less than 1.0 x 10 Pa are considered "thermoplastic" and have a storage modulus of 1.0 x 10 Pa at 30°C. 9 The storage modulus is 1.0×10 Pa or more in the temperature range within the glass transition temperature + 30°C. 8 Those showing a thermal expansion coefficient of 100 Pa or more were categorized as "non-thermoplastic."

[0122] [Measurement of coefficient of thermal expansion (CTE)] A 3 mm x 20 mm polyimide film was heated from 30°C to 260°C at a constant heating rate while applying a 5.0 g load using a thermomechanical analyzer (trade name: TMA / SS6100, manufactured by Hitachi High-Technologies Corporation (formerly Seiko Instruments Inc.)). After holding at that temperature for 10 minutes, the film was cooled at a rate of 5°C / min to determine the average thermal expansion coefficient (thermal expansion coefficient) from 250°C to 100°C.

[0123] [Measurement of relative permittivity and dielectric loss tangent] The relative permittivity (Dk) and dielectric loss tangent (Df) of the polyimide film at a frequency of 10 GHz were measured using a vector network analyzer (manufactured by Agilent, product name: E8363C) and a split post dielectric resonator (SPDR resonator). The Dk and Df values ​​after humidity control were measured after the polyimide film used for the measurement was left to stand for 24 hours under the conditions of a temperature of 24 to 26°C and a humidity of 45 to 55%. Dk and Df during water absorption were measured after the polyimide film used for the measurement was immersed in pure water for 48 hours, then removed and the pure water on the surface of the material was wiped off.

[0124] [Measurement of copper foil surface roughness] The surface roughness of the copper foil was measured in tapping mode over an area of ​​80 μm × 80 μm on the copper foil surface using an AFM (manufactured by Bruker AXS, product name: Dimension Icon type SPM) and a probe (manufactured by Bruker AXS, product name: TESPA (NCHV), tip curvature radius 10 nm, spring constant 42 N / m), and the ten-point average roughness (Rzjis) was calculated.

[0125] [Peel strength measurement] The copper foil of a copper-clad laminate (copper foil / multilayer polyimide layer) was processed into 1 mm wide circuits at 10 mm intervals in the resin coating direction, and then cut into 8 cm wide × 4 cm long pieces. Peel strength was measured using a Tensilon tester (manufactured by Toyo Seiki Seisakusho, product name: Strograph VE-1D) by fixing the polyimide layer surface of the cut measurement sample to an aluminum plate with double-sided tape and peeling the circuit-processed copper foil in a 180° direction at a rate of 50 mm / min until the copper foil had been peeled 10 mm from the polyimide layer, and this median strength was determined as the initial peel strength.

[0126] [Moisture absorption rate measurement] Two polyimide film test pieces (width: 4 cm × length: 25 cm) were prepared and dried at 80°C for 1 hour, then their weights were measured. After the weight measurement, they were placed in a constant temperature and humidity chamber at 23°C / 50% RH and left to stand for at least 24 hours, after which their weights were measured again and the moisture absorption rate was calculated using the following formula. Moisture absorption rate (weight %) = [(weight after moisture absorption - weight after drying) / weight after drying] × 100

[0127] [Water absorption measurement] A polyimide film test piece (width: 4 cm × length: 25 cm) was prepared and dried at 80°C for 1 hour, and then its weight was measured. After measuring the weight, the film was left to stand in pure water for at least 24 hours, then removed, and after wiping off the pure water on the film surface, its weight was measured and the water absorption was calculated using the following formula. Water absorption rate (weight %) = [(weight after water absorption - weight after drying) / weight after drying] × 100

[0128] [Tensile modulus] Using a Strograph R-1 (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a tensile test was carried out on a polyimide film measuring 12.7 mm wide x 127 mm long at 50 mm / min under an environment of 23°C temperature and 50% relative humidity, and the yield strength was calculated.

[0129] [Whether or not foaming occurs] The appearance of the obtained copper-clad laminate was visually observed to check whether bubbles were present.

[0130] [Film availability] For copper-clad laminates, when the copper foil is etched away using a ferric chloride solution to leave a polyimide film, those that can be handled as a single film without cracking are rated as "Acceptable," while those that crack and easily break are rated as "Not Acceptable."

[0131] [Measurement of polyimide layer thickness] The copper foil of the copper-clad laminate was etched away using an aqueous ferric chloride solution to obtain a polyimide film. The resulting polyimide film was cut into strips, embedded in resin, and then cut in the thickness direction using a microtome to prepare ultrathin sections approximately 100 nm thick. The prepared ultrathin sections were observed using the STEM function of a Hitachi High-Tech SEM (SU9000) at an accelerating voltage of 30 kV. The thickness of each polyimide layer was measured at five points, and the average value was used as the thickness of each polyimide layer. The sum of the thicknesses of the individual layers was used as the thickness of the multilayer polyimide film.

[0132] [Calculation of imide group concentration] The imide group was defined as (-(CO)2-N-) and the calculation was performed using the following formula. Imide group concentration (wt%) = (molecular weight of imide group / molecular weight of entire polyimide structure) × 100

[0133] [Calculation of ester group concentration] The ester group was defined as (-COO-) and the calculation was performed using the following formula. Ester group concentration (wt%) = (molecular weight of ester group / molecular weight of entire polyimide structure) × 100

[0134] [Calculation of the proportion of monomers containing biphenyl skeleton] The proportion (unit: mol %) of monomers having a biphenyl skeleton among all monomer components in the polyimide was taken as the proportion of monomers containing a biphenyl skeleton.

[0135] The abbreviations used in the Examples and Reference Examples represent the following compounds. BP-TME: p-biphenylenebis(trimellitic acid monoester anhydride), CAS number 10340-81-5) 26DHN-TME: 2,6-Naphthalenebis(trimellitic acid monoester anhydride), CAS number 115383-00-1) TAHQ: p-phenylenebis(trimellitic acid monoester acid anhydride) PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane PDA: p-phenylenediamine DMAc: N,N-dimethylacetamide

[0136] (Synthesis Example 1) Under a nitrogen stream, 12.1229 g of m-TB (0.05711 mol), 1.2338 g of BAPP (0.00301 mol), and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 31.6433 g of BP-TME (0.05921 mol) was added, and the polymerization reaction was continued with stirring at room temperature for 3 hours to obtain polyamic acid solution A. The solution viscosity of polyamic acid solution A was 26,800 cps.

[0137] (Synthesis Example 2) Under a nitrogen stream, 14.4565 g of m-TB (0.06810 mol) and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 ml separable flask and stirred at room temperature to dissolve. Next, 26.8858 g of BP-TME (0.05031 mol) and 3.6577 g of PMDA (0.01677 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution B. The solution viscosity of polyamic acid solution B was 25,500 cps.

[0138] (Synthesis Example 3) Under a nitrogen stream, 13.5308 g of m-TB (0.06374 mol), 1.3771 g of BAPP (0.00335 mol), and an amount of DMAc to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 26.4885 g of BP-TME (0.04956 mol) and 3.6036 g of PMDA (0.01652 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution C. The solution viscosity of polyamic acid solution C was 24,000 cps.

[0139] (Synthesis Example 4) Under a nitrogen stream, 11.7590 g of m-TB (0.05539 mol), 4.0127 g of BAPP (0.00977 mol), and an amount of DMAc to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 25.7282 g of BP-TME (0.04814 mol) and 3.5002 g of PMDA (0.01605 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding Polyamic Acid Solution D. The solution viscosity of Polyamic Acid Solution D was 21,300 cps.

[0140] (Synthesis Example 5) Under a nitrogen stream, 9.2841 g of m-TB (0.04373 mol), 7.6941 g of BAPP (0.01874 mol), and an amount of DMAc to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 24.6661 g of BP-TME (0.04615 mol) and 3.3557 g of PMDA (0.01538 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution E. The solution viscosity of polyamic acid solution E was 14,900 cps.

[0141] (Synthesis Example 6) Under a nitrogen stream, 9.6812 g of m-TB (0.04560 mol), 1.3372 g of BAPP (0.00326 mol), and 4.7612 g of TPE-R (0.01629 mol) were added to a 500 mL separable flask, along with DMAc in an amount to give a solids concentration of 15 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 25.7212 g of BP-TME (0.04813 mol) and 3.4992 g of PMDA (0.01604 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution F. The solution viscosity of polyamic acid solution F was 17,800 cps.

[0142] (Synthesis Example 7) Under a nitrogen stream, 14.8395 g of m-TB (0.06990 mol), 1.5103 g of BAPP (0.00368 mol), and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 19.3670 g of BP-TME (0.03624 mol), 5.3311 g of BPDA (0.01812 mol), and 3.9522 g of PMDA (0.01812 mol) were added, followed by stirring at room temperature for 3 hours to polymerize the mixture, yielding polyamic acid solution G. The solution viscosity of polyamic acid solution G was 35,200 cps.

[0143] (Synthesis Example 8) Under a nitrogen stream, 16.4284 g of m-TB (0.07739 mol), 1.6720 g of BAPP (0.00407 mol), and an amount of DMAc such that the solids concentration after polymerization was 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 10.7204 g of BP-TME (0.02006 mol), 11.8038 g of BPDA (0.04012 mol), and 4.3754 g of PMDA (0.02006 mol) were added, and the polymerization reaction was continued with stirring at room temperature for 3 hours to obtain polyamic acid solution H. The solution viscosity of polyamic acid solution H was 27,900 cps.

[0144] (Synthesis Example 9) Under a nitrogen stream, 19.1251 g of m-TB (0.09009 mol), 1.9465 g of BAPP (0.00474 mol), and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 13.7413 g of BPDA (0.04670 mol) and 10.1871 g of PMDA (0.04670 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution I. The solution viscosity of polyamic acid solution I was 31,400 cps.

[0145] (Synthesis Example 10) Under a nitrogen stream, 16.3417 g of m-TB (0.07698 mol), 1.6632 g of BAPP (0.00405 mol), and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 18.2906 g of TAHQ (0.03991 mol) and 8.7045 g of PMDA (0.03991 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution J. The solution viscosity of polyamic acid solution J was 27,800 cps.

[0146] (Synthesis Example 11) Under a nitrogen stream, 8.0852 g of PDA (0.07477 mol), 1.6154 g of BAPP (0.00394 mol), and an amount of DMAc sufficient to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 31.0722 g of BP-TME (0.05814 mol) and 4.2272 g of PMDA (0.01938 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution K. The solution viscosity of polyamic acid solution K was 28,700 cps.

[0147] (Synthesis Example 12) Under a nitrogen stream, 8.4131 g of PDA (0.07780 mol), 1.6809 g of BAPP (0.00409 mol), and an amount of DMAc to achieve a post-polymerization solids concentration of 15 wt% were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 30.5387 g of 26DHN-TME (0.06007 mol) and 4.3674 g of PMDA (0.02002 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution L. The solution viscosity of polyamic acid solution L was 26,500 cps.

[0148] (Synthesis Example 13) Under a nitrogen stream, 12.6149 g of m-TB (0.05942 mol), 1.2839 g of BAPP (0.00313 mol), and an amount of DMAc sufficient to achieve a solids concentration of 15 wt% after polymerization were added to a 500 ml separable flask and stirred at room temperature to dissolve. Next, 31.1012 g of 26DHN-TME (0.06117 mol) was added, and the polymerization reaction was continued with stirring at room temperature for 3 hours to obtain polyamic acid solution M. The solution viscosity of polyamic acid solution M was 73,900 cps.

[0149] (Synthesis Example 14) Under a nitrogen stream, 13.9957 g of m-TB (0.06593 mol), 1.4244 g of BAPP (0.00347 mol), and an amount of DMAc to achieve a solids concentration of 15 wt% after polymerization were added to a 500 mL separable flask and stirred at room temperature to dissolve. Next, 25.8789 g of 26DHN-TME (0.05090 mol) and 3.7010 g of PMDA (0.01697 mol) were added, and the polymerization reaction was continued with stirring at room temperature for 3 hours to obtain polyamic acid solution N. The solution viscosity of polyamic acid solution N was 43,800 cps.

[0150] (Synthesis Example 15) Under a nitrogen stream, 17.6242 g of m-TB (0.08302 mol), 1.7937 g of BAPP (0.00437 mol), and an amount of DMAc sufficient to achieve a solids concentration of 15 wt% after polymerization were added to a 500 mL separable flask and stirred at room temperature. Next, 11.5007 g of BP-TME (0.02152 mol) and 14.0815 g of PMDA (0.06456 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution O. The solution viscosity of polyamic acid solution O was 31,400 cps.

[0151] (Synthesis Example 16) Under a nitrogen stream, 7.8166 g of m-TB (0.03682 mol) and 10.7636 g of TPE-R (0.03682 mol) were added to a 500 ml separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 4.6984 g of BTDA (0.01458 mol) and 12.7214 g of PMDA (0.05832 mol) were added, and the mixture was stirred at room temperature for 3 hours to carry out the polymerization reaction, yielding polyamic acid solution P. The solution viscosity of polyamic acid solution P was 8,500 cps.

[0152] (Synthesis Example 17) Under a nitrogen stream, 2.9802 g of m-TB (0.01404 mol) and 16.4155 g of TPE-R (0.05615 mol) were added to a 500 ml separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 4.4784 g of BTDA (0.01390 mol) and 12.1258 g of PMDA (0.05559 mol) were added, followed by stirring at room temperature for 3 hours to carry out the polymerization reaction, yielding polyamic acid solution Q. The solution viscosity of polyamic acid solution Q was 1,800 cps.

[0153] (Synthesis Example 18) Under a nitrogen stream, 13.1525 g of m-TB (0.06196 mol) and 4.5279 g of TPE-R (0.01549 mol) were added to a 500 ml separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 4.9411 g of BTDA (0.01533 mol) and 13.3786 g of PMDA (0.06134 mol) were added, followed by stirring at room temperature for 3 hours to carry out the polymerization reaction, yielding polyamic acid solution R. The solution viscosity of polyamic acid solution R was 6,800 cps.

[0154] (Synthesis Example 19) Under a nitrogen stream, 2.8108 g of m-TB (0.01324 mol) and 15.4821 g of TPE-R (0.05296 mol) were added to a 500 ml separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 10.5594 g of BTDA (0.03277 mol) and 7.1477 g of PMDA (0.03277 mol) were added, followed by stirring at room temperature for 3 hours to carry out the polymerization reaction, yielding polyamic acid solution S. The solution viscosity of polyamic acid solution S was 2,100 cps.

[0155] (Synthesis Example 20) Under a nitrogen stream, 2.6596 g of m-TB (0.01253 mol) and 14.6492 g of TPE-R (0.05011 mol) were added to a 500 ml separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 15.9860 g of BTDA (0.04961 mol) and 2.7053 g of PMDA (0.01240 mol) were added, followed by stirring at room temperature for 3 hours to carry out the polymerization reaction, yielding polyamic acid solution T. The solution viscosity of polyamic acid solution T was 1,900 cps.

[0156] (Synthesis Example 21) Under a nitrogen stream, 2.7701 g of m-TB (0.01305 mol) and 15.2580 g of TPE-R (0.05219 mol) were added to a 500 mL separable flask, along with DMAc in an amount to give a solids concentration of 12 wt% after polymerization, and the mixture was stirred at room temperature to dissolve. Next, 13.6386 g of BPDA (0.04636 mol) and 4.3333 g of PMDA (0.01987 mol) were added, followed by stirring at room temperature for 3 hours to allow the polymerization reaction to proceed, yielding polyamic acid solution U. The solution viscosity of polyamic acid solution U was 1600 cps.

[0157] Example 1 Polyamic acid solution A was uniformly applied to copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rzjis on the resin side: 0.6 μm) to a cured thickness of approximately 25 μm, and then heated and dried at 120°C to remove the solvent. Further, stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, yielding copper-clad laminate A. No bubbles were observed on the film surface. Next, the copper foil of the resulting copper-clad laminate A was etched away using an aqueous ferric chloride solution to prepare polyimide film A. Table 1 lists the type of polyimide, imide group concentration, ester group concentration, biphenyl skeleton-containing monomer ratio, presence or absence of bubbles, and film-formability of the resulting polyimide film A, and the film's physical properties are shown in Tables 1 and 2.

[0158] (Examples 2 to 8, Comparative Examples 1 and 2, and Reference Examples 1 to 13) Copper-clad laminates were prepared for polyamic acids B to U, and the properties of the polyimide films obtained after etching the copper foil were evaluated in the same manner as in Example 1. The type of polyimide, imide group concentration, ester group concentration, biphenyl skeleton-containing monomer ratio, presence or absence of foaming, and film-formability of the obtained polyimide films are shown in Table 1, and the film physical property data are shown in Tables 1 and 2. It should be noted that film property data was not obtained for samples in which foaming occurred and samples in which film formation was not possible.

[0159] [Table 1]

[0160] [Table 2]

[0161] [Example 9] Polyamic acid solution P was uniformly applied to copper foil 1 as the first layer, which would contact the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in a copper-clad laminate X having a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the copper-clad laminate X having the obtained multilayer polyimide was measured and found to be 0.92 kN / m. The copper foil of the copper-clad laminate X having the multilayer polyimide was etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film X. The obtained multilayer polyimide film X had a Dk of 3.37 and a Df of 0.0027 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution P at 300°C is 8.3 × 10 8 Pa, and the storage modulus at 350°C is 1.9 × 10 8 It is Pa.

[0162] [Example 10] Polyamic acid solution Q was uniformly applied to copper foil 1 as the first layer, which would be in contact with the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in copper-clad laminate Y with a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the obtained copper-clad laminate Y having the multilayer polyimide was measured and found to be 0.71 kN / m. The copper foil of the copper-clad laminate Y having the multilayer polyimide was etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film Y. The obtained multilayer polyimide film Y had Dk=3.38 and Df=0.0027 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution Q at 300°C is 1.2 × 10 9 Pa, and the storage modulus at 350°C is 5.2 × 10 8 It is Pa.

[0163] [Example 11] Polyamic acid solution R was uniformly applied to copper foil 1 as the first layer, which would be in contact with the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in a copper-clad laminate Z having a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the copper-clad laminate Z having the obtained multilayer polyimide was measured and found to be 0.73 kN / m. The copper foil of the copper-clad laminate Z having the multilayer polyimide was etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film Z. The obtained multilayer polyimide film Z had a Dk of 3.38 and a Df of 0.0027 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution R at 300°C is 1.8 × 10 9 Pa, and the storage modulus at 350°C is 3.4 × 10 8 It is Pa.

[0164] [Example 12] Polyamic acid solution S was uniformly applied to copper foil 1 as the first layer, which would contact the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in a copper-clad laminate Aa with a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the resulting copper-clad laminate Aa having the multilayer polyimide was measured and found to be 0.77 kN / m. The copper foil of the copper-clad laminate Aa having the multilayer polyimide was then etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film Aa. The resulting multilayer polyimide film Aa had a Dk of 3.38 and a Df of 0.0027 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution S at 300°C is 4.6 × 10 8 Pa, and the storage modulus at 350°C is 2.4 × 10 8 It is Pa.

[0165] [Example 13] Polyamic acid solution T was uniformly applied to copper foil 1 as the first layer, which would contact the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in a copper-clad laminate Bb with a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the resulting copper-clad laminate Bb having the multilayer polyimide was measured and found to be 0.71 kN / m. The copper foil of the copper-clad laminate Bb having the multilayer polyimide was then etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film Bb. The resulting multilayer polyimide film Bb had a Dk of 3.38 and a Df of 0.0028 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution T at 300°C is 4.4 × 10 8 Pa, and the storage modulus at 350°C is 1.5 × 10 8 It is Pa.

[0166] [Example 14] Polyamic acid solution U was uniformly applied to copper foil 1 as the first layer, which would contact the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 20 minutes to complete the imidization, resulting in a copper-clad laminate Cc with a multilayer polyimide. No bubbles were observed on the film surface. The initial peel strength of the resulting copper-clad laminate Cc having the multilayer polyimide was measured and found to be 0.97 kN / m. The copper foil of the copper-clad laminate Cc having the multilayer polyimide was then etched away using an aqueous ferric chloride solution to prepare a multilayer polyimide film Cc. The resulting multilayer polyimide film Cc had a Dk of 3.38 and a Df of 0.0025 after humidity conditioning. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution U at 300°C is 3.1 × 10 7 Pa, and the storage modulus at 350°C is 1.4 × 10 7 It is Pa.

[0167] [Reference example 14] Polyamic acid solution U was uniformly applied to copper foil 1 as the first layer, which would contact the copper foil, to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, the second layer, was uniformly applied to the first layer to a thickness of 21 μm after curing, and then heated and dried at 120°C for 2 minutes to remove the solvent. Furthermore, polyamic acid solution U, the third layer, was uniformly applied to the second layer to a thickness of 2 μm after curing, and then heated and dried at 120°C for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment from 120°C to 360°C was performed over 10 minutes to complete the imidization, resulting in a copper-clad laminate Dd with a multilayer polyimide. During this process, bubbles were observed on the film surface. The storage modulus of the polyimide film prepared as the first layer by curing the polyamic acid solution U at 300°C is 3.1 × 10 7 Pa, and the storage modulus at 350°C is 1.4 × 10 7 It is Pa.

[0168] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible.

Claims

1. A polyimide film comprising a single or multiple polyimide layers, A polyimide film in which at least one of the polyimide layers contains acid dianhydride residues derived from an acid dianhydride component and diamine residues derived from a diamine component, and contains 25 mol% or more of acid dianhydride residues derived from an acid dianhydride represented by the following formula (1) relative to the total acid dianhydride residues. 【Chemistry 1】

2. The polyimide film according to claim 1, comprising a diamine residue derived from a diamine compound represented by the following general formula (2). 【Chemistry 2】 [In formula (2), Y independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms, and p and q independently represent integers from 0 to 4.]

3. The polyimide film according to claim 1, wherein the proportion of monomer residues having a biphenyl skeleton is 65 mo1% or more of the total monomer residues derived from the total monomer components.

4. The polyimide film according to claim 1, comprising a diamine residue derived from one or more diamine compounds represented by the following general formulas (3) to (6). 【Transformation 3】 In formulas (3) to (6), R independently represents a monovalent hydrocarbon group, alkoxy group, or alkylthio group having 1 to 6 carbon atoms; linking group A independently represents a divalent group selected from -O-, -SO₂-, -CH₂-, or -C(CH₃)₂-; linking group X independently represents -CH₂-, -O-CH₂-O-, -O-C₂H₄-O-, -O-C₃H₶-O-, -O-C₄H₸-O-, -O-C₅H₁₀-O-, -O-CH₂-C(CH₃)₂-CH₂-O-, -C(CH₃)₂-, -C(CF₃)₂-, or -SO₂ The expression indicates -, where m independently represents an integer from 1 to 4, and n independently represents an integer from 0 to 4. However, in equation (5), if the linking group A does not contain -CH₂-, -C(CH₃)₂-, or -SO₂-, then at least one of n is 1 or greater.

5. The polyimide film according to claim 1, comprising: a polyimide layer (A) containing a first polyimide as the main component of the resin component; and a polyimide layer (B) laminated on the polyimide layer (A) and containing a second polyimide different from the first polyimide as the main component of the resin component.

6. The polyimide film according to claim 1, wherein the dielectric loss tangent (Tanδ) at 10 GHz, measured by a split-post dielectric resonator (SPDR) in an environment with a temperature of 24 to 26°C and a humidity of 45 to 55%, is less than 0.003, and the coefficient of thermal expansion (CTE) is less than 25 ppm / K.

7. A metal-clad laminate comprising an insulating resin layer and a metal layer provided on at least one surface of the insulating resin layer, A metal-clad laminate characterized in that the insulating resin layer includes the polyimide film described in claim 1.

8. A circuit board comprising an insulating resin layer and a wiring layer provided on at least one surface of the insulating resin layer, A circuit board characterized in that the insulating resin layer includes the polyimide film described in claim 1.

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