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

Abstract

To provide a polyimide film that has low thermal expandability, low hygroscopicity, and high film formability and also has sufficiently low dielectric loss tangents.SOLUTION: A polyimide comprises an imidized polyamide acid that satisfies condition (i): it contains 25 mol% or more of residues of the following formula (1), condition (ii): it contains 50 mol% or more of diamine residues induced from compounds of the formula (2): H2 N-φ(Y)-φ(Y)-NH2, and condition (iii): the proportion of monomer residues having biphenyl skeletons is 65 mol% or more relative to all the monomer residues.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, with the high performance and high functionality of electric and electronic devices, high-speed transmission of information has been required, and components and members used in these devices are also required to cope with high-speed transmission. When transmitting high-frequency signals, inconveniences such as an increase in the loss of electrical signals and the delay time of signals are likely to occur. Therefore, improvements have been made to circuit boards such as flexible printed circuits (FPCs) used in high-frequency devices so as to have electrical characteristics corresponding to high-speed transmission. For this reason, regarding polymers used as FPC materials, studies have been made to reduce the dielectric loss tangent in order to reduce transmission loss.

[0003] Typical examples of polymers with a low dielectric loss tangent include fluororesins, liquid crystal polymers (LCPs), and modified polyimides (MPIs). However, fluororesins have problems in adhesion to low-profile copper foils, laser processability, copper plating properties, etc., and LCPs have problems such as low adhesion to low-profile copper foils and difficulty in multilayer formation. In addition, although MPIs do not have the problems of fluororesins and LCPs, they generally have problems such as high moisture absorption rate and high dielectric loss tangent.

[0004] In order to reduce the dielectric loss tangent of polyimide, it has been proposed to introduce an ester structure into the polyimide chain (for example, Patent Document 1). In addition, for the purpose of low thermal expansion and low moisture absorption, etc., it has also been proposed to introduce an ester structure into the polyimide chain (for example, Patent Documents 2 to 4).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In Patent Document 1, the dielectric tangent is reduced by introducing an ester structure into the polyimide chain. However, in its examples, the dielectric tangent at 10 GHz exceeds 0.003, which is not satisfactory from the viewpoint of reducing the transmission loss of high-frequency signals. Further, in Patent Document 1, since the imidization of polyimide is carried out with a ring-closing agent, there is a tendency that it is difficult to lower the dielectric tangent due to an increase in polar groups. 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 the film-forming property deteriorates.

[0007] Therefore, an object of the present invention is to provide a polyimide film having low thermal expansion properties, good film-forming properties, and a sufficiently low dielectric tangent required as an FPC material. [Means for Solving the Problems]

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

[0009] That is, the polyamic acid of 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 polyamic acid contains, based on all the dianhydride residues, 25 mol% or more of dianhydride residues derived from a dianhydride represented by the following formula (1).

[0011]

Chemical formula

[0012] Condition (ii): The polyamic acid contains, based on all the diamine residues, 50 mol% or more of diamine residues derived from a diamine compound represented by the following general formula (2).

[0013]

Chemical formula

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

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

[0016] The polyamic acid according to the first aspect of the present invention may contain, based on all the diamine residues, diamine residues derived from a diamine compound represented by the following general formulas (3) to (6) within a range of 1 to 50 mol%.

[0017]

Chemical formula

[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; the linking group A independently represents a divalent group selected from -O-, -SO2-, -CH2-, or -C(CH3)2-; the linking group X independently represents -CH2-, -O-CH2-O-, -O-C2H4-O-, -O-C3H6-O-, -O-C4H8-O-, -O-C5H 10 -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; n independently represents an integer of 0 to 4. However, in Formula (5), when the linking group A does not contain -CH2-, -C(CH3)2-, or -SO2-, any one of n is 1 or more.

[0019] The polyimide of the second aspect of the present invention is obtained by imidizing the polyamic acid of the first aspect.

[0020] The polyimide film of the third aspect of the present invention is a polyimide film including a single layer or a plurality of polyimide layers, wherein at least one layer of the polyimide layer contains the polyimide of the second aspect as a main component of the resin component.

[0021] The polyimide film according to the fourth aspect of the present invention may be a polyimide film including a polyimide layer (A) containing a first polyimide as a 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 a main component of the resin component. In the polyimide film of this fourth aspect, the first polyimide is a polyimide containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, and among all the acid dianhydride residues, the residue derived from pyromellitic dianhydride is 5 mol% or more and 90 mol% or less, and the residue derived from an acid dianhydride having a ketone group (-CO-) in the molecule is 10 mol% or more and 95 mol% or less, and the residue derived from pyromellitic dianhydride and the residue derived from an acid dianhydride having a ketone group (-CO-) in the molecule may be contained in a total proportion of 80 mol% or more. Further, the polyimide film of this fourth aspect may contain, in all the diamine residues, a residue derived from a diamine compound represented by the following general formula (A1) in a proportion of 5 mol% or more and 90 mol% or less. Furthermore, the polyimide film of this fourth aspect has a storage modulus E' at 300 °C measured using a dynamic viscoelasticity measuring device (DMA) of 1.0×10 8 Pa or more and a storage modulus E' at 350 °C of 1.0×10 7 Pa or more, and may be a polyimide. Furthermore, in the polyimide film of the fourth aspect, the second polyimide is the polyimide of the second aspect.

[0022]

Chemical formula

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

[0024] The metal-clad laminate according to the fifth aspect of the present invention is a metal-clad laminate including an insulating resin layer and a metal 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.

[0025] The circuit board according to the sixth aspect of the present invention is a circuit board including 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.

Advantages of the Invention

[0026] By satisfying the conditions (i) to (iii), the polyamic acid and polyimide of the present invention can form a polyimide film having an extremely low dielectric tangent without impairing low thermal expansibility and good film formability. Therefore, by using the polyimide film of the present invention as a circuit board material, a circuit board capable of coping with high-speed transmission can be provided.

Embodiments for Carrying Out the Invention

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

[0028] <Polyamic Acid - Polyimide> The polyamic acid according to an embodiment of the present invention is a precursor of polyimide, and is a polyamic acid obtained by reacting a specific acid dianhydride component and 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 above polyamic acid and contains a specific acid anhydride residue and a specific diamine residue. In the present invention, the acid anhydride residue represents a tetravalent group derived from an acid dianhydride, and the diamine residue represents a divalent group derived from a diamine compound. When the raw material acid dianhydride and diamine compound are reacted in approximately equimolar amounts, the types and molar ratios of the acid dianhydride residues and diamine residues contained in the polyimide can be made to correspond approximately to the types and molar ratios of the raw materials. In the present invention, when referring to "polyimide", it means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc., in addition to polyimide.

[0029] Hereinafter, the acid anhydride residues and diamine residues contained in the polyamic acid and polyimide of the present embodiment will be described 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): Containing 25 mol% or more of an acid anhydride residue derived from the acid dianhydride represented by the following formula (1) with respect to all acid anhydride residues. Hereinafter, the acid anhydride residue derived from the acid dianhydride represented by formula (1) may be referred to as "acid anhydride residue (1)".

[0032]

Chemical formula

[0033] The dianhydride represented by formula (1) is known as p-biphenylenebis(trimellitic acid monoester dianhydride) (BP-TME), and has a biphenyl skeleton in the molecule and two ester structures (-CO-O-) bonded to the biphenyl skeleton. Since the biphenyl skeleton has rigidity and the ester structure has an effect of imparting an ordered structure to the whole polymer, by containing the dianhydride residue (1), it becomes possible to reduce the coefficient of thermal expansion (lower CTE), and it becomes possible to effectively reduce the dielectric tangent (lower dielectric tangent) by improving the ordered structure of the molecule and suppressing the movement.

[0034] In the polyamic acid and polyimide of the present embodiment, the content of the dianhydride residue (1) is 25 mol% or more with respect to all dianhydride residues, preferably in the range of 25 to 100 mol%, and more preferably in the range of 40 to 80 mol%. When the content of the dianhydride residue (1) is less than 25 mol%, both the effects of lowering the dielectric tangent and lowering the CTE by improving the ordered structure of the molecule and suppressing the movement are not sufficiently exhibited. The upper limit of the content of the dianhydride residue (1) may be 100 mol%, but when other dianhydrides are used in combination for the purpose of imparting arbitrary functionality, the amount of the dianhydride represented by formula (1) can be adjusted according to the amount used.

[0035] Here, as an analog compound of the dianhydride represented by formula (1), those in which the biphenyl skeleton in formula (1) has a substituent such as a phenyl group are known (for example, Patent Document 2). However, due to the presence of the substituent bonded to the biphenyl skeleton, there is a demerit that the effect of suppressing the molecular movement of the polyimide becomes small and the dielectric tangent cannot be sufficiently reduced. In addition, as an acid dianhydride having two ester structures similar to the acid dianhydride represented by the formula (1), 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) is known. Since this TAHQ has a structure in which two ester structures are bonded to a phenylene group, although it has rigidity, the effect of lowering the dielectric tangent cannot be sufficiently obtained. Further, when TAHQ is compared with the acid dianhydride represented by the formula (1), since it does not have a biphenyl skeleton, the effect of suppressing molecular motion is small, which is disadvantageous for reducing the dielectric tangent. Also, since the molecular weight is small, polyimide using TAHQ has a demerit that the imide group concentration of the polyimide becomes relatively high and the hygroscopicity becomes high. Furthermore, as an acid dianhydride having two ester structures similar to the acid dianhydride represented by the formula (1), 2,6-naphthalenebis(trimellitic acid monoester anhydride) (26DHN-TME) having a structure in which the biphenyl skeleton in the formula (1) is replaced with a naphthalene skeleton is also known. This 26DHN-TME has a demerit that foaming is likely to occur due to the presence of the naphthalene ester skeleton, and the coefficient of thermal expansion (CTE) cannot be sufficiently reduced due to the decrease in the linearity of the polyimide.

[0036] Condition (ii): Containing 50 mol% or more of diamine residues derived from the diamine compound represented by the following general formula (2) with respect to all diamine residues. Hereinafter, the diamine residue derived from the diamine compound represented by the formula (2) may be referred to as "diamine residue (2)".

[0037]

Chemical formula

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

[0039] Since the diamine residue (2) has a rigid structure, it has the effect of imparting an ordered structure to the entire polymer. By containing the diamine residue (2), a polyimide with low hygroscopicity can be obtained, and the moisture inside the molecular chain can be reduced, so the dielectric loss tangent can be lowered. Also, since the diamine residue (2) contains a biphenyl skeleton as a structure common to the acid dianhydride residue (1), the effect of imparting an ordered structure to the entire polymer becomes greater, and moreover, since the molecular weight of the monomer-derived unit can be increased, the imide group concentration can be reduced.

[0040] Representative examples of the diamine compound represented by the 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), 4,4'-diaminobiphenyl, and the like.

[0041] The content of the diamine residue (2) in the polyamic acid and polyimide of the present embodiment is 50 mol% or more with respect to all diamine residues, preferably in the range of 60 to 100 mol%, and more preferably in the range of 60 to 95 mol%. If the content of the diamine residue (2) is less than 50 mol%, the effect of lowering the dielectric loss tangent is not sufficiently exhibited. From the perspective of reducing the dielectric loss tangent, it is preferable to make the ratio of the diamine residue (2) in all the diamine residues as large as possible, and the content of the diamine residue (2) may be 100 mol%. On the other hand, when considering foam suppression and shortening of the heat treatment time for thermal imidization described later, it is preferable to set the upper limit of the content of the diamine residue (2) within the range of 60 to 95 mol% with respect to all the diamine residues.

[0042] Condition (iii): The ratio of the monomer residue having a biphenyl skeleton (biphenyl skeleton-containing residue) is 65 mol% or more with respect to all the monomer residues derived from all the monomer components. Here, the biphenyl skeleton is a skeleton in which two phenyl groups are singly bonded. Therefore, examples of the biphenyl skeleton-containing residue include a biphenyldiyl group and a biphenyltetrayl group. When the ratio of the biphenyl skeleton-containing residue is 65 mol% or more with respect to all the monomer residues derived from all the monomer components, an ordered structure is likely to be formed in the whole polymer due to the rigid structure derived from the monomer, and the dielectric loss tangent can be reduced by suppressing the movement of molecules. When the ratio of the biphenyl skeleton-containing residue is less than 65 mol%, the dielectric loss tangent is not sufficiently reduced. For this reason, for example, when used for a circuit board, it becomes difficult to adapt to high-speed transmission. From such a perspective, the ratio of the biphenyl skeleton-containing residue is preferably 70 mol% or more, and more preferably 80 mol% or more.

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

[0044] (Other acid dianhydride residues) The polyamic acid and polyimide of the present embodiment can contain, in addition to the residue derived from the acid dianhydride represented by the above formula (1), the residue of an acid dianhydride generally used as a raw material for polyimide, as long as the effects of the invention are not impaired. 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(trimesic acid monoester) dianhydride (TAHQ), 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3- or 3.Acid dianhydride residues derived from aromatic tetracarboxylic dianhydrides such as 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-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 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 bisanhydrotrimellitate, etc. Among these, in particular, the acid dianhydride residue derived from BPDA (hereinafter also referred to as "BPDA residue") is preferable because it has rigidity, easily forms an ordered structure of the polymer, and can reduce the dielectric tangent by suppressing the molecular motion. The acid dianhydride residue derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residue") is preferable from the viewpoint of reducing 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), for example, a diamine residue derived from a diamine compound represented by the following general formulas (3) to (6).

[0046]

Chemical formula

[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, the linking group A independently represents a divalent group selected from -O-, -SO2-, -CH2-, or -C(CH3)2-, and the linking group X independently represents -CH2-, -O-CH2-O-, -O-C2H4-O-, -O-C3H6-O-, -O-C4H8-O-, -O-C5H 10 -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 the linking group A does not contain -CH2-, -C(CH3)2-, or -SO2-, any one of n is 1 or more. Here, "independently" means that in one or two or more of the above formulas (3) to (6), for a plurality of linking groups A, a plurality of linking groups X, a plurality of substituents R, or a plurality of m and n, they may be the same or different from each other. 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 independently means an arbitrary substituent such as an alkyl group) may be the case.

[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, bis(4-amino-3-ethyl-5-methylphenyl)methane, and the like.

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

[0051] Examples of the aromatic diamine represented by the general formula (6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), and the like.

[0052] Since the diamine compounds represented by the general formulas (3) to (6) have a bulky molecular structure, when forming a polyimide film by the casting method by using one or more of the diamine compounds represented by the general formulas (3) to (6) together with the diamine compound represented by the general formula (2), the diffusion efficiency of the organic solvent from the polyimide film is increased, foaming is suppressed, and the heat treatment time for thermal imidization can be shortened. From such a viewpoint and the viewpoint of reducing the CTE, the polyimide film of the present embodiment preferably contains, in total, diamine residues derived from the diamine compounds represented by the general formulas (3) to (6) in the range of preferably 1 to 50 mol%, more preferably 5 to 50 mol%, and most preferably 5 to 40 mol% with respect to all diamine residues.

[0053] The polyamic acid and polyimide of the present embodiment can contain, in addition to the residues derived from the diamine compounds represented by the above general formulas (2) and (3) to (6), residues of diamine compounds generally used as raw materials for polyimides, as long as the effects of the invention are not impaired. Examples of such diamine residues include 1,4-diaminobenzene (p-PDA), 4-aminophenyl-4'-aminobenzoate (APAB), 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenylether, 3,4'-diaminodiphenylether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylether, 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)bisoxy]bisaniline, bis[4,4'-(3-aminophenoxy)]benz anilide, 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, 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,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 two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups, etc. may be mentioned., Although 1,4-diaminobenzene (p-PDA) has rigidity, its molecular weight is smaller than that of the diamine compound represented by the general formula (2). Therefore, the polyimide using p-PDA may cause the film to become brittle and the film-forming property to deteriorate, or the imide group concentration of the polyimide may relatively increase and the hygroscopicity may increase. Thus, it is preferably not to use p-PDA, and even when using it, it is preferably that the usage amount is 50 mol% or less based on all diamine residues.,

[0054] In the polyamic acid and polyimide of the present embodiment, by selecting the types of the above acid dianhydride residues and diamine residues, and the respective molar ratios in the case of containing two or more types of acid dianhydride residues or diamine residues, hygroscopicity, dielectric properties, coefficient of thermal expansion, storage elastic modulus, tensile elastic modulus, etc. can be controlled. Further, in the polyamic acid and polyimide of the present embodiment, when having a plurality of structural units, they may be present as blocks or randomly, but it is preferably present randomly.,

[0055] Also, in the polyamic acid and polyimide of the present embodiment, it is preferable that the acid dianhydride residues and diamine residues are composed of aromatic acid dianhydride residues derived from aromatic tetracarboxylic acid dianhydrides and aromatic diamine residues derived from aromatic diamines. By making both the acid dianhydride residues and diamine residues contained in the polyamic acid and polyimide only residues having aromatic groups, the dimensional accuracy of the polyimide film under a high temperature environment can be improved.,

[0056] (Synthesis of polyamic acid and polyimide) Generally, polyimide can be produced by reacting an acid dianhydride with a diamine compound in a solvent to form a polyamic acid, which is a precursor of polyimide, and then subjecting it to thermal cyclization (imidization). For example, an acid dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature in the range of 0 to 100 °C for 30 minutes to 24 hours to carry out a polymerization reaction to obtain a polyamic acid. In the reaction, the reaction components are dissolved so that the resulting precursor is in the range of 5 to 30% by weight, preferably 10 to 20% by weight, in the organic solvent. Examples of the organic solvent 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, cresol, etc. These solvents can also be used in combination of two or more, and furthermore, a combination with aromatic hydrocarbons such as xylene and toluene is also possible. Also, the amount of such an organic solvent used is not particularly limited, but it is preferably adjusted to an amount such 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 reaction solvent solution, but can be concentrated, diluted or replaced with another organic solvent if necessary. Since polyamic acid generally has excellent solvent solubility, it is preferably used. The viscosity of the solution of polyamic acid is preferably in the range of 500 cps to 100,000 cps. If it is outside this range, defects such as thickness unevenness and streaks are likely to occur in the film during coating operations using a coater or the like.

[0058] In addition, the polyamic acid of the present embodiment can be in the form of a resin composition. The resin composition can contain, as optional components, for example, 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, a heat dissipating agent, etc. As the organic solvent, the same ones as those used in the polymerization reaction can be used. The content of the organic solvent is not particularly limited, but it is preferably adjusted so that the concentration of the polyamic acid is about 5 to 30% by weight.

[0059] The method for imidizing the polyamic acid is not particularly limited. For example, heat treatment such as heating in the above solvent at a temperature in the range of 80 to 400°C for 1 to 24 hours is preferably employed. When imidizing the polyamic acid by heating, it is preferable that the resin composition substantially does not contain a cyclization agent and an imidization catalyst. Here, "substantially does not contain a cyclization agent and an imidization catalyst" means that the content of the cyclization agent and the imidization catalyst is sufficiently less than the amount that can promote imidization, for example, 0.1% by weight or less.

[0060] (Imide group concentration) The imide group concentration of the polyimide of the present embodiment is preferably, for example, 30% by weight or less, and more preferably 25% by weight or less. Here, the "imide group concentration" means 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 structure of the polyimide. 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 above acid dianhydride and diamine compound and controlling the molecular orientation in the polyimide, it is possible to suppress the increase in CTE accompanying the decrease in the imide group concentration and ensure low hygroscopicity.

[0061] (Weight average molecular weight) The weight average molecular weight of the polyimide of the present embodiment is preferably in the range of, for example, 10,000 to 400,000, more preferably in the range of 50,000 to 350,000. When the weight average molecular weight is less than 10,000, the strength of the film tends to decrease and it tends to become brittle. On the other hand, when the weight average molecular weight exceeds 400,000, the viscosity increases excessively and defects such as film thickness unevenness and streaks are likely to occur during the coating operation.

[0062] [Polyimide Film] The polyimide film according to an embodiment of the present invention is a polyimide film including a single-layer or multiple-layer polyimide layer, wherein at least one layer of the polyimide layer contains, as a main component of the resin component, a polyimide satisfying the above conditions (i) to (iii). Preferably, the main polyimide layer preferably contains, as a main component of the resin component, a polyimide satisfying the above conditions (i) to (iii). Here, the "main component of the resin component" means a component contained in an amount exceeding 50% by weight based on all the resin components. The "main polyimide layer" means a layer occupying more than 50% of the total thickness of the polyimide film, preferably 60 to 100% of the thickness. The main polyimide layer preferably contains 70% by weight or more, more preferably 80% by weight or more, and most preferably all of the resin components are composed of the above polyimide, of the polyimide satisfying the above conditions (i) to (iii) based on all the resin components. By containing, as a main component of the resin component, a polyimide in which the main layer satisfies the above conditions (i) to (iii), it is possible to achieve a low dielectric tangent of the entire polyimide film.

[0063] The polyimide film of this embodiment may be a multilayer polyimide film including a polyimide layer (A) containing a first polyimide as a 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 a main component of the resin component. In this case, it is preferable that the polyimide layer (B) is a non-thermoplastic polyimide layer containing a non-thermoplastic polyimide and is a main polyimide layer containing a polyimide that satisfies the above conditions (i) to (iii) as a main component of the resin component. Here, the "non-thermoplastic polyimide" means that the storage elastic modulus at 30 °C measured using a dynamic viscoelasticity measuring device (DMA) is 1.0×10 9 Pa or more, and the storage elastic modulus in the temperature range within the glass transition temperature + 30 °C is 1.0×10 8 Pa or more. The "thermoplastic polyimide" means that the storage elastic modulus at 30 °C measured using a dynamic viscoelasticity measuring device (DMA) is 1.0×10 9 Pa or more, and the storage elastic modulus in the temperature range within the glass transition temperature + 30 °C is less than 1.0×10 8 Pa.

[0064] The multilayer polyimide film of this embodiment may have a structure in which two layers of polyimide layer (A) / polyimide layer (B) are laminated, or a three-layer laminated structure of polyimide layer (A) / polyimide layer (B) / polyimide layer (A), and furthermore, any polyimide layer may be laminated. The polyimide layer (B) composed of a polyimide that satisfies the above (i) to (iii) has relatively low gas permeability, and there is a tendency for foaming to easily occur due to the retention of a solvent or imidization water between the polyimide layer (A) and the polyimide layer (B). Therefore, by setting the main component of the resin component in the polyimide layer (A) to the configuration described below, it is possible to effectively suppress the occurrence of the foaming phenomenon 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 and 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, in all acid dianhydride residues, an acid dianhydride residue (PMDA residue) derived from pyromellitic dianhydride and an acid dianhydride residue (hereinafter sometimes referred to as "ketone group-containing residue") derived from a tetracarboxylic dianhydride having a ketone group (-CO-) in the molecule.

[0067] Here, the PMDA residue is excellent in planarity and rigidity in structure, can increase the stacking property between molecular chains, and can lower the dielectric tangent of the polyimide. Also, the elastic modulus at high temperature can be maintained at a relatively high level, and it is expected to suppress the occurrence of foaming phenomena. However, with only PMDA residues, there is little entanglement of molecular chains, the peel strength with the metal layer is likely to decrease, and the interlayer adhesion between the polyimide layer and other polyimide layers decreases, making it easier for foaming phenomena to occur. On the other hand, due to the presence of a ketone group, the ketone group-containing residue can improve the adhesion between polyimide layers and suppress the occurrence of foaming phenomena through interactions and chemical reactions with functional groups contained in adjacent laminated polyimide layers. Also, by using two or more types of acid dianhydride residues in combination, the entanglement of molecular chains can be improved, and an improvement in peel strength can be expected. Also, by reducing the regularity of the molecular arrangement, the mobility with respect to the electric field is suppressed, and a reduction in dielectric tangent can also be expected. Therefore, in the polyimide constituting the polyimide layer (A), in order to achieve a good balance among low dielectric tangent, suppression of foaming phenomena, and improvement of peel strength, the PMDA residue and the ketone group-containing residue are used in combination as acid dianhydride residues.

[0068] Such PMDA residues are preferably contained in an amount of 5 mol% or more and 90 mol% or less, more preferably 20 mol% or more and 80 mol% or less, based on the total amount of the tetracarboxylic dianhydride residues. If the content of the PMDA residues in the total amount of the tetracarboxylic dianhydride residues is less than this range, there is a concern about a decrease in dielectric properties and storage elastic modulus at 300 °C and 350 °C. If it exceeds this range, a foaming phenomenon is likely to occur, and the peel strength tends to decrease.

[0069] Also, the ketone group-containing residues are preferably contained in an amount of 10 mol% or more and 95 mol% or less, more preferably 20 mol% or more and 80 mol% or less, based on the total amount of the tetracarboxylic dianhydride residues. If the content of the ketone group-containing residues in the total amount of the tetracarboxylic dianhydride residues is less than this range, it becomes difficult to suppress the foaming phenomenon and improve the peel strength. If it exceeds this range, the dielectric properties tend to decrease.

[0070] Here, examples of the ketone group-containing residues include acid dianhydride residues derived from, for example, 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (BTDA), 2,3’,3,4’-benzophenone tetracarboxylic dianhydride, 2,2’,3,3’-benzophenone tetracarboxylic dianhydride, 4,4’-(paraphenylene dicarbonyl) diphthalic anhydride, 4,4’-(metaphenylene dicarbonyl) diphthalic anhydride, and the like. Among these, acid dianhydride residues derived from 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (BTDA) are preferred. Also, as the functional group having a property of interacting with the ketone group, there is no particular limitation as long as it can cause, for example, physical interaction due to intermolecular force or chemical interaction due to covalent bond with the ketone group. A typical example thereof is an amino group (-NH2).

[0071] In the polyimide constituting the polyimide layer (A), the contents of the PMDA residues and the ketone group-containing residues in the total amount of the tetracarboxylic dianhydride residues are preferably 80 mol% or more, more preferably 90 mol% or more, in total, in order to achieve a good balance among low dielectric loss tangent, suppression of the occurrence of the foaming phenomenon, and improvement of the peel strength.

[0072] (Other acid dianhydride residues) In addition to the above PMDA residues and ketone group-containing residues, the polyimide constituting the polyimide layer (A) can generally contain acid dianhydride residues derived from acid dianhydrides used as raw materials for polyimides.

[0073] (Diamine residues) Among the diamine residues constituting the polyimide layer (A), it is preferable that the diamine residues contain diamine residues derived from a diamine compound represented by the following general formula (A1) in all the diamine residues.

[0074] [Chemical formula]

[0075] In the general formula (A1), the linking group X1 represents a single bond or a divalent group selected from -CONH-, Y independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 3 carbon atoms, n1 represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. In the 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 each independently means an arbitrary substituent such as an alkyl group) may be the case.

[0076] Specific examples of the diamine residues derived from the diamine compounds of the 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, diamine residues derived from 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) can be preferably mentioned from the viewpoint of dielectric properties.

[0077] The diamine residue derived from the diamine compound represented by the general formula (A1) can improve the stacking property between molecular chains by improving the planarity and rigidity of the polyimide. Therefore, the mobility of the diamine residue can be reduced. As a result, the dielectric tangent of the polyimide can be lowered. In addition, since the planarity of the molecular skeleton of the polyimide can also be enhanced, the coefficient of thermal expansion in the plane direction can be lowered.

[0078] The diamine residue derived from the diamine compound represented by the general formula (A1) is preferably contained in the total diamine residues in an amount of 5 mol% or more and 90 mol% or less, more preferably 20 mol% or more and 80 mol% or less. When the content of the diamine residue derived from the diamine compound represented by the general formula (A1) in the total diamine residues is less than this range, it becomes difficult to lower the dielectric tangent and the coefficient of thermal expansion in the plane direction of the polyimide. When it exceeds this range, the rigidity of the diamine residue becomes too high and the amount of entanglement of the molecular chains decreases, so the peel strength with the metal layer decreases. In addition, as the regularity of the arrangement of the diamine residue portion increases, the responsiveness to the electric field changes and the dielectric tangent tends to deteriorate.

[0079] The polyimide constituting the polyimide layer (A) preferably contains, in the total diamine residues, in addition to the diamine residue derived from the diamine compound represented by the general formula (A1), diamine residues derived from the diamine compounds represented by the following general formulas (A2) to (A5). The diamine residues derived from the diamine compounds represented by the following general formulas (A2) to (A5) have, as a linking group of the aromatic ring, a divalent group independently selected from -O-, -S-, -CO-, -SO-, -SO2-, -CH2-, -C(CH3)2-, -NH-. Further, the aromatic ring to which the amino group is linked has a para-position bond. Therefore, the degree of freedom of rotation and bending of the polyimide molecular chain is high, and by improving the flexibility of the polyimide molecular chain, the balance between the interaction between molecular chains and the amount of entanglement can be achieved, so it becomes easy to achieve both suppression of the decrease in the storage elastic modulus E' in the high temperature range and improvement of the film strength.

[0080] [Chemistry]

[0081] In general formulas (A2) to (A5), R1 independently represents a monovalent hydrocarbon group or an 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-, -NH-, and n2 independently represents an integer of 0 to 4. Also, the linking position of the aromatic ring having no bond with the amino group is a position other than the ortho position. Here, "independently" means that in one or two or more of the above formulas (A2) to (A3), for a plurality of linking groups A', a plurality of substituents R1 or a plurality of n2, they may be the same or different from each other. In general formulas (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 independently means an arbitrary substituent such as an alkyl group) may be the case.

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

[0083] Specific examples of the diamine residue derived from the diamine compound represented by the 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'-bis(amino)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-aminophenyl)-2-propyl]benzene, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(4-aminophenoxy)]benz anilide, 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 diamine residues derived from 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 can be preferably mentioned from the viewpoints of the number of aromatic rings, linking groups, and linking positions.

[0084] (Other diamine residues) The polyimide constituting the polyimide layer (A) can 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 residue to diamine residue) In the polyimide constituting the polyimide layer (A), the total content (T1) of the diamine residue derived from the diamine compound represented by the general formula (A1), which is a rigid monomer, and the PMDA residue is desirably 90 mol% or more based on the total of the content of all acid dianhydride residues and the content of all diamine residues. When it is 90 mol% or more, the storage elastic modulus at high temperature can be maintained high due to the improvement in planarity and the improvement in stacking property between molecular chains. Further, the ratio (T1 / T2) of the total content (T1) of the diamine residue derived from the diamine compound represented by the general formula (A1), which is the rigid monomer, and the PMDA residue to the content (T2) of at least one diamine residue among the diamine residues derived from the diamine compounds represented by the general formulas (A2) to (A5), which are flexible monomers, is desirably greater than 1. By the ratio exceeding 1, the proportion of the rigid monomer becomes larger compared to the flexible monomer, and the movement of the molecular chain is suppressed, so that the dielectric loss tangent can be suppressed to be lower.

[0086] The polyimide constituting the polyimide layer (A) can 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 elastic modulus E' at 300 °C measured using a dynamic viscoelasticity measuring device (DMA) of 1.0×10 8 Pa or more, more preferably 5.0×10 8 Pa or more, and the storage elastic modulus E' at 350 °C is preferably 1.0×10 7 Pa or more. By setting the storage elastic modulus E' at 300 °C to 1.0×10 8 Pa or more and the storage elastic modulus E' at 350 °C to 1.0×10 7 Pa or more, it is possible to suppress the occurrence of a foaming phenomenon due to volume expansion caused by the vaporization of the solvent or imidized water during the heat treatment.

[0088] The weight average molecular weight of the polyimide constituting the polyimide layer (A) is preferably 10,000 or more and 400,000 or less, more preferably 50,000 or more and 350,000 or less. If the weight average molecular weight is below this range, the polyimide film tends to become brittle, and if it exceeds this range, the viscosity increases, and there is a concern that uneven thickness, streaks, etc. may occur during coating. The weight average molecular weight can be measured by a gel permeation chromatography apparatus.

[0089] The polyimide constituting the polyimide layer (A) can be produced by a conventional method in the same manner as the polyimide satisfying the above conditions (i) to (iii) constituting the polyimide layer (B).

[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 the metal-clad laminate. The adjustment of the coefficient of thermal expansion (CTE) of the polyimide layer (A) can be mainly adjusted 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 process.

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

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

[0093] <Coefficient of thermal expansion (CTE)> When the polyimide film of this embodiment is applied, for example, as an insulating resin layer of a circuit board, in order to prevent warping 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, warping may occur or dimensional stability may decrease. By appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions, a polyimide film having a desired CTE can be obtained.

[0094] <Dielectric tangent> When the polyimide film of this embodiment is applied, for example, as an insulating resin layer of a circuit board, in order to reduce dielectric loss during the transmission of high-frequency signals, the dielectric tangent (Tanδ) at 10 GHz, measured by a split post dielectric resonator (SPDR) in an environment of a temperature of 24 to 26°C and a humidity of 45 to 55%, for the entire film, is preferably less than 0.003. In order to improve the transmission loss of the circuit board, it is particularly important to control the dielectric tangent of the insulating resin layer. When the dielectric tangent (Tanδ) at 10 GHz is less than 0.003, the effect of reducing the transmission loss increases. Therefore, when the polyimide film is applied as the insulating resin layer of a high-frequency circuit board, the transmission loss can be efficiently reduced. If the dielectric tangent at 10 GHz is 0.003 or more, when the polyimide film is applied as the insulating resin layer of the circuit board, inconveniences such as an increase in the loss of electrical signals on the transmission path of high-frequency signals are likely to occur.

[0095] In addition, for the polyimide film of the present embodiment, for example, when measured by a split post dielectric resonator (SPDR) in a water absorption environment where the polyimide film is immersed in pure water for 48 hours, the dielectric tangent (Tanδ) at 10 GHz is preferably less than 0.006, and the water absorption rate is preferably 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 tangent of the insulating resin layer even during water absorption. When the dielectric tangent (Tanδ) at 10 GHz is less than 0.006, the change in transmission loss due to environmental influence can be reduced. Note that the lower limit value of the dielectric tangent is not particularly limited.

[0096] <Relative permittivity> When the polyimide film of the present embodiment is applied as an insulating resin layer of a circuit board, for example, in order to ensure impedance matching, the relative permittivity at 10 GHz when measured by a split post dielectric resonator (SPDR) in an environment of temperature 24 - 26°C and humidity 45 - 55% is preferably 4.0 or less. When the relative permittivity at 10 GHz exceeds 4.0, when the polyimide film is applied as an insulating resin layer of a circuit board, it will lead to deterioration of dielectric loss, and disadvantages such as an increase in the loss of electrical signals on the transmission path of high-frequency signals are likely to occur. Further, for the polyimide film of the present embodiment, the value of √Dk×Df (where Dk is the relative permittivity, Df is the dielectric tangent, and √Dk means the square root of the relative permittivity), which is an index of dielectric characteristics, is preferably 0.006 or less, more preferably 0.005 or less, when measured after leaving it for 24 hours under the conditions of temperature 24 - 26°C and humidity 45 - 55% (during humidity conditioning). Furthermore, the value of √Dk×Df is preferably 0.01 or less, more preferably 0.009 or less, when measured after immersing the polyimide film in pure water for 48 hours (during water absorption).

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

[0098] [Method for manufacturing polyimide film] As a preferred embodiment of the method for manufacturing the polyimide film of this embodiment, for example, the following [1] to [3] can be exemplified. [1] A method of manufacturing a polyimide film by repeatedly applying and drying a polyamic acid solution on a support substrate one or more times and then imidizing. [2] A method of manufacturing a polyimide film by repeatedly applying and drying a polyamic acid solution on a support substrate one or more times, then peeling off the gel film of the polyamic acid from the support substrate, and imidizing. [3] A method of manufacturing a polyimide film by simultaneously applying and drying a polyamic acid solution in a multilayer state by multilayer extrusion and then performing imidization (hereinafter, multilayer extrusion method).

[0099] The method of [1] above includes, for example, the following steps 1a to 1c; (1a) A step of applying a polyamic acid solution to a support substrate and drying it; (1b) A step of forming a polyimide layer by heat-treating the polyamic acid on the support substrate to imidize it; (1c) A step of obtaining a polyimide film by separating the support substrate and the polyimide layer; can be included.

[0100] The method of [2] above includes, for example, the following steps 2a to 2c; (2a) A step of applying a polyamic acid solution to a support substrate and drying it; (2b) A step of separating the support substrate and the gel film of the polyamic acid; (2c) A step of obtaining a polyimide film by heat-treating a gel film of polyamic acid to imidize it; can be included.

[0101] In the method of [1] or [2] above, a laminated structure of polyamic acid can be formed on a support substrate by repeating step 1a or step 2a a plurality of times. The method of applying the polyamic acid solution onto the support substrate is not particularly limited, and for example, it can be applied with a coater such as a comma, die, knife, lip, etc.

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

[0103] It is preferable that the imidization of polyamic acid is completed on the support substrate for the polyimide film manufactured in this embodiment. Since the resin layer of polyamic acid is imidized in a state fixed to the support substrate, the expansion and contraction changes of the polyimide layer in 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 an embodiment of the present invention is a metal-clad laminate including an insulating resin layer and a metal layer laminated on one or both sides thereof, wherein the insulating resin layer includes a single-layer or a plurality of polyimide layers, and at least one layer of the polyimide layers contains a polyimide satisfying the above conditions (i) to (iii) as the main component of the resin component.

[0105] As a preferred embodiment of the metal-clad laminate, the insulating resin layer has a plurality of 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 polyimide layer (B), which is the main polyimide layer, is a polyimide satisfying the above conditions (i) to (iii). Here, 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 has a low coefficient of thermal expansion (CTE) and a low dielectric tangent due to the polyimide layer (B), thereby enhancing the dimensional stability of the entire insulating resin layer and achieving a low dielectric tangent. However, the polyimide layer (B) composed of a polyimide satisfying the above (i) to (iii) has a relatively low gas permeability, and solvents and imidization water tend to accumulate between the polyimide layer (B) and the polyimide layer (A), making foaming likely to occur. Therefore, by configuring the polyimide layer (A) as described above, the occurrence of the foaming phenomenon can be effectively suppressed 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 for example, a range of 1 to 15 μm is preferable, and a range of 2 to 10 μm is more preferable. The polyimide layer (B) preferably has a thickness of more than 50%, more preferably 60% or more, based on the total thickness of the insulating resin layer.

[0107] (Metal layer) The metal layer constituting the metal-clad laminate of the present embodiment is not particularly limited, and examples 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 preferable. Note that the material of the wiring layer in the circuit board described later is the same as that of the metal layer.

[0108] The thickness of the metal layer is not particularly limited. However, for example, when using a metal foil typified by a copper foil, it is preferably 35 μm or less, more preferably in the range of 5 μm or more and 25 μm or less. From the viewpoints of production stability and handleability, the lower limit of the thickness of the metal foil is preferably 5 μm. When using a copper foil, either a rolled copper foil or an electrolytic copper foil may be used. Also, as the copper foil, commercially available copper foils can be used.

[0109] In addition, the ten-point average roughness (Rzjis) on 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 from a metal foil, by making the surface roughness Rzjis 1.2 μm or less, fine wiring processing corresponding to high-density mounting becomes possible, and also the transmission loss during high-frequency signal transmission can be reduced, so that it can be applied to a circuit board for high-frequency signal transmission.

[0110] Further, the metal layer may be subjected to surface treatment, for example, by a rust prevention treatment or for the purpose of improving adhesion, such as by siding, aluminum alcoholate, aluminum chelate, a silane coupling agent, or the like.

[0111] The metal-clad laminate of the present embodiment can be manufactured according to a conventional method. For example, the methods [1] and [2] below can be exemplified.

[0112] [1] A method of manufacturing a metal-clad laminate in which a polyamic acid solution is applied and dried to a metal foil to be a metal layer one or more times, and then imidized to form a polyimide insulating layer.

[0113] [2] A method of manufacturing a metal-clad laminate in which a polyamic acid solution is laminated in multiple layers by coextrusion and applied and dried to a metal foil to be a metal layer, and then imidized to form a polyimide insulating layer (hereinafter, the coextrusion method).

[0114] The method [1] above includes, for example, the following steps (1a) and (1b): (1a) A step of applying a polyamic acid solution to a metal foil and drying it; (1b) A step of forming a polyimide layer (A) by heat-treating 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 particularly the heating conditions during imidization in step (1b), the in-plane orientation of the polyimide can be controlled, and characteristics such as the birefringence and CTE of the polyimide can be controlled.

[0115] In the method of [1] above, for the polyamic acid solution that is the precursor of the polyimide constituting the polyimide layer (A) and the polyamic acid solution that is the precursor of the polyimide constituting the polyimide layer (B), by repeating step (1a), a laminated structure of polyamic acid can be formed on the metal foil. Note that the method of applying the polyamic acid solution onto the metal foil is not particularly limited, and for example, it can be applied using a coater such as a comma, die, knife, lip, etc.

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

[0117] The metal-clad laminate thus produced is imidized with the resin layer of polyamic acid fixed to the metal foil by completing the imidization of polyamic acid on the metal foil. Therefore, 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 insulating layer can be maintained.

[0118] [Circuit board] The metal-clad laminate of the present invention is mainly useful as a circuit board material such as an FPC. By processing the metal layer of the metal-clad laminate into a pattern by a conventional method to form a wiring layer, a circuit board according to an embodiment of the present invention can be manufactured. 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 the present embodiment includes an insulating resin layer including a single-layer or multiple-layer polyimide layer, and a wiring layer provided on at least one surface of the insulating resin layer, and the insulating resin layer may include the polyimide layer (B). Further, in order to enhance the adhesiveness between the insulating resin layer and the wiring layer, the layer in the insulating resin layer that contacts the wiring layer is preferably the polyimide layer (A).

Examples

[0119] Examples are shown below to more specifically explain the features of the present invention. However, the scope of the present invention is not limited to the examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[0120] [Measurement of Viscosity] Using an E-type viscometer (manufactured by Brookfield, trade name; DV-II+Pro), the viscosity at 25°C was measured. The rotation speed was set so that the torque was 10% to 90%, and after 2 minutes had elapsed since the start of the measurement, the value when the viscosity became stable was read.

[0121] [Glass Transition Temperature (Tg) and Classification of Polyimide Film into Non-Thermoplastic and Thermoplastic] The glass transition temperature was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by TA Instruments, trade name; RSA G2) for a polyimide film having a size of 5 mm × 70 mm at a heating rate of 4°C / min from 30°C to 400°C and a frequency of 1 Hz, and the temperature at which the change in elastic modulus (tanδ) was maximum was taken as the glass transition temperature. The storage elastic modulus at 30°C measured using DMA is 1.0×10 9 Pa or more, and the storage elastic modulus in the temperature range within the glass transition temperature + 30°C is 1.0×10 8Those showing less than Pa are designated as "thermoplastic", and those having a storage modulus at 30 °C of 1.0×10 9 Pa or more and showing a storage modulus in the temperature range within glass transition temperature + 30 °C of 1.0×10 8 Pa or more are designated as "non-thermoplastic".

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

[0123] [Measurement of relative permittivity and dielectric loss tangent] Using a vector network analyzer (manufactured by Agilent Technologies, trade name; E8363C) and a split post dielectric resonator (SPDR resonator), the relative permittivity (Dk) and dielectric loss tangent (Df) of the polyimide film at a frequency of 10 GHz were measured. Note that Dk and Df during humidity conditioning were measured after leaving the polyimide film used for measurement under the conditions of temperature; 24 - 26 °C, humidity; 45 - 55% for 24 hours. Also, Dk and Df during water absorption were measured after taking out the polyimide film used for measurement after immersing it in pure water for 48 hours, wiping off the pure water on the material surface, and then measuring.

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

[0125] [Measurement of Peel Strength] After the copper foil of the copper-clad laminate (copper foil / multilayer polyimide layer) was circuit-processed into a width of 1 mm in the resin coating direction at 10 mm intervals, it was cut into a width of 8 cm and a length of 4 cm. The peel strength was measured using a tensilon tester (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name: Strograph VE-1D). The polyimide layer surface of the cut measurement sample was fixed to an aluminum plate with double-sided tape, and the circuit-processed copper foil was peeled off at a speed of 50 mm / min in the 180° direction. The median strength when peeled 10 mm from the polyimide layer was determined and used as the initial peel strength.

[0126] [Measurement of Moisture Absorption Rate] Two test pieces of polyimide film (width: 4 cm × length: 25 cm) were prepared, dried at 80°C for 1 hour, and then weighed. After weighing, they were placed in a constant temperature and humidity chamber at 23°C / 50%RH, allowed to stand for 24 hours or more, and then weighed. The moisture absorption rate was calculated from the following formula. Moisture absorption rate (weight%) = [(weight after moisture absorption - weight after drying) / weight after drying] × 100

[0127] [Measurement of Water Absorption Rate] One test piece of polyimide film (width: 4 cm × length: 25 cm) was prepared, dried at 80°C for 1 hour, and then weighed. After weighing, it was placed in pure water and allowed to stand for 24 hours or more, taken out, the pure water on the film surface was wiped off, and then weighed. The water absorption rate was calculated from the following formula. Water absorption rate (weight%) = [(weight after water absorption - weight after drying) / weight after drying] × 100

[0128] [Tensile Elastic Modulus] Using a Strograph R-1 (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a tensile test was carried out on a polyimide film with a width of 12.7 mm and a length of 127 mm at a temperature of 23°C and a relative humidity of 50%RH at 50 mm / min and calculated.

[0129] [Presence or Absence of Foaming] When visually observing the appearance of the obtained copper-clad laminate, it was confirmed whether foaming occurred.

[0130] [Feasibility of Film Formation] Regarding copper-clad laminates, when the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film, those that did not develop cracks and could be handled as a single film were designated as [acceptable], while those that easily developed cracks and broke were designated as [unacceptable].

[0131] [Measurement of the Thickness of the Polyimide Layer] Regarding copper-clad laminates, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film. The obtained polyimide film was cut into strip shapes, resin-embedded, and then cut in the film thickness direction using a microtome to prepare ultra-thin sections of approximately 100 nm. For the prepared ultra-thin sections, observation was carried out at an acceleration voltage of 30 kV using the STEM function of a SEM (SU9000) manufactured by Hitachi High-Technologies Corporation. The thickness of each polyimide layer was measured at five points each, and the average value was taken as the thickness of each polyimide layer. The sum of the layers was taken as the thickness of the multi-layer polyimide film.

[0132] [Calculation of Imide Group Concentration] Taking the imide group as (-(CO)2-N-), it was calculated from the following formula. Imide group concentration (wt%) = (Molecular weight of the imide group / Molecular weight of the entire polyimide structure) × 100

[0133] [Calculation of Ester Group Concentration] Taking the ester group as (-(COO)-), it was calculated from the following formula. Ester group concentration (wt%) = (Molecular weight of the ester group / Molecular weight of the entire polyimide structure) × 100

[0134] [Calculation of the Ratio of Biphenyl-Skeleton-Containing Monomers] Among all the monomer components in the polyimide, the ratio (unit: mol%) occupied by the monomer having a biphenyl skeleton was defined as the ratio of biphenyl-skeleton-containing monomers.

[0135] The abbreviations used in the examples and reference examples represent the following compounds. BP-TME: p-biphenylene bis(trimellitic acid monoester anhydride), CAS No. 10340-81-5) 26DHN-TME: 2,6-Naphthalenedi(trimellitic monoester anhydride), CAS No. 115383-00-1) TAHQ: p-Phenylenebis(trimellitic monoester 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 such that the solid content concentration after polymerization was 15% by weight were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 31.6433 g of BP-TME (0.05921 mol) was added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution A. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15% by weight were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 26.8858 g of BP-TME (0.05031 mol) and 3.6577 g of PMDA (0.01677 mol) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution B. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15% by weight were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 26.4885 g of BP-TME (0.04956 mol) and 3.6036 g of PMDA (0.01652 mol) were added, and then the stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution C. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15% by weight were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 25.7282 g of BP-TME (0.04814 mol) and 3.5002 g of PMDA (0.01605 mol) were added, and then the stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution D. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15% by weight were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 24.6661 g of BP-TME (0.04615 mol) and 3.3557 g of PMDA (0.01538 mol) were added, and then the stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution E. The solution viscosity of the 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), 4.7612 g of TPE-R (0.01629 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 25.7212 g of BP-TME (0.04813 mol) and 3.4992 g of PMDA (0.01604 mol) were added, and then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution F. The solution viscosity of the 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 such that the solid content concentration after polymerization becomes 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. 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, and then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution G. The solution viscosity of the 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 solid content concentration after polymerization becomes 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. 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 then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution H. The solution viscosity of the 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 such that the solid content concentration after polymerization is 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 13.7413 g of BPDA (0.04670 mol) and 10.1871 g of PMDA (0.04670 mol) were added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution I. The solution viscosity of the 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 such that the solid content concentration after polymerization is 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 18.2906 g of TAHQ (0.03991 mol) and 8.7045 g of PMDA (0.03991 mol) were added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution J. The solution viscosity of the 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 such that the solid content concentration after polymerization is 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 31.0722 g of BP-TME (0.05814 mol) and 4.2272 g of PMDA (0.01938 mol) were added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution K. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 30.5387 g of 26DHN-TME (0.06007 mol) and 4.3674 g of PMDA (0.02002 mol) were added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution L. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 31.1012 g of 26DHN-TME (0.06117 mol) was added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution M. The solution viscosity of the 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 such that the solid content concentration after polymerization was 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 25.8789 g of 26DHN-TME (0.05090 mol) and 3.7010 g of PMDA (0.01697 mol) were added, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution N. The solution viscosity of the 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 such that the solid content concentration after polymerization becomes 15 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 11.5007 g of BP-TME (0.02152 mol) and 14.0815 g of PMDA (0.06456 mol) were added, and then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution O. The solution viscosity of the 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), 10.7636 g of TPE-R (0.03682 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 12 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 4.6984 g of BTDA (0.01458 mol) and 12.7214 g of PMDA (0.05832 mol) were added, and then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution P. The solution viscosity of the 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), 16.4155 g of TPE-R (0.05615 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 12 wt% were charged into a 500 ml separable flask, and stirred at room temperature until dissolved. Next, 4.4784 g of BTDA (0.01390 mol) and 12.1258 g of PMDA (0.05559 mol) were added, and then the polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution Q. The solution viscosity of the 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), 4.5279 g of TPE-R (0.01549 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 12 wt% were charged into a 500 ml separable flask, and 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, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution R. The solution viscosity of the 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), 15.4821 g of TPE-R (0.05296 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 12 wt% were charged into a 500 ml separable flask, and 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, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution S. The solution viscosity of the 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), 14.6492 g of TPE-R (0.05011 mol), and an amount of DMAc such that the solid content concentration after polymerization becomes 12 wt% were charged into a 500 ml separable flask, and 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, and then stirring was continued at room temperature for 3 hours to conduct a polymerization reaction, obtaining a polyamic acid solution T. The solution viscosity of the 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), 15.2580 g of TPE-R (0.05219 mol), and an amount of DMAc such that the solid content concentration after polymerization was 12 wt% were charged into a 500 ml separable flask and stirred at room temperature until dissolved. Next, 13.6386 g of BPDA (0.04636 mol) and 4.3333 g of PMDA (0.01987 mol) were added, and then the polymerization reaction was continued by stirring at room temperature for 3 hours to obtain a polyamic acid solution U. The solution viscosity of the polyamic acid solution U was 1600 cps.

[0157] (Example 1) On copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rzjis on the resin side: 0.6 μm), polyamic acid solution A was uniformly coated so that the thickness after curing was about 25 μm, and then heated and dried at 120 °C to remove the solvent. Further, a stepwise heat treatment from 120 °C to 360 °C was carried out for 10 minutes to complete imidization, and a copper-clad laminate A was obtained. At this time, no foaming was observed on the film surface. Next, for the obtained copper-clad laminate A, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a polyimide film A. Descriptions regarding the type of polyimide, imide group concentration, ester group concentration, proportion of biphenyl skeleton-containing monomer, presence or absence of foaming, and film formation ability of the obtained polyimide film A are shown in Table 1, and the film physical property data are shown in Table 1 and Table 2.

[0158] (Examples 2 to 8, Comparative Example 1, Comparative Example 2, and Reference Examples 1 to 13) Similar to Example 1, for polyamic acids B to U, the preparation of copper-clad laminates and the properties of the polyimide films after etching the copper foil were evaluated. Descriptions regarding the type of polyimide, imide group concentration, ester group concentration, proportion of biphenyl skeleton-containing monomer, presence or absence of foaming, and film formation ability of the obtained polyimide films are shown in Table 1, and the film physical property data are shown in Table 1 and Table 2. Note that for those with foaming and those that could not be formed into a film, film physical property data were not obtained.

[0159]

Table 1

[0160] [Table 2]

[0161] [Example 9] On copper foil 1, polyamic acid solution P in contact with the copper foil was uniformly coated so that the thickness after curing would be 2 μm, and then heated and dried at 120°C for 1 minute to remove the solvent. Next, polyamic acid solution C, which is the second layer, was uniformly coated on the first layer so that the thickness after curing would be 21 μm, and then heated and dried at 120°C for 2 minutes to remove the solvent. Further, polyamic acid solution U, which is the third layer, was uniformly coated on the second layer so that the thickness after curing would be 2 μm, 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 carried out for 10 minutes to complete imidization, and a copper-clad laminate X having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the obtained copper-clad laminate X having a multilayer polyimide, it was 0.92 kN / m. Also, for the copper-clad laminate X having a multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film X. The Dk = 3.37 and Df = 0.0027 of the obtained multilayer polyimide film X under humidity conditioning. The storage modulus of the polyimide film prepared by curing polyamic acid solution P as the first layer at 300°C is 8.3×10 8 Pa, and the storage modulus at 350°C is 1.9×10 8 Pa.

[0162] [Example 10] On the copper foil 1, the polyamic acid solution Q in contact with the copper foil was uniformly applied so that the thickness after curing would be 2 μm, and then it was heated and dried at 120 °C for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly applied on the first layer so that the thickness after curing would be 21 μm, and then it was heated and dried at 120 °C for 2 minutes to remove the solvent. Further, the polyamic acid solution U as the third layer was uniformly applied on the second layer so that the thickness after curing would be 2 μm, and then it was 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 carried out for 10 minutes to complete imidization, and a copper-clad laminate Y having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the obtained copper-clad laminate Y having a multilayer polyimide, it was 0.71 kN / m. Also, for the copper-clad laminate Y having a multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film Y. The Dk = 3.38 and Df = 0.0027 of the obtained multilayer polyimide film Y under humidity conditioning. In addition, the storage modulus of the polyimide film prepared by curing the polyamic acid solution Q as the first layer at 300 °C is 1.2×10 9 Pa, and the storage modulus at 350 °C is 5.2×10 8 Pa.

[0163] [Example 11] On the copper foil 1, the polyamic acid solution R in contact with the copper foil was uniformly applied so that the thickness after curing would be 2 μm, and then it was heated and dried at 120 °C for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly applied on the first layer so that the thickness after curing would be 21 μm, and then it was heated and dried at 120 °C for 2 minutes to remove the solvent. Further, the polyamic acid solution U as the third layer was uniformly applied on the second layer so that the thickness after curing would be 2 μm, and then it was 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 carried out for 10 minutes to complete imidization, and a copper-clad laminate Z having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the copper-clad laminate Z having the obtained multilayer polyimide, it was 0.73 kN / m. Further, for the copper-clad laminate Z having the multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film Z. The Dk at the time of humidity conditioning of the obtained multilayer polyimide film Z was 3.38, and the Df was 0.0027. Incidentally, the storage elastic modulus at 300 °C of the polyimide film produced by curing the polyamic acid solution R as the first layer is 1.8×10 9 Pa, and the storage elastic modulus at 350 °C is 3.4×10 8 Pa.

[0164] [Example 12] On the copper foil 1, after uniformly applying the polyamic acid solution S as the first layer in contact with the copper foil so that the thickness after curing becomes 2 μm, it was heated and dried at 120 °C for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly applied on the first layer so that the thickness after curing becomes 21 μm, and then heated and dried at 120 °C for 2 minutes to remove the solvent. Further, the polyamic acid solution U as the third layer was uniformly applied on the second layer so that the thickness after curing becomes 2 μm, 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 for 10 minutes to complete imidization, and a copper-clad laminate Aa having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the copper-clad laminate Aa having the obtained multilayer polyimide, it was 0.77 kN / m. Further, for the copper-clad laminate Aa having the multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film Aa. The Dk at the time of humidity conditioning of the obtained multilayer polyimide film Aa was 3.38, and the Df was 0.0027. Incidentally, the storage elastic modulus at 300 °C of the polyimide film produced by curing the polyamic acid solution S as the first layer is 4.6×10 8 Pa, and the storage elastic modulus at 350 °C is 2.4×10 8 Pa.

[0165] [Example 13] On copper foil 1, polyamic acid solution T in contact with the copper foil was uniformly applied so that the thickness after curing was 2 μm, and then heated and dried at 120 °C for 1 minute to remove the solvent. Next, polyamic acid solution C, which is the second layer, was uniformly applied on the first layer so that the thickness after curing was 21 μm, and then heated and dried at 120 °C for 2 minutes to remove the solvent. Further, polyamic acid solution U, which is the third layer, was uniformly applied on the second layer so that the thickness after curing was 2 μm, 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 for 10 minutes to complete imidization, and a copper-clad laminate Bb having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the obtained copper-clad laminate Bb having a multilayer polyimide, it was 0.71 kN / m. Also, for the copper-clad laminate Bb having a multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film Bb. The Dk = 3.38 and Df = 0.0028 of the obtained multilayer polyimide film Bb during moisture conditioning. The storage modulus of the polyimide film prepared by curing polyamic acid solution T as the first layer at 300 °C is 4.4×10 8 Pa, and the storage modulus at 350 °C is 1.5×10 8 Pa.

[0166] [Example 14] On copper foil 1, polyamic acid solution U in contact with the copper foil was uniformly applied so that the thickness after curing was 2 μm, and then heated and dried at 120 °C for 1 minute to remove the solvent. Next, polyamic acid solution C, which is the second layer, was uniformly applied on the first layer so that the thickness after curing was 21 μm, and then heated and dried at 120 °C for 2 minutes to remove the solvent. Further, polyamic acid solution U, which is the third layer, was uniformly applied on the second layer so that the thickness after curing was 2 μm, 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 for 20 minutes to complete imidization, and a copper-clad laminate Cc having a multilayer polyimide was obtained. At this time, no foaming was observed on the film surface. As a result of measuring the initial peel strength using the copper-clad laminate Cc having the obtained multilayer polyimide, it was 0.97 kN / m. Further, for the copper-clad laminate Cc having the multilayer polyimide, the copper foil was etched and removed using an aqueous ferric chloride solution to prepare a multilayer polyimide film Cc. The Dk during humidity conditioning of the obtained multilayer polyimide film Cc was 3.38, and the Df was 0.0025. In addition, the storage elastic modulus at 300 °C of the polyimide film prepared by curing the polyamic acid solution U as the first layer is 3.1×10 7 Pa, and the storage elastic modulus at 350 °C is 1.4×10 7 Pa.

[0167] [Reference Example 14] On the copper foil 1, after uniformly applying the cured polyamic acid solution U as the first layer in contact with the copper foil so that the thickness becomes 2 μm, it was heated and dried at 120 °C for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly applied on the first layer so that the thickness after curing becomes 21 μm, and then heated and dried at 120 °C for 2 minutes to remove the solvent. Further, the polyamic acid solution U as the third layer was uniformly applied on the second layer so that the thickness after curing becomes 2 μm, 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 for 10 minutes to complete imidization, and a copper-clad laminate Dd having a multilayer polyimide was obtained. At this time, foaming was observed on the film surface. In addition, the storage elastic modulus at 300 °C of the polyimide film prepared by curing the polyamic acid solution U as the first layer is 3.1×10 7 Pa, and the storage elastic modulus at 350 °C is 1.4×10 7 Pa.

[0168] As described above, the embodiments of the present invention have been described in detail for illustrative purposes, but the present invention is not limited to the above embodiments, and various modifications are possible.

Claims

1. A polyamic acid containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, satisfying the following conditions (i) to (iii); Condition (i): Containing 25 mol% or more of an acid dianhydride residue derived from the acid dianhydride represented by the following formula (1) with respect to all acid dianhydride residues; 【Chemical 1】 Condition (ii): Containing 50 mol% or more of a diamine residue derived from the diamine compound represented by the following general formula (2) with respect to all diamine residues; 【Chemical 2】 [In formula (2), Y independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 3 carbon atoms, and p and q independently represent an integer of 0 to 4.] Condition (iii): The proportion of the monomer residue having a biphenyl skeleton is 65 mol% or more with respect to all monomer residues derived from all monomer components, A polyamic acid characterized by satisfying the above.

2. The polyamic acid according to claim 1, containing a diamine residue derived from a diamine compound represented by the following general formulas (3) to (6) in the range of 1 to 50 mol% with respect to all diamine residues. 【Chemical Formula 3】 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, and the linking group A independently represents -O-, -SO ２ -, -CH ２ - or -C(CH ３ ) ２ -, a divalent group selected from, and the linking group X independently represents -CH ２ -, -O-CH ２ -O-, -O-C ２ H ４ -O-, -O-C ３ H ６ -O-, -O-C ４ H ８ -O-, -O-C ５ H １０ -O-, -O-CH ２ -C(CH ３ ) ２ -CH ２ -O-, -C(CH ３ ) ２ -, -C(CF ３ ) ２ - or -SO ２ -, m independently represents an integer of 1 to 4, and n independently represents an integer of 0 to 4. However, in formula (5), when the linking group A does not contain -CH ２ -, -C(CH ３ ) ２ - or -SO ２ -, any of n is 1 or more.]

3. A polyimide obtained by imidizing the polyamic acid according to claim 1 or 2.

4. A polyimide film including a single layer or a plurality of polyimide layers, At least one of the polyimide layers contains the polyimide according to claim 3 as a main component of the resin component.

5. A polyimide film including a polyimide layer (A) containing a first polyimide as a 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 a main component of the resin component, The first polyimide is a polyimide containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, Among all acid dianhydride residues, the residue derived from pyromellitic dianhydride is contained in an amount of 5 mol% or more and 90 mol% or less, the residue derived from an acid dianhydride having a ketone group (—CO—) in the molecule is contained in an amount of 10 mol% or more and 95 mol% or less, and the residue derived from pyromellitic dianhydride and the residue derived from an acid dianhydride having a ketone group (—CO—) in the molecule are contained in a total proportion of 80 mol% or more. The residue derived from the diamine compound represented by the following general formula (A1) is contained in the total diamine residues in a proportion of 5 mol% or more and 90 mol% or less. A polyimide having a storage modulus E' at 300 °C measured using a dynamic viscoelasticity measuring apparatus (DMA) of 1.0 × 10 ８ Pa or more and a storage modulus E' at 350 °C of 1.0 × 10 ７ Pa or more The polyimide film, wherein the second polyimide is the polyimide according to claim 3. 【Chemical 4】 [In formula (A1), the linking group X1 represents a divalent group selected from a single bond or -CONH-, Y independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 3 carbon atoms, n1 represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. ]

6. The polyimide film according to claim 4 or 5, wherein the dielectric tangent (Tanδ) at 10 GHz when measured by a split post dielectric resonator (SPDR) in an environment of 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. The metal-clad laminate, wherein the insulating resin layer contains the polyimide film according to any one of claims 4 to 6.

8. A circuit board comprising an insulating resin layer and a wiring layer provided on at least one surface of the insulating resin layer. The circuit board, wherein the insulating resin layer contains the polyimide film according to any one of claims 4 to 6.

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