JP2023006387A - Polyamide acid, polyimide, polyimide film, metal-clad laminate and circuit board - Google Patents

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

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

2. Description of the Related Art In recent years, as electric and electronic devices have become more sophisticated and functional, there has been a demand for high-speed transmission of information. When transmitting high-frequency signals, problems such as loss of electrical signals and longer signal delays are likely to occur. , and improvements are being made to have electrical characteristics compatible with high-speed transmission. Therefore, studies are being made to lower the dielectric loss tangent of polymers used as FPC materials in order to reduce transmission loss.

Typical examples of low dielectric loss tangent polymers include fluorine-based resins, liquid crystal polymers (LCP), and modified polyimides (MPI). However, fluorine-based resins have problems such as adhesion to low-roughened copper foil, laser processing, and copper plating. LCP has low adhesion to low-roughened copper foil and is difficult to multilayer. There is an issue. MPI does not have the problems of fluorine-based resins and LCP, but generally has the problem of high moisture absorption and dielectric loss tangent.

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). Also, for the purpose of low thermal expansion and low hygroscopicity, it has been proposed to introduce an ester structure into the polyimide chain (for example, Patent Documents 2 to 4).

JP 2021-074894 A Retable 2010-093021 JP-A-10-36506 Japanese Patent Application Laid-Open No. 2006-336011

In Patent Document 1, the dielectric loss tangent is lowered by introducing an ester structure into the polyimide chain. It was not satisfactory from the point of view. Further, in Patent Document 1, since polyimide is imidized with a cyclization agent, the dielectric loss tangent tends to be difficult to decrease due to an increase in polar groups.
On the other hand, when 1,4-diaminobenzene (p-PDA; paraphenylenediamine) is used as a diamine component as in Patent Documents 3 and 4, the polyimide film tends to become brittle, resulting in a problem of reduced film formability. rice field.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polyimide film which has low thermal expansion and good film formability required as an FPC material and which has a sufficiently low dielectric loss tangent.

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

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, Satisfies conditions (i) to (iii).

Condition (i):
Contain 25 mol % or more of acid dianhydride residues derived from the acid dianhydride represented by the following formula (1) with respect to all acid dianhydride residues.

Condition (ii):
Contain 50 mol % or more of diamine residues derived from a diamine compound represented by the following general formula (2) with respect to all diamine residues.

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

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

The polyamic acid of the first aspect of the present invention contains 1 to 50 mol% of diamine residues derived from diamine compounds represented by the following general formulas (3) to (6) with respect to all diamine residues. It may be contained within the range.

In formulas (3) to (6), each 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 -, wherein the linking group X is independently -CH ₂ -, -O-CH ₂ -O-, or -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 is independently an integer of 1 to 4, n is independently 0 to 4 _{is an integer of n _} is 1 or more.

The polyimide of the second aspect of the present invention is obtained by imidating the polyamic acid of the first aspect.

The polyimide film of the third aspect of the present invention is a polyimide film comprising a single or multiple polyimide layers,
At least one of the polyimide layers contains the polyimide of the second aspect as a main component of the resin component.

The polyimide film of the fourth aspect of the present invention is a polyimide layer (A) containing a first polyimide as a main component of the resin component, and is laminated on the polyimide layer (A), and the first polyimide and may be a polyimide film containing a polyimide layer (B) containing a different second polyimide as the main component of the resin component. In the polyimide film of the 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, In all acid dianhydride residues, 5 mol% or more and 90 mol% or less of residues derived from pyromellitic dianhydride, derived from acid dianhydride having a ketone group (-CO-) in the molecule A residue containing 10 mol% or more and 95 mol% or less, and a residue derived from pyromellitic dianhydride and a residue derived from an acid dianhydride having a ketone group (-CO-) in the molecule may be contained in a total ratio of 80 mol % or more. Further, the polyimide film of the fourth aspect contains residues 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 in all diamine residues. may Furthermore, the polyimide film of the fourth aspect has a storage elastic modulus E′ at 300° C. of 1.0×10 ⁸ Pa or more and a storage elastic modulus at 350° C. measured using a dynamic viscoelasticity measuring device (DMA). A polyimide having a modulus E′ of 1.0×10 ⁷ Pa or more may also be used.
Furthermore, in the polyimide film of the fourth aspect, the second polyimide is the polyimide of the second aspect.

式（Ａ１）において、連結基Ｘ１は単結合又は－ＣＯＮＨ－から選ばれる２価の基を示し、Ｙは独立に水素、炭素数１～３の１価の炭化水素基又はアルコキシ基を示し、ｎ１は０～２の整数を示し、ｐ及びｑは独立して０～４の整数を示す。

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

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

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

A circuit board according to a sixth aspect of the present invention is a circuit board comprising an insulating resin layer and a wiring layer provided on at least one surface of the insulating resin layer, the insulating resin layer comprising: The polyimide film of the third aspect or the fourth aspect is included.

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 loss tangent without impairing low thermal expansion and good film formability. Therefore, by using the polyimide film of the present invention as a circuit board material, it is possible to provide a circuit board capable of handling high-speed transmission.

Next, an embodiment of the invention will be described.

<Polyamide acid/polyimide>
Polyamic acid of one embodiment of the present invention is a polyimide precursor, polyamic acid obtained by reacting a specific acid dianhydride component and a specific diamine component, the acid dianhydride component It contains a diamine residue derived from a derived acid dianhydride residue and a diamine component.
Further, the polyimide of the present embodiment is obtained by imidating the 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 acid dianhydride and diamine compound as raw materials are reacted in approximately equimolar amounts, the type and amount of acid dianhydride residue and diamine residue contained in the polyimide with respect to the type and molar ratio of the raw materials. The molar ratio and the like can be almost matched.
In the present invention, the term "polyimide" means a resin composed of a polymer having an imide group in its molecular structure, such as polyimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazoleimide, in addition to polyimide. .

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

Polyamic acid and polyimide of the present embodiment satisfy the following conditions (i) to (iii).

Condition (i):
Contain 25 mol % or more of acid dianhydride residues derived from the acid dianhydride represented by the following formula (1) with respect to all acid dianhydride residues. Hereinafter, the acid dianhydride residue derived from the acid dianhydride represented by formula (1) may be referred to as "acid dianhydride residue (1)".

The acid dianhydride represented by formula (1) is known as p-biphenylene bis (trimellitic acid monoester acid anhydride) (BP-TME), and has a biphenyl skeleton and the It has two ester structures (--CO--O--) attached to the biphenyl skeleton. The biphenyl skeleton has rigidity, and the ester structure has the effect of imparting an ordered structure to the entire polymer. CTE) can be achieved, and the dielectric loss tangent can be effectively reduced (lower dielectric loss tangent) by improving the molecular ordered structure and suppressing motion.

The content of the acid dianhydride residue (1) in the polyamic acid and polyimide of the present embodiment is 25 mol% or more with respect to the total acid dianhydride residue, preferably in the range of 25 to 100 mol%, A range of 40 to 80 mol % is more preferable. If the content of the acid dianhydride residue (1) is less than 25 mol %, both effects of lowering the dielectric loss tangent and lowering the CTE due to the improvement of the molecular ordered structure and the suppression of motion are not sufficiently exhibited. The upper limit of the content of the acid dianhydride residue (1) may be 100 mol%, but when other acid dianhydrides are used in combination for the purpose of imparting arbitrary functionality, depending on the amount used The amount of acid dianhydride represented by formula (1) used can be adjusted.

Here, as analogous compounds of the acid dianhydride represented by the formula (1), those having a substituent such as a phenyl group in the biphenyl skeleton in the formula (1) are known (for example, Patent Document 2). . However, due to the presence of substituents bonded to the biphenyl skeleton, the effect of suppressing molecular motion of polyimide is reduced, and there is a demerit that the dielectric loss tangent cannot be sufficiently lowered.
Also, 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) is known as an acid dianhydride having two ester structures like the acid dianhydride represented by formula (1). It is 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 loss tangent is not sufficiently obtained. In addition, when TAHQ is compared with the acid dianhydride represented by formula (1), since it does not have a biphenyl skeleton, the effect of suppressing molecular motion is small, so it is disadvantageous for lowering the dielectric loss tangent. Due to its small size, polyimide using TAHQ has the disadvantage of relatively high imide group concentration and high hygroscopicity.
Furthermore, as an acid dianhydride having two ester structures like the acid dianhydride represented by formula (1), 2,6-naphthalene having a structure in which the biphenyl skeleton in formula (1) is replaced with a naphthalene skeleton Bis(trimellitic monoester anhydride) (26DHN-TME) is also known. This 26DHN-TME has the disadvantage that foaming is likely to occur due to the presence of the naphthalene ester skeleton, and the linearity of the polyimide is lowered, so that the coefficient of thermal expansion (CTE) cannot be sufficiently lowered.

Condition (ii):
Contain 50 mol % or more of diamine residues derived from a 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 formula (2) may be referred to as "diamine residue (2)".

In general formula (2), Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms or an alkoxy group, and p and q independently represent an integer of 0 to 4. In the above formula (2), the hydrogen atoms in the two terminal amino groups may be substituted, for example —NR _x R _y (where R _x and R _y are independently meaning any substituent).

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 water content inside the molecular chain can be reduced, so that the dielectric loss tangent can be lowered. In addition, 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 increases, and the molecular weight of the monomer-derived unit can be increased, the imide group concentration can be reduced.

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'-diamino biphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2 to mention '-di-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'-diaminobiphenyl, etc. can be done.

The content of the diamine residue (2) in the polyamic acid and polyimide of the present embodiment is 50 mol% or more, preferably in the range of 60 to 100 mol%, more preferably in the range of 60 to 95 mol%, relative to the total diamine residue. Inside is more preferred. When 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 viewpoint of reducing the dielectric loss tangent, it is preferable to increase the proportion of the diamine residue (2) in all diamine residues as much as possible. good too. On the other hand, when taking into consideration the reduction of the heat treatment time for foaming suppression and thermal imidization described later, the upper limit of the content of the diamine residue (2) is 60 to 95 mol% with respect to all diamine residues. is preferably set within the range of

Condition (iii):
The ratio of monomer residues having a biphenyl skeleton (biphenyl skeleton-containing residues) to all monomer residues derived from all monomer components is 65 mol or more.
Here, the biphenyl skeleton is a skeleton in which two phenyl groups are single bonded. Therefore, the biphenyl skeleton-containing residue includes, for example, a biphenyldiyl group, a biphenyltetrayl group, and the like. When the ratio of the biphenyl skeleton-containing residue to the total monomer residues derived from all the monomer components is 65 mol or more, the rigid structure derived from the monomer facilitates the formation of an ordered structure throughout the polymer, resulting in molecular motion. Suppression can lower the dissipation factor. If the ratio of the biphenyl skeleton-containing residue is less than 65 mol%, the dielectric loss tangent is not sufficiently reduced. For this reason, when it is used for a circuit board, for example, it becomes difficult to adapt to high-speed transmission. From this point of view, the ratio of the biphenyl skeleton-containing residue is preferably 70 mol% or more, more preferably 80 mol% or more.

Further, the polyamic acid and polyimide of the present embodiment are acid dianhydride residues derived from the acid dianhydride represented by the formula (1) having two ester structures (-CO-O-) in the molecule Since it contains (1) as a main structural unit, it is characterized by a relatively high concentration of ester groups. From the viewpoint of imparting an ordered structure to the entire polymer and reducing the dielectric loss tangent, the ester group concentration in the polyamic acid and polyimide of the present embodiment is preferably in the range of, for example, 3 to 15% by weight, and 7 to 15% by weight. It is more preferable to be within the range. Here, the ester group concentration can be calculated from the ratio of ester groups (--COO--) in the molecular weight of the entire polypolyimideimide structure.

(Other acid dianhydride residues)
Polyamic acid and polyimide of the present embodiment, in addition to the residue derived from the acid dianhydride represented by the above formula (1), to the extent that the effects of the invention is not impaired, generally used as a raw material of polyimide can contain residues of dianhydrides such as Such acid dianhydride residues include, for example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride pyromellitic dianhydride (PMDA), 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA) , 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, 2,2′,3,3′-, 2,3,3′,4′ - or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether anhydride, 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 3.4-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-anthracenetetracarboxylic dianhydride, 2,2-bis(3, 4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8- naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic 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 Acid dianhydride residues derived from aromatic tetracarboxylic dianhydrides such as bis-anhydrotrimellitate can be mentioned. Among these, in particular, an acid dianhydride residue derived from BPDA (hereinafter also referred to as "BPDA residue") has rigidity, so it is easy to form an ordered structure of a polymer, suppressing movement of molecules. An acid dianhydride residue derived from pyromellitic dianhydride (hereinafter also referred to as “PMDA residue”) is preferable from the viewpoint of lowering CTE.

(other diamine residues)
Polyamic acid and polyimide of the present embodiment, in addition to the residue derived from the diamine compound represented by the above formula (2), for example, represented by the following general formulas (3) ~ (6) It preferably contains a diamine residue derived from a diamine compound.

In formulas (3) to (6), each 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 -, wherein the linking group X is independently -CH ₂ -, -O-CH ₂ -O-, or -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 is independently an integer of 1 to 4, n is independently 0 to 4 _{is an integer of n _} is 1 or more. Here, the term “independently” refers to a plurality of linking groups A, a plurality of linking groups X, a plurality of substituents R or This means that a plurality of m and n may be the same or different. In the above formulas (3) to (6), the hydrogen atoms in the two terminal amino groups may be substituted, for example -NR _x R _y (where R _x and R _y are independently (meaning any substituent such as an alkyl group).

Examples of aromatic diamines represented by formula (3) include 2,6-diamino-3,5-diethyltoluene and 2,4-diamino-3,5-diethyltoluene.

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

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

Examples of aromatic diamines represented by general formula (6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

Since the diamine compounds represented by general formulas (3) to (6) have a bulky molecular structure, they are represented by general formulas (3) to (6) together with the diamine compound represented by general formula (2). By using at least one diamine compound together, when forming a polyimide film by a casting method, 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 this point of view and the point of view of lowering CTE, the polyimide film of the present embodiment contains diamine residues derived from diamine compounds represented by general formulas (3) to (6) with respect to all diamine residues. The total content is preferably within the range of 1 to 50 mol%, more preferably within the range of 5 to 50 mol%, and most preferably within the range of 5 to 40 mol%.

The polyamic acid and polyimide of the present embodiment do not impair the effects of the invention in addition to the residues derived from the diamine compounds represented by the above general formula (2) and general formulas (3) to (6). Within the range, it is possible to contain residues of diamine compounds generally used as raw materials for polyimides. Examples of such diamine residues include 1,4-diaminobenzene (p-PDA), 4-aminophenyl-4'-aminobenzoate (APAB), 3,3'-diaminodiphenylmethane, 3,3'-diamino Diphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'- diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4, 4'-diaminodiphenyl ether, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, (3,3'-bisamino)diphenylamine, 1,4-bis(3-aminophenoxy ) Benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy]benzenamine, 1,3-bis(4-aminophenoxy)benzene (TPE- R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl- (1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline, bis[4,4'-(3-aminophenoxy)]benzanilide, 4- [3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, bis[4-(4-aminophenoxy)phenyl]ether ( BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), 2,2-bis-[4-(3-amino phenoxy)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, 4,4'- diaminobenzanilide, diamine residues derived from aromatic diamine compounds such as 6-amino-2-(4-aminophenoxy)benzoxazole, two terminal carboxylic acid groups of dimer acid are primary aminomethyl groups or amino Examples thereof include diamine residues derived from aliphatic diamine compounds such as dimer acid-type diamines substituted with groups.
Although 1,4-diaminobenzene (p-PDA) has rigidity, it has a smaller molecular weight than the diamine compound represented by the general formula (2). Therefore, the polyimide using p-PDA may have a brittle film, resulting in poor film formability, or may have a relatively high concentration of imide groups in the polyimide, resulting in increased hygroscopicity. Therefore, it is preferable not to use p-PDA, and even if it is used, it is preferably used in an amount of 50 mol % or less with respect to all diamine residues.

In the polyamic acid and polyimide of the present embodiment, the types of the acid dianhydride residue and the diamine residue, and the respective molar ratios when containing two or more acid dianhydride residues or diamine residues are Hygroscopicity, dielectric properties, coefficient of thermal expansion, storage elastic modulus, tensile elastic modulus, etc. can be controlled by selection. In addition, when the polyamic acid and polyimide of the present embodiment have a plurality of structural units, they may be present as blocks or randomly, but are preferably present randomly.

Further, in the polyamic acid and polyimide of the present embodiment, the acid dianhydride residue and the diamine residue are derived from an aromatic tetracarboxylic dianhydride and an aromatic dianhydride residue and an aromatic diamine. It preferably consists of derivatized aromatic diamine residues. The acid dianhydride residue and diamine residue contained in the polyamic acid and polyimide are both only residues having an aromatic group, so that the dimensional accuracy of the polyimide film in a high-temperature environment can be improved. .

(Synthesis of polyamic acid and polyimide)
In general, polyimide can be produced by reacting an acid dianhydride and a diamine compound in a solvent to produce a polyamic acid, which is a polyimide precursor, and then heat ring closure (imidization). For example, an acid dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts, and the mixture is stirred at a temperature within the range of 0 to 100° C. for 30 minutes to 24 hours for a polymerization reaction to obtain a polyamic acid. In the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is within the range of 5 to 30% by weight, preferably within the range of 10 to 20% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such an organic solvent used is not particularly limited, but the amount used is adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. is preferred.

It is usually advantageous to use the synthesized polyamic acid as a reaction solvent solution, but if necessary, it can be concentrated, diluted, or replaced with another organic solvent. Polyamic acid is generally excellent in solvent solubility, and is thus advantageously used. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If the thickness is out of this range, defects such as thickness unevenness and streaks are likely to occur in the film during the coating operation using a coater or the like.

Moreover, the polyamic acid of the present embodiment can be in the form of a resin composition. The resin composition contains, 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 radiation agent, and the like. can do. As the organic solvent, the same organic solvent as used in the polymerization reaction can be used. Although the content of the organic solvent is not particularly limited, it is preferable that the polyamic acid concentration is about 5 to 30% by weight.

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

(Imide group concentration)
The imide group concentration of the polyimide of the present embodiment is, for example, preferably 30% by weight or less, more preferably 25% by weight or less. Here, "imide group concentration" means a 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 increase in polar groups increases the hygroscopicity. By selecting the combination of the acid dianhydride and the diamine compound, the orientation of the molecules in the polyimide can be controlled, thereby suppressing the increase in CTE due to the decrease in the imide group concentration and ensuring low hygroscopicity. can.

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

[Polyimide film]
A polyimide film according to one embodiment of the present invention is a polyimide film containing a single or multiple polyimide layers, wherein at least one of the polyimide layers is a polyimide that satisfies the above conditions (i) to (iii). It is contained as a main component of the resin component, and preferably, the main polyimide layer contains a polyimide that satisfies the above conditions (i) to (iii) as a main component of the resin component. Here, the "main component of the resin component" means a component contained in an amount exceeding 50% by weight with respect to the total resin component. Further, the "main polyimide layer" means a layer occupying more than 50%, preferably 60 to 100% of the thickness of the entire polyimide film. The main polyimide layer preferably contains 70% by weight or more, more preferably 80% by weight or more, of the polyimide that satisfies the above conditions (i) to (iii) with respect to the total resin component. is most preferably composed of the above polyimide. When the main layer contains polyimide satisfying the above conditions (i) to (iii) as the main component of the resin component, the dielectric loss tangent of the entire polyimide film can be reduced.

The polyimide film of the present embodiment includes a polyimide layer (A) containing a first polyimide as a main component of the resin component, and a polyimide layer (A) laminated on the polyimide layer (A). and a polyimide layer (B) containing the polyimide of No. 2 as a main component of the resin component. In this case, 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 the main component of the resin component. is preferred. Here, the "non-thermoplastic polyimide" has a storage modulus of 1.0 × 10 ⁹ Pa or more at 30 ° C. measured using a dynamic viscoelasticity measurement device (DMA), and a glass transition temperature It means that the storage elastic modulus in the temperature range within +30°C is 1.0×10 ⁸ Pa or more. The “thermoplastic polyimide” has a storage modulus of 1.0 × 10 ⁹ Pa or more at 30 ° C. measured using a dynamic viscoelasticity measurement device (DMA), and a glass transition temperature within +30 ° C. It means that the storage elastic modulus in the temperature range is less than 1.0×10 ⁸ Pa.

The multilayer polyimide film of the present embodiment may have a structure in which two layers of polyimide layer (A) / polyimide layer (B) are laminated, or polyimide layer (A) / polyimide layer (B) / polyimide layer (A) A three-layer laminate structure may be used, and an arbitrary polyimide layer may be further laminated. The polyimide layer (B) made of polyimide that satisfies the above (i) to (iii) has relatively low gas permeability, and a solvent or imidized water stays between the polyimide layer (A). , foaming tends to occur easily. Therefore, by making the main component of the resin component in the polyimide layer (A) as described below, the occurrence of the foaming phenomenon can be effectively suppressed even if the gas permeability of the polyimide layer (B) is low.

<Structure 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 an acid dianhydride derived from an acid dianhydride. It contains residues and diamine residues derived from diamine compounds.

(Acid dianhydride residue)
The polyimide constituting the polyimide layer (A) has an acid dianhydride residue (PMDA residue) derived from pyromellitic dianhydride and a ketone group ( —CO—) and an acid dianhydride residue derived from a tetracarboxylic dianhydride having (hereinafter sometimes referred to as “ketone group-containing residue”).

Here, the PMDA residue is structurally excellent in planarity and rigidity, can increase the stacking property between molecular chains, and can lower the dielectric loss tangent of the polyimide. In addition, the elastic modulus at high temperatures can be maintained at a relatively high level, and it can be expected to suppress the occurrence of the foaming phenomenon. However, when the PMDA residue is used alone, the molecular chains are less entangled, the peel strength with the metal layer is likely to decrease, and the interlayer adhesion between other polyimide layers is decreased, resulting in a foaming phenomenon. . On the other hand, since the ketone group-containing residue has a ketone group, it interacts with and chemically reacts with the functional groups contained in the adjacently laminated polyimide layers to improve the adhesiveness between the polyimide layers. , the occurrence of the foaming phenomenon can be suppressed. Further, by using two or more kinds of acid dianhydride residues in combination, it is expected that the entanglement of the molecular chains is improved and the peel strength is improved. In addition, the decrease in the regularity of the molecular arrangement suppresses the motility against an electric field, and is expected to reduce the dielectric loss tangent. Therefore, in the polyimide constituting the polyimide layer (A), in order to achieve a good balance between low dielectric loss tangent, suppression of foaming phenomenon and improvement of peel strength, PMDA residue and ketone group are contained as acid dianhydride residues. used in combination with residues.

Such a PMDA residue is 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, in all dianhydride residues. If the content of the PMDA residue in the total acid dianhydride residue is below this range, there is a concern that the dielectric properties and the storage elastic modulus at 300 ° C. and 350 ° C. will decrease, and if it exceeds this range, the foaming phenomenon will occur. It tends to occur easily, and the peel strength tends to decrease.

The ketone group-containing residue is 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, in all acid dianhydride residues. When the content of the ketone group-containing residue in the total acid dianhydride residue is below this range, it becomes difficult to suppress the foaming phenomenon and improve the peel strength. be.

Here, the ketone group-containing residue includes, for example, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 2,3′,3,4′-benzophenonetetracarboxylic dianhydride 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 4,4′-(paraphenylene dicarbonyl) diphthalic dianhydride, 4,4′-(metaphenylene dicarbonyl) diphthalic acid Acid dianhydride residues derived from dianhydrides and the like can be mentioned. Among these, acid dianhydride residues derived from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) are preferred. In addition, as the functional group having the property of interacting with the ketone group, any functional group that can cause physical interaction with the ketone group, such as physical interaction due to intermolecular force or chemical interaction due to covalent bonding, can be used. Although not particularly limited, an amino group (--NH ₂ ) can be mentioned as a representative example.

In the polyimide constituting the polyimide layer (A), the content of the PMDA residue and the ketone group-containing residue in the total acid dianhydride residue reduces the dielectric loss tangent, suppresses the occurrence of the foaming phenomenon, and improves the peel strength. is preferably 80 mol % or more, more preferably 90 mol % or more in total, in order to achieve a good balance.

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

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

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

Specific examples of the diamine residue derived from the diamine compound of general formula (A1) include 1,4-diaminobenzene (p-PDA), 2,2'-dimethyl-4,4'-diaminobiphenyl, 2, Diamine residues derived from 2'-n-propyl-4,4'-diaminobiphenyl, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, and the like can be mentioned. Among these, a diamine residue derived from 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB) is preferred from the viewpoint of dielectric properties.

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

The diamine residue derived from the diamine compound represented by the general formula (A1) is preferably 5 mol% or more and 90 mol% or less, more preferably 20 mol% or more and 80 mol% or less of the total diamine residue. It is better to let When the content of diamine residues derived from the diamine compound represented by the general formula (A1) in all diamine residues is below this range, the dielectric loss tangent of the polyimide and the coefficient of thermal expansion in the plane direction can be lowered. If this range is exceeded, the rigidity of the diamine residue becomes too high and the amount of entanglement of the molecular chains decreases, resulting in a decrease in peel strength with the metal layer. In addition, the increased regularity of the arrangement of the diamine residue moieties changes the responsiveness to an electric field, and the dielectric loss tangent tends to deteriorate.

Polyimide constituting the polyimide layer (A), in all diamine residues, in addition to the diamine residue derived from the diamine compound represented by the general formula (A1), the following general formulas (A2) ~ (A5) It preferably contains a diamine residue derived from a diamine compound represented by. Diamine residues derived from diamine compounds represented by the following general formulas (A2) to (A5) are independently -O-, -S-, -CO-, -SO- , —SO ₂ —, —CH ₂ —, —C(CH ₃ ) ₂ —, and —NH—. Also, the aromatic ring to which the amino group is linked has a para-position bond. For this reason, the polyimide molecular chain has a high degree of freedom in rotation and bending, and by improving the flexibility of the polyimide molecular chain, it is possible to balance the interaction and the amount of entanglement between the molecular chains. It becomes easy to achieve both suppression of reduction in elastic modulus E′ and improvement in film strength.

In the general formulas (A2) to (A5), R ₁ independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 6 carbon atoms, and the linking group A' is independently -O-, -S-, - a divalent group selected from CO-, -SO-, -SO ₂ -, -CH ₂ -, -C(CH ₃ ) ₂ -, and -NH-, n2 independently represents an integer of 0 to 4; . In addition, the linking position of the aromatic ring that does not have a bond with an amino group is a position other than the ortho position. Here, the term “independently” refers to multiple linking groups A′, multiple substituents R ₁ or multiple n2 in one or more of the above formulas (A2) to (A3). , may be the same or different. 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 and R _y are independently (meaning any substituent such as an alkyl group).

The total content of the diamine residues derived from the diamine compounds represented by the general formulas (A2) to (A5) in all diamine residues is preferably 10 mol% or more and 95 mol% or less, more preferably 20 mol % or more and 80 mol % or less is preferable. Below this range, the amount of entanglement between molecular chains decreases due to the decrease in flexibility of the molecular chains, and the peel strength with the metal layer decreases. On the other hand, when this range is exceeded, the degree of freedom of rotation and bending of the polyimide molecular chain becomes too high, making it difficult to suppress the movement of molecules, and the dielectric loss tangent tends to increase.

Specific examples of diamine residues derived from diamine compounds represented by general formulas (A2) to (A5) include 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'- Diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-bisamino)diphenylamine, 4,4'-methylenedi-o-toluidine, 4 ,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy) Benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, bis[4-(4 -aminophenoxy)]benzanilide, bis[4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis-[4-(4 -aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl] Diamine residues derived from methane and 4,4'-bis(4-aminophenoxy)biphenyl are preferred. Among them, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis[2-(4-aminophenyl)-2 in terms of aromatic number, linking group and linking position Preference may be given to diamine residues derived from -propyl]benzene.

(Other diamine residues)
The polyimide constituting the polyimide layer (A) may contain, in addition to the diamine residue described above, a diamine residue derived from a diamine component generally used as a raw material for polyimide.

(Ratio of acid dianhydride residue and diamine residue)
In the polyimide constituting the polyimide layer (A), the sum of the content of diamine residues derived from the diamine compound represented by the general formula (A1), which is a rigid monomer, and the content of PMDA residues (T1) is , preferably 90 mol % or more of the total content of all acid dianhydride residues and all diamine residues. When it is 90 mol % or more, a high storage elastic modulus at high temperatures can be maintained due to improvement in planarity and stacking property between molecular chains. Further, the sum (T1) of the diamine residue content and the PMDA residue content derived from the diamine compound represented by the general formula (A1), which is a rigid monomer, is a flexible monomer. The ratio (T1/T2) of the diamine residues derived from the diamine compounds represented by formulas (A2) to (A5) to the content (T2) of at least one diamine residue is preferably greater than 1. When the above ratio exceeds 1, the ratio of the rigid monomer becomes higher than that of the flexible monomer, and the motion of the molecular chain is suppressed, so that the dielectric loss tangent can be suppressed to a lower level.

The polyimide constituting the polyimide layer (A) can contain the same optional components as the polyimide constituting the polyimide layer (B).

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 The storage elastic modulus E′ at 5.0×10 ⁸ Pa or more and 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, the solvent and imidized water are vaporized during the heat treatment. It is possible to suppress the occurrence of a foaming phenomenon due to volume expansion due to.

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 concern that defects such as uneven thickness and streaks may occur during coating. The weight average molecular weight can be measured using a gel permeation chromatography device.

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).

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 thermal expansion coefficient to 60 ppm/K or less, it becomes easy to control the dimensional change rate of the polyimide film or metal-clad laminate. Adjustment of the coefficient of thermal expansion (CTE) of the polyimide layer (A) is mainly adjusted by the type and abundance of acid dianhydride residues and diamine residues in the polyimide that constitutes the polyimide, and the heat treatment conditions in the imidization process. can do.

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 completely imidized structure is most preferable in order to suppress the diffusion of copper. However, part of the polyimide may be amic acid. The imidization rate is around 1015 cm ⁻¹ by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation). is calculated from the absorbance of C═O stretching derived from the imide group at 1780 cm ⁻¹ based on the benzene ring absorber of .

<Form of polyimide film>
The polyimide film of the present embodiment (including a multilayer polyimide film having the polyimide layer (A) and the polyimide layer (B); the same applies hereinafter) may be a film (sheet) made of an insulating resin. , a metal foil such as copper foil, a glass plate, a resin sheet such as a polyimide film, a polyamide film, and a polyester film.

<Coefficient of thermal expansion (CTE)>
The polyimide film of the present embodiment has a coefficient of thermal expansion (CTE) of less than 30 ppm/K in order to prevent warping and deterioration of dimensional stability when applied as an insulating resin layer of a circuit board, for example. 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. When the coefficient of thermal expansion (CTE) of the polyimide film is 30 ppm/K or more, warpage occurs and dimensional stability decreases. A polyimide film having a desired CTE can be obtained by appropriately changing the combination of raw materials to be used, thickness, and drying/curing conditions.

<Dielectric loss tangent>
For example, when the polyimide film of the present embodiment is applied as an insulating resin layer of a circuit board, in order to reduce dielectric loss during transmission of high-frequency signals, the film as a whole has a temperature of 24 to 26 ° C. and a humidity of 45 to 45 ° C. Preferably, the dissipation factor (Tan δ) at 10 GHz is less than 0.003 as measured by a split-post dielectric resonator (SPDR) under 55% environment. In order to improve the transmission loss of the circuit board, it is particularly important to control the dielectric loss tangent of the insulating resin layer, and the dielectric loss tangent (Tan δ) at 10 GHz is less than 0.003. Increases effect. Therefore, when a polyimide film is applied as an insulating resin layer of a high frequency circuit board, transmission loss can be efficiently reduced. If the dielectric loss tangent at 10 GHz is 0.003 or more, when the polyimide film is applied as an insulating resin layer of a circuit board, problems such as increased electrical signal loss on the high-frequency signal transmission path are likely to occur.

Further, the polyimide film of the present embodiment has, for example, a dielectric loss tangent (Tan δ) at 10 GHz when measured by a split post dielectric resonator (SPDR) in a water absorption environment in which the polyimide film is immersed in pure water for 48 hours. , is preferably less than 0.006, and the water absorption 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 loss tangent of the insulating resin layer even when water is absorbed. When it is less than 0.006, it is possible to reduce changes in transmission loss due to environmental influences.
Note that the lower limit value of the dielectric loss tangent is not particularly limited.

<Dielectric constant>
For example, when the polyimide film of the present embodiment is applied as an insulating resin layer of a circuit board, in order to ensure impedance matching, a split post dielectric film is formed under an environment of a temperature of 24 to 26 ° C. and a humidity of 45 to 55%. It is preferable that the dielectric constant at 10 GHz measured by a resonator (SPDR) is 4.0 or less. If the relative dielectric constant at 10 GHz exceeds 4.0, when the polyimide film is applied as an insulating resin layer of a circuit board, it leads to deterioration of dielectric loss, and the loss of electrical signals on the transmission path of high frequency signals increases. inconvenience is more likely to occur. In addition, the polyimide film of the present embodiment has a value of √Dk×Df, which is an index of dielectric properties (where Dk is the dielectric constant, Df is the dielectric loss tangent, and √Dk is the square root of the dielectric constant. ) is preferably 0.006 or less, more preferably 0.005 or less when measured after being left for 24 hours under conditions of a temperature of 24 to 26° C. and a humidity of 45 to 55% (at the time of humidity control). Furthermore, the value of √Dk×Df is preferably 0.01 or less, more preferably 0.009 or less, when measured after the polyimide film is immersed in pure water for 48 hours (at the time of water absorption).

<Thickness>
The thickness of the polyimide film of the present embodiment is not particularly limited, and is preferably in the range of 5 to 60 μm, 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, for example, preferably in the range of 1-15 μm, more preferably in the range of 2-10 μm. The polyimide layer (B) preferably has a thickness of more than 50%, more preferably 60% or more of the total thickness of the insulating resin layer.

[Method for producing polyimide film]
[1] to [3] below can be exemplified as preferred aspects of the method for producing the polyimide film of the present embodiment.
[1] A method of producing a polyimide film by repeating coating and drying a polyamic acid solution on a supporting substrate once or several times, followed by imidization.
[2] A method of producing a polyimide film by repeatedly applying and drying a polyamic acid solution to a supporting substrate once or several times, then peeling off the polyamic acid gel film from the supporting substrate and imidizing it.
[3] A method of manufacturing a polyimide film by simultaneously applying and drying a polyamic acid solution in a multilayered state by multilayer extrusion, followed by imidization (hereinafter referred to as multilayer extrusion method).

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

The method [2] above includes, for example, the following steps 2a to 2c;
(2a) applying a polyamic acid solution to a supporting substrate and drying;
(2b) separating the supporting substrate from the polyamic acid gel film;
(2c) obtaining a polyimide film by heat-treating a polyamic acid gel film for imidization;
can include

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

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

In the polyimide film produced in the present embodiment, it is preferable to complete the imidization of the polyamic acid on the support substrate. Since the polyamic acid resin layer is imidized in a state of being fixed to the supporting base material, it is possible to suppress the change in expansion and contraction of the polyimide layer during the imidization process, and to maintain the thickness and dimensional accuracy of the polyimide film.

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

As a preferred embodiment of the metal-clad laminate, the insulating resin layer has a polyimide layer (A) in contact with the metal layer and a plurality of polyimide layers including a polyimide layer (B) laminated on the polyimide layer (A). However, the polyimide constituting the polyimide layer (B), which is the main polyimide layer, can be a polyimide that satisfies 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 polyimide layer (B) with a low coefficient of thermal expansion (CTE) and a low dielectric loss tangent, thereby improving the dimensional stability of the entire insulating resin layer and achieving a low dielectric loss tangent. can be done. However, the polyimide layer (B) made of polyimide that satisfies the above (i) to (iii) has relatively low gas permeability, and the solvent and imidized water remain between the polyimide layer (A). As a result, foaming tends to occur easily. Therefore, by configuring the polyimide layer (A) as described above, it is possible to effectively suppress the occurrence of the foaming phenomenon even if the polyimide layer (B) has low gas permeability.

The thickness of the polyimide layer (A) in the metal-clad laminate is not particularly limited, and is preferably in the range of 1 to 15 μm, 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 of the total thickness of the insulating resin layer.

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

The thickness of the metal layer is not particularly limited, but when a metal foil such as copper foil is used, the thickness is preferably 35 μm or less, more preferably 5 μm or more and 25 μm or less. The lower limit of the thickness of the metal foil is preferably 5 μm from the viewpoint of production stability and handling. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Moreover, as a copper foil, the copper foil marketed can be used.

The surface of the metal layer in contact with the polyimide layer (A) has a ten-point average roughness (Rzjis) of preferably 1.2 μm or less, more preferably 1.0 μm or less. When the metal layer is made of metal foil, by setting the surface roughness Rzjis to 1.2 μm or less, fine wiring processing corresponding to high-density mounting becomes possible, and transmission loss during high-frequency signal transmission can be reduced. Therefore, it can be applied to a circuit board for high frequency signal transmission.

The metal layer may be subjected to surface treatment with, for example, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, or the like, for the purpose of rust prevention treatment or improvement of adhesive strength.

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

[1] A method of producing a metal-clad laminate in which a polyimide insulating layer is formed by repeating the application and drying of a polyamic acid solution on a metal foil to be a metal layer once or several times, followed by imidization.

[2] A method of manufacturing a metal clad laminate in which a polyimide insulating layer is formed by applying and drying a polyamic acid solution in a multilayered state by simultaneously applying and drying a polyamic acid solution on a metal foil that will be a metal layer by multilayer extrusion, followed by imidization. (Hereinafter, multilayer extrusion method).

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) forming a polyimide layer (A) by heat-treating polyamic acid on a metal foil to imidize it. In this case, by adjusting the heating conditions in the drying step of the step (1a), and particularly the heating conditions during the imidization in the step (1b), the in-plane orientation of the polyimide can be controlled, and the birefringence of the polyimide and the Properties such as CTE can be controlled.

In the method [1] above, the step (1a) is repeated for the polyamic acid solution of the precursor of the polyimide that constitutes the polyimide layer (A) and the polyamic acid solution of the precursor of the polyimide that constitutes the polyimide layer (B). By carrying out, a laminate structure of polyamic acid can be formed on the metal foil. The method of applying the polyamic acid solution onto the metal foil is not particularly limited, and can be applied by a coater such as a comma, die, knife, lip, or the like.

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

The metal-clad laminate produced in this way is imidized in a state where the resin layer of polyamic acid is fixed to the metal foil by completing the imidization of the polyamic acid on the metal foil, so the imidization process The thickness and dimensional accuracy of the polyimide insulating layer can be maintained by suppressing the expansion and contraction change of the polyimide layer.

[Circuit board]
The metal-clad laminate of the present invention is useful mainly as a circuit board material such as FPC. A circuit board according to one embodiment of the present invention can be manufactured 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 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. The resin layer should just contain the said polyimide layer (B). Moreover, in order to enhance the adhesiveness between the insulating resin layer and the wiring layer, the layer in the insulating resin layer that is in contact with the wiring layer is preferably a polyimide layer (A).

EXAMPLES Examples are given below to more specifically describe 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.

[Measurement of viscosity]
The viscosity at 25° C. was measured using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro). The number of revolutions was set so that the torque was 10% to 90%, and after 2 minutes from the start of the measurement, the value was read when the viscosity stabilized.

[Glass transition temperature (Tg) and classification of non-thermoplastic and thermoplastic polyimide films]
For the glass transition temperature, a polyimide film having a size of 5 mm × 70 mm was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by TA Instruments, trade name; RSA G2) from 30 ° C. to 400 ° C. at a heating rate. Measurement was performed at 4° C./min and a frequency of 1 Hz, and the temperature at which the change in elastic modulus (tan δ) 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 a temperature range within +30°C of the glass transition temperature is less than 1.0 × 10 ⁸ Pa. is defined as “thermoplastic”, and has a storage modulus of 1.0×10 ⁹ Pa or more at 30° C., and a storage modulus of 1.0×10 ⁸ Pa in a temperature range within +30° C. of the glass transition temperature. Those exhibiting the above were defined as "non-thermoplastic".

[Measurement of coefficient of thermal expansion (CTE)]
A polyimide film with a size of 3 mm × 20 mm is heated at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (Hitachi High-Tech Technology Co. (former Seiko Instruments), trade name: TMA / SS6100). The temperature was raised from 30° C. to 260° C., held at that temperature for 10 minutes, cooled at a rate of 5° C./min, and the average thermal expansion coefficient (thermal expansion coefficient) from 250° C. to 100° C. was determined.

[Measurement of dielectric constant and dielectric loss tangent]
Using a vector network analyzer (manufactured by Agilent, trade name; E8363C) and a split post dielectric resonator (SPDR resonator), the dielectric constant (Dk) and dielectric loss tangent (Df) of the polyimide film at a frequency of 10 GHz were measured. .
Dk and Df under humidity control were measured after leaving the polyimide film used for measurement under conditions of temperature: 24 to 26° C. and humidity: 45 to 55% for 24 hours.
Dk and Df at the time of water absorption were measured after the polyimide film used for measurement was immersed in pure water for 48 hours, taken out, and the pure water was wiped off the surface of the material.

[Measurement of surface roughness of copper foil]
The surface roughness of the copper foil is measured by AFM (manufactured by Bruker AXS, trade name; Dimension Icon type SPM), probe (manufactured by Bruker AXS, trade name; TESPA (NCHV), tip curvature radius 10 nm, Using a spring constant of 42 N/m), measurement was performed in a tapping mode in an area of 80 μm×80 μm on the surface of the copper foil to determine the ten-point average roughness (Rzjis).

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

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

[Measurement of water absorption]
A test piece of polyimide film (width: 4 cm x length: 25 cm) was prepared, dried at 80°C for 1 hour, and weighed. After the weight measurement, the film was allowed to stand still in pure water for 24 hours or longer, and then taken out.
Water absorption (% by weight) = [(weight after water absorption - weight after drying) / weight after drying] x 100

[Tensile modulus]
Using Strograph R-1 (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a polyimide film with a width of 12.7 mm and a length of 127 mm was subjected to a tensile test at 50 mm / min in an environment with a temperature of 23 ° C. and a relative humidity of 50% RH. and calculated.

[Presence or absence of foaming]
When the appearance of the obtained copper-clad laminate was visually observed, it was confirmed whether foaming would occur.

[Possibility of filming]
Regarding copper-clad laminates, when the copper foil is removed by etching with an aqueous solution of ferric chloride to form a polyimide film, the film can be handled as a single film without cracks [Acceptable]. Those that were easily broken were rated as [not acceptable].

[Measurement of thickness of polyimide layer]
The copper foil of the copper-clad laminate was removed by etching using an aqueous solution of ferric chloride to obtain a polyimide film. The resulting polyimide film was cut into strips, embedded in a resin, and then cut in the thickness direction of the film with a microtome to prepare ultra-thin slices of about 100 nm. For the ultra-thin section produced, using the STEM function of SEM (SU9000) manufactured by Hitachi High-Tech Technology Corporation, observed at an acceleration voltage of 30 kV, the thickness of each polyimide layer was measured at 5 points, and the average value of each polyimide layer. The total thickness of each layer was taken as the thickness of the multilayer polyimide film.

[Calculation of imide group concentration]
The imide group was defined as (-(CO) ₂ -N-) and calculated from the following formula.
Imide group concentration (% by weight) = (molecular weight of imide group/molecular weight of entire structure of polyimide) x 100

[Calculation of ester group concentration]
It was calculated from the following formula, with the ester group as (-COO-).
Ester group concentration (% by weight) = (molecular weight of ester group/molecular weight of entire structure of polyimide) x 100

[Calculation of ratio of biphenyl skeleton-containing monomer]
The ratio (unit: mol %) of the monomer having a biphenyl skeleton in all the monomer components in the polyimide was defined as the ratio of the biphenyl skeleton-containing monomer.

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

(Synthesis example 1)
Under a nitrogen stream, 12.1229 g of m-TB (0.05711 mol) and 1.2338 g of BAPP (0.00301 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 31.6433 g of BP-TME (0.05921 mol), a polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution A. The solution viscosity of polyamic acid solution A was 26,800 cps.

(Synthesis example 2)
Under a nitrogen stream, 14.4565 g of m-TB (0.06810 mol) and DMAc in an amount such that the solid content concentration after polymerization is 15% by weight are added to a 500 ml separable flask, and stirred at room temperature. Dissolved. Next, after adding 26.8858 g of BP-TME (0.05031 mol) and 3.6577 g of PMDA (0.01677 mol), the polymerization reaction was continued at room temperature for 3 hours to perform a polymerization reaction. got The solution viscosity of polyamic acid solution B was 25,500 cps.

(Synthesis Example 3)
Under a nitrogen stream, 13.5308 g of m-TB (0.06374 mol) and 1.3771 g of BAPP (0.00335 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 26.4885 g of BP-TME (0.04956 mol) and 3.6036 g of PMDA (0.01652 mol), the polymerization reaction was continued at room temperature for 3 hours, and the polyamic acid solution C got The solution viscosity of polyamic acid solution C was 24,000 cps.

(Synthesis Example 4)
Under a nitrogen stream, 11.7590 g of m-TB (0.05539 mol) and 4.0127 g of BAPP (0.00977 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 25.7282 g of BP-TME (0.04814 mol) and 3.5002 g of PMDA (0.01605 mol), the polymerization reaction was continued at room temperature for 3 hours, and polyamic acid solution D got The solution viscosity of polyamic acid solution D was 21,300 cps.

(Synthesis Example 5)
Under a nitrogen stream, 9.2841 g of m-TB (0.04373 mol) and 7.6941 g of BAPP (0.01874 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 24.6661 g of BP-TME (0.04615 mol) and 3.3557 g of PMDA (0.01538 mol), the polymerization reaction was continued at room temperature for 3 hours to perform a polymerization reaction. got The solution viscosity of polyamic acid solution E was 14,900 cps.

(Synthesis Example 6)
Under a nitrogen stream, 9.6812 g of m-TB (0.04560 mol), 1.3372 g of BAPP (0.00326 mol) and 4.7612 g of TPE-R (0.01629 mol) were added to a 500 ml separable flask. ) and DMAc in such an amount that the solid concentration after polymerization becomes 15% by weight, and stirred at room temperature for dissolution. Next, after adding 25.7212 g of BP-TME (0.04813 mol) and 3.4992 g of PMDA (0.01604 mol), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction, polyamic acid solution F got The solution viscosity of polyamic acid solution F was 17,800 cps.

(Synthesis Example 7)
Under a nitrogen stream, 14.8395 g of m-TB (0.06990 mol) and 1.5103 g of BAPP (0.00368 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Then add 19.3670 g BP-TME (0.03624 mol), 5.3311 g BPDA (0.01812 mol) and 3.9522 g PMDA (0.01812 mol), then stir at room temperature for 3 hours were continued to carry out a polymerization reaction to obtain a polyamic acid solution G. The solution viscosity of polyamic acid solution G was 35,200 cps.

(Synthesis Example 8)
Under a nitrogen stream, 16.4284 g of m-TB (0.07739 mol) and 1.6720 g of BAPP (0.00407 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Then add 10.7204 g BP-TME (0.02006 mol), 11.8038 g BPDA (0.04012 mol) and 4.3754 g PMDA (0.02006 mol), then stir at room temperature for 3 hours were continued to carry out a polymerization reaction to obtain a polyamic acid solution H. The solution viscosity of polyamic acid solution H was 27,900 cps.

(Synthesis Example 9)
Under a nitrogen stream, 19.1251 g of m-TB (0.09009 mol) and 1.9465 g of BAPP (0.00474 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 13.7413 g of BPDA (0.04670 mol) and 10.1871 g of PMDA (0.04670 mol), the polymerization reaction was continued at room temperature for 3 hours to obtain polyamic acid solution I. rice field. The solution viscosity of polyamic acid solution I was 31,400 cps.

(Synthesis Example 10)
Under a nitrogen stream, 16.3417 g of m-TB (0.07698 mol) and 1.6632 g of BAPP (0.00405 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 18.2906 g of TAHQ (0.03991 mol) and 8.7045 g of PMDA (0.03991 mol), a polymerization reaction was performed by continuing stirring at room temperature for 3 hours to obtain polyamic acid solution J. rice field. The solution viscosity of polyamic acid solution J was 27,800 cps.

(Synthesis Example 11)
Under a nitrogen stream, 8.0852 g of PDA (0.07477 mol) and 1.6154 g of BAPP (0.00394 mol) are placed in a 500 ml separable flask, and the amount of solid content after polymerization is 15% by weight. DMAc was added and dissolved by stirring at room temperature. Next, after adding 31.0722 g of BP-TME (0.05814 mol) and 4.2272 g of PMDA (0.01938 mol), the polymerization reaction was continued at room temperature for 3 hours, and polyamic acid solution K got The solution viscosity of polyamic acid solution K was 28,700 cps.

(Synthesis Example 12)
Under a nitrogen stream, 8.4131 g of PDA (0.07780 mol) and 1.6809 g of BAPP (0.00409 mol) are placed in a 500 ml separable flask, and an amount that makes the solid content concentration after polymerization 15% by weight. DMAc was added and dissolved by stirring at room temperature. Next, after adding 30.5387 g of 26DHN-TME (0.06007 mol) and 4.3674 g of PMDA (0.02002 mol), the polymerization reaction was continued at room temperature for 3 hours, and the polyamic acid solution L got The solution viscosity of polyamic acid solution L was 26,500 cps.

(Synthesis Example 13)
Under a nitrogen stream, 12.6149 g of m-TB (0.05942 mol) and 1.2839 g of BAPP (0.00313 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 31.1012 g of 26DHN-TME (0.06117 mol), a polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution M. The solution viscosity of the polyamic acid solution M was 73,900 cps.

(Synthesis Example 14)
Under a nitrogen stream, 13.9957 g of m-TB (0.06593 mol) and 1.4244 g of BAPP (0.00347 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 25.8789 g of 26DHN-TME (0.05090 mol) and 3.7010 g of PMDA (0.01697 mol), the polymerization reaction was carried out at room temperature for 3 hours with continuous stirring. got The solution viscosity of polyamic acid solution N was 43,800 cps.

(Synthesis Example 15)
Under a nitrogen stream, 17.6242 g of m-TB (0.08302 mol) and 1.7937 g of BAPP (0.00437 mol) are placed in a 500 ml separable flask, and the solid content concentration after polymerization is 15% by weight. amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 11.5007 g of BP-TME (0.02152 mol) and 14.0815 g of PMDA (0.06456 mol), the polymerization reaction was continued at room temperature for 3 hours, and the polyamic acid solution O got The solution viscosity of the polyamic acid solution O was 31,400 cps.

(Synthesis Example 16)
Under a nitrogen stream, 7.8166 g of m-TB (0.03682 mol) and 10.7636 g of TPE-R (0.03682 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 4.6984 g of BTDA (0.01458 mol) and 12.7214 g of PMDA (0.05832 mol), a polymerization reaction was performed by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution P. rice field. The solution viscosity of the polyamic acid solution P was 8,500 cps.

(Synthesis Example 17)
Under a nitrogen stream, 2.9802 g of m-TB (0.01404 mol) and 16.4155 g of TPE-R (0.05615 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 4.4784 g of BTDA (0.01390 mol) and 12.1258 g of PMDA (0.05559 mol), a polymerization reaction was carried out by continuing stirring at room temperature for 3 hours to obtain polyamic acid solution Q. rice field. The solution viscosity of polyamic acid solution Q was 1,800 cps.

(Synthesis Example 18)
Under a nitrogen stream, 13.1525 g of m-TB (0.06196 mol) and 4.5279 g of TPE-R (0.01549 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 4.9411 g of BTDA (0.01533 mol) and 13.3786 g of PMDA (0.06134 mol), the polymerization reaction was continued at room temperature for 3 hours to obtain polyamic acid solution R. rice field. The solution viscosity of polyamic acid solution R was 6,800 cps.

(Synthesis Example 19)
Under a nitrogen stream, 2.8108 g of m-TB (0.01324 mol) and 15.4821 g of TPE-R (0.05296 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 10.5594 g of BTDA (0.03277 mol) and 7.1477 g of PMDA (0.03277 mol), a polymerization reaction was performed by continuing stirring at room temperature for 3 hours to obtain polyamic acid solution S. rice field. The solution viscosity of the polyamic acid solution S was 2,100 cps.

(Synthesis Example 20)
Under a nitrogen stream, 2.6596 g of m-TB (0.01253 mol) and 14.6492 g of TPE-R (0.05011 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 15.9860 g of BTDA (0.04961 mol) and 2.7053 g of PMDA (0.01240 mol), a polymerization reaction was performed by continuing stirring at room temperature for 3 hours to obtain polyamic acid solution T. rice field. The solution viscosity of the polyamic acid solution T was 1,900 cps.

(Synthesis Example 21)
Under a nitrogen stream, 2.7701 g of m-TB (0.01305 mol) and 15.2580 g of TPE-R (0.05219 mol) and a solid content concentration after polymerization of 12% by weight were placed in a 500 ml separable flask. An amount of DMAc was added and dissolved by stirring at room temperature. Next, after adding 13.6386 g of BPDA (0.04636 mol) and 4.3333 g of PMDA (0.01987 mol), a polymerization reaction was performed by continuing stirring at room temperature for 3 hours to obtain a polyamic acid solution U. rice field. The solution viscosity of the polyamic acid solution U was 1600 cps.

(Example 1)
Polyamic acid solution A was evenly applied on copper foil 1 (electrolytic copper foil, thickness: 12 μm, resin side surface roughness Rzjis: 0.6 μm) so that the thickness after curing was about 25 μm, The solvent was removed by heat drying at 120°C. Further, stepwise heat treatment was performed from 120° C. to 360° C. 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, polyimide film A was prepared by removing the copper foil from copper clad laminate A obtained by etching using an aqueous solution of ferric chloride. Table 1 shows the polyimide type, imide group concentration, ester group concentration, ratio of biphenyl skeleton-containing monomer, presence or absence of foaming, and feasibility of film formation of polyimide film A obtained.

(Examples 2 to 8, Comparative Example 1, Comparative Example 2 and Reference Examples 1 to 13)
In the same manner as in Example 1, polyamic acids B to U were used to prepare copper-clad laminates and to evaluate the properties of polyimide films after etching copper foils. Table 1 shows the type of polyimide, imide group concentration, ester group concentration, ratio of biphenyl skeleton-containing monomer, presence or absence of foaming, and whether or not the polyimide film can be formed into a film.
Data on the physical properties of the films were not obtained for those with foaming and those that could not be formed into films.

[Example 9]
Polyamic acid solution P was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization and obtain a copper-clad laminate X having multilayer polyimide. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate X having multilayer polyimide was measured and found to be 0.92 kN/m. A multilayer polyimide film X was prepared by removing the copper foil from the copper-clad laminate X having the multilayer polyimide by etching using an aqueous solution of ferric chloride. The obtained multilayer polyimide film X had Dk=3.37 and Df=0.0027 at the time of humidity conditioning.
The storage elastic modulus at 300° C. of the polyimide film produced by curing the polyamic acid solution P as the first layer is 8.3×10 ⁸ Pa, and the storage elastic modulus at 350° C. is 1.9×10 ⁸ Pa.

[Example 10]
Polyamic acid solution Q was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization, and a copper-clad laminate Y having multilayer polyimide was obtained. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate Y having multilayer polyimide was measured and found to be 0.71 kN/m. A multilayer polyimide film Y was prepared by removing the copper foil from the copper-clad laminate Y having the multilayer polyimide by etching using an aqueous solution of ferric chloride. The obtained multilayer polyimide film Y had Dk=3.38 and Df=0.0027 at the time of humidity conditioning.
The storage elastic modulus at 300° C. of the polyimide film produced by curing the polyamic acid solution Q as the first layer is 1.2×10 ⁹ Pa, and the storage elastic modulus at 350° C. is 5.2×10 ⁸ Pa.

[Example 11]
Polyamic acid solution R was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization, and a copper-clad laminate Z having multilayer polyimide was obtained. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate Z having multilayer polyimide was measured and found to be 0.73 kN/m. A multilayer polyimide film Z was prepared by removing the copper foil from the copper-clad laminate Z having the multilayer polyimide by etching using an aqueous solution of ferric chloride. The obtained multilayer polyimide film Z had Dk=3.38 and Df=0.0027 at the time of humidity conditioning.
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.

[Example 12]
Polyamic acid solution S was uniformly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization and obtain a copper-clad laminate Aa having multilayer polyimide. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate Aa having multilayer polyimide was measured and found to be 0.77 kN/m. Further, the copper foil of the copper-clad laminate Aa having multilayer polyimide was removed by etching using an aqueous solution of ferric chloride to prepare a multilayer polyimide film Aa. The obtained multilayer polyimide film Aa had Dk=3.38 and Df=0.0027 at the time of humidity conditioning.
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.

[Example 13]
Polyamic acid solution T was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization and obtain a copper-clad laminate Bb having multilayer polyimide. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate Bb having multilayer polyimide was measured and found to be 0.71 kN/m. Also, the copper foil of the copper-clad laminate Bb having multilayer polyimide was removed by etching using an aqueous solution of ferric chloride to prepare a multilayer polyimide film Bb. The obtained multilayer polyimide film Bb had Dk=3.38 and Df=0.0028 at the time of humidity conditioning.
The storage elastic modulus at 300° C. of the polyimide film produced by curing the polyamic acid solution T as the first layer is 4.4×10 ⁸ Pa, and the storage elastic modulus at 350° C. is 1.5×10 ⁸ Pa.

[Example 14]
Polyamic acid solution U was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, a stepwise heat treatment was performed from 120° C. to 360° C. for 20 minutes to complete imidization and obtain a copper-clad laminate Cc having multilayer polyimide. At this time, no foaming was observed on the film surface.
The initial peel strength of the obtained copper-clad laminate Cc having multilayer polyimide was measured and found to be 0.97 kN/m. Further, the copper foil of the copper-clad laminate Cc having multilayer polyimide was removed by etching using an aqueous solution of ferric chloride to prepare a multilayer polyimide film Cc. The obtained multilayer polyimide film Cc had Dk=3.38 and Df=0.0025 at the time of humidity conditioning.
The storage elastic modulus at 300° C. of the polyimide film produced 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.

[Reference Example 14]
Polyamic acid solution U was evenly coated on the copper foil 1 as a first layer in contact with the copper foil so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Next, the polyamic acid solution C as the second layer was uniformly coated on the first layer so that the thickness after curing was 21 μm, and then dried by heating at 120° C. for 2 minutes to remove the solvent. Furthermore, the polyamic acid solution U, which is the third layer, was evenly coated on the second layer so that the thickness after curing was 2 μm, and then dried by heating at 120° C. for 1 minute to remove the solvent. Subsequently, stepwise heat treatment was performed from 120° C. to 360° C. for 10 minutes to complete imidization, and a copper-clad laminate Dd having multilayer polyimide was obtained. At this time, foaming was observed on the film surface.
The storage elastic modulus at 300° C. of the polyimide film produced 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.

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

Claims (8)

A polyamic acid containing an acid dianhydride residue derived from an acid dianhydride component and a diamine residue derived from a diamine component, wherein the following conditions (i) to (iii);
Condition (i):
Containing 25 mol% or more of an acid dianhydride residue derived from an acid dianhydride represented by the following formula (1) with respect to all acid dianhydride residues,

Condition (ii):
Containing 50 mol% or more of diamine residues derived from a diamine compound represented by the following general formula (2) with respect to all diamine residues;

[In Formula (2), Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms or an alkoxy group, and p and q independently represent an integer of 0 to 4. ]
Condition (iii):
The ratio of monomer residues having a biphenyl skeleton to all monomer residues derived from all monomer components is 65 mol or more,
A polyamic acid characterized by satisfying The polyamide according to claim 1, which contains 1 to 50 mol% of diamine residues derived from diamine compounds represented by the following general formulas (3) to (6) with respect to all diamine residues. acid.

[In the 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 —, wherein the linking group X is independently —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 is independently an integer of 1 to 4, n is independently 0 to represents an integer of 4, but in formula (5), if the linking group A does not contain -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -SO ₂ -, Any one of n is 1 or more. ] A polyimide obtained by imidating the polyamic acid according to claim 1 or 2. A polyimide film comprising a single or multiple polyimide layers,
A polyimide film in which at least one of the polyimide layers contains the polyimide according to claim 3 as a main component of the resin component. A polyimide layer (A) containing a first polyimide as a main component of the resin component, and a second polyimide layer laminated on the polyimide layer (A) and different from the first polyimide as a main component of the resin component A polyimide film containing a polyimide layer (B) containing as
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,
In all acid dianhydride residues, 5 mol% or more and 90 mol% or less of residues derived from pyromellitic dianhydride, derived from acid dianhydride having a ketone group (-CO-) in the molecule A residue containing 10 mol% or more and 95 mol% or less, and a residue derived from pyromellitic dianhydride and a residue derived from an acid dianhydride having a ketone group (-CO-) in the molecule contains a total of 80 mol% or more,
In all diamine residues, residues derived from a diamine compound represented by the following general formula (A1) are contained at a ratio of 5 mol% or more and 90 mol% or less,
A storage modulus E′ at 300° C. of 1.0×10 ⁸ Pa or more and a storage modulus E′ of 1.0×10 ⁷ Pa or more at 350° C. measured using a dynamic viscoelasticity measuring device (DMA). is polyimide,
A polyimide film, wherein the second polyimide is the polyimide according to claim 3 .

[In the formula (A1), the linking group X1 represents a single bond or a divalent group selected from —CONH—, and Y independently represents hydrogen, a monovalent hydrocarbon group having 1 to 3 carbon atoms, or an alkoxy group. , n1 represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. ] The dielectric loss tangent (Tanδ) at 10 GHz when measured by a split post dielectric resonator (SPDR) in an environment of temperature 24 to 26 ° C. and humidity 45 to 55% is less than 0.003, and the coefficient of thermal expansion (CTE ) is less than 25 ppm/K. A metal-clad laminate comprising an insulating resin layer and a metal layer provided on at least one surface of the insulating resin layer,
A metal-clad laminate, wherein the insulating resin layer comprises the polyimide film according to any one of claims 4 to 6. A circuit board comprising an insulating resin layer and a wiring layer provided on at least one surface of the insulating resin layer,
A circuit board, wherein the insulating resin layer comprises the polyimide film according to any one of claims 4 to 6.