JP2023079202A - Polyimide-based resin precursor - Google Patents

Abstract

To provide a polyimide-based resin precursor which enables formation of a polyimide-based film that has low Df and is excellent in bending resistance even at a low heat imidization temperature.SOLUTION: A polyimide-based resin precursor contains a structural unit (A) derived from a tetracarboxylic acid anhydride and a structural unit (B) derived from diamine, wherein the structural unit (A) contains a structural unit (A1) derived from an ester bond-containing tetracarboxylic acid anhydride and a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic acid anhydride, the structural unit (A) satisfies a relation of Expression (X): (content of structural unit (A3) derived from tetracarboxylic acid anhydride other than structural unit (A1) and structural unit (A2))/(total amount of structural unit (A1) and structural unit (A2))<0.67, the structural unit (B) includes a structural unit (B1) derived from biphenyl skeleton-containing diamine, the content of the structural unit (B1) exceeds 30 mol% with respect to the total amount of the structural unit (B), and the weight average molecular weight of the polyimide-based resin precursor in terms of polystyrene is larger than 100,000.SELECTED DRAWING: None

Description

The present invention relates to a polyimide resin precursor that can be used as a substrate material compatible with high-frequency printed circuit boards and antenna substrates.

Flexible printed circuit boards (hereinafter sometimes referred to as FPCs) are thin, lightweight, and flexible, so they can be mounted three-dimensionally and at high density. It is used and contributes to its miniaturization and weight reduction. Conventionally, polyimide resins, which are excellent in heat resistance, mechanical properties, and electrical insulation, have been widely used for FPCs.
In recent years, a fifth-generation mobile communication system called 5G is becoming popular in earnest. Conventionally used polyimide materials have problems such as large transmission loss, electrical signal loss, and signal delay time when transmitting high-frequency signals used in 5G communications. Therefore, a polyimide film having a low dielectric loss tangent (hereinafter sometimes referred to as Df) and a low dielectric constant (hereinafter sometimes referred to as Dk) has been studied for the purpose of reducing transmission loss.
In addition, the use of FPC is expanding to the wiring of movable parts of electronic equipment, and parts such as cables and connectors, and the demand for FPC with higher bending resistance is increasing, such as the market launch of foldable devices. . Accordingly, there is a demand for a polyimide film that has low Df and Dk and excellent bending resistance.

For example, in Patent Document 1, a tetracarboxylic anhydride component containing an ester-containing tetracarboxylic anhydride and a biphenyltetracarboxylic anhydride is reacted with a diamine component containing 75 mol% or more of p-phenylenediamine. and a polyimide resin obtained by curing the polyimide resin precursor. Patent Document 2 discloses a non-thermoplastic polyimide layer containing a non-thermoplastic polyimide and a thermoplastic polyimide layer containing a thermoplastic polyimide, wherein the non-thermoplastic polyimide is 3,3′,4,4′-biphenyl tetra Tetracarboxylic acid residue (BPDA residue) derived from carboxylic acid dianhydride (BPDA) and tetracarboxylic acid residue derived from 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) A polyimide film comprising a tetracarboxylic acid residue containing at least one such group (TAHQ residue) and a diamine residue derived from a specific diamine compound is disclosed. Further, Patent Document 3 discloses a composition containing a polyimide precursor resin obtained by condensation polymerization of an aromatic tetracarboxylic dianhydride and a diamine, wherein the aromatic tetracarboxylic dianhydride and the diamine are At least one of them has a biphenyl skeleton, and the content of the biphenyl skeleton is 40 mol% or more with respect to the total amount of the aromatic tetracarboxylic dianhydride and the diamine, and the aromatic Group tetracarboxylic acid dianhydride contains p-phenylene bis (trimellitic acid monoester acid anhydride) in an amount of 5 mol% or more with respect to the total amount polyimide precursor resin composition and the polyimide resin obtained from the composition A membrane is disclosed.

JP 2018-150544 A WO2018/061727 JP 2014-208793 A

As a metal-clad laminate such as a copper-clad laminate (hereinafter sometimes referred to as CCL) used for FPC, a metal foil such as a copper foil layer is provided on one or both sides of a single-layer or multiple-layer polyimide resin. Laminates are widely used. A metal-clad laminate such as CCL having a polyimide film is produced by casting a polyimide resin precursor solution onto a metal foil such as copper foil and thermally imidizing the coating film of the polyimide resin precursor. The thermal imidization is usually carried out by heating at a high temperature of about 360°C.
In the transmission of high-frequency current, a phenomenon called skin effect, in which current flows densely near the surface of a conductor, becomes conspicuous. Therefore, when a metal-clad laminate such as CCL is used in a high-frequency circuit, roughening or oxidation of the surface of a metal foil such as a copper foil tends to cause a decrease in transmission loss. For example, when a copper foil is heated at a high temperature of 350° C. or higher, the surface of the copper foil becomes rough, the crystal grain size increases, oxidation occurs, and the interface tends to become rough. Furthermore, when the crystal grain size on the surface of the copper foil increases, the bending resistance of the copper foil tends to decrease, and the bending resistance of the CCL tends to decrease.
Therefore, exposure of metal foil such as copper foil together with polyimide resin to high temperature in the process of thermal imidization can cause a decrease in transmission loss and a decrease in bending resistance.

According to studies by the present inventors, conventional polyimide resins sometimes fail to sufficiently reduce the Df and Dk of the resulting polyimide film when thermal imidization is performed at a low temperature of less than 350°C. In order to sufficiently reduce the Df and Dk of these polyimide resins and polyimide films, thermal imidization is performed at a high temperature of 350 ° C. or higher to produce a metal-clad laminate such as CCL. Metal-clad lamination such as CCL, which suppresses the roughness and oxidation of the metal foil surface and reduces the Df of the polyimide layer, and has low transmission loss when used in high-frequency circuits. Forming a plate is difficult. Additionally, conventional polyimide films may not have sufficient flex resistance.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a polyimide resin precursor capable of forming a polyimide film having a low Df and excellent bending resistance even at a low thermal imidization temperature.

The present inventors arrived at the present invention as a result of intensive studies in order to solve the above problems. That is, the present invention provides the following preferred aspects.

［式（ａ１）中、Ｚは２価の有機基を表し、
Ｒ^ａ１は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｓは互いに独立に、０～３の整数を表す］
で表されるテトラカルボン酸無水物由来の構成単位（ａ１）である、〔１〕に記載のポリイミド系樹脂前駆体。
〔３〕 前記構成単位（Ａ２）は、式（ａ２）：

［式（ａ２）中、Ｒ^ａ２は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｔは、互いに独立に、０～３の整数を表す］
で表されるテトラカルボン酸無水物由来の構成単位（ａ２）である、〔１〕又は〔２〕に記載のポリイミド系樹脂前駆体。
〔４〕 前記構成単位（Ｂ１）は、式（ｂ１）：

［式（ｂ１）中、Ｒ^ｂ１は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｐは０～４の整数を表す］
で表されるジアミン由来の構成単位（ｂ１）である、〔１〕～〔３〕のいずれかに記載のポリイミド系樹脂前駆体。
〔５〕 前記構成単位（Ｂ）は、式（ｂ２）：

［式（ｂ２）中、Ｒ^ｂ２は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
Ｗは、互いに独立に、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＣＯＯ－、－ＯＯＣ－、－ＳＯ_２－、－Ｓ－、－ＣＯ－又は－Ｎ（Ｒ^ｃ）－を表し、Ｒ^ｃは水素原子、ハロゲン原子で置換されていてもよい炭素数１～１２の一価の炭化水素基を表し、
ｍは１～４の整数であり、
ｑは互いに独立に、０～４の整数を表す］
で表されるジアミン由来の構成単位（ｂ２）をさらに含む、〔１〕～〔４〕のいずれかに記載のポリイミド系樹脂前駆体。
〔６〕 前記構成単位（ｂ２）中、ｍが３であり、Ｗが互いに独立に、－Ｏ－又は－Ｃ（ＣＨ_３）_２－である、〔５〕に記載のポリイミド系樹脂前駆体。
〔７〕 〔１〕～〔６〕のいずれかに記載のポリイミド系樹脂前駆体から得られるポリイミド系樹脂。
〔８〕 ガラス転移温度は２００～２９０℃である、〔７〕に記載のポリイミド系樹脂。
〔９〕 ２８０℃における貯蔵弾性率は３×１０^８Ｐａ未満である、〔７〕又は〔８〕に記載のポリイミド系樹脂。
〔１０〕 〔７〕～〔９〕のいずれかに記載のポリイミド系樹脂を含むポリイミド系フィルム。
〔１１〕 １０ＧＨｚにおける誘電正接は０．００４以下である、〔１０〕に記載のポリイミド系フィルム。
〔１２〕 〔１０〕又は〔１１〕に記載のポリイミド系フィルムの片面又は両面に金属箔層を含む積層フィルム。
〔１３〕 〔１０〕又は〔１１〕に記載のポリイミド系フィルムを含むフレキシブルプリント回路基板。 [1] A polyimide resin precursor containing a structural unit (A) derived from a tetracarboxylic anhydride and a structural unit (B) derived from a diamine,
The structural unit (A) includes a structural unit (A1) derived from an ester bond-containing tetracarboxylic anhydride and a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic anhydride,
The structural unit (A) has the formula (X):
(Content of structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2))/(total amount of structural unit (A1) and structural unit (A2)) <0.67 (X)
satisfy the relationship of
The structural unit (B) contains a structural unit (B1) derived from a biphenyl skeleton-containing diamine, and the content of the structural unit (B1) exceeds 30 mol% relative to the total amount of the structural unit (B),
A polyimide-based resin precursor, wherein the polystyrene-equivalent weight-average molecular weight of the polyimide-based resin precursor is greater than 100,000.
[2] The structural unit (A1) has the formula (a1):

[In the formula (a1), Z represents a divalent organic group,
R ^a1 each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
s independently represents an integer of 0 to 3]
The polyimide resin precursor according to [1], which is a structural unit (a1) derived from a tetracarboxylic anhydride represented by:
[3] The structural unit (A2) has the formula (a2):

[In the formula (a2), R ^a2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
t independently represents an integer of 0 to 3]
The polyimide resin precursor according to [1] or [2], which is a structural unit (a2) derived from a tetracarboxylic anhydride represented by:
[4] The structural unit (B1) has the formula (b1):

[In the formula (b1), each R ^b1 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
p represents an integer from 0 to 4]
The polyimide resin precursor according to any one of [1] to [3], which is a diamine-derived structural unit (b1) represented by:
[5] The structural unit (B) has the formula (b2):

[In the formula (b2), each R ^b2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
W are independently of each other -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, —COO—, —OOC—, —SO ₂ —, —S—, —CO— or —N(R ^c )—, where R ^c is a hydrogen atom or has 1 to 1 carbon atoms optionally substituted with a halogen atom represents 12 monovalent hydrocarbon radicals,
m is an integer from 1 to 4,
q independently represents an integer of 0 to 4]
The polyimide resin precursor according to any one of [1] to [4], further comprising a diamine-derived structural unit (b2) represented by:
[6] The polyimide resin precursor according to [5], wherein in the structural unit (b2), m is 3, and W is independently -O- or -C(CH ₃ ) ₂ -.
[7] A polyimide resin obtained from the polyimide resin precursor according to any one of [1] to [6].
[8] The polyimide resin according to [7], which has a glass transition temperature of 200 to 290°C.
[9] The polyimide resin according to [7] or [8], which has a storage modulus of less than 3×10 ⁸ Pa at 280°C.
[10] A polyimide film containing the polyimide resin according to any one of [7] to [9].
[11] The polyimide film of [10], which has a dielectric loss tangent of 0.004 or less at 10 GHz.
[12] A laminated film comprising a metal foil layer on one or both sides of the polyimide film of [10] or [11].
[13] A flexible printed circuit board comprising the polyimide film of [10] or [11].

According to the present invention, it is possible to provide a polyimide resin precursor capable of forming a polyimide film having a low Df and excellent bending resistance even when the thermal imidization temperature is low.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the gist of the present invention.

[Polyimide resin precursor]
The polyimide resin precursor of the present invention includes a tetracarboxylic anhydride-derived structural unit (A) (hereinafter, sometimes simply referred to as a structural unit (A)) and a diamine-derived structural unit (B) (hereinafter, simply , sometimes abbreviated as a structural unit (B)), and the structural unit (A) is a structural unit (A1) derived from an ester bond-containing tetracarboxylic anhydride (hereinafter simply abbreviated as a structural unit (A1) ) and a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic anhydride (hereinafter sometimes simply referred to as structural unit (A2)), wherein structural unit (A) is represented by formula (X): (Content of structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2))/(Total amount of structural unit (A1) and structural unit (A2)) <0.67 The relationship of (X) is satisfied, and the structural unit (B) includes a structural unit (B1) derived from a biphenyl skeleton-containing diamine (hereinafter sometimes simply referred to as the structural unit (B1)), and the structural unit (B1) The content of exceeds 30 mol% with respect to the total amount of the structural unit (B), and the polystyrene-equivalent weight average molecular weight of the polyimide resin precursor of the present invention (hereinafter, the weight average molecular weight may be referred to as Mw) is greater than 100,000.
In this specification, polyimide may be referred to as PI. In the present invention, "structural unit derived" means "structural unit derived", for example, "structural unit (A) derived from tetracarboxylic anhydride" refers to "structural unit derived from tetracarboxylic anhydride ( A)”.

The present inventors found that in the PI-based resin precursor, the structural unit (A) satisfies the relationship of formula (X), the content of the structural unit (B1) exceeds 30 mol%, and Mw is 100,000 It has been found that when the ratio is larger, a PI-based resin precursor can be obtained that can form a PI-based film having a low Df and excellent bending resistance even if the thermal imidization temperature is low. This is because when the structural unit (A) satisfies the relationship of the formula (X), the content of the structural unit (B1) is within the above range, and Mw is within the above range, the PI-based resin precursor is thermally imidized. When obtaining a PI-based resin by means of heat treatment, even if the thermal imidization temperature is low, the amic acid site and the imide site tend to move simultaneously to form a higher-order structure, and the resulting PI-based resin has a molecular chain as a whole. It is presumed that this is because it becomes easier to form a preferable higher-order structure with suppressed rotation, so that the rotation of the polar groups in the PI-based resin is suppressed, and the loss of electrical energy as thermal motion is reduced. Therefore, the PI-based resin precursor of the present invention can form a PI-based film capable of reducing Df while maintaining excellent bending resistance even when the thermal imidization temperature is low.

The structural unit (A) contained in the PI-based resin precursor has the formula (X):
(Content of structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2))/(Total amount of structural unit (A1) and structural unit (A2)) <0.67 (X)
that is, the value of the left side of the formula (X) is less than 0.67. Therefore, since the imide group concentration of the PI-based resin obtained from the PI-based resin precursor of the present invention tends to decrease, the moisture absorption resistance of the obtained PI-based resin is improved, and the Df of the obtained PI-based film is reduced. As a result, even if the imidization temperature of the PI-based resin is low, the Df of the resulting PI-based film can be easily reduced.

In one embodiment of the present invention, the value of the left side of the formula (X) is preferably 0.6 from the viewpoint of easily reducing the Df of the PI-based film even if the imidization temperature is low and easily improving the mechanical properties. Below, it is more preferably 0.5 or less, still more preferably 0.4 or less, even more preferably 0.3 or less, and particularly preferably 0.20 or less. Moreover, the lower limit of the value of the left side of the formula (X) is not particularly limited, and may be 0 or more.

The denominator on the left side of the formula (X), that is, the total amount of the structural units (A1) and (A2) with respect to the total amount of the structural units (A) is not particularly limited as long as the formula (X) is satisfied. From the viewpoint of easily reducing the Df of the PI film obtained even at a low temperature and easily improving the bending resistance, it is preferably 50 mol% or more, more preferably 50 mol% or more, relative to the total amount of the structural units (A). is 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and particularly preferably 90 mol % or more. Moreover, the upper limit of the total amount of the structural unit (A1) and the structural unit (A2) is not particularly limited, and may be, for example, 100 mol % or less. The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The molecule on the left side of the formula (X), that is, the structural unit (A3) derived from a tetracarboxylic anhydride other than the structural unit (A1) and the structural unit (A2) relative to the total amount of the structural units (A) (hereinafter simply referred to as structural The content of the units (sometimes abbreviated as units (A3)) is not particularly limited as long as it satisfies the formula (X). is 40 mol% or less, more preferably 35 mol% or less, still more preferably 30 mol% or less, particularly preferably 25 mol% or less, particularly preferably 20 mol% or less, and even more preferably 15% or less, and , preferably 0 mol % or more, more preferably 0.01 mol % or more, still more preferably 10 mol % or more. When the content of the structural unit (A3) is within the above range, the resulting PI-based resin tends to be oriented, so the Df of the resulting PI-based film tends to decrease, and the bending resistance tends to improve.
The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.
In the present specification, the “structural unit (A3) derived from a tetracarboxylic anhydride other than the structural unit (A1) and the structural unit (A2)” refers to any of the structural unit (A1) and the structural unit (A2). means a structural unit derived from a tetracarboxylic anhydride that does not correspond to the do.

The content of the structural unit (B1), preferably the structural unit (b1) described later, is from the viewpoint of easily reducing the Df of the PI-based film obtained even when the imidization temperature is low and improving the bending resistance. , more than 30 mol%, preferably 35 mol% or more, more preferably 40 mol% or more, still more preferably 60 mol% or more, still more preferably 70 mol% or more, relative to the total amount of the structural units (B); Especially preferably 80 mol % or more, particularly more preferably 90 mol % or more. The upper limit of the content of the structural unit (B1), preferably the structural unit (b1) described below, is not particularly limited, and may be 100 mol % or less based on the total amount of the structural units (B). The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

Mw of the PI-based resin precursor is greater than 100,000, preferably 110,000 or more, more preferably 110,000 or more in terms of polystyrene, from the viewpoint of easily reducing the Df of the resulting PI-based film and easily improving the bending resistance. 120,000 or more, more preferably 130,000 or more, and particularly preferably 140,000 or more. In addition, from the viewpoint of workability during film formation, the , 000 or less.

The ratio (Mw/Mn) between Mw and the number average molecular weight (hereinafter, the number average molecular weight may be referred to as Mn) of the PI-based resin precursor is preferably in terms of polystyrene from the viewpoint of easily improving bending resistance. is 3.5 or more, more preferably 4.0 or more, still more preferably 4.2 or more, even more preferably 4.5 or more, particularly preferably 4.7 or more, preferably 8.0 or less, more preferably is 7.0 or less, more preferably 6.0 or less, and particularly preferably 5.5 or less.
In addition, Mw and Mn can be obtained by performing gel permeation chromatography (hereinafter sometimes referred to as GPC) measurement and converting to standard polystyrene, for example, by the method described in Examples.

<Structural unit (A) derived from tetracarboxylic anhydride>
The PI-based resin precursor of the present invention contains a structural unit (A) derived from tetracarboxylic anhydride.

(Structural Unit (A1) Derived from Ester Bond-Containing Tetracarboxylic Anhydride)
The structural unit (A) contains a structural unit (A1) derived from an ester bond-containing tetracarboxylic anhydride. When the structural unit (A) contains the structural unit (A1), an ester bond having molecular orientation is incorporated into the PI-based resin precursor. It is easily oriented in the step of imidizing the film, and the Df of the resulting PI-based film is easily reduced even when the imidization temperature is low. In addition, since the ester bond site can rotate and maintain flexibility, the bending resistance of the resulting PI-based film can be easily improved, and the coefficient of linear expansion (hereinafter sometimes referred to as CTE) can be reduced. It is easy to improve the dimensional stability of the PI-based film.

［式（ａ１）中、Ｚは２価の有機基を表し、
Ｒ^ａ１は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｓは互いに独立に、０～３の整数を表す］
で表されるテトラカルボン酸無水物由来の構成単位（ａ１）であることが好ましい。 In one embodiment of the present invention, the structural unit (A1) is not particularly limited as long as it contains an ester bond, and the number of ester bonds contained in the structural unit (A1) may be one or two or more. Although it may be, even if the imidization temperature is low, the Df of the resulting PI-based film is easily reduced and the bending resistance is easily improved, the formula (a1):

[In the formula (a1), Z represents a divalent organic group,
R ^a1 each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
s independently represents an integer of 0 to 3]
It is preferably a structural unit (a1) derived from a tetracarboxylic anhydride represented by.

R ^a1 in formula (a1) independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom, and even if the imidization temperature is low, From the viewpoint of easily reducing the Df of the resulting PI-based film, each independently preferably represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms.
Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2- Examples include methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group and the like.
Alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy and hexyloxy groups. and a cyclohexyloxy group.
Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group and biphenyl group.
The hydrogen atoms contained in R ^a1 may be independently substituted with halogen atoms, and examples of the halogen atoms include fluorine, chlorine, bromine and iodine atoms.
Among these, from the viewpoint of easily reducing the Df of the PI film even when the imidization temperature is low, each R ^a1 is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms. includes an alkyl group having 1 to 3 carbon atoms.
Each s in formula (a1) independently represents an integer of 0 to 3, preferably 0 or 1, more preferably 0.

［式（ｚ１）～式（ｚ３）中、Ｒ^ｚ１１～Ｒ^ｚ１４は、互いに独立に、水素原子、又はハロゲン原子を有してもよい１価の炭化水素基を表し、
Ｒ^ｚ２は、互いに独立に、ハロゲン原子を有してもよい１価の炭化水素基を表し、
ｎは１～４の整数を表し、
ｊは、互いに独立に、０～３の整数を表し、
＊は結合手を表す］
で表される２価の有機基であることが好ましく、式（ｚ１）で表される２価の有機基であることがより好ましい。 Z in the formula (a1) represents a divalent organic group, and the divalent organic group preferably represents a divalent organic group having 4 to 40 carbon atoms, more preferably having a cyclic structure and having 4 to 4 carbon atoms. It represents a 40 divalent organic group, more preferably an aromatic ring-containing divalent organic group having 4 to 40 carbon atoms. Among these, even if the imidization temperature is low, from the viewpoint of easily reducing the Df of the resulting PI-based film, Z is the formula (z1), the formula (z2), the formula (z3):

[In the formulas (z1) to (z3), R ^z11 to R ^z14 each independently represent a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom,
R ^z2 each independently represents a monovalent hydrocarbon group optionally having a halogen atom,
n represents an integer of 1 to 4,
j independently represents an integer of 0 to 3,
* represents a bond]
is preferably a divalent organic group represented by the formula (z1), and more preferably a divalent organic group represented by the formula (z1).

In one embodiment of the present invention, R ^z11 to R ^z14 in formula (z1) each independently represent a hydrogen atom or a monovalent hydrocarbon group optionally having a halogen atom.
Examples of monovalent hydrocarbon groups include aromatic hydrocarbon groups, alicyclic hydrocarbon groups and aliphatic hydrocarbon groups.
The aromatic hydrocarbon group includes aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenyl group.
The alicyclic hydrocarbon group includes cycloalkyl groups such as cyclopentyl group and cyclohexyl group.
Examples of aliphatic hydrocarbon groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3 -methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group and the like.
Halogen atoms include those described above.
R ^z11 to R ^z14 are each independently from the viewpoint of easily reducing the Df of the PI film even when the imidization temperature is low, preferably a hydrogen atom, or an alkyl group optionally having a halogen atom, and more Preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms which may have a halogen atom, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a halogen atom, particularly preferably represents a hydrogen atom.

In one embodiment of the present invention, the benzene ring having R z11 to R z14 ⁱⁿ formula (z1) has R ^z11 to R ^z14 from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature ^is low. may be a monovalent hydrocarbon group which may have a halogen atom, but all of R ^z11 to R ^z14 are preferably hydrogen atoms.

In the formula (z1), n represents an integer of 1 to 4, preferably an integer of 1 to 3, more preferably 1 or represents 2, particularly preferably 2;

In one embodiment of the present invention, R ^z2 in formula (z2) each independently represents a monovalent hydrocarbon group which may have a halogen atom, and examples of the monovalent hydrocarbon group include are listed. From the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, R ^z2 independently of each other preferably has an alkyl group which may have a halogen atom, more preferably has a halogen atom. represents an alkyl group having 1 to 6 carbon atoms which may optionally have a halogen atom, more preferably an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

Each j in the formula (z2) independently represents 0 to 3. In one embodiment of the present invention, j is independently of each other, preferably 0 or 1, more preferably 0, and still more preferably from the viewpoint of easily reducing the Df of the PI film even when the imidization temperature is low. are all 0.

で表されることが好ましい。ＰＩ系樹脂前駆体が、構成単位（Ａ１）として、式（ａ１）、特に式（ａ１’）又は式（ａ１”）で表されるテトラカルボン酸無水物由来の構成単位を含むと、イミド化温度が低温であっても、得られるＰＩ系フィルムのＤｆを低減しやすく、屈曲耐性を向上しやすい。 In one preferred embodiment of the invention, formula (a1) is represented by formula (a1′) or formula (a1″):

is preferably represented by When the PI-based resin precursor contains a structural unit derived from a tetracarboxylic anhydride represented by the formula (a1), particularly the formula (a1′) or the formula (a1″) as the structural unit (A1), imidization Even if the temperature is low, the Df of the resulting PI-based film is likely to be reduced, and the bending resistance is likely to be improved.

In one embodiment of the present invention, the content of the structural unit (A1) is preferably 10 mol% or more, more preferably 15 mol% or more, still more preferably 20 mol%, relative to the total amount of the structural units (A). Above, more preferably 30 mol % or more, particularly preferably 35 mol % or more, particularly preferably 40 mol % or more. The content of the structural unit (A1) is preferably 75 mol% or less, more preferably 70 mol% or less, still more preferably 65 mol% or less, particularly preferably 60 mol% or less, relative to the total amount of the structural units (A). mol% or less. When the content of the structural unit (A1) is within the above range, the resulting PI-based resin is likely to be oriented, the Df of the resulting PI-based film is likely to be reduced, and the bending resistance is likely to be improved. The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

(Structural Unit (A2) Derived from Biphenyl Skeleton-Containing Tetracarboxylic Anhydride)
The structural unit (A) contains a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic anhydride. When the structural unit (A) contains the structural unit (A2), the Df of the resulting PI-based film can be easily reduced and the bending resistance can be easily improved even if the imidization temperature is low.

In one embodiment of the present invention, the structural unit (A2) is not particularly limited as long as it contains a biphenyl skeleton, and the number of biphenyl skeletons contained in the structural unit (A2) may be one or two or more. There may be. In one embodiment of the present invention, the structural unit (A2) is preferably a structural unit that contains a biphenyl skeleton and does not contain an ester bond. The structural unit derived from the tetracarboxylic anhydride is classified not as the structural unit (A2) but as the structural unit (A1) derived from the ester bond-containing tetracarboxylic anhydride.

［式（ａ２）中、Ｒ^ａ２は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｔは、互いに独立に、０～３の整数を表す］
で表されるテトラカルボン酸無水物由来の構成単位（ａ２）であることが好ましい。 In one embodiment of the invention, building block (A2) has the formula (a2):

[In the formula (a2), R ^a2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
t independently represents an integer of 0 to 3]
It is preferably a structural unit (a2) derived from a tetracarboxylic anhydride represented by.

R ^a2 in formula (a2) each independently represent a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom, and even if the imidization temperature is low, From the viewpoint of easily reducing the Df of the resulting PI-based film and easily improving the bending resistance, preferably independently of each other, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or 6 to 12 carbon atoms represents an aryl group of Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms are exemplified above. The hydrogen atoms contained in R ^a2 may be independently substituted with halogen atoms, and the halogen atoms are exemplified above. Among these, even if the imidization temperature is low, the Df of ^the resulting PI-based film can be easily reduced and the bending resistance can be easily improved. is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred.
Each t in formula (a2) independently represents an integer of 0 to 3, preferably 0 or 1, more preferably 0.

The bonding positions of the two carboxylic acid anhydrides bonded to the benzene ring constituting the biphenyl skeleton in formula (a2) are not particularly limited, and based on the single bond bonding the two benzene rings, 3, 4 -, or may be 2,3-, even if the imidization temperature is low, it is easy to reduce the Df of the resulting PI-based film, and from the viewpoint of easily improving the bending resistance, it is 3,4- Preferably.

で表されることが好ましい。ＰＩ系樹脂前駆体が、構成単位（Ａ２）として、式（ａ２）、特に式（ａ２’）で表されるテトラカルボン酸無水物由来の構成単位を含むと、イミド化温度が低温であっても、得られるＰＩ系フィルムのＤｆを低減しやすく、屈曲耐性を向上しやすい。 In one preferred embodiment of the invention, formula (a2) is represented by formula (a2′):

is preferably represented by When the PI-based resin precursor contains a structural unit derived from a tetracarboxylic anhydride represented by formula (a2), particularly formula (a2'), as the structural unit (A2), the imidization temperature is low. Also, the Df of the resulting PI-based film is likely to be reduced, and the bending resistance is likely to be improved.

In one embodiment of the present invention, the content of the structural unit (A2) is preferably 25 mol% or more, more preferably 30 mol% or more, still more preferably 35 mol%, relative to the total amount of the structural units (A). More preferably, it is 40 mol % or more. The content of the structural unit (A2) is preferably 90 mol% or less, more preferably 85 mol% or less, even more preferably 80 mol% or less, still more preferably It is 70 mol % or less, particularly preferably 60 mol % or less. When the content of the structural unit (A2) is within the above range, the orientation of the PI-based resin tends to occur, and the Df of the PI-based film tends to decrease. The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

(Constituent unit (A3))
In one embodiment of the present invention, the structural unit (A) may contain a tetracarboxylic anhydride-derived structural unit (A3) other than the structural unit (A1) and the structural unit (A2).

［式（１）中、Ｙは、式（３１）～式（３８）：

〔式（３１）～式（３８）中、Ｒ^１９～Ｒ^２６及びＲ^２３’～Ｒ^２６’は、互いに独立に、水素原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基又は炭素数６～１２のアリール基を表し、Ｒ^１９～Ｒ^２６及びＲ^２３’～Ｒ^２６’に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｖ^１及びＶ^２は、互いに独立に、単結合（ただし、ｅ＋ｄ＝１のときを除く）、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＳＯ_２－、－Ｓ－、－ＣＯ－、－Ｎ（Ｒ^ｊ）－、又は式（ａ）

（式（ａ）中、Ｒ^２７～Ｒ^３０は、互いに独立に、水素原子又は炭素数１～６のアルキル基を表し、
Ｄは互いに独立に、単結合、－Ｃ（ＣＨ_３）_２－又は－Ｃ（ＣＦ_３）_２－を表し、
ｉは１～３の整数を表し、
＊は結合手を表す）を表し、
Ｒ^ｊは、水素原子、又はハロゲン原子で置換されていてもよい炭素数１～１２の一価の炭化水素基を表し、
ｅ及びｄは、互いに独立に、０～２の整数を表し（ただし、ｅ＋ｄは０ではない）、
ｆは０～３の整数を表し、
ｇ及びｈは、互いに独立に、０～４の整数を表し、
＊は結合手を表す〕
で表される４価の有機基を表す］
で表されるテトラカルボン酸無水物由来の構成単位が挙げられる。 In one embodiment of the present invention, the structural unit (A3) is a structural unit derived from a tetracarboxylic anhydride containing neither an ester bond nor a biphenyl skeleton, such as formula (1):

[In formula (1), Y represents formulas (31) to (38):

[In the formulas (31) to (38), R ¹⁹ to R ²⁶ and R ^23′ to R ^26′ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, hydrogen atoms contained in R ¹⁹ to R ²⁶ and R ^23′ to R ^26′ may be independently substituted with halogen atoms,
V ¹ and V ² are each independently a single bond (except when e+d=1), -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, —SO ₂ —, —S—, —CO—, —N(R ^j )—, or formula (a)

(In formula (a), R ²⁷ to R ³⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
D each independently represents a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -;
i represents an integer of 1 to 3,
* represents a bond),
R ^j represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
e and d independently represent an integer of 0 to 2 (provided that e + d is not 0);
f represents an integer from 0 to 3,
g and h independently represent an integer of 0 to 4,
* represents a bond]
represents a tetravalent organic group represented by]
A structural unit derived from a tetracarboxylic anhydride represented by is mentioned.

In formulas (31) to (33), R ¹⁹ to R ²⁶ and R ^23′ to R ^26′ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. or represents an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms are exemplified above. Hydrogen atoms contained in R ¹⁹ to R ²⁶ and R ^23′ to R ^26′ may be independently substituted with halogen atoms, and halogen atoms include those exemplified above. Among these, R ¹⁹ to R ²⁶ and R ^23′ to R ^26′ are each independently a hydrogen atom or a An alkyl group is preferred, a hydrogen atom or an alkyl group having 1 to 3 carbon atoms is more preferred, and a hydrogen atom is even more preferred. Mechanical properties mean mechanical properties including bending resistance and elastic modulus, and improving mechanical properties means, for example, increasing bending resistance and/or elastic modulus. In addition, thermal properties mean thermal properties including glass transition temperature (hereinafter sometimes referred to as Tg), CTE, little denaturation and deterioration due to heat, and little deformation after heating. Improving physical properties means, for example, increasing Tg and/or decreasing CTE.

In formula (31), V ¹ and V ² are each independently a single bond (except when e+d=1), -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH (CH ₃ )—, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, —SO ₂ —, —S—, —CO—, —N(R ^j )— or formula (a) From the viewpoint of easily improving the mechanical properties and thermophysical properties of the PI-based film, preferably a single bond (except when e + d = 1), -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -CO-, more preferably a single bond (except when e + d = 1), -O-, -C(CH ₃ ) ₂ - or -C( represents CF ₃ ) ₂ -. R ^j represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n- pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group and n-decyl group etc., which may be substituted with a halogen atom. Halogen atoms include those mentioned above.

In formula (31), e and d independently represent an integer of 0 to 2 (however, e + d is not 0), and even if the imidization temperature is low, the Df of the PI-based film is easily reduced. From the point of view, it preferably represents 0 or 1. Also, e+d preferably represents 1. In formula (31), when e is 0, it means that the two benzene rings are not bonded at ^V1 , and when d is 0, the two benzene rings are not bonded at ^V2 . indicates that

In the formulas (32) and (33), f represents an integer of 0 to 3, preferably 0 or 1, more preferably 0 or 1, more preferably from the viewpoint of easily reducing the Df of the PI-based film even if the imidization temperature is low. represents 0.

In formula (33), g and h each independently represent an integer of 0 to 4, preferably an integer of 0 to 2, more preferably an integer from the viewpoint of easily improving the mechanical properties and thermophysical properties of the PI-based film. Represents 0 or 1. Also, g+h preferably represents an integer of 0-2. In addition, when f is 1 or more, a plurality of g and h may be the same or different independently of each other.

In formula (a), R ²⁷ to R ³⁰ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms are exemplified above. Among these, from the viewpoint of easily improving the mechanical properties and thermophysical properties of the PI-based film, R ²⁷ to R ³⁰ each independently preferably represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably represents a hydrogen atom.

In formula (a), D represents a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -. When D has such a structure, the mechanical properties and thermophysical properties of the PI-based film are likely to be improved. i represents an integer of 1 to 3, preferably 1 or 2 from the viewpoint of easily improving the mechanical properties and thermophysical properties of the PI film. When i is 2 or more, a plurality of D and R ²⁷ to R ³⁰ may be independently the same or different.

で表されるテトラカルボン酸無水物由来の構成単位、より好ましくは式（１）中のＹが式（４２）、式（４３）、式（４６）、式（４９）又は式（５３）で表されるテトラカルボン酸無水物由来の構成単位、さらに好ましくは式（１）中のＹが式（４２）、式（４６）、式（４９）又は式（５３）で表されるテトラカルボン酸無水物由来の構成単位である。なお、これらの式中、＊は結合手を表す。 Among these, even if the imidization temperature is low, the Df of the resulting PI-based film can be easily reduced and the bending resistance can be easily improved. Formula (49) or Formula (53):

A structural unit derived from a tetracarboxylic anhydride represented by, more preferably Y in formula (1) is formula (42), formula (43), formula (46), formula (49) or formula (53) A structural unit derived from a tetracarboxylic anhydride represented, more preferably a tetracarboxylic acid in which Y in formula (1) is represented by formula (42), formula (46), formula (49) or formula (53) It is a structural unit derived from an anhydride. In these formulas, * represents a bond.

<Structural unit (B) derived from diamine>
The PI-based resin precursor of the present invention contains a structural unit (B) derived from diamine.

(Structural Unit (B1) Derived from Biphenyl Skeleton-Containing Diamine)
The structural unit (B) contains a structural unit (B1) derived from a biphenyl skeleton-containing diamine. The PI-based resin precursor in which the structural unit (B) contains the structural unit (B1) has a low imidization temperature, but the Df of the resulting PI-based film is likely to be reduced. The circuit tends to reduce transmission loss. Further, when the structural unit (B) contains the structural unit (B1), the bending resistance of the obtained PI-based film is likely to be improved.

［式（ｂ１）中、Ｒ^ｂ１は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
ｐは０～４の整数を表す］
で表されるジアミン由来の構成単位（ｂ１）であることが好ましい。 In one embodiment of the present invention, the structural unit (B1) is not particularly limited as long as it contains a biphenyl skeleton, and the number of biphenyl skeletons contained in the structural unit (B1) may be one or two or more. There may be. In one embodiment of the present invention, the structural unit (B1) easily reduces the Df of the PI film obtained even if the imidization temperature is low, and from the viewpoint of easily improving the bending resistance, the formula (b1) :

[In the formula (b1), each R ^b1 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
p represents an integer from 0 to 4]
It is preferably a diamine-derived structural unit (b1) represented by.

In formula (b1), each R ^b1 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, preferably a halogen atom or a halogen atom. may be an alkyl group, an alkoxy group or an aryl group, more preferably a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. The hydrogen atoms contained in R ^b1 may be independently substituted with halogen atoms, and examples of the halogen atoms include those exemplified above. From the viewpoint of easily reducing the Df of the resulting PI-based film and easily improving the bending resistance and dimensional stability, R ^b1 is independently an alkyl group having 1 to 6 carbon atoms or an alkyl fluoride having 1 to 6 carbon atoms. is preferably a group, and from the viewpoint of easily improving adhesion to a substrate such as a copper foil, it is more preferably an alkyl group having 1 to 6 carbon atoms that does not contain fluorine, and 1 to 1 carbon atoms that do not contain fluorine. An alkyl group of 3 is more preferred, and a methyl group is particularly preferred.

In formula (b1), p represents an integer of 0 to 4 independently of each other, and is preferably an integer of 0 to 2 from the viewpoint of easily reducing the Df of the PI-based film and easily increasing bending resistance and dimensional stability. , more preferably 0 or 1.

In formula (b1), the —NH ₂ group bonded to each benzene ring is ortho-, meta-, or para-position, or α-position, β-position, or It may be bound to any of the γ-positions, and from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, and from the viewpoint of easily increasing the dimensional stability, preferably the meta-position or the para-position, Alternatively, it can be bound at the β- or γ-position, more preferably at the para- or γ-position.

で表されることが好ましい。ＰＩ系樹脂前駆体が、構成単位（Ｂ１）として、式（ｂ１）、特に式（ｂ１’）で表されるジアミン由来の構成単位を含むと、イミド化温度が低温であっても、得られるＰＩ系フィルムのＤｆが低減しやすく、屈曲耐性を向上しやすい。 In one preferred embodiment of the invention, formula (b1) is represented by formula (b1′):

is preferably represented by When the PI-based resin precursor contains a diamine-derived structural unit represented by the formula (b1), particularly the formula (b1′), as the structural unit (B1), the imidization temperature is low, even if it is obtained The Df of the PI-based film is likely to be reduced, and the bending resistance is likely to be improved.

(Constituent unit (B2))
In one embodiment of the present invention, the structural unit (B) has two or more aromatic rings, and each aromatic ring is bonded via a divalent organic group. Hereinafter, it is preferable to include a structural unit (B2), which may be simply abbreviated. Examples of the divalent organic group in the structural unit (B2) include an alkylene group optionally having a halogen atom, —O—, —COO—, —OOC—, —SO ₂ —, —S—, —CO - or -N(R ^c )-, etc., where R ^c represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Among these, the divalent organic group in the structural unit (B2) includes -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )- is preferred.

［式（ｂ２）中、Ｒ^ｂ２は、互いに独立に、ハロゲン原子、又はハロゲン原子を有してもよいアルキル基、アルコキシ基、アリール基若しくはアリールオキシ基を表し、
Ｗは、互いに独立に、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＣＯＯ－、－ＯＯＣ－、－ＳＯ_２－、－Ｓ－、－ＣＯ－又は－Ｎ（Ｒ^ｃ）－を表し、Ｒ^ｃは水素原子、ハロゲン原子で置換されていてもよい炭素数１～１２の一価の炭化水素基を表し、
ｍは１～４の整数を表し、
ｑは互いに独立に、０～４の整数を表す］
で表されるジアミン由来の構成単位（ｂ２）（以下、単に、構成単位（ｂ２）と略すことがある）、式（２）：

［式（２）中、Ｘは、式（６５）：

（式（６５）中、＊は結合手を表す）で表される２価の有機基を表す］
で表されるジアミン由来の構成単位等が挙げられる。これらの中でも、イミド化温度が低温であっても、得られるＰＩ系フィルムのＤｆが低減しやすく、屈曲耐性を向上しやすい観点から、構成単位（Ｂ２）は構成単位（ｂ２）であることが好ましい。構成単位（Ｂ）が構成単位（Ｂ２）、特に構成単位（ｂ２）を含むと、イミド化温度が低温であっても得られるＰＩ系フィルムのＤｆが低減しやすい結果、イミド化温度が低温であっても得られるＰＩ系フィルムを含んでなる電子回路の伝送損失を低減しやすく、また、得られるＰＩ系フィルムの屈曲耐性が向上しやすい。 As the structural unit (B2), the formula (b2):

[In the formula (b2), each R ^b2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
W are independently of each other -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, —COO—, —OOC—, —SO ₂ —, —S—, —CO— or —N(R ^c )—, where R ^c is a hydrogen atom or has 1 to 1 carbon atoms optionally substituted with a halogen atom represents 12 monovalent hydrocarbon radicals,
m represents an integer of 1 to 4,
q independently represents an integer of 0 to 4]
Structural unit (b2) derived from diamine represented by (hereinafter sometimes simply referred to as structural unit (b2)), formula (2):

[In the formula (2), X is the formula (65):

(in formula (65), * represents a bond) represents a divalent organic group]
Structural units derived from diamine represented by and the like. Among these, even if the imidization temperature is low, the Df of the resulting PI-based film is likely to be reduced, and the flex resistance is likely to be improved, so that the structural unit (B2) is the structural unit (b2). preferable. When the structural unit (B) contains the structural unit (B2), particularly the structural unit (b2), the Df of the PI film obtained even when the imidization temperature is low tends to be reduced, and the imidization temperature is low. Even if there is, the transmission loss of the electronic circuit containing the obtained PI-based film can be easily reduced, and the bending resistance of the obtained PI-based film can be easily improved.

In formula (b2), each R ^b2 independently represents a halogen atom, or an alkyl group optionally having a halogen atom, an alkoxy group, an aryl group or an aryloxy group, preferably a halogen atom having 1 to 6 alkyl group, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above. The hydrogen atoms contained in R ^b2 may be independently substituted with halogen atoms, and examples of the halogen atoms include those exemplified above. Even if the imidization temperature is low, it is easy to reduce the Df of the resulting PI-based film, and from the viewpoint of easy improvement in bending resistance and dimensional stability, R ^b2 is an alkyl group having 1 to 6 carbon atoms independently of each other. Alternatively, it is preferably a fluorinated alkyl group having 1 to 6 carbon atoms, and from the viewpoint of easily increasing adhesion to a substrate such as a copper foil, it is more preferable to be an alkyl group having 1 to 6 carbon atoms that does not contain fluorine. An alkyl group containing no fluorine and having 1 to 3 carbon atoms is preferred, and a methyl group is particularly preferred.

In formula (b2), q independently represents an integer of 0 to 4, and even if the imidization temperature is low, the Df of the resulting PI-based film is easily reduced, and the bending resistance and dimensional stability are improved. It is preferably an integer of 0 to 2, more preferably 0 or 1, from the viewpoint of easy increase.

In formula (b2), W each independently represents -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C( CF ₃ ) ₂ —, —COO—, —OOC—, —SO ₂ —, —S—, —CO— or —N(R ^c )—, and even if the imidization temperature is low, the resulting PI -O-, -CH ₂ -, -C(CH 3 ) 2 -, -C(CF ₃ ) ₂ -, -C(CF ₃ ) ₂ -, from the viewpoint of easily reducing the Df of the system film and easily increasing the bending resistance and dimensional stability. Represents -COO-, -OOC- or -CO-, and more preferably -O-, -CH ₂ - or -C(CH ₃ ) ₂ from the viewpoint of easily increasing adhesion to a substrate such as a copper foil. -, more preferably -O- or -C(CH ₃ ) ₂ -. ^Rc represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those exemplified above, and these may be substituted with a halogen atom. Halogen atoms include those mentioned above.

In the formula (b2), m is an integer of 1 to 4, and even if the imidization temperature is low, the Df of the resulting PI-based film can be easily reduced, and the bending resistance and dimensional stability can be easily improved. It is preferably an integer of 1-3, more preferably 2 or 3. In formula (b2), a plurality of W, R ^b2 , and q may be the same or different, and the positions of —W— relative to —NH ₂ of each benzene ring are also the same. There may be, and it may be different.

In formula (b2), -W- is bound at either the ortho-, meta-, or para-position, or the α-, β-, or γ-position relative to the _-NH2 of each benzene ring. Even if the imidization temperature is low, the Df of the resulting PI film can be easily reduced, and the bending resistance and dimensional stability can be easily improved. or γ-position, more preferably para- or γ-position.

で表されることがより好ましい。ＰＩ系樹脂前駆体が、構成単位（ｂ２）、特に式（ｂ２’）で表されるジアミン由来の構成単位を含むと、イミド化温度が低温であっても、Ｄｆが低く、かつ、銅箔等の金属箔との接着性に優れるＰＩ系フィルムを得やすい。 In one embodiment of the present invention, even if the imidization temperature is low, the Df of the resulting PI-based film is easily reduced, the bending resistance is easily improved, and the resulting PI-based film and metal such as copper foil From the viewpoint of easily improving the adhesiveness to the foil, in formula (b2), it is preferable that m is 3 and W independently represents -O- or -C(CH ₃ ) ₂ -, and the formula ( b2) is represented by the formula (b2′):

is more preferably represented by When the PI-based resin precursor contains the structural unit (b2), particularly the diamine-derived structural unit represented by the formula (b2′), even if the imidization temperature is low, Df is low and copper foil It is easy to obtain a PI-based film having excellent adhesiveness with metal foil such as.

In one embodiment of the present invention, the structural unit (b2) is a diamine-derived structural unit represented by formula (b2′), or in place of the structural unit, wherein m is 1 in formula (b2). and W may contain a diamine-derived structural unit representing —O—.

In one embodiment of the present invention, the content of the structural unit (B2) is preferably 0 mol% or more, more preferably 0.3 mol% or more, still more preferably 0 mol% or more, relative to the total amount of the structural units (B). 0.5 mol % or more, more preferably 0.8 mol % or more, particularly preferably 1 mol % or more, even more preferably 5 mol % or more, and even more preferably 8 mol % or more. When the content of the structural unit (B2) is at least the above lower limit, the adhesion of the resulting PI-based film to a substrate such as a copper foil is likely to be improved. The upper limit of the content of the structural unit (B2) is preferably 75 mol% or less, more preferably 60 mol% or less, still more preferably 40 mol% or less, and even more preferably, based on the total amount of the structural unit (B). is 30 mol % or less, particularly preferably 20 mol % or less. When the content of the structural unit (B2) is equal to or less than the above upper limit, mechanical properties such as CTE of the resulting PI-based film tend to be improved. The ratio of the structural units can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

［式（６１）中、Ｒ^ａ、Ｒ^ｂ、Ｗ、ｔ、ｕ及びｎは、互いに独立に、式（６０）中のＲ^ａ、Ｒ^ｂ、Ｗ、ｔ、ｕ及びｎと同様であり、
式（６２）中、環Ａは炭素数３～８のシクロアルカン環を表し、
Ｒ^ｄは炭素数１～２０のアルキル基を表し、
ｒは０以上であって、（環Ａの炭素数－２）以下の整数を表し、
Ｓ１及びＳ２は、互いに独立に、０～２０の整数を表し、
式（６１）～式（６４）中、＊は結合手を表す。］
で表されるジアミン由来の構成単位等が挙げられる。
本明細書において、「構成単位（Ｂ１）及び構成単位（Ｂ２）以外のジアミン由来の構成単位（Ｂ３）」とは、構成単位（Ｂ１）及び構成単位（Ｂ２）の何れとも異なるジアミン由来の構成単位を意味する。 (Constituent unit (B3))
In the PI-based resin precursor, as the structural unit (B), a structural unit (B3) derived from a diamine other than the structural unit (B1) and the structural unit (B2) (hereinafter sometimes simply referred to as the structural unit (B3)) may include As the structural unit (B3), for example, a structural unit derived from a diamine in which m is 0 in formula (b2), X in formula (2) is formula (61) to formula (64):

[In formula (61), R ^a , R ^b , W, t, u and n are independently the same as R ^a , R ^b , W, t, u and n in formula (60),
In formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms,
R ^d represents an alkyl group having 1 to 20 carbon atoms,
r is 0 or more and represents an integer of (the number of carbon atoms in ring A -2) or less,
S1 and S2 independently represent an integer from 0 to 20,
In formulas (61) to (64), * represents a bond. ]
Structural units derived from diamine represented by and the like.
In the present specification, the term “a diamine-derived structural unit (B3) other than the structural unit (B1) and the structural unit (B2)” refers to a diamine-derived structure different from both the structural unit (B1) and the structural unit (B2). means unit.

In formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms. The cycloalkane ring includes, for example, cyclopropane ring, cyclobutane ring, cyclopentane ring, cyclohexane ring, cycloheptane ring and cyclooctane ring, preferably a cycloalkane ring having 4 to 6 carbon atoms. In ring A, each bond may or may not be adjacent to each other. For example, when ring A is a cyclohexane ring, the two bonds may have a positional relationship of α-position, β-position or γ-position, preferably β-position or γ-position.

R ^d in formula (62) represents an alkyl group having 1 to 20 carbon atoms, preferably an alkyl group having 1 to 10 carbon atoms, examples of which include those exemplified above. r in formula (62) represents an integer of 0 or more and "the number of carbon atoms in ring A-2" or less. r is preferably 0 or more and preferably 4 or less. S1 and S2 in formula (62) each independently represent an integer of 0 to 20. S1 and S2 are each independently preferably 0 or more, more preferably 2 or more, and preferably 15 or less.

As specific examples of the structural unit (B3), X in formula (2) is represented by formula (71), formula (74), formula (77), formula (78), formula (89) and formula (90). Among these, a diamine-derived structural unit (p-phenylenediamine-derived structural unit) in which X in formula (2) is represented by formula (74) is preferable. In these formulas, * represents a bond.

In one embodiment of the present invention, when the structural unit (B) contains the structural unit (B3), the content of the structural unit (B3) is preferably 25 mol% or less with respect to the total amount of the structural units (B). , more preferably 20 mol % or less, still more preferably 10 mol % or less, and preferably 0.01 mol % or more.

In one embodiment of the present invention, the PI-based resin precursor may contain halogen atoms, preferably fluorine atoms, which can be introduced by, for example, the above halogen-containing atom substituents. When the PI-based resin precursor contains fluorine atoms, the dielectric constant of the resulting PI-based film is likely to be reduced. Preferred fluorine-containing substituents for allowing the PI-based resin precursor to contain fluorine atoms include, for example, a fluoro group and a trifluoromethyl group.
In another embodiment of the present invention, the PI-based resin precursor does not contain a fluorine atom from the viewpoint of easily increasing the adhesiveness of the obtained PI-based film to a base material such as a copper foil. is preferred. In addition, if the PI-based resin precursor contains fluorine, the interaction between molecular chains tends to be weakened. The rotation tends to be suppressed, the Df of the resulting PI-based film tends to decrease, and the bending resistance tends to improve.

When the PI-based resin precursor contains halogen atoms, the content of halogen atoms, particularly fluorine atoms, in the PI-based resin precursor is preferably 0.1 to 35% by mass based on the mass of the PI-based resin precursor. , more preferably 0.1 to 30% by mass, still more preferably 0.1 to 20% by mass, particularly preferably 0.1 to 10% by mass. When the halogen atom content is at least the above lower limit, the heat resistance and dielectric properties of the resulting PI-based film are likely to be enhanced. If the halogen atom content is equal to or less than the above upper limit, it is advantageous in terms of cost, the CTE of the PI-based film can be easily reduced, and the PI-based resin can be easily synthesized. Dielectric properties refer to dielectric properties including relative permittivity and dielectric loss tangent, and increased or improved dielectric properties indicate a decrease in relative permittivity and/or loss tangent.

[Method for producing polyimide resin precursor]
The PI-based resin precursor of the present invention is obtained by reacting a tetracarboxylic anhydride and a diamine. In addition to the tetracarboxylic acid compound, a dicarboxylic acid compound and a tricarboxylic acid compound may be reacted.

Tetracarboxylic acid anhydrides used in the synthesis of the PI-based resin precursor include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydrides; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydrides. acid compound; and the like. A tetracarboxylic acid compound may be used independently and may be used in combination of 2 or more type. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.
Examples of the tetracarboxylic acid compound include tetracarboxylic anhydrides represented by the above formula (1), preferably tetracarboxylic anhydrides represented by the formula (a1) and the tetracarboxylic anhydrides represented by the formula (a2). and tetracarboxylic anhydrides.

Specific examples of tetracarboxylic acid compounds include pyromellitic anhydride (hereinafter sometimes referred to as PMDA), 4,4'-(4,4'-isopropylidenediphenoxy) diphthalic anhydride (hereinafter referred to as BPADA ), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (hereinafter referred to as BPDA ), 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (hereinafter sometimes referred to as 6FDA), 4,4'-oxydiphthalic dianhydride (hereinafter referred to as ODPA) some), 2,2′,3,3′-, 2,3,3′,4′- or 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, 2,3′,3, 4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylene bis(trimellitic acid monoester dianhydride) (hereinafter referred to as TAHQ) an ester of trimellitic anhydride and 2,2′,3,3′,5,5′-hexamethyl-4,4′-biphenol (hereinafter sometimes referred to as TMPBP), 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl (hereinafter sometimes referred to as BP-TME), 2,3',3,4 '-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3",4,4"-p-terphenyltetracarboxylic dianhydride, 2,3, 3″,4″-p-terphenyltetracarboxylic dianhydride, 2,2″,3,3″-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxy phenyl)-propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-di carboxyphenyl)methane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2, 7,8-, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride, 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,2-bis(3,4-di carboxyphenyl)tetrafluoropropane dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (hereinafter sometimes referred to as HPMDA), 2,3,5,6-cyclohexanetetracarboxylic dianhydride anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride anhydride, 4,4′-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (hereinafter sometimes referred to as CBDA), norbornane-2-spiro-α'-spiro-2″-norbornane-5,5′,6,6′-tetracarboxylic anhydride, p-phenylenebis(trimellitate anhydride), 3,3′,4,4 '-diphenylsulfonetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1 , 2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8 -tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-2,3 ,6,7-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5,8-tetrachloronaphthalene -2,3,6,7-tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride , pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride and the like. Among these, BPDA, TAHQ, and BP-TME are preferable from the viewpoint of easily reducing the Df of the PI-based film obtained even at a low imidization temperature and easily improving the bending resistance. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

Examples of diamine compounds used for synthesizing PI-based resin precursors include aliphatic diamines, aromatic diamines, and mixtures thereof. In addition, in this embodiment, the “aromatic diamine” represents a diamine having an aromatic ring, and may contain an aliphatic group or other substituents in a part of its structure. This aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, benzene ring, naphthalene ring, anthracene ring, and fluorene ring. Among these, a benzene ring is preferred. The term "aliphatic diamine" refers to a diamine having an aliphatic group, which may contain other substituents in part of its structure, but does not have an aromatic ring.
The diamine compound includes, for example, the diamine compound represented by the above formula (2), preferably the diamine compound represented by the formula (b1) or the diamine compound represented by the formula (b2).

Specific examples of diamine compounds include 1,4-diaminocyclohexane, 4,4'-diamino-2,2'-dimethylbiphenyl (hereinafter sometimes referred to as m-Tb), 4,4'-diamino- 3,3'-dimethylbiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (hereinafter sometimes referred to as TFMB), 4,4'-diaminodiphenyl ether, 1,3 -Bis(3-aminophenoxy)benzene (hereinafter sometimes referred to as 1,3-APB), 1,4-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-Q) , 1,3-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (sometimes referred to as BAPP), 2,2′-dimethyl-4, 4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy) ]biphenyl, bis[4-(3-aminophenoxy)biphenyl, bis[1-(4-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy ) phenyl]methane, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, bis[4 -(4-aminophenoxy)]benzophenone, bis[4-(3-aminophenoxy)]benzophenone, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis- [4-(3-aminophenoxy)phenyl]hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6- diethylaniline, 4,4'-methylenedianiline, 3,3'-methylenedianiline, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3, 3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3, 3′-dimethoxybenzidine, 4,4″-diamino-p-terphenyl, 3,3″-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine (sometimes referred to as p-PDA) , resorcinol-bis(3-aminophenyl)ether, 4,4′-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4′-[1,3-phenylenebis(1-methylethylidene) )] bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-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-tert -butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, piperazine, 4,4' -diamino-2,2′-bis(trifluoromethyl)bicyclohexane, 4,4′-diaminodicyclohexylmethane, 4,4″-diamino-p-terphenyl, bis(4-aminophenyl)terephthalate, 1,4 -bis(4-aminophenoxy)-2,5-di-tert-butylbenzene, 4,4'-(1,3-phenylenediisopropylidene)bisaniline, 1,4-bis[2-(4-aminophenyl )-2-propyl]benzene, 2,4-diamino-3,5-diethyltoluene, 2,6-diamino-3,5-diethyltoluene, 4,4′-bis(3-aminophenoxy)biphenyl, 4, 4′-(Hexafluoropropylidene)dianiline, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,2- diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 2-methyl-1,2-diaminopropane, 2-methyl-1,3-diaminopropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, bis[4-(4-aminophenoxy)phenyl]sulfone , bis[4-(3-aminophenoxy)phenyl]sulfone, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene , 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 2,5-diamino-1,3,4-oxa diazole, bis[4,4'-(4-aminophenoxy)]benzanilide, bis[4,4'-(3-aminophenoxy)]benzanilide, 2,6-diaminopyridine, 2,5-diaminopyridine and the like mentioned. Among these, m-Tb, BAPP, TPE-Q, 1,3-bis ( 4-Aminophenoxy)benzene and the like are preferred, and m-Tb, BAPP and the like are more preferred. A diamine compound can be used individually or in combination of 2 or more types.

In addition to the tetracarboxylic acid compound used in the synthesis of the above PI-based resin precursor, the PI-based resin precursor of the present invention can be used in addition to other tetracarboxylic acids within a range that does not impair the various physical properties of the resulting PI-based film. , dicarboxylic acids and tricarboxylic acids, and their anhydrides and derivatives may be further reacted.

Other tetracarboxylic acids include water adducts of the above tetracarboxylic acid compound anhydrides.

Examples of dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, their analogous acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; compounds in which two benzoic acids are linked by a single bond, —O—, —CH ₂ —, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, —SO ₂ — or a phenylene group; acid chloride compounds.

Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, their analogous acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include anhydride of 1,2,4-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; a single bond between phthalic anhydride and benzoic acid; , —CH ₂ —, —C(CH ₃ ) ₂ —, —C(CF ₃ ) ₂ —, —SO ₂ — or compounds linked by a phenylene group.

In the production of the PI-based resin precursor, the amount of the diamine compound, tetracarboxylic acid compound, dicarboxylic acid compound and tricarboxylic acid compound used can be appropriately selected according to the desired ratio of each structural unit of the PI-based resin precursor.
In the present invention, the amine ratio is defined as the total number of moles of the diamine compound used per 1 mole of the total amount of the tetracarboxylic acid compound. In a preferred embodiment of the present invention, the amine ratio is preferably 0.90 mol or more and preferably 0.999 mol or less per 1 mol of the total amount of the tetracarboxylic acid compound. In another embodiment, the amine ratio is preferably 1.001 mol or more and preferably 1.10 mol or less with respect to 1 mol of the total amount of the tetracarboxylic acid compound.
In one embodiment of the present invention, when the amine ratio is 1 or less, the amine ratio is preferably 0.90 mol or more and 0.999 mol or less, more preferably 0.95 mol or more and 0.997 mol or less, even more preferably It is 0.97 mol or more and 0.995 mol or less.
In one embodiment of the present invention, when the amine ratio is 1 or more, the amine ratio is preferably 1.001 mol or more and 1.1 mol or less, more preferably 1.002 mol or more and 1.05 mol or less, even more preferably 1.003 mol or more and 1.03 mol or less When the amine ratio is close to 1.0 mol, there is a tendency for the molecular weight to increase rapidly during synthesis, and when the molecular weight of the PI resin obtained is significantly different from 1.0 mol tends to decline. If the molecular weight increases abruptly, it tends to grow unevenly in the synthetic mass, making it difficult to stabilize the physical properties of the PI-based resin obtained from the PI-based resin precursor. On the other hand, if the molecular weight is too low, the mechanical properties tend to deteriorate.

The reaction temperature between the diamine compound and the tetracarboxylic acid compound is preferably 50° C. or lower, more preferably 40° C. or lower, and even more preferably 30° C. or lower. When the reaction temperature is equal to or lower than the above upper limit, the Df of the resulting PI film is likely to be reduced, and the bending resistance is likely to be improved. This is particularly noticeable in a PI-based film containing a resin, particularly a PI-based resin obtained from a PI-based resin precursor containing the structural unit (A1). Also, the reaction temperature of the diamine compound and the tetracarboxylic acid compound is preferably 5° C. or higher, more preferably 10° C. or higher, and still more preferably 15° C. or higher. When the reaction temperature is equal to or higher than the above lower limit, there is a tendency that the reaction rate can be easily increased and the polymerization time can be shortened.
The reaction time is not particularly limited, and may be, for example, about 0.5 to 72 hours, preferably 3 to 24 hours. When the reaction time is within the above range, the Df of the resulting PI film can be easily reduced even if the imidization temperature is low.

The reaction between the diamine compound and the tetracarboxylic acid compound is preferably carried out in a solvent. The solvent is not particularly limited as long as it does not affect the reaction, but examples include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, alcohol solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; phenol solvents such as phenol and cresol; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate and ethyl lactate; Lactone solvents such as γ-butyrolactone (hereinafter sometimes referred to as GBL) and γ-valerolactone; Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone and methyl isobutyl ketone; Aliphatic hydrocarbon solvents such as hexane and heptane; Alicyclic hydrocarbon solvents such as ethylcyclohexane; Aromatic hydrocarbon solvents such as toluene and xylene; Nitrile solvents such as acetonitrile; Ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N,N-dimethylacetamide (hereinafter sometimes referred to as DMAc) and N,N-dimethylformamide (hereinafter sometimes referred to as DMF); sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; pyrrolidone-based solvents such as N-methylpyrrolidone (hereinafter sometimes referred to as NMP); and combinations thereof etc. Among these, from the viewpoint of solubility, phenolic solvents, lactone solvents, amide solvents, pyrrolidone solvents, and more preferably amide solvents can be suitably used.

In one embodiment of the present invention, the boiling point of the solvent used for the reaction of the diamine compound and the tetracarboxylic acid compound is such that even if the imidization temperature is low, the Df of the resulting PI-based film is easily reduced, and the bending resistance is improved. From the viewpoint of easy improvement, the temperature is preferably 230° C. or lower, more preferably 200° C. or lower, and even more preferably 180° C. or lower. Moreover, the boiling point of the solvent is preferably 100° C. or higher, more preferably 120° C. or higher, from the viewpoint of easily reducing the Df of the resulting PI-based film even if the imidization temperature is low.

The reaction between the diamine compound and the tetracarboxylic acid compound may be carried out under an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere or under reduced pressure conditions, if necessary, and an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. It is preferable to carry out the reaction in a strictly controlled dehydrated solvent while stirring.

The PI-based resin precursor may be separated and purified by a conventional method such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination thereof. Alternatively, the reaction liquid containing the PI-based resin precursor obtained by synthesizing the PI-based resin precursor may be used for the production of the PI-based resin without isolation.

[Polyimide resin]
The present invention also includes a PI-based resin obtained from the PI-based resin precursor of the present invention. As will be described later, the PI-based resin of the present invention is a PI-based resin obtained by imidating the above-mentioned PI-based resin precursor.

Since the PI-based resin of the present invention is obtained from the PI-based resin precursor of the present invention, each structural unit contained in the PI-based resin precursor of the present invention, such as the structural unit (A1), the structural unit (A2), the structural unit It contains the same structural unit as the unit (B1) etc. in the same content. Therefore, with respect to the types and contents of the structural units contained in the PI-based resin, the descriptions regarding the types and contents of the respective structural units in the section [Polyimide Resin Precursor] also apply.

In one embodiment of the present invention, the PI-based resin may contain halogen atoms, preferably fluorine atoms, which can be introduced by, for example, the above halogen-containing substituents. When the PI-based resin contains fluorine atoms, the dielectric constant of the resulting PI-based film is likely to be reduced. Preferred fluorine-containing substituents for allowing the PI resin to contain fluorine atoms include, for example, a fluoro group and a trifluoromethyl group.
Further, in another embodiment of the present invention, the PI-based resin preferably does not contain a fluorine atom from the viewpoint of easily increasing the adhesiveness of the obtained PI-based film to a substrate such as a copper foil. . Further, if the PI resin contains fluorine, it tends to weaken the interaction between molecular chains. Therefore, if it does not contain a fluorine atom, it is easy to form a higher-order structure in which the molecular rotation of the PI resin is suppressed, As a result, there is a tendency to obtain the effects of the present invention easily.

When the PI-based resin contains halogen atoms, the content of halogen atoms, particularly fluorine atoms, in the PI-based resin is preferably 0.1 to 35% by mass, more preferably 0.1 to 35% by mass, based on the mass of the PI-based resin. 1 to 30% by mass, more preferably 0.1 to 20% by mass, particularly preferably 0.1 to 10% by mass. When the halogen atom content is at least the above lower limit, the heat resistance and dielectric properties of the resulting PI-based film are likely to be enhanced. If the halogen atom content is equal to or less than the above upper limit, it is advantageous in terms of cost, the CTE of the PI-based film can be easily reduced, and the PI-based resin can be easily synthesized.

In one embodiment of the present invention, the imidization rate of the PI-based resin is preferably 90% or higher, more preferably 93% or higher, still more preferably 95% or higher, and usually 100% or lower. From the viewpoint of easily improving mechanical properties, thermophysical properties, and dielectric properties, the imidization rate is preferably at least the above lower limit. The imidization ratio indicates the ratio of the molar amount of imide bonds in the PI-based resin to twice the molar amount of the structural units derived from the tetracarboxylic acid compound in the PI-based resin. In the case where the PI-based resin contains a tricarboxylic acid compound, a value twice the molar amount of the structural units derived from the tetracarboxylic acid compound in the PI-based resin, and the molar amount of the structural units derived from the tricarboxylic acid compound and the ratio of the molar amount of imide bonds in the PI-based resin to the total of Also, the imidization rate can be determined by IR method, NMR method, or the like.

In one embodiment of the present invention, the polystyrene equivalent Mw of the PI resin is preferably greater than 100,000, more preferably 110,000 or more, still more preferably 120,000 or more, and particularly preferably 130,000 or more. preferably 1,000,000 or less, more preferably 700,000 or less, still more preferably 500,000 or less, and particularly preferably 300,000 or less. When Mw is at least the above lower limit, it is easy to improve mechanical properties such as bending resistance. When Mw is equal to or less than the above upper limit, it is advantageous from the viewpoint of workability during film formation.

In one embodiment of the present invention, the ratio of Mw to Mn (Mw/Mn) of the PI resin is preferably 3.5 or more, more preferably 4.0 or more, and still more preferably 4.2 in terms of polystyrene. more preferably 4.5 or more, particularly preferably 4.7 or more, preferably 8.0 or less, more preferably 7.0 or less, still more preferably 6.0 or less, particularly preferably 5.5 It is below. In addition, Mw and Mn can be determined by performing gel permeation chromatography (hereinafter sometimes referred to as GPC) measurement and standard polystyrene conversion.

In one embodiment of the present invention, the Tg of the PI-based resin is preferably from the viewpoint of easily reducing the Df of the resulting PI-based film and improving the bending resistance even when the thermal imidization temperature is low. 290° C. or lower, more preferably lower than 290° C., still more preferably 280° C. or lower, even more preferably 275° C. or lower, particularly preferably 260° C. or lower, particularly preferably 250° C. or lower, particularly preferably 240° C. or lower, It is preferably 200° C. or higher, more preferably 202° C. or higher, and even more preferably 205° C. or higher, from the viewpoint of easily reducing the Df of the PI-based film and from the viewpoint of easily increasing the heat resistance of the PI-based film. The Tg of the PI-based resin can be measured by dynamic viscoelasticity measurement, for example, by the method described in Examples.

The Tg of the PI-based resin can be adjusted by appropriately adjusting the types and configurations of the structural units constituting the PI-based resin, the molecular weight of the PI-based resin and the production method, particularly the imidization conditions, etc. For example, It can be adjusted within the above range by adjusting within the range described as a preferred embodiment in the above description.

In one embodiment of the present invention, the storage elastic modulus of the PI-based resin at 280 ° C. (hereinafter sometimes referred to as E ') is easy to reduce the Df of the resulting PI-based film and easily improve the bending resistance. From the viewpoint, it is preferably 3×10 ⁸ Pa or less, more preferably 2×10 ⁸ Pa or less, still more preferably 1.5×10 ⁸ Pa or less, even more preferably 1×10 ⁸ Pa or less, particularly preferably 0.5×10 8 Pa or less. It is 8×10 ⁸ Pa or less, and is preferably 1×10 ⁴ Pa or more, more preferably 1×10 ⁵ Pa or more, still more preferably 1×10 ⁶ from the viewpoint of easily suppressing deformation during processing of the PI-based film. Pa or more. E' of the PI resin can be measured by dynamic viscoelasticity measurement, for example, by the method described in Examples.

E' of the PI resin at 280 ° C. is adjusted by appropriately adjusting the type of structural units constituting the PI resin and their constitution, the molecular weight of the PI resin and the production method, especially the imidization conditions, etc. For example, it can be adjusted within the above range by adjusting within the range described as the preferred embodiment in the above description.

[Method for producing polyimide resin]
The PI-based resin of the present invention can be produced by imidizing the PI-based resin precursor of the present invention, and is preferably produced by imidizing the PI-based resin precursor by heat treatment at 200°C or higher and lower than 350°C.

The PI-based resin precursor in the present invention can reduce the Df of the PI-based film containing the obtained PI-based resin even when imidized at a low temperature, and can improve the bending resistance, so the imidization temperature is preferably 350 ° C. less than, more preferably 340° C. or lower, still more preferably 330° C. or lower, even more preferably 310° C. or lower, and particularly preferably 300° C. or lower. The imidization temperature is preferably 200° C. or higher, more preferably 210° C. or higher, and even more preferably 220° C. or higher, from the viewpoint of easily improving the imidization rate sufficiently. Further, the heating may be performed stepwise. For example, after removing the solvent by heating at a relatively low temperature of 50 to 150°C, heating is performed stepwise to a temperature in the range of 200°C or higher and lower than 350°C. Imidization may be performed.

In one embodiment of the invention, the reaction time for imidization is preferably 30 minutes to 24 hours, more preferably 1 to 12 hours. Also, in one embodiment of the present invention, the time for maintaining the temperature of 200° C. or higher is preferably 5 to 90 minutes, more preferably 15 to 70 minutes, and even more preferably 20 to 50 minutes. When the reaction time at 200° C. or higher in imidization is within the above range, the imidization rate can be sufficiently improved, the oxidation deterioration of the resin can be easily prevented, and the dielectric properties and bending resistance can be easily improved.

The PI-based resin can be separated and purified by a conventional method such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination thereof.

[Polyimide film]
The PI-based film of the present invention contains a PI-based resin obtained from the PI-based resin precursor of the present invention. The PI-based film of the present invention has a low Df and excellent bending resistance even when the imidization temperature is low. Therefore, the present invention also includes a PI-based film containing the PI-based resin of the present invention. The present invention also includes a PI-based film containing a PI-based resin obtained by imidizing a PI-based resin precursor by heat treatment at 200°C or higher and lower than 350°C.

In one embodiment of the present invention, the content of the PI-based resin in the PI-based film is preferably 60% by mass or more, more preferably 70% by mass or more, and still more preferably, based on the mass of the PI-based film of the present invention. is 80% by mass or more, particularly preferably 90% by mass or more. The upper limit of the content of the PI-based resin is not particularly limited, and is, for example, 100% by mass or less, preferably 99% by mass or less, more preferably 95% by mass or less, relative to the mass of the PI-based film. When the content of the PI-based resin is within the above range, it is easy to improve mechanical properties and thermophysical properties.

The PI-based film of the present invention can contain a filler if necessary. Examples of fillers include metal oxide particles such as silica and alumina, inorganic salts such as calcium carbonate, fluororesins, and polymer particles such as cycloolefin polymers. A filler can be used individually or in combination of 2 or more types. When a filler is included, the content thereof is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and preferably 0.01, relative to the total mass of the PI-based film. It is mass % or more.

Moreover, in one embodiment of the present invention, the PI-based film of the present invention can contain additives as necessary. Additives include, for example, antioxidants, flame retardants, cross-linking agents, surfactants, compatibilizers, imidization catalysts, weathering agents, lubricants, anti-blocking agents, antistatic agents, anti-fogging agents, non-dropping agents, pigments. etc. Additives can be used singly or in combination of two or more. The content of various additives can be appropriately selected within a range that does not impair the effects of the present invention, and when various additives are included, the total content is preferably 7% by mass or less with respect to the mass of the PI-based film. It is more preferably 5% by mass or less, still more preferably 4% by mass or less, and preferably 0.001% by mass or more.

In one embodiment of the present invention, the CTE of the PI-based film is preferably 50 ppm/K or less, more preferably 40 ppm/K or less, even more preferably 30 ppm/K or less, still more preferably 25 ppm/K or less, and preferably is 0 ppm/K or more, more preferably 5 ppm/K or more, still more preferably 8 ppm/K or more, and even more preferably 12 ppm/K or more. By setting the thickness within the above range, the CTE of the copper foil and the PI layer become close to each other, so peeling of the laminated film can be suppressed. The CTE can be measured by, for example, a thermomechanical analyzer (hereinafter sometimes referred to as "TMA") and determined by the method described in Examples.

Printed circuits are required to have low transmission loss. Transmission loss is represented by the sum of dielectric loss, which is loss caused by an electric field generated in a dielectric, and conductor loss, which is loss caused by current flowing through a conductor. It is known that the dielectric loss is approximately proportional to the index E represented by the formula (i).

E=Df×(Dk) ^1/2 (i)
[In formula (i), Df represents a dielectric loss tangent, and Dk represents a dielectric constant]

Since dielectric loss tends to increase in the high frequency range used in 5G FPCs, materials with a small value of the index E and capable of suppressing dielectric loss are particularly desired.
On the other hand, high-frequency signals concentrate the current on the very surface of the conductor. Therefore, conductor loss is related to the dielectric properties of the dielectric in contact and is known to be approximately proportional to (Dk) ^1/2 .

In the PI-based film of the present invention obtained from the PI-based resin precursor of the present invention, as described above, in the PI-based resin precursor, the structural unit (A) satisfies the relationship of formula (X), and the structural unit (B1) content is more than 30 mol% and Mw is more than 100,000, Df and Dk are reduced, the index E of dielectric loss and conductor loss are also reduced, and in a circuit containing the PI-based film Transmission loss can be reduced.

In one embodiment of the present invention, the dielectric loss index E of the PI-based film at 10 GHz is preferably 0.01 or less, more preferably 0.009 or less, still more preferably 0.008 or less, and even more preferably 0.008 or less. 007 or less, particularly preferably 0.006 or less. The smaller the index E, the lower the transmission loss of the electronic circuit containing the PI-based film.

In one embodiment of the present invention, the Df of the PI-based film at 10 GHz is preferably less than 0.004, more preferably 0.0038 or less, from the viewpoint of easily reducing the transmission loss of an electronic circuit containing the PI-based film. , more preferably 0.0035 or less, still more preferably 0.0033 or less, particularly preferably 0.0030 or less, even more preferably 0.0027 or less, and particularly preferably 0.0024 or less. The smaller the Df, the lower the transmission loss of the electronic circuit containing the PI-based film.

In one embodiment of the present invention, the Dk at 10 GHz of the PI-based film is preferably less than 3.50, more preferably 3.45 or less, even more preferably 3.40 or less, even more preferably 3.38 or less, especially It is preferably 3.36 or less, particularly more preferably 3.33 or less, even more preferably 3.30 or less, particularly preferably 3.27 or less, and particularly preferably 3.22 or less.

Df and Dk of the PI-based film can be measured using a vector network analyzer and a resonator, for example, by the method described in Examples.

In the PI-based film of the present invention obtained from the PI-based resin precursor of the present invention, as described above, in the PI-based resin precursor, the structural unit (A) satisfies the relationship of the formula (X), and the structural unit (B1 ) is more than 30 mol % and Mw is more than 100,000, it has excellent bending resistance, especially bending resistance. The number of times of bending until breakage in the MIT folding endurance test in accordance with ASTM D2176-16 of the PI-based film of the present invention is preferably 20,000 times or more, more preferably 30,000 times or more, and still more preferably 50 times. ,000 times or more, more preferably 100,000 times or more, particularly preferably 150,000 times or more, and even more preferably 200,000 times or more. When the number of times of bending is equal to or more than the above lower limit, it is possible to effectively suppress the occurrence of cracks, fractures, creases, and the like even after repeated bending. Moreover, the upper limit of the number of times of bending is not particularly limited, and may be, for example, 10,000,000 times or less. The MIT folding endurance test can be measured using an MIT folding endurance tester, for example, it can be measured by the method described in the Examples.

In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film and increasing the bending resistance, the E 'at 280 ° C. of the PI-based resin and the CTE of the PI-based film containing the PI-based resin are expressed by the formula (Y):
120,000 ≤ (CTE of PI-based film) x (E' of PI-based resin at 280°C) ^1/2 ≤ 850,000
It is preferable to satisfy the relationship of

In one embodiment of the present invention, the value of the formula (Y) is preferably more than 120,000, more preferably 125,000 or more, from the viewpoint of easily reducing the Df of the PI-based film and easily increasing the bending resistance. More preferably 135,000 or more, preferably 750,000 or less, more preferably 500,000 or less, still more preferably 450,000 or less, even more preferably 400,000 or less, particularly preferably 300,000 or less, More preferably, it is 200,000 or less, and even more preferably 190,000 or less.

The thickness of the PI-based film of the present invention can be appropriately selected depending on the application, and is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, preferably 500 μm or less, more preferably 300 μm or less. It is preferably 100 μm or less, particularly preferably 80 μm or less, and particularly preferably 50 μm or less. The thickness of the film can be measured using a film thickness meter or the like. When the film of the present invention is a multilayer film, the above thickness represents the thickness of a single layer portion.

The PI-based film of the present invention may be subjected to surface treatment such as corona discharge treatment, plasma treatment, ozone treatment, etc., by a method generally employed industrially.

Since the PI-based film of the present invention has a low Df and excellent bending resistance, it can be suitably used as a substrate material compatible with printed circuit boards and antenna substrates for high-frequency bands. Metal-clad laminates such as CCL used in FPCs are widely used laminates having a thin metal layer such as a copper foil layer on one or both sides of a single layer or multiple layers of PI resin. When the PI-based film of the present invention is used as a resin layer, the PI-based film of the present invention can lower Df even when the imidization temperature is low. Even if a metal-clad laminate such as a CCL is produced by thermally imidizing the precursor coating film, deterioration of the metal foil surface can be suppressed, so a CCL having excellent high-frequency characteristics can be obtained.

[Method for producing polyimide film]
The PI-based film of the present invention can be prepared, for example, by the following steps:
A method comprising the steps of applying a PI-based resin precursor solution containing the PI-based resin precursor of the present invention onto a substrate, and imidizing the PI-based resin precursor by heat treatment at 200°C or higher and lower than 350°C. can be manufactured by

<Process of applying polyimide resin precursor solution>
(Preparation of PI-based resin precursor solution)
The PI-based resin precursor solution contains the PI-based resin precursor of the present invention and a solvent, and can be prepared by mixing the PI-based resin precursor of the present invention and the solvent. Further, in one embodiment of the present invention, the reaction liquid containing the PI-based resin precursor obtained by synthesizing the PI-based resin precursor is appropriately diluted with a solvent as necessary and used as a PI-based resin precursor solution. You may

Solvents contained in the PI-based resin precursor solution include those exemplified as solvents used in the reaction of the diamine compound and the tetracarboxylic acid compound in the production of the PI-based resin precursor, preferably lactone-based solvents and amide-based solvents. , a pyrrolidone-based solvent, more preferably an amide-based solvent. Further, in one embodiment of the present invention, the boiling point of the solvent contained in the PI-based resin precursor solution is such that even if the imidization temperature is low, the Df of the resulting PI-based film is easily reduced, and the bending resistance is improved. The temperature is preferably 230° C. or lower, more preferably 200° C. or lower, still more preferably 180° C. or lower, and particularly preferably 170° C. or lower, from the viewpoint of ease of heating. In addition, the boiling point of the solvent is preferably 100° C. or higher, more preferably 120° C. or higher, from the viewpoint of easily reducing the Df of the resulting PI-based film and easily improving the bending resistance.

The content of the PI-based resin precursor contained in the PI-based resin precursor solution is preferably 8% by mass or more, more preferably 10% by mass or more, and still more preferably 12% by mass, relative to the total amount of the PI-based resin precursor solution. % by mass or more, particularly preferably 13% by mass or more, preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 23% by mass or less, and particularly preferably 20% by mass or less. When the content of the PI-based resin precursor is within the above range, the processability during film formation is excellent.

(Coating of polyimide resin precursor solution)
The step of applying the PI-based resin precursor solution is a step of applying the PI-based resin precursor solution onto the substrate to form a coating film.

In the coating step, a coating film is formed by coating the composition on the substrate by a known coating method or application method. Examples of known coating methods include wire bar coating, reverse coating, roll coating such as gravure coating, die coating, comma coating, lip coating, spin coating, screen printing coating, fountain coating, and dipping. method, spray method, curtain coating method, slot coating method, casting method, and the like. When the solution of the PI-based resin precursor is coated or applied onto the substrate, even if a single layer of the PI-based resin precursor is coated on the substrate, multiple layers of the PI-based resin precursor are applied to the substrate. It can be coated on top. When a plurality of layers of the PI-based resin precursor is applied onto the base material, it may be applied in a plurality of times and dried, or may be applied in multiple layers at the same time.

Examples of substrates include copper plates such as copper foil, SUS foils, SUS plates such as SUS belts, glass substrates, PET films, PEN films, other PI-based resin films other than the PI-based film of the present invention, and polyamide-based resins. A film etc. are mentioned. Among them, copper plate, SUS plate, glass substrate, PET film, PEN film and the like are preferable from the viewpoint of excellent heat resistance, and copper plate, SUS plate and glass substrate are more preferable from the viewpoint of adhesion to the film and cost. Or a PET film etc. are mentioned.

<Imidation step>
The imidization step is a step of imidating the PI-based resin precursor coated on the substrate by heat treatment at 200°C or higher and lower than 350°C.
In one embodiment of the present invention, the imidization step includes, before imidization of the PI-based resin precursor, the PI-based resin precursor solution coated on the substrate is heated at a relatively low temperature of, for example, less than 200°C. It is preferable to imidize the dried film of the PI-based resin precursor obtained by heating and drying by heat treatment at 200°C or more and less than 350°C.
Further, in one embodiment of the present invention, a PI-based film may be obtained by imidizing the dry film of the PI-based resin precursor on the substrate, and the dry film of the PI-based resin precursor is peeled off from the substrate, The dry film peeled from the substrate may be imidized to obtain a PI-based film.

In one embodiment of the present invention, the drying temperature of the PI-based resin precursor coated on the substrate is not particularly limited as long as it is within the temperature range where the solvent dries and solidifies, but the surface roughens due to rapid drying. From the viewpoint of avoiding the occurrence of this and from the viewpoint of suppressing wrinkles and wrinkles that occur during processing, it is preferably less than 300 ° C., more preferably 260 ° C. or less, still more preferably 200 ° C. or less, and even more preferably 180 ° C. or less. From the viewpoint of productivity, the temperature is preferably 50° C. or higher, more preferably 80° C. or higher, and even more preferably 100° C. or higher.

The PI-based resin precursor in the present invention can reduce the Df of the obtained PI-based film and improve the bending resistance even when imidized at a low temperature. The heat treatment temperature in the imidization step, that is, the imidization temperature is preferably less than 350°C, more preferably 340°C or less, still more preferably 330°C or less, even more preferably 310°C or less, and particularly preferably 300°C or less. . When the imidization temperature is equal to or lower than the above upper limit, even when a metal foil such as copper foil is used as the base material, thermal deterioration of the metal foil, especially copper foil, can be suppressed. Easy to obtain excellent CCL. The imidization temperature is preferably 200° C. or higher, more preferably 210° C. or higher, and even more preferably 220° C. or higher, from the viewpoint of easily improving the imidization rate sufficiently. Moreover, from the viewpoint of easily obtaining a smooth film, it is preferable to perform heating in stages. For example, after removing the solvent by heating at a relatively low temperature of 50 to 150° C., imidization may be performed by stepwise heating to a temperature in the range of 200° C. or more and less than 350° C.

In one embodiment of the invention, the reaction time for imidization is preferably 30 minutes to 24 hours, more preferably 1 to 12 hours. Also, in one embodiment of the present invention, the time for maintaining the temperature of 200° C. or higher is preferably 10 minutes to 90 minutes, more preferably 15 minutes to 70 minutes, even more preferably 20 minutes to 50 minutes.

After imidization, a PI-based film can be obtained by peeling off the coating film formed on the substrate from the substrate. In one embodiment of the present invention, when the substrate is a metal foil such as copper foil, a PI-based film is formed without peeling the coating film from the metal foil such as copper foil, and the obtained copper foil or the like is A laminated film in which a PI-based film is laminated on a metal foil can also be used for the CCL.

When the film of the present invention is a multilayer film, it can be produced by a multilayer film forming method such as a coextrusion method, an extrusion lamination method, a heat lamination method, a dry lamination method, or the like.

[Laminated film]
Since the PI-based film of the present invention has a low Df and excellent bending resistance, it can be suitably used for forming a metal-clad laminate used for FPC. Therefore, the PI-based film of the present invention is used as a PI layer to include a laminated film including a PI layer and a metal foil layer. In one embodiment of the present invention, the laminated film of the present invention may contain the metal foil layer on only one side of the PI layer, or may contain it on both sides.

In one embodiment of the present invention, the metal foil includes, for example, copper foil, SUS foil, aluminum foil, etc. From the viewpoint of conductivity and metal workability, copper foil is preferred.

The PI-based film of the present invention is a preferred embodiment of the present invention because it can be suitably used for forming a CCL having a low Df, excellent high-frequency characteristics and bending resistance even when the thermal imidization temperature is low. In , the laminated film of the present invention is preferably a laminated film containing a copper foil layer on one side or both sides of the PI-based film of the present invention.

In one embodiment of the present invention, the thickness of the metal foil layer, particularly the copper foil layer, is preferably 1 μm or more, more preferably 5 μm or more, and facilitates miniaturization of the circuit and improvement of bending resistance. From the viewpoint, it is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less. The thickness of the metal foil layer, particularly the copper foil layer, can be measured using a film thickness meter or the like. When both sides of the PI-based film contain metal foil layers, particularly copper foil layers, the thickness of each metal foil layer, particularly each copper foil layer, may be the same or different.

In one embodiment of the present invention, the thickness of the laminated film is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 15 μm or more, and preferably 100 μm or less, more preferably 80 μm or less, further preferably 60 μm or less. is. The thickness of the laminated film can be measured using a film thickness meter or the like.

The laminated film of the present invention may contain other layers such as functional layers in addition to the PI-based film and the metal foil layer, particularly the copper foil layer. The functional layer includes the layers exemplified above, and may be, for example, a thermoplastic PI-based resin layer containing a thermoplastic PI-based resin, an adhesive layer, or the like. A functional layer can be used individually or in combination of 2 or more types.

In one embodiment of the present invention, the laminated film of the present invention is composed of a metal foil layer, a PI layer and an adhesive layer, even if it is a two-layer metal-clad laminate composed of a metal foil layer and a PI layer. Although it may be a layered metal-clad laminate, it is preferably a two-layered metal-clad laminate that does not contain an adhesive layer from the viewpoint of heat resistance, dimensional stability and weight reduction.
In addition, the PI-based film of the present invention has a low Df even when the imidization temperature is low, and has excellent bending resistance. Even if a laminated film in which the metal foil is a copper foil is produced, deterioration of the copper foil surface can be suppressed. Therefore, the laminated film of the present invention has excellent high frequency characteristics even if it does not contain an adhesive layer.

In one embodiment of the present invention, the PI-based film of the present invention and the metal foil layer, particularly the copper foil layer, may be in direct contact, and between the PI-based film and the metal foil layer, particularly the copper foil layer, A functional layer may be inserted and these may be in contact with each other through the functional layer. preferably.
The functional layer that may be inserted between the PI-based film of the present invention and the metal foil layer may be a thermoplastic PI layer. From the viewpoint of easily improving mechanical properties and thermophysical properties, the layer in direct contact with the metal foil layer, particularly the copper foil layer, is preferably the PI film of the present invention or a thermoplastic PI layer as a functional layer.

[Method for producing laminated film]
The laminated film of the present invention can be produced, for example, by the following steps:
A step of applying a PI-based resin precursor solution containing the PI-based resin precursor of the present invention onto a substrate, and a heat treatment at 200 ° C. or higher and lower than 350 ° C. to imidize the PI-based resin precursor to obtain the PI-based resin precursor of the present invention. It can be produced by a method including a step of forming a PI-based film on a substrate.

In the method for producing a laminated film of the present invention, "the step of applying a PI-based resin precursor solution containing the PI-based resin precursor of the present invention onto a substrate" and "by heat treatment at 200 ° C. or higher and lower than 350 ° C., the PI-based For the step of imidizing a resin precursor to form the PI-based film of the present invention on a base material, the description of each step described in the section [Method for producing polyimide-based film] applies similarly.

In one embodiment of the invention, the substrate is preferably a metal foil, particularly preferably a copper foil. For metal foils, particularly copper foils, the descriptions for metal foils described in the section [Laminated film] apply similarly.

The laminated film of the present invention can be produced by a method other than the above method, for example, by coating a PI-based resin precursor solution containing the PI-based resin precursor of the present invention on another substrate other than the metal foil contained in the laminated film and A dry film of the PI-based resin precursor obtained by drying may be peeled off from the substrate, and the peeled dry film of the PI-based resin precursor may be bonded to a metal foil. As a method for laminating the dry film of the PI-based resin precursor and the metal foil, a method using a press, a laminating method using a hot roll, or the like may be employed. Imidization may be carried out simultaneously. However, the PI-based film of the present invention has a low Df even at a low imidization temperature and is excellent in bending resistance. Even if the laminated film is produced using a copper foil, deterioration of the copper foil surface can be suppressed. Therefore, the laminated film of the present invention has excellent high-frequency characteristics and bending resistance even if it is produced without passing through the lamination process as described above.

[Flexible printed circuit board]
Since the PI-based film obtained from the PI-based resin precursor of the present invention has a low Df and excellent bending resistance, it can be suitably used as an FPC substrate material, particularly as an FPC substrate material for foldable devices. The present invention also includes an FPC board containing the PI-based film.

EXAMPLES The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

The abbreviations used in Examples, Comparative Examples and Reference Examples represent the following compounds.
BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride TAHQ: p-phenylene bis (trimellitic acid monoester dianhydride)
PMDA: pyromellitic anhydride BP-TME: 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl m-Tb: 4,4'-diamino-2 ,2′-dimethylbiphenyl BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane TPE-Q: 1,4-bis(4-aminophenoxy)benzene

[Synthesis of polyimide resin precursor]
(Example 1)
After 27.00 g (127.2 mmol) of m-Tb was dissolved in 421 g of DMAc, 28.86 g (63.0 mmol) of TAHQ was added and stirred at 20° C. for 1 hour under a nitrogen atmosphere. After that, 18.52 g (63.0 mmol) of BPDA was added and stirred at 20° C. for 24 hours under a nitrogen atmosphere to obtain a PI resin precursor composition. The molar ratio of diamine monomer to dianhydride monomer used was 1.01. The polystyrene equivalent molecular weight of the resulting PI resin precursor was Mn of 35,000 and Mw of 170,000.

(Examples 2 to 11, Comparative Examples 2 and 3)
A PI resin precursor composition was obtained in the same manner as in Example 1, except that the monomer type and monomer composition used were changed as shown in Table 1. The order of adding the monomers is, unless otherwise specified, the order of diamine and dianhydride, and the diamine is the structural units (B1), (B2), and (B3) in the order of diamines that induce the structural units (B3), and the acid dianhydride is Acid dianhydrides leading to structural units (A1), (A2) and (A3) were added in this order.

[Manufacturing of polyimide film]
Using the solvent used in the synthesis of the PI resin precursor, the PI resin precursor compositions obtained in Examples 1 to 11 and Comparative Examples 2 and 3 were prepared so that the content of the PI resin precursor was 10% by mass or more. A PI resin precursor solution was prepared by appropriately diluting within the range to adjust the viscosity to 40,000 cps or less. As shown in Table 1, each of the PI resin precursor solutions was formed under any of the following film forming conditions 1 to 4 to obtain a PI film made of the PI resin.

<Film forming condition 1>
The PI resin precursor solution was cast on a glass substrate, and an applicator was used to form a coating film of the PI resin precursor solution at a linear speed of 0.4 m/min. The coating film was heated at 120° C. for 30 minutes, the obtained film was peeled from the glass substrate, and then fixed to a metal frame. The film fixed to the metal frame was heated from 30° C. to 270° C. over 19 minutes in an atmosphere with an oxygen concentration of 7%, and then cooled to 200° C. over 35 minutes to prepare a PI film. The time during which the temperature was maintained at 220°C or higher was 23 minutes. Moreover, the time during which the temperature was maintained at 200° C. or higher was 34 minutes.

<Film forming condition 2>
The PI resin precursor solution is cast on the roughened surface side (surface roughness: Rz = 1.3 μm) of an electrolytic copper foil (manufactured by JX Metals Co., Ltd., JXEFL-BHM, thickness 12 μm), and using an applicator. , a coating film of the PI resin precursor solution was formed at a linear speed of 0.4 m/min. The coating film was dried by heating at 120° C. for 30 minutes. After that, the laminated film of the copper foil and the precursor was fixed to the metal frame, and the temperature was raised from 30° C. to 320° C. over 9 minutes in an atmosphere with an oxygen concentration of 1%, then heated at 320° C. for 6 minutes, and then heated for 15 minutes. After cooling to 200° C., a laminated film of the PI film and the copper foil was produced. The time during which the temperature was maintained at 220°C or higher was 21 minutes. Moreover, the time during which the temperature was maintained at 200° C. or higher was 25 minutes.
The obtained laminated film of the PI film and the copper foil was immersed in a large volume of aqueous solution of ferric chloride having a concentration of 40% by mass at room temperature for 10 minutes. and dried for 1 hour to obtain a single PI film.

<Film forming condition 3>
The PI resin precursor solution was cast on a glass substrate, and an applicator was used to form a coating film of the resin precursor solution at a linear speed of 0.4 m/min. The coating film was heated at 120° C. for 30 minutes, the obtained film was peeled from the glass substrate, and then fixed to a metal frame. The film fixed to the metal frame was heated from 30 ° C. to 320 ° C. over 9 minutes in an atmosphere with an oxygen concentration of 1%, heated at 320 ° C. for 6 minutes, and cooled to 200 ° C. over 15 minutes. was made. The time during which the temperature was maintained at 220°C or higher was 21 minutes. Moreover, the time during which the temperature was maintained at 200° C. or higher was 25 minutes.

<Film forming condition 4>
The PI resin precursor solution was cast on a glass substrate, and an applicator was used to form a coating film of the PI resin precursor solution at a linear speed of 0.4 m/min. The coating film was heated at 120° C. for 30 minutes, the obtained film was peeled from the glass substrate, and then fixed to a metal frame. The film fixed to the metal frame was heated from 30 ° C. to 320 ° C. over 5 minutes in an atmosphere with an oxygen concentration of 1%, heated at 320 ° C. for 5 minutes, and cooled to 200 ° C. over 15 minutes. was made. The time during which the temperature was maintained at 220°C or higher was 17 minutes. Moreover, the time during which the temperature of 200° C. or higher was maintained was 21 minutes.

[Synthesis of polyimide resin precursor and production of polyimide film]
(Comparative example 1)
After 70.33 g (331 mmol) of m-Tb was dissolved in 720 g of NMP, 73.06 g (248 mmol) of BPDA and 37.94 g (83 mmol) of TAHQ were added and stirred at room temperature for 1 hour under nitrogen atmosphere. After that, the mixture was stirred at 60° C. for 20 hours to obtain a PI resin precursor composition. In addition, Mw of the polystyrene equivalent of the PI resin precursor was 91,000, and Mn was 27,000. A PI resin precursor solution is prepared by diluting the PI resin precursor composition appropriately with NMP to adjust the viscosity, and the resulting PI resin precursor solution is formed under the film forming conditions 1 to obtain a PI film. rice field.
The obtained PI film had a thickness of 30 μm, Dk of 3.45, Df of 0.0040, index E of 0.0074, and the number of times of bending until breaking was 886. and the CTE was 38.2 ppm. Further, the Tg of the PI resin was 255°C, E' at 280°C was 5.53×10 ⁸ Pa, and CT×(E′) ^1/2 was 8.98×10 ⁵ .
Moreover, the Tg obtained from the storage modulus curve using the tangent line method was 230°C.

Each measurement and evaluation were performed on the PI resin precursors and PI films obtained in Examples and Comparative Examples. Measurement and evaluation methods are described below.

<Measurement of Weight Average Molecular Weight and Number Average Molecular Weight>
The polystyrene-equivalent Mw and Mn of the PI resin precursor obtained in the synthesis were measured using GPC. GPC measurement was performed under the following conditions.
(1) Pretreatment method A sample was diluted with DMF and then filtered through a 0.45 μm membrane filter to obtain a measurement solution.
(2) Measurement conditions Column: Two TSKgel SuperAWM-H (inner diameter 6.0 mm, length 150 mm) connected Eluent: DMF (10 mmol/L lithium bromide added, 30 mmol/L phosphoric acid added)
Flow rate: 0.6 mL/min Detector: RI detector Column temperature: 40°C
Injection volume: 20 μL
Molecular weight standard: standard polystyrene

<Measurement of glass transition temperature (Tg)>
The Tg of the PI resins obtained in Examples and Comparative Examples was obtained by measuring PI films as follows.
Using a dynamic viscoelasticity measuring device (manufactured by IT Keisoku Co., Ltd., DVA-220), it is measured under the following sample and conditions, and the storage modulus (Storage modulus, E ') and loss elastic modulus (Loss modulus, E″) was obtained.
Test piece: Cuboid 40 mm long, 5 mm wide, 50 μm thick (thickness varies depending on the film used) Experimental mode: single frequency, constant heating rate Experimental mode: tension Length between sample grips: 15 mm
Measurement start temperature: Room temperature to 342°C
Heating rate: 5°C/min Frequency: 10Hz
Static/dynamic stress ratio: 1.8
Main data collected:
(1) Storage modulus (E')
(2) Loss modulus (E″)
(3) tan δ (E″/E′)

<Measurement of storage modulus (E′)>
E′ at 280° C. of the PI resins obtained in Examples and Comparative Examples was determined by dynamic viscoelasticity measurement in the same manner as Tg measurement.

<Measurement of coefficient of linear thermal expansion (CTE)>
The CTE of the PI films obtained in Examples and Comparative Examples was measured using TMA under the following conditions, and the CTE at 50°C to 100°C was calculated.
Apparatus: TMA/SS7100 manufactured by Hitachi High-Tech Science Co., Ltd.
Load: 50.0mN
Temperature program: from 20°C to 130°C at a rate of 5°C/min Test piece: rectangular parallelepiped with a length of 40 mm, a width of 5 mm, and a thickness of 50 µm (the thickness varies depending on the film used)

<Evaluation of index E of dielectric loss>
The dielectric loss index E of the film was calculated by the following formula.

E=Df×(Dk) ^1/2 (i)

Df: dielectric loss tangent Dk: dielectric constant

(Measurement of Df and Dk)
Measurement samples of 50 mm×50 mm were cut out from the PI films obtained in Examples and Comparative Examples, and Df and Dk were measured under the following conditions. The measurement was performed after the measurement sample was conditioned at 25° C./55% RH for 24 hours.
Apparatus: Compact USB vector network analyzer manufactured by Anritsu Corporation (product name: MS46122B)
AET Corporation Cavity Resonator (TE mode 10 GHz type)
Measurement frequency: 10GHz
Measurement atmosphere: 23°C/50% RH

<Evaluation of bending resistance>
The bending resistance of the PI films obtained in Examples and Comparative Examples was evaluated by measuring the number of times the films were bent under the following conditions. The film was cut into strips with a length of 100 mm and a width of 10 mm using a dumbbell cutter. The cut film was set in an MIT folding endurance tester (MIT-DA manufactured by Toyo Seiki Seisakusho Co., Ltd.) conforming to ASTM standard D2176-16, a test speed of 175 cpm, a bending angle of 135 °, a load of 750 g, and The film was alternately folded in both the front and back directions under the condition that the R of the folding clamp was 1.0 mm, and the number of folds until the film broke was measured. The greater the number of times of bending, the better the resistance to bending.

Table 1 shows the measurement and evaluation results of the PI resin precursors, PI resins and PI films obtained in Examples and Comparative Examples, and the amine ratio. In Table 1, CT×(E′) ^1/2 indicates CT×(E′ of PI resin at 280° C.) ^1/2 of the PI film.

As shown in Table 1, the PI films obtained from the PI resin precursors of Examples 1 to 11, even if the maximum imidization temperature was as low as 270 ° C. or 320 ° C., compared to the comparative examples, It was confirmed that the Df was low and the bending resistance was excellent. Therefore, the PI-based film obtained from the PI-based resin precursor of the present invention is produced by casting the PI-resin precursor solution on a metal foil such as a copper foil, and heating the coating film of the PI-resin precursor solution on the metal foil. Even if it is manufactured by imidization, thermal degradation such as surface roughness of the metal foil can be suppressed, so it can be applied to high frequency bands and can be applied to foldable devices. can be used for As a result, an FPC with small dielectric loss can be provided.
In addition, by using the PI resin precursor of the present invention, even if imidation is performed in a structure laminated with a metal foil such as a copper foil, it is possible to manufacture an FPC without exposing the metal foil to high temperatures. As a result, the surface roughness and oxidation of the metal foil are suppressed, and the conductor loss is also reduced. Therefore, it is possible to provide an FPC in which the transmission loss, which is the sum of the dielectric loss and the conductor loss, is suppressed. Furthermore, since the metal foil such as copper foil is not exposed to high temperatures, it is possible to suppress the decrease in bending resistance due to the increase in crystal grain size of the metal foil due to heating, and both the PI film and the metal foil can withstand continuous bending. can provide an excellent FPC.

Claims (13)

A polyimide resin precursor containing a structural unit (A) derived from a tetracarboxylic anhydride and a structural unit (B) derived from a diamine,
The structural unit (A) includes a structural unit (A1) derived from an ester bond-containing tetracarboxylic anhydride and a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic anhydride,
The structural unit (A) has the formula (X):
(Content of structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2))/(total amount of structural unit (A1) and structural unit (A2)) <0.67 (X)
satisfy the relationship of
The structural unit (B) contains a structural unit (B1) derived from a biphenyl skeleton-containing diamine, and the content of the structural unit (B1) exceeds 30 mol% relative to the total amount of the structural unit (B),
A polyimide-based resin precursor, wherein the polystyrene-equivalent weight-average molecular weight of the polyimide-based resin precursor is greater than 100,000. The structural unit (A1) has the formula (a1):

[In the formula (a1), Z represents a divalent organic group,
R ^a1 each independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
s independently represents an integer of 0 to 3]
2. The polyimide resin precursor according to claim 1, which is a structural unit (a1) derived from a tetracarboxylic anhydride represented by. The structural unit (A2) has the formula (a2):

[In the formula (a2), R ^a2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
t independently represents an integer of 0 to 3]
The polyimide resin precursor according to claim 1 or 2, which is a structural unit (a2) derived from a tetracarboxylic anhydride represented by. The structural unit (B1) has the formula (b1):

[In the formula (b1), each R ^b1 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
p represents an integer from 0 to 4]
The polyimide resin precursor according to any one of claims 1 to 3, which is a diamine-derived structural unit (b1) represented by. The structural unit (B) has the formula (b2):

[In the formula (b2), each R ^b2 independently represents a halogen atom, or an alkyl group, alkoxy group, aryl group or aryloxy group optionally having a halogen atom,
W are independently of each other -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, —COO—, —OOC—, —SO ₂ —, —S—, —CO— or —N(R ^c )—, where R ^c is a hydrogen atom or has 1 to 1 carbon atoms optionally substituted with a halogen atom represents 12 monovalent hydrocarbon radicals,
m is an integer from 1 to 4,
q independently represents an integer of 0 to 4]
The polyimide resin precursor according to any one of claims 1 to 4, further comprising a diamine-derived structural unit (b2) represented by: 6. The polyimide resin precursor according to claim 5, wherein in the structural unit (b2), m is 3, and W is independently -O- or -C(CH ₃ ) ₂ -. A polyimide resin obtained from the polyimide resin precursor according to any one of claims 1 to 6. The polyimide resin according to claim 7, which has a glass transition temperature of 200 to 290°C. The polyimide resin according to claim 7 or 8, which has a storage modulus at 280°C of less than 3 x ^108Pa . A polyimide film comprising the polyimide resin according to any one of claims 7 to 9. 11. The polyimide film according to claim 10, which has a dielectric loss tangent of 0.004 or less at 10 GHz. A laminated film comprising a metal foil layer on one side or both sides of the polyimide film according to claim 10 or 11. A flexible printed circuit board comprising the polyimide film according to claim 10 or 11.