KR20230078556A - Polyimide-based film - Google Patents

Abstract

A polyimide-based resin containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine is included, and the polyimide-based resin has a storage modulus at 280°C of 3×10 ⁸ A polyimide-based film having a glass transition temperature of less than Pa and a glass transition temperature of 200 to 290°C.

Description

Polyimide-based film {POLYIMIDE-BASED FILM}

It relates to a polyimide-based film that can be used as a substrate material compatible with printed circuit boards and antenna substrates for high frequency bands.

Flexible printed circuit boards (hereinafter sometimes referred to as FPCs) are thin, lightweight, and flexible, allowing three-dimensional and high-density mounting, and are used in many electronic devices such as mobile phones and hard disks, and their miniaturization , contributing to weight reduction. Conventionally, polyimide resins with excellent heat resistance, mechanical properties, and electrical insulation properties have been widely used for FPCs.

In recent years, a fifth generation mobile communication system called 5G is in full swing. In polyimide materials that have been used in the past, when transmitting high-frequency signals used for 5G communication, transmission loss is large, and disadvantages such as electrical signal loss and signal delay time increase occur. For this reason, polyimide films with low dielectric loss tangents (hereinafter sometimes referred to as Df) and relative dielectric constants (hereinafter sometimes referred to as Dk) are being studied for the purpose of reducing transmission loss.

For example, in Patent Document 1, a polyi obtained by reacting a tetracarboxylic acid anhydride component containing ester-containing tetracarboxylic acid anhydride and biphenyltetracarboxylic acid anhydride with a diamine component containing 75 mol% or more of p-phenylenediamine. A mid resin precursor and a polyimide resin obtained by curing the polyimide resin precursor are disclosed. Further, Patent Document 2 has a non-thermoplastic polyimide layer containing non-thermoplastic polyimide and a thermoplastic polyimide layer containing thermoplastic polyimide, and the non-thermoplastic polyimide has a 3,3',4,4'-b A tetracarboxylic acid residue derived from phenyltetracarboxylic dianhydride (BPDA) (BPDA residue) and a tetracarboxylic acid residue derived from 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) (TAHQ residue) ), and a polyimide film comprising a tetracarboxylic acid residue containing at least one of the following, and a diamine residue derived from a specific diamine compound is disclosed.

Japanese Unexamined Patent Publication No. 2018-150544 International Publication No. 2018/061727

It relates to a metal-clad laminate used for FPC, and is a copper-clad laminate (hereinafter sometimes referred to as CCL), a copper foil layer on one side or both sides of a single-layer or multi-layer polyimide-based resin. Laminates having are widely used. CCL may be produced by forming a film by casting a polyimide-based resin precursor solution on copper foil and thermally imidating the coating film of the polyimide-based resin precursor. It is done by heating to a high temperature.

In transmission of high-frequency current, a phenomenon called skin effect, in which current flows densely near the surface of a conductor, becomes remarkable. For this reason, when a metal-clad laminate such as CCL is used for a high-frequency circuit, roughening or oxidation of the surface of the metal foil tends to cause a decrease in transmission loss. For example, when copper foil is heated at a high temperature of 350° C. or higher, the surface of the copper foil becomes rough, grain size increases, oxidation, etc. occur, and the interface tends to become rough. Therefore, in the step of thermal imidation, exposure of metal foil such as copper foil to high temperatures together with polyimide-based resin may cause reduction in transmission loss.

However, when thermal imidation is performed at a low temperature of less than 350°C in conventional production of polyimide resins and polyimide films, Df and Dk may not be sufficiently reduced. In order to sufficiently reduce the Df and Dk of the polyimide resin or polyimide film, when thermal imidation is performed at a high temperature of 350 ° C. or higher to produce CCL, as described above, roughness of the copper foil surface occurs. It is difficult to form a CCL with a low transmission loss when used in a high-frequency circuit with both suppression of roughening and oxidation of the copper foil surface and reduction of Df of the polyimide layer.

Accordingly, an object of the present invention is to provide a polyimide-based film having a low Df, capable of forming a metal-clad laminate such as CCL having low transmission loss in a high frequency band by suppressing roughening of the surface of a metal foil such as copper foil. there is.

The inventors of the present invention have reached the present invention as a result of intensive studies to solve the above problems. That is, this invention provides the following preferred aspects.

[1] A polyimide-based resin containing a structural unit derived from tetracarboxylic anhydride (A) and a structural unit derived from diamine (B), wherein the polyimide-based resin has a storage modulus of 3 at 280°C A polyimide-based film that is less than ×10 ⁸ Pa and has a glass transition temperature of 200 to 290°C.

[2] The polyimide-based film according to [1], wherein the structural unit (A) includes a structural unit (A1) derived from an ester bond-containing tetracarboxylic acid anhydride.

[3] The polyimide-based film according to [2], wherein the structural unit (A) further includes a structural unit (A2) derived from a biphenyl backbone-containing tetracarboxylic acid anhydride.

[4] The structural unit (A) is Formula (X):

(Content of tetracarboxylic acid anhydride-derived structural units (A3) other than the structural unit (A1) and structural unit (A2))/(total amount of structural units (A1) and (A2)) <1.1 (X)

The polyimide-based film according to [3], which satisfies the relationship of

[5] The structural unit (A1) is Formula (a1):

[In formula (a1), Z represents a divalent organic group,

R ^a1 independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

s, independently of each other, represents an integer from 0 to 3]

The polyimide-based film according to any one of [2] to [4], which is the structural unit (a1) derived from tetracarboxylic acid anhydride represented by .

[6] The structural unit (A2) has the formula (a2):

[In formula (a2), R ^a2 independently represents a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

t represents, independently of each other, an integer from 0 to 3]

The polyimide-based film according to any one of [3] to [5], which is the structural unit (a2) derived from tetracarboxylic acid anhydride represented by .

[7] The polyimide-based film according to any one of [1] to [6], wherein the structural unit (B) includes a structural unit (B1) derived from diamine containing a biphenyl skeleton.

[8] The structural unit (B1) is Formula (b1):

[In formula (b1), R ^b1 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

p represents an integer from 0 to 4]

The polyimide-based film according to [7], which is a structural unit (b1) derived from diamine represented by .

[9] The polyimide-based film according to [7] or [8], wherein the content of the structural unit (B1) exceeds 30 mol% with respect to the total amount of the structural unit (B).

[10] The structural unit (B) is formula (b2):

[In formula (b2), R ^b2 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

W is, independently of each other, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, Represents -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, and R ^c is a monovalent group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. represents a hydrocarbon group,

m represents an integer of 1 to 4,

q represents, independently of each other, an integer from 0 to 4]

The polyimide-based film according to any one of [1] to [9], containing a diamine-derived structural unit (b2) represented by

[11] The polyimide-based film according to [10], wherein m is 3 and W independently represents -O- or -C(CH ₃ ) ₂ - in the structural unit (b2).

[12] A laminated film comprising a metal foil layer on one side or both sides of the polyimide-based film according to any one of [1] to [11].

[13] A flexible printed circuit board comprising the polyimide-based film according to any one of [1] to [11].

[14] A step of coating a polyimide-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine on a substrate, and

A laminated film comprising a step of imidizing a polyimide-based resin precursor by heat treatment at 200° C. or more and less than 350° C. to form the polyimide-based film according to any one of [1] to [11] on a substrate manufacturing method.

[15] The method for producing a laminated film according to [14], wherein the substrate is a metal foil.

According to the present invention, it is possible to provide a low Df polyimide-based film capable of forming a metal clad laminate such as CCL with low transmission loss in a high frequency band by suppressing roughness of the surface of a metal foil such as copper foil.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail. In addition, the scope of the present invention is not limited to the embodiments described herein, and various changes can be made without departing from the gist of the present invention.

[Polyimide film]

The polyimide-based film of the present invention contains a polyimide-based resin containing a structural unit (A) derived from tetracarboxylic anhydride and a structural unit (B) derived from diamine. In this specification, polyimide is sometimes described as PI. In the present invention, "derived structural unit" means "derived structural unit", for example, "structural unit (A) derived from tetracarboxylic acid anhydride" means "structural unit derived from tetracarboxylic acid anhydride ( A)” means.

<Polyimide-based resin>

The PI-based resin has a storage modulus (hereinafter sometimes referred to as E') at 280°C of less than 3 × 10 ⁸ Pa, and a glass transition temperature (hereinafter sometimes referred to as Tg) of 200 ~290°C. The inventors of the present invention, when using a PI-based resin having E' at 280°C of less than 3×10 ⁸ Pa and having a Tg of 200 to 290°C, a PI-based film having a low Df even when the thermal imidization temperature is low. found this to be obtained. This is because when E' and Tg of the PI-based resin at 280 ° C. are within the above ranges, it is easy to form a desirable higher-order structure in which the rotational motion of the PI-based resin is suppressed, so rotation of the polar groups in the PI-based resin is suppressed, It is assumed that this is because the loss of electrical energy as thermal motion is reduced.

Polyamic acid, which is a PI-based resin precursor, starts imidation at about 200°C. In general, polyamic acid has a high degree of freedom in molecular structure, but after imidation, it becomes relatively rigid and the degree of freedom in molecular structure decreases. If the Tg of the PI-based resin is 200 to 290° C., even if the thermal imidization temperature is low during imidation, the thermal imidization temperature exceeds the Tg of the PI-based resin, so that the amic acid portion and the imide portion is moved simultaneously to form a higher-order structure, so it is thought that a preferable higher-order structure in which rotational motion is suppressed in the resin as a whole is easily formed. In addition, when E' at 280°C is less than 3×10 ⁸ Pa, the imide moiety can sufficiently flexibly move when forming a higher order structure, so that the resin can form a preferable higher order structure in which rotational motion is suppressed as a whole. It is thought that an easy effect can be obtained.

E' of the PI-based resin at 280°C is less than 3×10 ⁸ Pa, preferably 2×10 ⁸ Pa or less, more preferably 1.5×10 ⁸ from the viewpoint of easily reducing the Df of the PI-based film. Pa or less, more preferably 1×10 ⁸ Pa or less, particularly preferably 0.8×10 ⁸ Pa or less. In addition, E' of the PI-based resin at 280°C is preferably 1×10 ⁴ Pa or more, more preferably 1×10 ⁵ Pa or more, from the viewpoint of easily suppressing deformation of the PI-based film during processing. , more preferably 1×10 ⁶ Pa or more. E' of the PI-based resin can be measured by a dynamic viscoelasticity measurement, for example, by the method described in Examples.

E' of the PI-based resin at 280 ° C. can be adjusted by appropriately adjusting the types of structural units constituting the PI-based resin, their configuration, the molecular weight of the PI-based resin, and the production method, particularly the imidation conditions. For example, it can be adjusted within the above range by adjusting within the range described as a preferred mode in the description below.

The Tg of the PI-based resin is 290°C or less, preferably less than 290°C, more preferably 280°C or less, from the viewpoint of easily reducing the Df of the obtained PI-based film even if the thermal imidization temperature is low. is 275°C or less, more preferably 260°C or less, particularly preferably 250°C or less, and particularly preferably 240°C or less. Further, the Tg of the PI-based resin is 200°C or higher, more preferably 202°C or higher, still more preferably 205°C, from the viewpoint of easily reducing the Df of the PI-based film and easily increasing the heat resistance of the PI-based film More than that. The Tg of the PI-based resin can be measured by a 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 of structural units constituting the PI-based resin, their configurations, the molecular weight of the PI-based resin, and the production method, particularly the imidation conditions, etc., for example, as described later. It can be adjusted within the said range by adjusting within the range described as a preferable aspect in the description of.

(Structural unit (A) derived from tetracarboxylic acid anhydride)

The PI-based resin contains a structural unit (A) derived from tetracarboxylic acid anhydride (hereinafter sometimes simply abbreviated as structural unit (A)). The structural unit (A) is not particularly limited as long as E' and Tg at 280 ° C. of the PI-based resin are within the above ranges, but, for example, formula (1):

[In formula (1), Y represents a tetravalent organic group]

It is preferable that it is a structural unit derived from the tetracarboxylic acid anhydride represented by.

In Formula (1), Y independently represents a tetravalent organic group, preferably represents a tetravalent organic group having 4 to 40 carbon atoms, more preferably a tetravalent organic group having 4 to 40 carbon atoms and having a cyclic structure. indicate As a cyclic structure, an alicyclic ring, an aromatic ring, and a heterocyclic structure are mentioned. In the organic group, a hydrogen atom in the organic group may be substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group, and in that case, these groups preferably have 1 to 8 carbon atoms. The PI-based resin of the present invention may contain plural types of Y, and the plural types of Y may be the same as or different from each other. As Y, it is group or structure represented by Formula (31) - Formula (40); The hydrogen atoms in the groups represented by formulas (31) to (40) are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluoro , a group substituted with a chloro group or a trifluoromethyl group; A tetravalent C1-C8 chain hydrocarbon group etc. are mentioned.

[In Formulas (31) to (40), 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 a carbon number represents an aryl group of 6 to 12, and the 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, independently of each other, 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 )-, 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, independently of each other, represents a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -;

i represents an integer of 1 to 3;

* indicates a binding hand)

represents,

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 of each other, represent integers from 0 to 2 (provided that e + d is not 0),

f represents an integer from 0 to 3,

g and h represent, independently of each other, an integer from 0 to 4;

In formula (39), Z represents a divalent organic group,

R ^a1 independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

s independently represents an integer from 0 to 3;

In formula (40), R ^a2 independently represents a halogen atom or an alkyl, alkoxy, aryl or aryloxy group which may have a halogen atom;

t represents, independently of each other, an integer from 0 to 3;

* indicates bonded hands].

The PI-based resin in the present invention is Y in formula (1) from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, and formulas (31), (32), (33), It is preferable to include at least one structure selected from the group consisting of structures represented by (39) and formula (40), and at least one structure selected from the group consisting of a structure containing an ester bond and a structure containing a biphenyl skeleton. It is more preferable to include the structure of, and it is still more preferable to include at least one structure selected from the group consisting of structures represented by formulas (39) and (40). In addition, in this specification, mechanical properties mean mechanical properties including bending resistance, folding resistance, and elastic modulus, and improving mechanical properties indicates, for example, that bending resistance and/or elastic modulus increase. . Further, thermal properties mean thermal properties including Tg, coefficient of linear expansion (hereinafter sometimes referred to as CTE), less denaturation and deterioration due to heat, and less deformation after heating, and the thermal properties are improved. The column indicates, for example, that Tg is increased and/or that CTE is decreased.

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, an alkoxy group having 1 to 6 carbon atoms, or a carbon number 6-12 aryl groups are shown.

Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and 2-methyl-butyl. group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group and the like.

Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, n-butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, and hexyloxy group. and a cyclohexyloxy group.

As a C6-C12 aryl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a biphenyl group, etc. are mentioned. The hydrogen atom contained in R ¹⁹ to R ²⁶ and R ^23' to R ^26' may be independently substituted with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. can be heard Among these, from the viewpoint of easily improving the mechanical properties and thermal properties of the PI-based film, R ¹⁹ to R ²⁶ and R ^23' to R ^26' are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. , A hydrogen atom or an alkyl group having 1 to 3 carbon atoms is more preferable, and a hydrogen atom is still more preferable.

In Formula (31), V ¹ and V ² are, independently of each other, 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 the formula (a) is shown, and from the viewpoint of easily improving the mechanical and thermal 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(CF ₃ ) ₂ -. R ^j represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. As the monovalent hydrocarbon group having 1 to 12 carbon atoms, 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. and these may be substituted with a halogen atom. As a halogen atom, the thing similar to the above is mentioned.

In formula (31), e and d represent integers of 0 to 2 independently of each other (provided that e+d is not 0), and even if the imidation temperature is low, it is easy to reduce the Df of the PI-based film. From this point of view, it preferably represents 0 or 1. Also, e+d preferably represents 1. In Formula (31), when e is 0, the two benzene rings are not bonded by V ¹ , and when d is 0, the two benzene rings are not bonded by V ² . .

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

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

As a C1-C6 alkyl group, the thing illustrated above is mentioned. Among these, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, R ²⁷ to R ³⁰ independently of each other preferably represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably hydrogen represent atoms.

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

In formula (39), Z represents a divalent organic group, preferably represents a divalent organic group having 4 to 40 carbon atoms, more preferably cyclic, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film. Represents a divalent organic group having a structure of 4 to 40 carbon atoms, more preferably a divalent organic group having 4 to 40 carbon atoms having an aromatic ring, particularly preferably formula (z1), formula (z2) or formula (z3 ):

[In 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 independently represents a monovalent hydrocarbon group which may have a halogen atom;

n represents an integer of 1 to 4;

j, independently of each other, represents an integer from 0 to 3;

* indicates bonded hands]

represents a divalent organic group represented by , and more preferably represents a divalent organic group represented by formula (z1).

In formula (z1), R ^z11 to R ^z14 each independently represent a hydrogen atom or a monovalent hydrocarbon group which may have a halogen atom.

As a monovalent hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and an aliphatic hydrocarbon group are mentioned.

As an aromatic hydrocarbon group, aryl groups, such as a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group, etc. are mentioned.

As an alicyclic hydrocarbon group, cycloalkyl groups, such as a cyclopentyl group and a cyclohexyl group, etc. are mentioned.

Examples of the aliphatic hydrocarbon group include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3- Alkyl groups, such as a 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, are mentioned.

As the halogen atom, those described above are exemplified.

R ^z11 to R ^z14 are independently of each other, preferably a hydrogen atom or an alkyl group which may have a halogen atom, more preferably a hydrogen atom, or An alkyl group of 1 to 6 carbon atoms which may have a halogen atom, more preferably a hydrogen atom, or an alkyl group of 1 to 3 carbon atoms which may have a halogen atom, particularly preferably a hydrogen atom.

In formula (z1), n represents an integer of 1 to 4, and is preferably an integer of 1 to 3, more preferably 1 from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low. or 2, particularly preferably 2.

In the formula (z2), R ^z2 independently represents a monovalent hydrocarbon group which may have a halogen atom, and examples of the monovalent hydrocarbon group include those exemplified above. R ^z2 is, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, independently of each other, preferably an alkyl group which may have a halogen atom, more preferably an alkyl group which may have a halogen atom and has 1 to 6 carbon atoms. An alkyl group, more preferably an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

In the formula (z2), j independently represents an integer of 0 to 3, and is preferably 0 or 1, more preferably 0 or 1, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low. is 0.

In Formula (39), R ^a1 independently represents a halogen atom or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, and improves the mechanical and thermal properties of the PI-based film From an easy point of view, preferably each independently 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.

As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, the thing illustrated above is mentioned.

The hydrogen atom contained in R ^a1 may be mutually independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, R ^a1 is independently of each other, preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. indicate

In formula (39), s independently represents an integer of 0 to 3, and from the viewpoint of easily improving mechanical and thermal properties of the PI-based film, s is preferably an integer of 0 to 2, more preferably represents 0 or 1.

In the formula (40), R ^a2 represents, independently of each other, a halogen atom or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, and to improve the mechanical and thermal properties of the PI-based film From an easy point of view, preferably each independently 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.

As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, the thing illustrated above is mentioned.

The hydrogen atom contained in R ^a2 may be independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, as R ^a2 , independently of each other, preferably an alkyl group of 1 to 6 carbon atoms, more preferably an alkyl group of 1 to 3 carbon atoms can be cited. there is.

In formula (40), t represents an integer of 0 to 3 independently of each other, and from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, preferably an integer of 0 to 2, more preferably represents 0 or 1.

As a specific example of the structure represented by Formula (31) - Formula (33), Formula (39), and Formula (40), the structure represented by Formula (41) - Formula (56) is mentioned. In these formulas, * represents a bond.

In one embodiment of the present invention, as Y in formula (1), at least one selected from the group consisting of structures represented by formulas (31) to (33), formula (39) and formula (40) is included. In this case, the ratio of structural units derived from tetracarboxylic acid anhydride in which Y in formula (1) is represented by at least one selected from the group consisting of structures represented by formulas (31) to (33), formula (39) and formula (40) In particular, the ratio of structural units derived from tetracarboxylic acid anhydride in which Y in formula (1) is represented by at least one selected from the group consisting of structures represented by formula (39) and formula (40) is the total molar amount of structural unit (A) , is preferably 30 mol% or more, more preferably 50 mol% or more, even more preferably 70 mol% or more, particularly preferably 90 mol% or more, and preferably 100 mol% or less. When the ratio is within the above range, it is easy to reduce the Df of the PI-based film. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Structural unit derived from ester bond-containing tetracarboxylic anhydride (A1))

In one embodiment of the present invention, the structural unit (A) includes a structural unit (A1) derived from an ester bond-containing tetracarboxylic acid anhydride (hereinafter sometimes simply abbreviated as the structural unit (A1)). desirable. When the structural unit (A) includes the structural unit (A1), an ester bond having molecular orientation is incorporated into the PI-based resin, so a step of coating the PI-based resin precursor solution on the substrate and imidizing the coated film. , and easy to reduce Df even if the imidation temperature is low. Also, for the same reason, it is easy to reduce CTE and easily increase the dimensional stability of the PI-based film.

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, but the imidization temperature Even at a low temperature, from the viewpoint of easily reducing the Df of the PI-based film, formula (a1):

[In formula (a1), Z represents a divalent organic group,

R ^a1 independently represents a halogen atom, or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

s, independently of each other, represents an integer from 0 to 3]

It is preferable that it is a structural unit (a1) derived from tetracarboxylic acid anhydride represented by.

R ^a1 in formula (a1) independently represents a halogen atom or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, and even if the imidation temperature is low, Df of the PI-based film From the viewpoint of easy reduction, preferably each independently represents an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or an aryl group of 6 to 12 carbon atoms.

As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, the thing illustrated above is mentioned.

The hydrogen atom contained in R ^a1 may be mutually independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above.

Among these, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, as R ^a1 , independently of each other, preferably an alkyl group having 1 to 6 carbon atoms is exemplified, more preferably 1 to 6 carbon atoms. The alkyl group of 3 is mentioned.

In addition, s in Formula (a1) represents an integer of 0-3 mutually independently, Preferably it represents 0 or 1, More preferably, it represents 0.

Z in the formula (a1) represents a divalent organic group, and examples of the divalent organic group include those exemplified above as the divalent organic group in the formula (39). Among these, from the viewpoint of easily reducing the Df of the PI-based film even when the imidation temperature is low, Z is formula (z1), formula (z2), formula (z3):

[In 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 independently represents a monovalent hydrocarbon group which may have a halogen atom;

n represents an integer of 1 to 4;

j, independently of each other, represents an integer from 0 to 3;

* indicates bonded hand]

It is preferable that it is a divalent organic group represented by, and it is more preferable that it is a divalent organic group represented by 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 which may have a halogen atom.

Examples of the monovalent hydrocarbon group include those exemplified above.

R ^z11 to R ^z14 are each independently preferably a hydrogen atom or an alkyl group which may have a halogen atom, more preferably a hydrogen atom, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low. , 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 a hydrogen atom.

In one embodiment of the present invention, R ^z2 in the formula (z2) each independently represents a monovalent hydrocarbon group which may have a halogen atom, and examples of the monovalent hydrocarbon group include those exemplified above. . R ^z2 is, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, independently of each other, preferably an alkyl group which may have a halogen atom, more preferably an alkyl group which may have a halogen atom and has 1 to 6 carbon atoms. An alkyl group, more preferably an alkyl group having 1 to 3 carbon atoms which may have a halogen atom.

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

j in Formula (z2) represents 0-3 mutually independently. In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, j is independently of each other, preferably 0 or 1, more preferably 0, and even more preferably where j is all 0.

In the formula (z1), n represents an integer of 1 to 4, and is preferably an integer of 1 to 3, more preferably 1 or 3, from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low. 2, particularly preferably 2.

In a preferred embodiment of the present invention, formula (a1) is formula (a1') or formula (a1"):

It is preferable to appear as If the PI-based resin contains, as the structural unit (A1), a structural unit derived from tetracarboxylic acid anhydride represented by formula (a1), particularly formula (a1') or formula (a1"), even if the imidization temperature is low, It is easy to reduce Df of the obtained PI-based film.

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% or more, relative to the total amount of the structural unit (A). mol% or more, still more preferably 30 mol% or more, particularly preferably 35 mol% or more, and even more 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 65 mol% or less, based on the total amount of the structural unit (A). is 60 mol% or less. When the content of the structural unit (A1) is within the above range, orientation of the PI-based resin tends to occur, and Df of the PI-based film tends to decrease. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Structural unit (A2) derived from biphenyl backbone-containing tetracarboxylic anhydride)

In one embodiment of the present invention, the structural unit (A) includes a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic acid anhydride (hereinafter sometimes simply abbreviated as structural unit (A2)). It is desirable to do When the structural unit (A) contains the aforementioned structural unit (A2), even if the imidation temperature is low, the Df of the resulting PI-based film can be easily reduced.

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. 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, and in the present specification, the ester bond and the biphenyl skeleton Structural units derived from tetracarboxylic anhydride containing both are classified not as structural units (A2) but as structural units derived from tetracarboxylic anhydrides containing ester bonds (A1).

In one embodiment of the present invention, the structural unit (A2) has the formula (a2):

[In formula (a2), R ^a2 independently represents a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

t represents, independently of each other, an integer from 0 to 3]

It is preferable that it is a structural unit (a2) derived from the tetracarboxylic acid anhydride represented by.

R ^a2 in formula (a2) independently represents a halogen atom or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, and even if the imidation temperature is low, Df of the PI-based film From the viewpoint of easy reduction, preferably each independently represents an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or an aryl group of 6 to 12 carbon atoms. As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, the thing illustrated above is mentioned. The hydrogen atom contained in R ^a2 may be independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. Among these, from the viewpoint of easily reducing the Df of the PI-based film even when the imidation temperature is low, R ^a2 is independently preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms.

In addition, t in Formula (a2) represents an integer of 0-3 mutually independently, Preferably it represents 0 or 1, More preferably, it represents 0.

The bonding position of the two carboxylic acid anhydrides bonded to the benzene ring constituting the biphenyl skeleton in formula (a2) is not particularly limited, and on the basis of the single bond bonding the two benzene rings, independently of each other, 3 ,4- or 2,3- may be used, and 3,4- is preferable from the viewpoint of easily reducing the Df of the PI-based film even when the imidation temperature is low.

In one preferred embodiment of the present invention, formula (a2) is formula (a2'):

It is preferable to appear as If the PI-based resin contains, as the structural unit (A2), a structural unit derived from tetracarboxylic acid anhydride represented by formula (a2), particularly formula (a2'), Df of the PI-based film obtained even if the imidization temperature is low is easy to reduce

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% or more, relative to the total amount of the structural unit (A). mol% or more, particularly preferably 40 mol% or more. The content of the structural unit (A2) is preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, and even more preferably 80 mol% or less, relative to the total amount of the structural unit (A). It is preferably 70 mol% or less, particularly preferably 60 mol% or less. When the content of the structural unit (A1) is within the above range, orientation of the PI-based resin tends to occur, and Df of the PI-based film tends to decrease. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

In one embodiment of the present invention, the total amount of the structural unit (A1) and the structural unit (A2) relative to the total amount of the structural unit (A) is from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low. , relative to the total amount of the structural unit (A), it is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, particularly preferably is 90 mol% or more. In addition, the upper limit in particular of the total amount of structural unit (A1) and structural unit (A2) is not restrict|limited, For example, it may be 100 mol% or less. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Constituent Unit (A3))

In one embodiment of the present invention, the structural unit (A) is a structural unit (A3) derived from tetracarboxylic acid anhydride other than the structural unit (A1) and the structural unit (A2) (hereinafter simply referred to as the structural unit (A3). may be abbreviated).

In addition, in this specification, “structural unit (A3) derived from tetracarboxylic anhydride other than structural unit (A1) and structural unit (A2)” refers to both structural unit (A1) and structural unit (A2). Structural units derived from tetracarboxylic acid anhydride that do not apply are meant, and "content of structural unit (A3)" means the total amount of structural units (A3) when there are a plurality of structural units (A3).

In one embodiment of the present invention, as the structural unit (A3), a structural unit derived from tetracarboxylic acid anhydride containing neither an ester bond nor a biphenyl skeleton, for example, Y in formula (1) is ) to tetracarboxylic acid anhydride-derived structural units represented by formula (38), from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low, preferably Y in formula (1) is the formula (42) to a structural unit derived from tetracarboxylic acid anhydride represented by formula (49) or formula (53), more preferably Y in formula (1) is formula (42), formula (46), formula (49) or It is a structural unit derived from tetracarboxylic acid anhydride represented by Formula (53).

In one embodiment of the present invention, when the structural unit (A3) is included, the content may be, for example, 0.01 to 55 mol% or 0.01 to 40 mol% with respect to the total amount of the structural unit (A). , preferably 40 mol% or less, more preferably 35 mol% or less, still more preferably 30 mol% or less, particularly preferably 25 mol% or less, and usually 0.01 mol% or more, preferably 10 mol% more than % When the content of the structural unit (A3) is within the above range, orientation of the PI-based resin tends to occur, and Df of the PI-based film tends to decrease. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

In one embodiment of the present invention, structural unit (A3), preferably Y in formula (1), is a structural unit derived from tetracarboxylic acid anhydride represented by formula (32), more preferably Y in formula (1) When contains a structural unit derived from tetracarboxylic acid anhydride represented by formula (32) in which f = 0, the content thereof is preferably 10 mol% or more, more preferably 10 mol% or more, based on the total amount of the structural unit (A). 20 mol% or more, more preferably 30 mol% or more, particularly preferably 40 mol% or more, preferably 90 mol% or less, more preferably 80 mol% or less, still more preferably 70 mol% or less, Especially preferably, it is 60 mol% or less. When the content is within the above range, the Df of the PI-based film tends to decrease. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

In one embodiment of the present invention, when the structural unit (A) includes the structural units (A1) and (A2), the structural unit (A) has the formula (X):

(content of structural unit (A3)) / (total amount of structural unit (A1) and structural unit (A2)) <1.1 (X)

It is desirable to satisfy the relationship of When the structural unit (A) satisfies the relationship of formula (X), that is, when the value of the left side of formula (X) is less than 1.1, particularly less than 0.67, the resulting PI-based film tends to have a reduced Df, resulting in a PI-based Even if the imidization temperature of the resin is low, it is easy to reduce the Df of the obtained PI-based film, and a PI-based film excellent in balance with mechanical properties can be obtained.

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

In one embodiment of the present invention, the structural unit (A) is a structural unit derived from tetracarboxylic acid anhydride represented by formula (a2) from the viewpoint of easily reducing Df of the PI-based film, and/or formula (1 ) preferably contains a structural unit derived from tetracarboxylic anhydride represented by formula (32) in which Y in f=0. In one embodiment of the present invention, the structural unit (A) is a structural unit derived from tetracarboxylic acid anhydride represented by formula (a1) and tetracarboxylic acid represented by formula (a2) from the viewpoint of easily reducing Df of the PI-based film. It is preferable to include at least one selected from the group consisting of a structural unit derived from a carboxylic acid anhydride and a structural unit derived from a tetracarboxylic acid anhydride represented by formula (32) in which Y in formula (1) is f = 0, In addition to the structural unit derived from tetracarboxylic acid anhydride represented by (a1), the structural unit derived from tetracarboxylic acid anhydride represented by formula (a2) and/or Y in formula (1) represented by formula (32) where f=0 It is more preferable to include a structural unit derived from tetracarboxylic acid anhydride.

(Diamine-derived structural unit (B))

The PI-based resin contains a structural unit (B) derived from diamine (hereinafter sometimes simply abbreviated as structural unit (B)). The structural unit (B) is not particularly limited as long as E' and Tg at 280°C of the PI-based resin are within the above ranges, but, for example, formula (2):

[In formula (2), X represents a divalent organic group]

It is preferable that it is a structural unit derived from diamine represented by.

In Formula (2), X represents a divalent organic group, Preferably it represents a C2-C100 divalent organic group. Examples of the divalent organic group include a divalent aromatic group and a divalent aliphatic group, and examples of the divalent aliphatic group include a divalent acyclic aliphatic group and a divalent cyclic aliphatic group. Among these, a divalent cyclic aliphatic group and a divalent aromatic group are preferable, and a divalent aromatic group is more preferable from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film. The divalent organic group may have a hydrogen atom in the organic group substituted with a halogen atom, a hydrocarbon group, an alkoxy group, or a halogenated hydrocarbon group, and in that case, these groups preferably have 1 to 8 carbon atoms. In addition, in this specification, a divalent aromatic group is a divalent organic group which has an aromatic group, and may contain an aliphatic group or another substituent in a part of the structure. In addition, a divalent aliphatic group is a divalent organic group having an aliphatic group, and may contain other substituents in a part of its structure, but does not contain an aromatic group.

In one embodiment of the present invention, the PI-based resin may contain multiple types of X, and the multiple types of X may be the same or different. Examples of X in formula (2) include groups (structures) represented by formulas (60) to (65); The hydrogen atoms in the groups represented by formulas (60) to (65) are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluoro , a group substituted with a chloro group or a trifluoromethyl group, and the like.

[In formulas (60) and (61), R ^a and R ^b each independently represent a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom,

W is, independently of each other, a single bond, -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 )-, wherein R ^c has 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom represents a monovalent hydrocarbon group of

t represents an integer of 0 to 4, u represents an integer of 0 to 4, n represents an integer of 0 to 4,

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 equal to or less than (carbon number of ring A - 2);

S1 and S2, independently of each other, represent integers from 0 to 20,

In formulas (60) to (65), * represents a bond.]

Other examples of X in Formula (2) include ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylene, 1,2-butanediyl, and 1,3-butanedi. Divalent acyclic aliphatic groups such as linear or branched chain alkylene groups such as diyl group, 1,12-dodecanediyl group, 2-methyl-1,2-propanediyl group, and 2-methyl-1,3-propanediyl group can be heard The hydrogen atom in the divalent acyclic aliphatic group may be substituted with a halogen atom, and the carbon atom may be substituted with a hetero atom such as an oxygen atom or a nitrogen atom.

Among these, from the viewpoint of easily improving the mechanical and thermal properties of the PI-based film, the PI-based resin in the present invention has a structure represented by formulas (60) and (61) as X in formula (2). It is preferable to include, and it is more preferable to include a structure represented by Formula (60).

In the formulas (60) and (61), the bond of each benzene ring or each cyclohexane ring is -W- or based on the single bond connecting each benzene ring or each cyclohexane ring, respectively, ortho position, It may be bonded to any of the meta-position, the para-position, the α-position, the β-position, or the γ-position, and even if the imidation temperature is low, the PI-based film can be easily reduced in Df and easily increase dimensional stability. In, preferably, it can bind to the meta-position or the para-position, or the β-position or the γ-position, more preferably the para-position or the γ-position.

R ^a and R ^b each independently represent a halogen atom or an alkyl group, alkoxy group, aryl group or aryloxy group which may have a halogen atom, preferably a halogen atom, an alkyl group which may have a halogen atom, or an alkoxy group represents a group or an aryl group, more preferably a halogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or an aryl group of 6 to 12 carbon atoms. As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, what was illustrated above is mentioned. The hydrogen atom contained in R ^a and R ^b may be mutually independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. From the standpoint of easily reducing Df of the PI-based film and facilitating dimensional stability, R ^a and R ^b are each independently preferably an alkyl group of 1 to 6 carbon atoms or a fluorinated alkyl group of 1 to 6 carbon atoms, and copper foil From the standpoint of easily improving adhesion to substrates such as the like, a fluorine-free alkyl group of 1 to 6 carbon atoms is more preferred, a fluorine-free alkyl group of 1 to 3 carbon atoms is more preferred, and a methyl group is preferred. particularly preferred.

In formulas (60) and (61), t and u are independently integers of 0 to 4, and from the viewpoint of easily reducing Df of the PI-based film and increasing dimensional stability, preferably 0 It is an integer of -2, more preferably 0 or 1.

In Formulas (60) and (61), W is, independently of each other, a single bond, -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 )-, From the standpoint of easily reducing Df and increasing dimensional stability, preferred are -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC It represents - or -CO-, and from the viewpoint of increasing adhesion to substrates such as copper foil, more preferably a single bond, -O-, -CH ₂ - or -C(CH ₃ ) ₂ -, and further Preferably -O- or -C(CH ₃ ) ₂ -. R ^c represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include those exemplified above.

In formulas (60) and (61), n is an integer of 0 to 4, and is preferably an integer of 0 to 3 from the viewpoint of easily reducing the Df of the PI-based film and increasing the dimensional stability. Preferably it is 1-3. When n is 2 or more, a plurality of W, R ^a , and t may be the same or different from each other, and the position of the bond of each benzene ring relative to -W- may be the same or different.

When the PI-based resin in the present invention contains two or more structures represented by formulas (60) and (61) as X in formula (2), one of formulas (60) and (61) W , n , R ^a , R ^b , t and u are, independently of each other, the same as W, n, R ^a , R ^b , t and u in the other formulas (60) and (61) It may or may not be different.

In formula (62), ring A represents a cycloalkane ring having 3 to 8 carbon atoms. Examples of the cycloalkane ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring and a cyclooctane ring, preferably a cycloalkane ring having 4 to 6 carbon atoms. there is. 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 be in a positional relationship at the α-position, β-position, or γ-position, preferably at the β-position or γ-position.

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

As a specific example of the structure represented by Formula (60) - Formula (62), the structure represented by Formula (71) - Formula (92) is mentioned. In these formulas, * represents a bond.

In a preferred embodiment of the present invention, when at least one constituent unit derived from diamine represented by formulas (60) and (61) is included as X in formula (2), X in formula (2) is the formula ( 60) and the ratio of structural units derived from diamine represented by formula (61), particularly the ratio of structural units derived from diamine in formula (60), where n is 1 and W represents a single bond, structural unit (B) With respect to the total molar amount of, preferably 25 mol% or more, more preferably more than 30 mol%, even more preferably 50 mol% or more, even more preferably 70 mol% or more, particularly preferably 90 mol% or more and is preferably 100 mol% or less. The ratio of constituent units derived from diamines in which X in formula (2) is represented by formulas (60) and (61), particularly the ratio of constituent units derived from diamines in which at least one W represents a single bond in formula (60) Within this range, the Df of the PI-based film can be easily reduced and the dimensional stability can be easily improved. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Structural unit derived from diamine containing biphenyl skeleton (B1))

In one embodiment of the present invention, the structural unit (B) preferably includes a structural unit (B1) derived from diamine containing a biphenyl skeleton (hereinafter sometimes simply abbreviated as structural unit (B1)). do. The PI-based resin in which the structural unit (B) includes the structural unit (B1) easily reduces the Df of the obtained PI-based film even when the imidization temperature is low, so that it is a PI-based film obtained even when the imidization temperature is low. The electric circuit made is easy to reduce transmission loss.

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. In one embodiment of the present invention, the structural unit (B1) has the formula (b1) from the viewpoint of easily reducing the Df of the PI-based film even when the imidization temperature is low:

[In formula (b1), R ^b1 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

p represents, independently of each other, an integer from 0 to 4]

It is preferable that it is a structural unit (b1) derived from the diamine represented by

In the formula (b1), R ^b1 each 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 may have a halogen atom. , An alkyl group, an alkoxy group or an aryl group, more preferably a halogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms, or an aryl group of 6 to 12 carbon atoms. As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, what was illustrated above is mentioned. The hydrogen atom contained in ^Rb1 may be mutually independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. From the standpoint of easily reducing the Df of the PI-based film and easily increasing the dimensional stability, each R ^b1 is preferably an alkyl group of 1 to 6 carbon atoms or a fluorinated alkyl group of 1 to 6 carbon atoms independently of each other, and a base material such as copper foil From the standpoint of easily increasing adhesion with, a fluorine-free alkyl group having 1 to 6 carbon atoms is more preferable, a fluorine-free alkyl group having 1 to 3 carbon atoms is more preferable, and a methyl group is particularly preferable. .

In the formula (b1), p represents an integer of 0 to 4 independently of each other, and from the viewpoint of easily reducing the Df of the PI-based film and increasing the dimensional stability, preferably an integer of 0 to 2; Preferably it is 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, relative to the single bond connecting each benzene ring. Alternatively, it may be bonded 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 increasing the dimensional stability, preferably the meta position or para position, or the β position or It can bind to the γ-position, more preferably the para-position, or the γ-position.

In one preferred embodiment of the present invention, formula (b1) is formula (b1'):

It is preferable to appear as When the PI-based resin contains, as the structural unit (B1), a structural unit derived from diamine represented by formula (b1), particularly formula (b1'), Df of the obtained PI-based film is less likely to be reduced even when the imidization temperature is low. easy.

In one embodiment of the present invention, the structural unit (B1), preferably the content of the structural unit (b1), relative to the total amount of the structural unit (B), is preferably 25 mol% or more, more preferably 30 More than mol%, more preferably 35 mol% or more, still more preferably 40 mol% or more, particularly preferably 60 mol% or more, particularly preferably 70 mol% or more, particularly more preferably 80 mol% or more , More preferably, it is 90 mol% or more. If the content of the structural unit (B1), preferably the structural unit (b1) is equal to or greater than the lower limit, the Df can be easily reduced even if the imidation temperature is low. Further, the upper limit of the content of the structural unit (B1), preferably the structural unit (b1), is not particularly limited, and may be 100 mol% or less with respect to the total amount of the structural unit (B). The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Constituent Unit (B2))

In one embodiment of the present invention, the structural unit (B) is a structural unit (B2) derived from diamine having two or more aromatic rings and each aromatic ring bonded via a divalent organic group (hereinafter simply referred to as structural unit). unit (B2)) is preferably included. As a divalent organic group in structural unit (B2), the alkylene group which may have a halogen atom, -O-, -COO-, -OOC-, _-SO2- , -S-, -CO, for example - or -N(R ^c )-, where R ^c represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Among these, as the divalent organic group in the structural unit (B2), -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 )- are preferred.

In one embodiment of the present invention, the structural unit (B) is a structural unit (B2), and the formula (b2):

[In formula (b2), R ^b2 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;

W is, independently of each other, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, Represents -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, and R ^c is a monovalent group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. represents a hydrocarbon group,

m represents an integer of 1 to 4,

q represents, independently of each other, an integer from 0 to 4]

It is preferable to include a structural unit (b2) derived from diamine represented by (hereinafter sometimes simply abbreviated as structural unit (b2)). When the structural unit (B) includes the structural unit (B2), particularly the structural unit (b2), Df of the PI-based film obtained even when the imidization temperature is low is likely to decrease, and as a result, the PI-based film obtained even when the imidization temperature is low. It is easy to reduce the transmission loss of the electronic circuit comprising the.

In formula (b2), R ^b2 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 an alkyl group having 1 to 6 carbon atoms. , A C1-C6 alkoxy group or C6-C12 aryl group is shown. As a C1-C6 alkyl group, a C1-C6 alkoxy group, and a C6-C12 aryl group, what was illustrated above is mentioned. The hydrogen atom contained in R ^b2 may be mutually independently substituted with a halogen atom, and examples of the halogen atom include those exemplified above. From the standpoint of easily reducing the Df of the PI-based film and increasing the dimensional stability, each R ^b2 is preferably an alkyl group of 1 to 6 carbon atoms or a fluorinated alkyl group of 1 to 6 carbon atoms independently of each other, and a base material such as copper foil From the standpoint of easily increasing adhesion with, a fluorine-free alkyl group having 1 to 6 carbon atoms is more preferable, a fluorine-free alkyl group having 1 to 3 carbon atoms is more preferable, and a methyl group is particularly preferable. .

In the formula (b2), q 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 increasing the dimensional stability. Preferably it is 0 or 1.

In Formula (b2), W is, independently of each other, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C Represents (CF ₃ ) ₂ -, -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, easily reduces Df of the PI-based film, and has dimensional stability. From the viewpoint of increasing, preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -COO-, -OOC- or -CO-, Further, from the viewpoint of easily increasing adhesion with substrates such as copper foil, more preferably -O-, -CH ₂ - or -C(CH ₃ ) ₂ -, still more preferably -O- or -C(CH ₃ ) indicates ₂ -. R ^c represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or 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. As a halogen atom, the thing similar to the above is mentioned.

In the formula (b2), m is an integer of 1 to 4, and is preferably an integer of 1 to 3, more preferably 2 or 3, from the viewpoint of easily reducing the Df of the PI-based film and increasing the dimensional stability. am. In formula (b2), a plurality of W, R ^b2 , and q may be the same or different from each other, and the position of -W- relative to -NH ₂ of each benzene ring may be the same or different. .

In formula (b2), -W- is bonded to -NH ₂ of each benzene ring, respectively, at an ortho position, a meta position, or a para position, or an α position, a β position, or a γ position, and From the viewpoint of easily reducing the Df of the PI-based film and easily increasing the dimensional stability even when the imidization temperature is low, preferably the meta position or the para position, or the β position or the γ position, more preferably the para position. position, or at the γ position.

In one embodiment of the present invention, 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 improving the adhesion between the PI-based film and a substrate such as copper foil, the formula (b2 ), m is 3, and W is independently of each other, -O- or -C (CH ₃ ) ₂ It is preferable to represent -, formula (b2), formula (b2'):

It is more preferable to appear as When the PI-based resin contains a structural unit (b2), particularly a structural unit derived from diamine represented by formula (b2'), it is easy to reduce E' at 280°C, and as a result, even with low-temperature thermal imidation, the PI-based resin Since the Df of the resin tends to decrease, it is easy to obtain a PI-based film having a low Df and excellent adhesion to copper foil even when the imidization temperature is low.

In one embodiment of the present invention, the structural unit (b2) is in addition to the diamine-derived structural unit represented by formula (b2'), or instead of the structural unit, m is 1 in formula (b2), W may contain the structural unit derived from the diamine which represents -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 0.5 mol% with respect to the total amount of the structural unit (B). mol% or more, still more preferably 0.8 mol% or more, particularly preferably 1 mol% or more, particularly more preferably 5 mol% or more, still more preferably 8 mol% or more. When the content of the structural unit (B2) is equal to or greater than the above lower limit, it is easy to improve the adhesiveness of the resulting PI-based film with substrates such as copper foil. The upper limit of the content of the structural unit (B2) is preferably 75% by mol or less, more preferably 60% by mol or less, still more preferably 40% by mol or less, and even more, with respect to the total amount of the structural unit (B). Preferably it is 30 mol% or less, and 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 tend to be easily improved. The ratio of the constituent units can be measured, for example, using ¹ H-NMR, or can be calculated from the introduction ratio of raw materials.

(Constituent Unit (B3))

The PI-based resin may also contain a structural unit (B3) derived from diamine other than the structural unit (B1) and the structural unit (B2) (hereinafter sometimes simply abbreviated as the structural unit (B3)). As the structural unit (B3), for example, a structural unit derived from diamine in which m in formula (b2) is 0, a structural unit derived from diamine in which X in formula (2) is represented by formulas (61) to (64), etc. Among these, X in formula (2) is a structure derived from diamine represented by formula (71), formula (74), formula (77), formula (78), formula (89) and formula (90). A unit is preferable, and a structural unit derived from diamine represented by Formula (74) (a structural unit derived from p-phenylenediamine) is more preferable. In the present specification, "structural units derived from diamines other than structural units (B1) and structural units (B2) (B3)" are constituents derived from diamines different from either of the structural units (B1) and the structural units (B2). means unit.

In one embodiment of the present invention, when the structural unit (B) includes the structural unit (B3), the content of the structural unit (B3) is preferably 25 mol% relative to the total amount of the structural unit (B). or less, 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 may contain a halogen atom, preferably a fluorine atom, which can be introduced by, for example, the halogen-containing substituent described above. When the PI-based resin contains fluorine atoms, the dielectric constant of the obtained PI-based film is easily reduced. Preferable fluorine-containing substituents for incorporating a fluorine atom into the PI-based resin include, for example, a fluoro group and a trifluoromethyl group.

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 adhesion of the resulting PI-based film to a base material such as copper foil. In addition, since the PI-based resin containing fluorine tends to weaken the interaction between molecular chains, if the PI-based resin does not contain fluorine atoms, it is easy to form a higher-order structure in which molecular rotation of the PI-based resin is suppressed. It tends to be easy to obtain the effect of an invention.

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. 0.1 to 30% by mass, more preferably 0.1 to 20% by mass, particularly preferably 0.1 to 10% by mass. When the content of halogen atoms is equal to or greater than the above lower limit, the heat resistance and dielectric properties of the resulting PI-based film are likely to be improved. When 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 mean properties related to dielectrics including relative permittivity and dielectric loss tangent, and that dielectric properties increase or improve means that the relative permittivity and/or dielectric loss tangent decrease.

In one embodiment of the present invention, the imidation rate of the PI-based resin is preferably 90% or more, more preferably 93% or more, still more preferably 95% or more, and is usually 100% or less. From the standpoint of easily improving mechanical properties, thermal properties, and dielectric properties, the imidation ratio is preferably equal to or greater than the above lower limit. The imidation rate represents the ratio of the molar amount of imide bonds in the PI-based resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the PI-based resin. In addition, when the PI-based resin contains a tricarboxylic acid compound, the value of twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the PI-based resin and the molar amount of the structural unit derived from the tricarboxylic acid compound The ratio of the molar amount of the imide bond in the PI-based resin to the total of In addition, the imidation rate can be obtained by IR method, NMR method or the like.

In one embodiment of the present invention, the weight average molecular weight of the PI-based resin in terms of polystyrene (hereinafter, the weight average molecular weight may be referred to as Mw) is preferably 100,000 or more, more preferably greater than 100,000, More preferably 110,000 or more, still more preferably 120,000 or more, 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, particularly preferably 300,000 or less am. When Mw is equal to or greater than the above lower limit, it is easy to improve mechanical properties such as folding resistance. If Mw is below the above upper limit, it is advantageous from the viewpoint of workability during film formation.

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

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 70% by mass or more relative to the mass of the PI-based film of the present invention. Preferably it is 80% by mass or more, and particularly preferably 90% by mass or more. In addition, 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, and more preferably 95% by mass or less with respect to the mass of the PI-based film. When the content of the PI-based resin is within the above range, mechanical properties and thermal properties are easily improved.

The PI-based film of the present invention may contain a filler, if necessary. Examples of the filler include metal oxide particles such as silica and alumina, inorganic salts such as calcium carbonate, and polymer particles such as fluororesins and 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% by mass, based on the total mass of the PI-based film. mass % or more.

Further, in one embodiment of the present invention, the PI-based film of the present invention may contain additives, if necessary. Examples of additives include antioxidants, flame retardants, crosslinking agents, surfactants, compatibilizers, imidation catalysts, weathering agents, lubricants, antiblocking agents, antistatic agents, antifogging agents, and anti-drip agents. ), pigments, and the like. Additives can be used alone 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 including various additives, the total content is preferably 7% by mass or less with respect to the total 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.

<Polyimide film>

The PI-based film of the present invention includes a PI-based resin containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine, and the PI-based resin has an E at 280°C. Since ' is less than 3 × 10 ⁸ Pa and the Tg is 200 to 290 ° C, even if the thermal imidization temperature is low, Df can be reduced, so it is suitable for metal-clad laminates such as CCL that can respond to high-frequency bands. available. Further, 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 more and less than 350°C.

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, still more preferably 30 ppm/K or less, and still more preferably 25 ppm/K or less, preferably 0ppm/K or more, more preferably 5ppm/K or more, still more preferably 8ppm/K or more, still more preferably 12ppm/K or more. By setting it as said range, since CTE of a copper foil and a PI layer approaches, peeling of laminated|multilayer film can be suppressed. In addition, CTE can be measured by, for example, a thermomechanical analyzer (sometimes described as "TMA"), and is obtained by the method described in Examples.

A printed circuit is required to have a small transmission loss. Transmission loss is the sum of dielectric loss, which is a loss caused by an electric field generated in a dielectric, and conductor loss, which is a loss caused by a current flowing through a conductor. And it is known that dielectric loss is approximately proportional to the index E represented by Formula (i).

E=Df×(Dk) ^1/2 (i)

[In Formula (i), Df represents a dielectric loss tangent, and Dk represents a relative permittivity]

Since dielectric loss tends to increase in the high-frequency region used in FPC for 5G, a material having a small value of the index E and capable of suppressing dielectric loss is particularly required.

On the other hand, in the high-frequency signal, current is concentrated on the surface of the conductor. Therefore, it is known that conductor loss is approximately proportional to (Dk) ^1/2 , in relation to the dielectric properties of the dielectrics in contact.

As described above, the PI-based film of the present invention includes a PI-based resin containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine, and the PI-based resin has a 280 Since E' at °C is less than 3 × 10 ⁸ Pa and Tg is 200 to 290 °C, as Df and Dk decrease, the dielectric loss index E and conductor loss also decrease, including 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 0.009 or less, more preferably 0.008 or less, still more preferably 0.007 or less, particularly preferably 0.006 or less. am. The smaller the index E, the lower the transmission loss of the electronic circuit including the PI-based film. Therefore, the lower limit of the index E is not particularly limited, and may be, for example, 0 or more.

In one embodiment of the present invention, Df of the PI-based film at 10 GHz is preferably less than 0.004, more preferably 0.0038 from the viewpoint of facilitating reduction of transmission loss in an electronic circuit including the PI-based film. or less, more preferably 0.0035 or less, even more preferably 0.0033 or less, particularly preferably 0.003 or less, particularly more preferably 0.0027 or less, particularly preferably 0.0024 or less. The smaller the Df, the lower the transmission loss of the electronic circuit including the PI-based film. Therefore, the lower limit of the Df is not particularly limited, and may be, for example, 0 or more.

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

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

In one embodiment of the present invention, the number of bends to breakage in the MIT bending resistance fatigue test based on ASTM standard D2176-16 of the PI-based film of the present invention is 15,000 or more, preferably 20,000 or more, more preferably It is preferably 50,000 times or more, more preferably 100,000 times or more, still more preferably 150,000 times or more, and particularly preferably 200,000 times or more. If the number of times of bending is equal to or greater than the above lower limit, generation of cracks, cracks, creases and the like can be effectively suppressed even if repeatedly bent. In addition, the upper limit of the number of times of bending is not particularly limited, and may be, for example, 10,000,000 or less. In addition, the MIT internal fatigue test can be measured using an MIT internal fatigue tester, and can be measured, for example, by the method described in Examples.

In one embodiment of the present invention, from the viewpoint of easily reducing the Df of the PI-based film and increasing the mechanical properties, E' at 280 ° C. of the PI-based resin and the PI-based film containing the PI resin CTE is, formula (Y):

(CTE of PI-based film) x (E' at 280 ° C. of PI-based resin) ^1/2 ≥ 30,000

It is desirable to satisfy the relationship of

In one embodiment of the present invention, the value of the left side of formula (Y) is preferably 40,000 or more, more preferably 50,000 or more, from the viewpoint of easily reducing the Df of the PI-based film and easily increasing the bending resistance; More preferably 100,000 or more, even more preferably 120,000 or more, particularly preferably 125,000 or more, preferably 1,500,000 or less, more preferably 1,000,000 or less, still more preferably 850,000 or less, still more preferably 700,000 or less, particularly preferably 500,000 or less, more particularly preferably 450,000 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, and more It is preferably 300 μm or less, more preferably 100 μm or less, particularly preferably 80 μm or less, and even more preferably 50 μm or less. The thickness of the film can be measured using a film thickness gauge or the like. In addition, when the film of the present invention is a multilayer film, the thickness indicates the thickness of a single layer portion.

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

Since the PI-based film of the present invention has a low Df, it can be suitably used as a substrate material compatible with printed circuit boards and antenna boards for high frequency bands. Metal-clad laminates such as CCL used in FPC are widely used as laminates having metal foils such as copper foil layers on one side or both sides of a single layer or multiple layers of PI-based resin. When the PI-based film of the present invention is used as a resin layer, since the PI-based film of the present invention can have a low Df even if the imidization temperature is low, the PI-based resin precursor coating film is thermally imidized on a metal foil such as copper foil. Since deterioration of the copper foil surface can be suppressed even if it manufactures the said metal clad laminated board, such as CCL by doing, the metal clad laminated board, such as CCL, which has excellent high frequency characteristics can be obtained.

[Method for producing polyimide film]

The method for producing the PI-based film of the present invention is not particularly limited, but includes, for example, the following steps:

A step of coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine on a substrate, and

It can be manufactured by a method including a step of imidizing the PI-based resin precursor by heat treatment at 200°C or more and less than 350°C.

<Coating step of polyimide-based resin precursor solution>

(Preparation of PI-based resin precursor solution)

The PI-based resin precursor solution contains a PI-based resin precursor containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine, and a solvent, by mixing the PI-based resin precursor and the solvent. can be prepared In one embodiment of the present invention, the reaction solution containing the PI-based resin precursor obtained by the synthesis of the PI-based resin precursor may be appropriately diluted with a solvent as necessary and used as the PI-based resin precursor solution. .

The PI-based resin precursor in the present invention is obtained by reacting tetracarboxylic acid anhydride with diamine. In addition to the tetracarboxylic acid compound, a dicarboxylic acid compound or a tricarboxylic acid compound may be reacted.

Examples of the tetracarboxylic acid anhydride used in the synthesis of the PI-based resin precursor include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. A tetracarboxylic acid compound may be used independently or may be used in combination of 2 or more types. The tetracarboxylic acid compound may be an analog of a tetracarboxylic acid compound such as an acid chloride compound other than a dianhydride.

As said tetracarboxylic acid compound, the tetracarboxylic acid anhydride represented by the said formula (1) is mentioned, for example, Preferably, the tetracarboxylic acid anhydride represented by the formula (a1) and the tetracarboxylic represented by the formula (a2) are mentioned, for example. Tetracarboxylic acid anhydrides in which Y in formula (1) is represented by formula (32) are mentioned.

Specific examples of the tetracarboxylic acid compound include pyromellitic anhydride (hereinafter sometimes referred to as PMDA) and 4,4'-(4,4'-isopropylidenediphenoxy) diphthalic anhydride (hereinafter referred to as BPADA). may be described), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as BPDA) , 4,4'-(Hexafluoroisopropylidene)diphthalic dianhydride (hereinafter sometimes referred to as 6FDA), 4,4'-oxydiphthalic dianhydride (hereinafter sometimes referred to as ODPA) ), 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4 '-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester acid dianhydride) (hereinafter referred to as TAHQ) may), esterified product 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'-diphenylethertetracarboxylic 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 -Dicarboxyphenyl)-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-dicarboxyphenyl) Tetrafluoropropane dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (hereinafter sometimes referred to as HPMDA), 2,3,5,6-cyclohexanetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, 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 acid anhydride, p-phenylenebis(trimellitate anhydride), 3,3',4, 4'-Diphenylsulfonetetracarboxylic dianhydride, 2,3,6,7-anthracentetracarboxylic 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-tetra Carbonic acid dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid 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-dicarboxy Phenyl) sulfone dianhydride etc. are mentioned. Among these, BPDA, PMDA, TAHQ, and BP-TME are preferable, and BPDA, TAHQ, and BP-TME are more preferable from the viewpoint of easily reducing Df of the obtained PI-based film even when the imidization temperature is low. These tetracarboxylic acid compounds can be used individually or in combination of 2 or more types.

Examples of the diamine compound used in the synthesis of the PI-based resin precursor include aliphatic diamines, aromatic diamines, and mixtures thereof.

As said diamine compound, the diamine compound represented by said formula (2) is mentioned, for example, Preferably, the diamine compound represented by formula (b1) and the diamine compound represented by formula (b2) are mentioned.

In addition, in this embodiment, "aromatic diamine" shows diamine which has an aromatic ring, and may contain an aliphatic group or another substituent in a part of the structure. This aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Among these, a benzene ring is preferable. In addition, "aliphatic diamine" shows diamine which has an aliphatic group, and may contain other substituents in a part of the structure, but does not have an aromatic ring.

Specific examples of the diamine compound 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 (hereinafter sometimes referred to as TPE-R), 2,2'-bis[4-( 4-aminophenoxy)phenyl]propane (hereinafter 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-amino) Phenoxy)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'-dia Minodiphenylpropane, 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 (hereinafter 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-phenylenediiso Propylidene)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-diamino Butane, 2-methyl-1,2-diaminopropane, 2-methyl-1,3-diaminopropane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, Norbornandiamine, 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'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 2,5-dia Mino-1,3,4-oxadiazole, bis[4,4'-(4-aminophenoxy)]benzanilide, bis[4,4'-(3-aminophenoxy)]benzanilide, 2, 6-diaminopyridine, 2,5-diaminopyridine, etc. are mentioned. Among these, m-Tb, BAPP, TPE-Q, TPE-R and the like are preferable, and m-Tb, BAPP and the like are more preferable from the viewpoint of easily reducing the Df of the obtained PI-based film even when the imidization temperature is low. . A diamine compound can be used individually or in combination of 2 or more types.

In addition, the PI-based resin precursor, in addition to the tetracarboxylic acid compound used in the synthesis of the PI-based resin precursor, other tetracarboxylic acids, dicarboxylic acids, and tricarboxylic acids, within a range that does not impair various physical properties of the PI-based film What made this acid and their anhydride and derivative further react may be used.

As another tetracarboxylic acid, the water adduct of the anhydride of the said tetracarboxylic acid compound is mentioned.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds and acid anhydrides, and two or more may be used in combination. As a specific example, terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; A dicarboxylic acid compound of a chain hydrocarbon having 8 or less carbon atoms and two benzoic acids having a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, - SO ₂ - or compounds linked with a phenylene group, and acid chloride compounds thereof.

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

In production of the PI-based resin precursor, the amount of the diamine compound, the tetracarboxylic acid compound, the dicarboxylic acid compound, and the tricarboxylic acid compound used can be appropriately selected according to the desired ratio of each constituent unit of the PI-based resin.

In the present invention, the total number of moles of the diamine compound used per 1 mole of the total amount of the tetracarboxylic acid compound is defined as the amine ratio. In one preferred embodiment of the present invention, the amine ratio is preferably 0.90 mol or more and preferably 0.999 mol or less with respect to 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, still more preferably 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, still more preferably 1.003 mol or more and 1.03 mol or less. .

When the amine ratio is close to 1.0 mol, the molecular weight tends to increase rapidly during synthesis, and when it is greatly away from 1.0 mol, the molecular weight of the obtained PI-based resin tends to decrease. If the molecular weight increases rapidly, it tends to grow non-uniformly in the synthetic mass, making it difficult to stabilize the physical properties of the PI-based resin. On the other hand, when the molecular weight is too low, mechanical properties tend to deteriorate.

The reaction temperature of the diamine compound and the tetracarboxylic acid compound is preferably 50°C or lower, more preferably 40°C or lower, and still more preferably 30°C or lower. If the reaction temperature is equal to or less than the above upper limit, it is easy to reduce the Df of the obtained PI-based film, and this tendency is a PI-based resin containing an ester bond, particularly a PI-based resin containing a structural unit (A1). This is particularly remarkable in films. 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 greater than the above lower limit, the reaction rate tends to be increased and the polymerization time tends to 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. If the reaction time is within the above range, even if the imidation temperature is low, it is easy to reduce Df of the obtained PI-based film.

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, and examples thereof include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy- alcohol solvents such as 2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; phenolic 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 pentane, 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 dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; pyrrolidone solvents such as N-methylpyrrolidone (hereinafter sometimes referred to as NMP); and combinations thereof. Among these, from the viewpoint of solubility, preferably a phenolic solvent, a lactone solvent, an amide solvent, and a pyrrolidone solvent, and more preferably an amide solvent can be suitably used.

In one embodiment of the present invention, the boiling point of the solvent used for the reaction between the diamine compound and the tetracarboxylic acid compound is preferably from the viewpoint of easily reducing the Df of the obtained PI-based film even when the imidation temperature is low. It is preferably 230°C or lower, more preferably 200°C or lower, and still more preferably 180°C or lower. 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 obtained PI-based film.

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 a reduced pressure, as required, under an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. , It is preferable to carry out with stirring in a strictly controlled dehydration solvent.

The solvent contained in the PI-based resin precursor solution includes exemplified solvents used for the reaction between a diamine compound and a tetracarboxylic acid compound, preferably lactone-based solvents, amide-based solvents, and pyrrolidone-based solvents, more preferably Preferably, it is an amide-based solvent. In one embodiment of the present invention, the boiling point of the solvent contained in the PI-based resin precursor solution is preferably 230°C or less from the viewpoint of easily reducing the Df of the obtained PI-based film even when the imidization temperature is low. , More preferably 200°C or less, still more preferably 180°C or less, and particularly preferably 170°C or less. 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 obtained PI-based film.

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. above, particularly preferably 13% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, still 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, workability during film formation is excellent.

(Coating of polyimide-based resin precursor solution)

The coating step of the PI-based resin precursor solution is a step of coating the PI-based resin precursor solution on a substrate to form a coating film.

In the coating step, a coating film is formed by coating the composition on a substrate by a known coating method or coating method. As a known coating method, for example, a wire bar coating method, a reverse coating method, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen printing coating method, and a mounting coating method , a dipping method, a spray method, a curtain coating method, a slot coating method, a casting method, and the like. When coating or applying the solution of the PI-based resin precursor onto the substrate, a single layer of the PI-based resin precursor may be applied on the substrate or a plurality of layers of the PI-based resin precursor may be applied onto the substrate. In the case of coating a plurality of layers of the PI-based resin precursor on a substrate, the coating may be divided into a plurality of times and dried, or a plurality of layers may be coated simultaneously.

Examples of the substrate include metal plates such as metal foil (eg copper foil) (eg copper plates), SUS foils, SUS plates such as SUS belts, glass substrates, PET films, PEN films, and PI-based films of the present invention. Other PI-based resin films, polyamide-based resin films, and the like are exemplified. Among them, from the viewpoint of excellent heat resistance, preferably copper plate, SUS plate, glass substrate, PET film, PEN film, etc. are mentioned, and from the viewpoint of adhesion to the film and cost, more preferably copper plate, SUS plate, A glass substrate or PET film etc. are mentioned.

<Imidization process>

The imidation step is a step of imidizing the PI-based resin precursor coated on the substrate by heat treatment at 200°C or more and less than 350°C.

In one embodiment of the present invention, in the imidation step, prior to imidation of the PI-based resin precursor, the PI-based resin precursor solution coated on the substrate is heated and dried under a relatively low temperature, for example, less than 200 ° C. , It is preferable that the dried film of the obtained PI-based resin precursor is imidized by heat treatment at 200°C or more and less than 350°C.

Further, in one embodiment of the present invention, the dried film of the PI-based resin precursor on the substrate may be imidized to obtain the PI-based film, the dried film of the PI-based resin precursor is separated from the substrate, and the dried film peeled from the substrate It 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 at which the solvent is dried and solidified, but from the viewpoint of avoiding surface roughness due to rapid drying, and From the viewpoint of suppressing wrinkles and creases that occur during processing, the temperature is preferably less than 300°C, more preferably 260°C or less, still more preferably 200°C or less, even more preferably 180°C or less, and From the viewpoint of productivity, it is preferably 50°C or higher, more preferably 80°C or higher, and still more preferably 100°C or higher.

Even if the PI-based resin precursor in the present invention is imidized at a low temperature, Df of the obtained PI-based film can be reduced. The heat treatment temperature in the imidation 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, particularly preferably It is preferably 300 ° C or less. If the imidization temperature is equal to or less than the above upper limit, even when a metal foil such as copper foil is used as a base material, thermal deterioration of the metal foil or the like, particularly the copper foil, can be suppressed, so that CCL excellent in high frequency characteristics is easy to obtain. In addition, the imidation temperature is preferably 200°C or higher, more preferably 210°C or higher, still more preferably 220°C or higher, from the viewpoint of sufficiently improving the imidation rate. Moreover, from the viewpoint of easy obtaining of a smooth film, it is preferable to heat in stages. For example, after removing the solvent by heating at a relatively low temperature of 50 to 150°C, it may be heated stepwise to a temperature in the range of 200°C or more and less than 350°C to imidize.

In one embodiment of the present invention, the reaction time in imidation is preferably 0.5 to 24 hours, more preferably 1 to 12 hours. In one embodiment of the present invention, the time for maintaining the temperature at 200°C or higher is preferably 10 minutes to 90 minutes, more preferably 15 minutes to 70 minutes, still more preferably 20 minutes to 50 minutes. . If the reaction time of 200 ° C. or more in imidation is within the above range, it is easy to sufficiently improve the imidation rate, easily prevent oxidative degradation of the resin, and easily improve the dielectric properties and bending resistance of the resulting PI-based film.

After imidation, a PI-based film can be obtained by peeling 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 PI-based film is formed on the obtained metal foil such as copper foil. The laminated laminated film can also be used for metal clad laminates such as CCL.

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

[Laminate film]

Since the PI-based film of the present invention has a low Df, 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, and a laminated film including a PI layer and a thin metal layer is included. In one embodiment of the present invention, the laminated film of the present invention may include the metal foil layer only on one side of the PI layer, or may include it on both sides.

In one embodiment of the present invention, examples of the metal foil include copper foil, SUS foil, and aluminum foil, but from the viewpoint of conductivity and metal workability, copper foil is preferable.

Since the PI-based film of the present invention has a low Df even when the thermal imidization temperature is low and can be suitably used for forming CCL with excellent high-frequency characteristics, in one preferred embodiment of the present invention, the laminated film of the present invention Silver is preferably a laminated film including 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 it is easy to make the circuit finer and improve the folding resistance. From this point of view, it is preferably 100 μm or less, more preferably 50 μm or less, still 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. Further, when metal foil layers, particularly copper foil layers, are included on both sides of the PI-based film, the thicknesses 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, preferably 100 μm or less, more preferably It is 80 micrometers or less, More preferably, it is 60 micrometers or less. The thickness of the laminated film can be measured using a film thickness gauge or the like.

The laminated film of the present invention may contain other layers such as a functional layer in addition to the PI-based film and the metal foil layer, particularly the copper foil layer. Examples of the functional layer include the layers of the above examples, and may be, for example, a thermoplastic PI-based resin layer or an adhesive layer containing a thermoplastic PI-based resin. 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 may be a two-layer metal-clad laminate composed of a metal foil layer and a PI layer, or a three-layer metal-clad laminate composed of a metal foil layer, a PI layer, and an adhesive layer, but heat resistance , From the viewpoint of dimensional stability and weight reduction, it is preferable that the two-layer metal-clad laminate does not contain an adhesive layer.

In addition, since the PI-based film of the present invention has a low Df even if the imidization temperature is low, even if a laminated film in which the metal foil is copper foil is produced by performing thermal imidation of the PI-based resin precursor coating film on the copper foil, the surface of the copper foil Deterioration can be suppressed. Therefore, the laminated film of the present invention has excellent high-frequency characteristics even without 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 a functional layer is inserted between the PI-based film and the metal foil layer, particularly the copper foil layer. , These may be in contact through a functional layer, but from the viewpoint of easy mechanical and thermal properties, it is preferable that the PI-based film and the metal foil layer, particularly the copper foil layer, are in direct contact.

The functional layer that may be interposed 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 thermal properties, the metal foil layer, particularly the layer in direct contact with the copper foil layer, is preferably the PI film of the present invention or a thermoplastic PI layer as a functional layer.

[Manufacturing method of laminated film]

The present invention, the following steps:

A step of coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine on a substrate, and

Process of forming the PI-based film of the present invention on a substrate by imidizing the PI-based resin precursor by heat treatment at 200 ° C. or higher and lower than 350 ° C.

Including, also includes a method for producing a laminated film.

"Process of coating a PI-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine on a substrate" in the method for producing a laminated film of the present invention; and " Regarding the process of imidizing the PI-based resin precursor by heat treatment at 200 ° C. or higher and lower than 350 ° C. to form the PI-based film of the present invention on a substrate,” described in the section [Method for producing a polyimide-based film] A description of each process is equally suitable.

In one embodiment of the present invention, the substrate is preferably a metal foil, and particularly preferably a copper foil. As for the substrate related to metal foil, particularly copper foil, the description related to the metal foil described in the section of [Laminate Film] is similarly suitable.

In the laminated film of the present invention, a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine are prepared by a method other than the above method, for example, on a substrate other than a metal foil included in the laminated film. The dried film of the PI-based resin precursor obtained by coating and drying the containing PI-based resin precursor solution may be peeled off from the substrate, and the peeled dried film of the PI-based resin precursor may be bonded to a metal foil. do. As a method of bonding the dried film of the PI-based resin precursor and the metal foil, a pressing method, a lamination method using a hot roll, or the like may be employed. In the bonding step, imidation of the PI-based resin precursor may be performed simultaneously. . However, since the PI-based film of the present invention has a low Df even if the imidization temperature is low, even if a laminated film in which the metal foil is copper foil is produced by performing thermal imidation of a PI-based resin precursor coating film on a copper foil, for example, copper Deterioration of the foil surface can be suppressed. Therefore, the laminated film of the present invention has excellent high-frequency characteristics even if it is manufactured without passing through the bonding process as described above.

[Flexible printed circuit board]

Since the PI-based film of the present invention has a low Df, the transmission loss of an electric circuit made of the PI-based film can be reduced, and can be suitably used as an FPC substrate material. The present invention also includes an FPC board comprising the PI-based film.

[Example]

Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The symbols used in Examples, Comparative Examples, and Reference Examples represent the following compounds.

BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

TAHQ: p-phenylenebis(trimellitic acid monoester acid dianhydride)

PMDA: pyromellitic anhydride

BP-TME: 4,4'-bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-ylcarbonyloxy)biphenyl

OPDA: 4,4'-oxydiphthalic dianhydride

BPADA: 4,4'-(4,4'-isopropylidenephenoxy)diphthalic anhydride

m-Tb: 4,4'-diamino-2,2'-dimethylbiphenyl

BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane

TPE-R: 1,3-bis(4-aminophenoxy)benzene

TPE-Q: 1,4-bis(4-aminophenoxy)benzene

PDA: p-phenylenediamine

[Synthesis of Polyimide Resin Precursor]

(Example 1)

After dissolving 17.93 g (84.4 mmol) of m-Tb and 0.35 g (0.9 mmol) of BAPP in 284 g of DMAc, 19.35 g (42.2 mmol) of TAHQ was added and stirred at 20°C in a nitrogen atmosphere for 1 hour. Thereafter, 12.42 g (42.2 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 the diamine monomer to the acid dianhydride monomer used was 1.01.

(Examples 2 to 16 and Comparative Examples 1 to 5)

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

[Manufacture of polyimide film]

Using the solvent used in the synthesis of the PI resin precursor, the PI resin precursor composition obtained in Examples 1 to 16 and Comparative Examples 1 to 5 was appropriately diluted in a range where the content of the PI resin precursor was 10% by mass or more, and the viscosity was adjusted. A PI resin precursor solution was prepared by adjusting to 40,000 cps or less. As shown in Table 1, the PI resin precursor solution was formed into a film under any one of the following film forming conditions 1 to 4 to obtain a PI film made of a PI resin.

<Unveiling condition 1>

The PI resin precursor solution was molded by casting on a glass substrate, and a coating film of the PI resin precursor solution was formed using an applicator at a linear speed of 0.4 m/min. After heating the said coating film at 120 degreeC for 30 minute(s) and peeling the obtained film from the glass substrate, the film was fixed to the mold frame. The film fixed to the mold 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 when the temperature was maintained at 220°C or higher was 23 minutes. In addition, the time when the temperature was maintained at 200°C or higher was 34 minutes.

<Unveiling condition 2>

The PI resin precursor solution was cast-molded on the roughened surface side (surface roughness: Rz = 1.3 μm) of an electrolytic copper foil (manufactured by JX Metal Co., Ltd., JXEFL-BHM thickness 12 μm), using an applicator, A coating film of the PI resin precursor solution was molded 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 mold, and the temperature was raised from 30°C to 320°C over 9 minutes in an atmosphere with an oxygen concentration of 1%, followed by heating at 320°C for 6 minutes, and then over 15 minutes. It cooled to 200 degreeC, and the laminated|multilayer film of PI film and copper foil was produced. The time when the temperature was maintained at 220°C or higher was 21 minutes. In addition, the time when the temperature was maintained at 200°C or higher was 25 minutes.

The resulting laminated film of the PI film and the copper foil was immersed in a large volume of 40% by mass ferric chloride aqueous solution at room temperature for 10 minutes, and after visually confirming that no copper remained, it was dried at 80 ° C. for 1 hour, and alone. of PI film was obtained.

<Unveiling condition 3>

The PI resin precursor solution was molded by casting on a glass substrate, and a coating film of the resin precursor solution was formed using an applicator at a linear speed of 0.4 m/min. After heating the said coating film at 120 degreeC for 30 minute(s) and peeling the obtained film from the glass substrate, the film was fixed to the mold frame. The film fixed to the mold was heated from 30 ° C. to 320 ° C. over 9 minutes in an oxygen concentration of 1% atmosphere, then heated at 320 ° C. for 6 minutes and cooled to 200 ° C. over 15 minutes to produce a PI film. The time when the temperature was maintained at 220°C or higher was 21 minutes. In addition, the time when the temperature was maintained at 200°C or higher was 25 minutes.

<Unveiling condition 4>

The PI resin precursor solution was molded by casting on a glass substrate, and a coating film of the PI resin precursor solution was formed using an applicator at a linear speed of 0.4 m/min. After heating the said coating film at 120 degreeC for 30 minute(s) and peeling the obtained film from the glass substrate, the film was fixed to the mold frame. The film fixed to the mold was heated from 30 ° C to 320 ° C over 5 minutes in an oxygen concentration of 1% atmosphere, then heated at 320 ° C for 5 minutes and cooled to 200 ° C over 15 minutes to produce a PI film. The time when the temperature was maintained at 220°C or higher was 17 minutes. In addition, the time when the temperature was maintained at 200°C or higher was 21 minutes.

[Synthesis of Polyimide Resin Precursor and Production of Polyimide Film]

(Comparative Example 6)

After dissolving 70.33 g (331 mmol) of m-Tb in 720 g of NMP, 73.06 g (248 mmol) of BPDA and 37.94 g (83 mmol) of TAHQ were added, followed by stirring at room temperature in a nitrogen atmosphere for 1 hour. After that, the mixture was stirred at 60°C for 20 hours to obtain a PI resin precursor composition. In addition, Mw of the PI resin precursor in terms of polystyrene was 91,000, and Mn was 27,000. The PI resin precursor composition was appropriately diluted with NMP to adjust the viscosity to prepare a PI resin precursor solution, and the obtained PI resin precursor solution was formed into a film under the above film forming condition 1 to obtain a PI film.

The obtained PI film had a thickness of 30 μm, Dk was 3.45, Df was 0.0040, index E was 0.0074, and CTE was 38.2 ppm. In addition, the Tg of the PI resin was 255°C, and E' at 280°C was 5.53×10 ⁸ Pa.

Moreover, Tg calculated|required using the tangential method from the storage elastic modulus curve was 230 degreeC.

Measurements and evaluations were performed on the PI films obtained in Examples and Comparative Examples. Measurement and evaluation methods are described below.

<Measurement of glass transition temperature (Tg)>

Tg of the PI resin obtained in Examples and Comparative Examples was obtained by measuring the PI film as follows.

Using a dynamic viscoelasticity measuring device (manufactured by IT Instrumentation Control Co., Ltd., DVA-220), measured under the following samples and conditions, the storage modulus (Storage modulus, E') and loss modulus (Loss modulus, E") A tanδ curve, which is the ratio of the values of , was obtained, and the highest point of the peak of the tanδ curve was designated as Tg.

Test piece: rectangular parallelepiped with a length of 40 mm, a width of 5 mm, and a thickness of 50 μm (in addition, the thickness varies depending on the film used)

Experiment mode: single frequency, constant rate heating

Experiment Form: Seal

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) tanδ(E"/E')

<Measurement of storage modulus (E')>

E' at 280°C of the PI resins obtained in Examples and Comparative Examples was determined by measuring dynamic viscoelasticity in the same manner as measuring Tg.

<Measurement of weight average molecular weight Mw and number average molecular weight Mn>

Mw and Mn in terms of polystyrene of the PI resin precursor obtained by synthesis were measured using GPC. GPC measurement was performed under the following conditions.

(1) Pretreatment method

After diluting the sample with DMF, what was filtered through a 0.45 µm membrane filter was referred to as a measurement solution.

(2) Measurement conditions

Column: Connect two TSKgel Super AWM-H (internal diameter 6.0 mm, length 150 mm)

Eluent: DMF (10 mmol/L lithium bromide added, 30 mmol/L phosphoric acid added)

Flow rate: 0.6mL/min

Detector: RI detector

Column temperature: 40°C

Injection volume: 20μL

Molecular Weight Standard: Standard Polystyrene

<Measurement of Coefficient of Linear Thermal Expansion (CTE)>

The CTE of the PI film obtained in Examples and Comparative Examples was measured using TMA under the following conditions, and the CTE from 50°C to 100°C was calculated.

Apparatus: Hitachi High-Tech Science Co., Ltd. TMA/SS7100

Load: 50.0mN

Temperature program: temperature rise at a rate of 5°C/min from 20°C to 130°C

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 index E of the dielectric loss of the film was calculated by the following formula.

E=Df×(Dk) ^1/2 (i)

Df: dielectric loss tangent

Dk: relative permittivity

(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. After humidity control of the sample at 25 degreeC/55%RH for 24 hours, the measurement was performed.

Device: Compact USB Vector Network Analyzer (product name: MS46122B) manufactured by Anritz Co., Ltd.

Cavity resonator (TE mode 10GHz type) made by AT Co., Ltd.

Measurement frequency: 10 GHz

Measurement atmosphere: 23℃/50%RH

<Evaluation of bending resistance>

The bending resistance of the PI films obtained in Examples 4, 10, 13, 14 and 15 was evaluated by measuring the number of bending times of the film 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 internal bending fatigue tester (manufactured by Toyo Seiki Manufacturing Co., Ltd., MIT-DA) in accordance with ASTM standard D2176-16, and the test speed was 175 cpm, bending angle 135 °, load 750 g, and bending clamp R = 1.0 mm, the film was alternately bent in both front and back directions, and the number of times of bending until breakage was measured. The greater the number of times of bending, the better the bending resistance.

The number of times of bending of the PI films obtained in Examples 4, 10, 13, 14, and 15 was 240,000, 150,000, 160,000, 130,000, and 20,000, respectively. In addition, for the PI films obtained in Examples 4, 10, 13, 14 and 15, the value of (CTE of PI-based film) × (E' of PI-based resin at 280 ° C.) ^1/2 is, respectively, They were 136141, 115683, 141751, 121951, 116579.

Table 1 shows the measurement and evaluation results and the amine ratio for the PI films obtained in Examples and Comparative Examples.

As shown in Table 1, the PI films obtained in Examples 1 to 16 had a low Df and a dielectric loss index E compared to Comparative Examples even when the maximum temperature of the imidation treatment was as low as 270°C or 320°C. low was confirmed. Therefore, even if the PI-based film of the present invention is produced by casting a PI resin precursor solution on copper foil and thermally imidating the coating film of the PI resin precursor solution on a metal foil such as copper foil, the surface of the metal foil such as copper foil is rough. Since thermal deterioration of loads and the like can be suppressed, it can be suitably used for metal-clad laminates such as CCL with low transmission loss capable of handling high-frequency bands.

Claims (15)

A polyimide-based resin containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine is included, and the polyimide-based resin has a storage modulus at 280°C of 3×10 ⁸ A polyimide-based film having a glass transition temperature of less than Pa and a glass transition temperature of 200 to 290°C. According to claim 1,
The polyimide-based film in which the structural unit (A) includes a structural unit (A1) derived from an ester bond-containing tetracarboxylic acid anhydride. According to claim 2,
The structural unit (A) further includes a structural unit (A2) derived from a biphenyl skeleton-containing tetracarboxylic acid anhydride. According to claim 3,
The structural unit (A) has the formula (X):
(Content of tetracarboxylic acid anhydride-derived structural units (A3) other than the structural unit (A1) and structural unit (A2))/(total amount of structural units (A1) and (A2)) <1.1 (X)
A polyimide-based film that satisfies the relationship of According to claim 2,
The structural unit (A1) has the formula (a1):

[In formula (a1), Z represents a divalent organic group,
R ^a1 independently represents a halogen atom or an alkyl group, an alkoxy group, an aryl group or an aryloxy group which may have a halogen atom;
s represents an integer from 0 to 3, independently of each other]
A polyimide-based film which is a structural unit (a1) derived from tetracarboxylic acid anhydride represented by . According to claim 3,
The structural unit (A2) has the formula (a2):

[In formula (a2), R ^a2 independently represents a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;
t represents, independently of each other, an integer from 0 to 3]
A polyimide-based film that is a structural unit (a2) derived from tetracarboxylic acid anhydride represented by . According to claim 1,
The polyimide-based film in which the structural unit (B) includes a structural unit (B1) derived from diamine containing a biphenyl skeleton. According to claim 7,
The structural unit (B1) has the formula (b1):

[In formula (b1), R ^b1 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;
p represents an integer from 0 to 4]
A polyimide-based film that is a structural unit (b1) derived from diamine represented by . According to claim 7,
The content of the structural unit (B1) exceeds 30 mol% with respect to the total amount of the structural unit (B), the polyimide-based film. According to claim 1,
The structural unit (B) has the formula (b2):

[In formula (b2), R ^b2 represents, independently of each other, a halogen atom or an alkyl group, an alkoxy group, an aryl group, or an aryloxy group which may have a halogen atom;
W is, independently of each other, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, Represents -COO-, -OOC-, -SO ₂ -, -S-, -CO- or -N(R ^c )-, and R ^c is a monovalent group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. represents a hydrocarbon group,
m represents an integer from 1 to 4,
q represents an integer from 0 to 4 independently of each other]
A polyimide-based film containing a structural unit (b2) derived from diamine represented by . According to claim 10,
Among the structural units (b2), m is 3, and W is each independently -O- or -C(CH ₃ ) ₂ -, a polyimide-based film. A laminated film comprising a metal foil layer on one side or both sides of the polyimide film according to any one of claims 1 to 11. A flexible printed circuit board comprising the polyimide-based film according to any one of claims 1 to 11. A step of coating a polyimide-based resin precursor solution containing a structural unit (A) derived from tetracarboxylic acid anhydride and a structural unit (B) derived from diamine on a substrate, and
Lamination comprising a step of imidizing a polyimide-based resin precursor by heat treatment at 200°C or more and less than 350°C to form the polyimide-based film according to any one of claims 1 to 11 on a substrate How to make a film. 15. The method of claim 14,
A method for producing a laminated film in which the substrate is a metal foil.