JP2018165346A - Polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film that can be used for e.g. a flexible printed circuit board.SOLUTION: The polyimide film has a dielectric loss tangent of 0.007 or less, a water absorption of 0.8% or less, and a linear expansion coefficient at 50-200°C of 30 ppm/°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a polyimide film and the like.

In electrical products, miniaturization and thinning have progressed, and a flexible printed circuit board (FPC) has been required. In recent years, in addition to these, the speed of wireless Internet and communication equipment has increased, and the frequency of operation has increased, and a circuit board capable of realizing a high transmission rate has been demanded.
As a specific example, a thing used for the antenna part of a smart phone or a tablet terminal is mentioned, and since these are progressing in miniaturization and thinning, it is raised as a required characteristic.

It is known that the transmission speed of a semiconductor element is limited mainly by the occurrence of a delay between metal wires carrying signals. In order to reduce the signal transmission delay, an insulating layer having a low dielectric constant is disposed between the wires, thereby reducing the capacitive coupling between the wires, thereby increasing the operation speed and reducing the noise disturbance.
The insulating layer can block the flow of current, and when the dielectric constant is low, the transmission speed is improved. When the dielectric loss tangent is low, the transmission loss can be reduced. That is, the high-frequency circuit board must have a low coefficient of thermal expansion (CTE, linear expansion coefficient), and a dielectric constant (Dk) and dielectric loss tangent (Tanδ) that are stable and low. Moreover, since it is conveyed by the roll to roll in a manufacturing process, it is calculated | required that it is high intensity | strength and high elasticity. Also, high heat resistance is required in the soldering process when forming the circuit board.

The use of a laminated film of a fluororesin film and a polyimide film has been studied as such an insulating layer.
For example, Patent Document 1 describes a laminated film in which a fluorine resin is laminated on both sides or one side of a polyimide film.

  Moreover, in patent document 2, both surfaces were discharged on both surfaces or one surface of an aromatic polyimide film having a main acid skeleton derived from biphenyltetracarboxylic acid, which was discharged on both surfaces. A laminated film in which a fluororesin film is laminated is described.

JP-A-8-276547 Japanese Patent Publication No. 5-59828

  An object of the present invention is to provide a novel polyimide film.

  As described above, a laminated film of a fluororesin film and a polyimide film is used for an insulating layer such as FPC. The combination of the two resin films as described above is considered in consideration of the balance of various physical properties. For example, while communication speed may not be sufficient for polyimide film, strength and dimensional stability may not be sufficient for fluororesin film, but it is assumed that these defects can be reduced by combining these. Is done.

However, according to the study by the present inventors, even in such a laminated film, there are still cases where dimensional accuracy is not sufficient or selection of through-hole formation is narrow (for example, a CO ₂ laser cannot be used). I found that there are some points to be improved.

  Therefore, the present inventors have examined whether a film that can be used for FPC or the like can be formed by using a single layer film of polyimide instead of laminating different resins. However, in the case of polyimide single-layer film, sufficient low dielectric properties and low water absorption performance may not be obtained, and there are cases where dimensional accuracy is not sufficient, etc. Extremely difficult.

  Under such circumstances, the present inventors have conducted extensive research, and as a result, by selecting the aspect of the gel film that is the raw material of polyimide or the precursor of the film, even if it is a single-layer film of polyimide, the above-mentioned The inventors have found that such characteristics can be satisfied, and have further studied to complete the present invention.

That is, this invention relates to the following polyimide films etc.
[1]
A polyimide film having a dielectric loss tangent of 0.007 or less, a water absorption of 0.8% or less, and a linear expansion coefficient at 50 to 200 ° C. of 30 ppm / ° C. or less.
[2]
The polyimide film as described in [1] whose relative dielectric constant is 3.3 or less.
[3]
Any one of [1] to [2], wherein at least one component selected from the diamine component (A) and the tetracarboxylic acid component (B), which is a polymerization component of polyimide constituting the polyimide film, contains fluorine. The polyimide film described in 1.
[4]
The polyimide film according to [3], wherein the diamine component (A) contains 60 mol% or more of the fluorine-containing diamine component (A1).
[5]
The polyimide film according to [3] or [4], wherein the diamine component (A) contains 65 mol% or more of 2,2′-bis (trifluoromethyl) benzidine.
[6]
The polyimide film according to any one of [3] to [5], wherein the diamine component (A) includes a fluorine-containing diamine component (A1) and a fluorine-free diamine component (A2).
[7]
The polyimide film according to any one of [3] to [6], wherein the tetracarboxylic acid component (B) contains 60 mol% or more of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride.
[8]
The polyimide film according to any one of [1] to [7], which is used for a base film of a copper-clad laminate and / or a coverlay.
[9]
A method for producing a polyimide film according to any one of [1] to [8], wherein a self-supporting gel film is obtained by a chemical ring closure method, and the gel film is used.
[10]
The metal laminated body using the polyimide film in any one of [1]-[8].
[11]
The metal laminate according to [10], which is a copper-clad laminate using a polyimide film as a base film.
[12]
The metal laminate according to [10] or [11], wherein the polyimide film constitutes a coverlay that protects the metal layer.

In the present invention, a novel polyimide film can be provided.
Such a polyimide film has characteristics such as low dielectric constant and low water absorption (and consequently low water vapor and gas permeability). Therefore, for example, it can be suitably used as an FPC film (base film, coverlay, etc.), and can be suitably used particularly for high-frequency compatible substrates.
Moreover, the polyimide film of the present invention often has a relatively low CTE (linear expansion coefficient). For this reason, even when laminated on a metal layer, the dimensional stability is high, which is suitable for FPC applications.
It is not easy to achieve both low dielectric constant and low water absorption, and high dimensional accuracy, and it is surprising that both can be achieved in a single layer polyimide film, and the usefulness of the present invention is extremely high. It is.
Furthermore, since the polyimide film of the present invention does not require lamination of a resin film, it can easily cope with thinning.

[Polyimide film]
The polyimide film of the present invention satisfies a specific range in dielectric properties and water absorption. In addition, the polyimide film of this invention should just satisfy at least one among the dielectric characteristics of such a specific range, and the water absorption rate of a specific range, and may satisfy either one or both. Good.

The dielectric loss tangent of the polyimide film of the present invention can be selected from a range of about 0.015 or less (for example, 0.012 or less), for example, 0.01 or less (for example, 0.0095 or less), preferably 0.009 or less. (For example, 0.0085 or less), more preferably 0.008 or less (for example, 0.0075 or less), particularly 0.007 or less (for example, 0.0065 or less), particularly preferably 0.006 or less (for example, 0 .0058 or less), 0.0055 or less, 0.0050 or less, or the like.
The lower limit value of the dielectric loss tangent is not particularly limited, and may be, for example, 0.001, 0.0015, 0.002, 0.0025, 0.0030, 0.0035, and the like.

The relative dielectric constant of the polyimide film can be selected from a range of about 3.5 or less (for example, 3.4 or less), for example, less than 3.4 (for example, 3.37 or less), preferably 3.35 or less (for example, 3.32 or less), more preferably 3.3 or less (eg 3.25 or less), 3.2 or less (eg 3.15 or less), 3.1 or less (eg 3.15 or less). 05 or less), 3.0 or less (for example, 2.95 or less), or the like.
The lower limit value of the relative dielectric constant is not particularly limited, but may be, for example, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, or the like.

  In addition, the measuring method of a dielectric loss tangent and a dielectric constant is not specifically limited, You may follow a conventionally well-known method. The measurement frequency of dielectric loss tangent and dielectric constant may be, for example, 2.54 GHz, 5.8 GHz, or the like.

  The polyimide film satisfying a specific range of dielectric characteristics may satisfy the above range in at least one of dielectric loss tangent and relative dielectric constant among the dielectric characteristics. Preferably, the above range may be satisfied at least in the dielectric loss tangent, and more preferably, the above range may be satisfied in both the dielectric loss tangent and the relative dielectric constant.

The water absorption of the polyimide film can be selected from a range of about 2% or less (for example, 1.5% or less), for example, 1.2% or less (for example, 1.1% or less), preferably 1.0% or less. (For example, 0.95% or less), more preferably 0.9% or less (for example, 0.85% or less), particularly 0.8% or less (for example, 0.75% or less), particularly preferably 0.7 % Or less (for example, 0.65% or less), 0.6% or less (for example, 0.55% or less), 0.5% or less (for example, 0.45% or less), 0.4 % Or less (for example, 0.35% or less).
The lower limit of the water absorption rate is not particularly limited. For example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0 0.08%, 0.09%, 0.10%, etc. may be sufficient.

  In addition, the measuring method of a water absorption rate is not specifically limited, For example, you may follow JISK7209 etc., and you may measure a water absorption rate by the method as described in the Example mentioned later.

The polyimide film may have a specific linear expansion coefficient.
The linear expansion coefficient (absolute value of the linear expansion coefficient) of the polyimide film can be selected from a range of about 40 ppm / ° C. or less (eg, 37 ppm / ° C. or less), for example, 35 ppm / ° C. or less (eg, 33 ppm / ° C. or less), Preferably it is 32 ppm / ° C. or less (eg, 31 ppm / ° C. or less), more preferably 30 ppm / ° C. or less (eg, 28 ppm / ° C. or less), particularly 25 ppm / ° C. or less (eg, 22 ppm / ° C. or less), particularly preferably 20 ppm / It may be not higher than ° C (for example, not higher than 19 ppm / ° C), and may be not higher than 18 ppm / ° C.
In addition, the lower limit value of the linear expansion coefficient (or its absolute value) is not particularly limited and can be selected according to the use and the like, 0 ppm / ° C., 2 ppm / ° C., 3 ppm / ° C., 5 ppm / ° C., 8 ppm / ° C., 10 ppm It may be / ° C.
In particular, when configuring a metal laminate as described later, for example, the linear expansion coefficient of the polyimide film may be close to the linear expansion coefficient of the metal layer or metal constituting the metal layer described later, and the same or smaller. Also good. For example, when the metal constituting the metal layer or the metal layer is copper, the linear expansion coefficient of the polyimide film is 0 to 25 ppm / ° C, 5 to 22 ppm / ° C, 8 to 20 ppm / ° C, 10 to 18 ppm / ° C, and the like. There may be.
The linear expansion coefficient may be a linear expansion coefficient in a specific temperature range (for example, 50 to 200 ° C.).

  The measuring method of a linear expansion coefficient is not specifically limited, For example, you may measure by the method as described in the Example mentioned later.

The glass transition temperature of the polyimide film (or polyimide constituting the polyimide film) is not particularly limited, but is, for example, 150 ° C. or higher (for example, 180 to 450 ° C.), preferably 200 ° C. or higher (for example, 230 to 400 ° C.), More preferably, it may be 250 ° C. or higher (eg, 260 to 380 ° C.).
The thickness of the polyimide film is not particularly limited, and can be appropriately selected according to the use. For example, the polyimide film may have a thickness of 1 to 200 μm (for example, 2 to 150 μm), preferably 3 to 100 μm (for example, 4 to 90 μm), and more preferably 5 to 80 μm (for example, 7 to 60 μm). , 50 μm or less, 40 μm or less, 30 μm or less, and the like.
Since the polyimide film of the present invention can satisfy the desired performance without being laminated with the fluororesin film, it can easily cope with thinning.

  In addition, the laminated body of a some polyimide film may be sufficient as a polyimide film, and a single polyimide film may be sufficient normally.

[Production method of polyimide and polyimide film]
The polyimide film (or polyimide constituting the polyimide film or polyamic acid) has a diamine component and a tetracarboxylic acid component as polymerization components. The polymerization component may contain other polymerization components as long as the diamine component and the tetracarboxylic acid component are the main components.

  Specifically, when producing a polyimide (or polyimide film), first, a diamine component (diamine component (A)) and a tetracarboxylic acid component (tetracarboxylic acid component (B)) are polymerized in an organic solvent. Thus, a polyamic acid (polyimide precursor) solution is obtained.

  The polyamic acid is subjected to a cyclization reaction. In the present invention, it is preferable to cyclize by a chemical ring closure method as described later. Therefore, the polyamic acid (diamine component (A) and tetracarboxylic acid component (B)) is a component (or a component that can be efficiently cyclized by the chemical cyclization method) that can be applied with a chemical cyclization method (or a chemical cyclization method). Is preferred.

  The diamine component (A) usually contains at least an aromatic diamine component. The tetracarboxylic acid component (B) usually contains an aromatic tetracarboxylic acid component.

  The polyimide may usually contain fluorine. In such a fluorine-containing polyimide (polyimide film), the method for containing fluorine is not particularly limited, but usually, at least a fluorine-containing polymerization component may be used as the polymerization component.

Specifically, at least one component selected from the diamine component (A) and the tetracarboxylic acid component (B) (particularly at least the diamine component (A)) may contain fluorine.
In addition, it does not specifically limit as an aspect containing a fluorine, For example, the aspect etc. which substitute the hydrogen atom which comprises a diamine component and a tetracarboxylic-acid component by a fluorine atom, etc. may be sufficient. For example, as a diamine component or a tetracarboxylic acid component, a skeleton substituted with a fluorine atom {for example, a fluoroalkane skeleton [for example, a perfluoroalkane skeleton (or a perfluoroalkyl group) such as a trifluoromethane skeleton (or trifluoromethyl group)] ], A component having a hydrocarbon skeleton such as a fluoroarene skeleton (e.g., a fluorobenzene skeleton) may be used.

  Specific examples of the diamine component (A) can be broadly classified into a fluorine-free diamine component (A2) and a fluorine-containing diamine component (A1).

  Examples of the fluorine-free diamine component (A2) include diaminoarene (for example, paraphenylenediamine, metaphenylenediamine, 1,5-diaminonaphthalene, etc.), diaminobiaryl [or bis (aminoaryl), for example, benzidine, 3 , 3′-dimethoxybenzidine], di (aminoalkyl) arene (eg, paraxylylenediamine), di (aminoaryl) ether (eg, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, etc.) Di (aminoaryl) alkanes (eg, 4,4′-diaminodiphenylmethane, 3,3′-dimethyl-4,4′-diaminodiphenylmethane), di (aminoaryl) sulfones (eg, 4,4′-diaminodiphenyl) Sulfone), di (ami) Aryl) arene [eg, 1,4-bis (3-methyl-5-aminophenyl) benzene, etc.], di (aminoaryloxy) arene [eg, 1,3-bis (4-aminophenoxy) benzene, 1, 4-bis (4-aminophenoxy) benzene], di [(aminoaryloxy) aryl] alkane {eg, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, etc.}, their amide-forming properties Non-fluorine-containing aromatic diamine components such as derivatives are exemplified.

  You may use a fluorine-free diamine component (A2) individually or in combination of 2 or more types.

  Among these, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene and the like are preferable. . Therefore, the diamine component (A2) contains 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis (4-aminophenoxy) benzene, and 1,4-bis (4-amino). It may contain at least one selected from phenoxy) benzene.

As the fluorine-containing diamine component (A1), a compound in which hydrogen (atom) constituting the fluorine-free diamine component (A2) is substituted with fluorine (atom), for example, fluorine-containing diaminobiaryl {or fluorine-containing bis (aminoaryl) ), for example, fluoroalkyl benzidine [e.g., 2,2'-bis (trifluoromethyl) benzidine, 3,3'-bis (fluoroalkyl _{C 1-10} alkyl benzidine, such as trifluoromethyl) benzidine, preferably perfluoro C _1-4 alkylbenzidine etc.], fluorine-containing di (aminoaryl) alkane {eg di (aminophenyl) fluoroalkane [eg di (amino such as 2,2-bis (4-aminophenyl) hexafluoropropane] phenyl) fluoro _{C 1-10} alkanes, preferably Etc. (aminophenyl) perfluoro C _1-4 alkanes]}, the fluorine-containing aromatic diamine component such as these amide-forming derivatives.

  Of these, fluoroalkylbenzidine [particularly 2,2′-bis (trifluoromethyl) benzidine] is preferable.

  You may use a fluorine-containing diamine component (A1) individually or in combination of 2 or more types.

  You may use a diamine component (A) individually or in combination of 2 or more types.

  In particular, the diamine component (A) may contain at least a fluorine-containing diamine component (A1).

  When the diamine component (A) includes the fluorine-containing diamine component (A1), the proportion of the fluorine-containing diamine component (A1) is, for example, 20 mol% or more (for example, 25 to 100 mol%) of the diamine component (A), Preferably, it may be 30 mol% or more (for example, 40 mol% or more), more preferably 50 mol% or more (for example, 55 mol% or more), particularly 60 mol% or more (for example, 65 mol% or more), It can also be 70 mol% or more (for example, 75 mol% or more), 80 mol% or more (for example, 85 mol% or more), 90 mol% or more (for example, 95 mol% or more), and the like.

  Moreover, you may combine suitably a fluorine-containing diamine component (A1) and a fluorine-free diamine component (A2).

  In such a case, the ratio of the fluorine-containing diamine component (A1) and the fluorine-free diamine component (A2) is, for example, fluorine-containing diamine component (A1) / fluorine-free diamine component (A2) (molar ratio) = 99. 0.9 / 0.1 / 1/99 (for example, 99.5 / 0.5 to 5/95), preferably 99/1 to 10/90 (for example, 98/2 to 20/80), more preferably 97 / 3-30 / 70 (e.g. 96 / 4-35 / 65), especially 95 / 5-40 / 60 (e.g. 93 / 7-45 / 50), particularly preferably 92 / 8-50 / 50 ( For example, it may be about 90/10 to 55/45), and usually 99/1 to 60/40 (for example, 95/5 to 65/35).

  Specific tetracarboxylic acid components (B) can be broadly classified into, for example, fluorine-free tetracarboxylic acid components (B2) and fluorine-containing tetracarboxylic acid components (B1).

  Examples of the non-fluorine-containing tetracarboxylic acid component (B2) include non-fluorine-containing tetracarboxylic acid and amide-forming derivatives thereof, such as arenetetracarboxylic acid components [for example, pyromellitic acid, 2,3,6,7-naphthalenetetra Carboxylic acid, pyridine-2,3,5,6-tetracarboxylic acid, acid anhydrides thereof (such as pyromellitic acid anhydride)], bis (dicarboxyaryl) ether component (for example, 4,4′-oxydiphthalate) Acid, 4,4′-oxydiphthalic anhydride, etc.), biaryltetracarboxylic acid component [for example, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid Acid, these acid anhydrides (such as 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride)], diarylketone Lacarboxylic acid component (for example, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid and its anhydride), bis [(dicarboxyphenoxy) phenyl] alkane component {for example, 5,5 ′-[1-methyl -1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) and the like}.

  The fluorine-free tetracarboxylic acid component (B2) may be used alone or in combination of two or more.

As the fluorine-containing tetracarboxylic acid component (B1), a compound in which hydrogen (atom) constituting the fluorine-free tetracarboxylic acid component is substituted with fluorine (atom), for example, a fluorine-containing bis (dicarboxyaryl) alkane {for example, Bis (dicarboxyphenyl) fluoroalkanes [for example, bis (dicarboxyphenyl) fluoroC _1-10 alkanes such as 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride, preferably bis (dicarboxyphenyl) per Fluoro C _1-4 alkane] and the like}.

  You may use a fluorine-containing tetracarboxylic-acid component (B1) individually or in combination of 2 or more types.

  The tetracarboxylic acid component (B) may be used alone or in combination of two or more.

Among these, 3,3 ′, 4,4′-biphenyltetracarboxylic acid components (such as anhydrides) may be preferably used. Therefore, the tetracarboxylic acid component (B) may contain at least a 3,3 ′, 4,4′-biphenyltetracarboxylic acid component.
By using 3,3 ′, 4,4′-biphenyltetracarboxylic acid component, it is easy to apply the chemical ring closure method described later, and furthermore, the desired properties (dielectric properties, water absorption, CTE, etc.) are realized. Cheap.

  When the tetracarboxylic acid component (B) includes a 3,3 ′, 4,4′-biphenyltetracarboxylic acid component, the ratio of the 3,3 ′, 4,4′-biphenyltetracarboxylic acid component is, for example, tetracarboxylic 20 mol% or more (for example, 25 to 100 mol%) of the acid component (B), preferably 30 mol% or more (for example, 40 mol% or more), more preferably 50 mol% or more (for example, 55 mol% or more) In particular, it may be 60 mol% or more (for example, 65 mol% or more), 70 mol% or more (for example, 75 mol% or more), 80 mol% or more (for example, 85 mol% or more), 90 mol% or more. (For example, 95 mol% or more).

  Moreover, the tetracarboxylic acid component (B) may suitably contain a fluorine-containing tetracarboxylic acid component (B1). In such a case, the fluorine-containing tetracarboxylic acid component (B1) and the fluorine-free tetracarboxylic acid The component (B2) can also be combined.

  When the tetracarboxylic acid component (B) includes the fluorine-containing tetracarboxylic acid component (B1), the ratio of the fluorine-containing tetracarboxylic acid component (B1) is, for example, 1 mol% or more of the tetracarboxylic acid component (B) (for example, 1 to 100 mol%), preferably 2 mol% or more (eg 3 to 80 mol%), more preferably 5 mol% or more (eg 6 to 50 mol%), particularly 10 mol% or more (eg 10 ˜40 mol% or more), and usually 1 to 50 mol% (other examples are 3 to 40 mol%, 5 to 35 mol%).

  Specific examples of the organic solvent used for forming the polyamic acid solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, N , N-dimethylacetamide, N, N-diethylacetamide and other acetamide solvents, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and other pyrrolidone solvents, phenol, o-, m-, or p- Examples thereof include phenolic solvents such as cresol, xylenol, halogenated phenol, and catechol, and aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone, and these are used alone or as a mixture using two or more thereof. It is desirable that xylene, The use of aromatic hydrocarbons such as toluene are also possible.

The polymerization method may be carried out by any known method. For example, (1) the total amount of the diamine component is first put in the solvent, and then the tetracarboxylic acid component is equivalent to the total amount of the diamine component (equal mole). In addition, a polymerization method.
(2) A method in which the total amount of the tetracarboxylic acid component is first put in a solvent, and then the diamine component is added so as to be equivalent to the tetracarboxylic acid component for polymerization.
(3) After mixing one diamine component (a1) in a solvent, after mixing for a time required for the reaction at a ratio of 95 to 105 mol% of one tetracarboxylic acid component (b1) with respect to the reaction component The other diamine component (a2) is added, and then the other tetracarboxylic acid component (b2) is added and polymerized so that the total diamine component and the total tetracarboxylic acid component are approximately equivalent. .
(4) After one tetracarboxylic acid component (b1) is put in a solvent, after mixing for a time required for the reaction at a ratio of 95 to 105 mol% of one diamine component (a1) with respect to the reaction component The other tetracarboxylic acid component (b2) is added, and then the other diamine component (a2) is added and polymerized so that the total diamine component and the total tetracarboxylic acid component are approximately equivalent.
(5) A polyamic acid solution (A) is prepared by reacting one diamine component and a tetracarboxylic acid component in a solvent so that either one becomes excessive, and the other diamine component and the tetracarboxylic acid in another solvent. The polyamic acid solution (B) is prepared by reacting either component in excess. A method in which the polyamic acid solutions (A) and (B) thus obtained are mixed to complete the polymerization. The polymerization method is not limited to these, and other known methods may be used.
The polymerization method is not limited to these, and other known methods may be used.

  The polyamic acid solution usually contains a solid content of about 5 to 40% by weight, and preferably may contain a solid content of about 10 to 30% by weight. The viscosity of the polyamic acid solution may be usually about 10 to 2000 Pa · s as measured with a Brookfield viscometer, and preferably about 100 to 1000 Pa · s for stable liquid feeding. Good. Moreover, the polyamic acid in the organic solvent solution may be partially imidized.

  Next, the manufacturing method of a polyimide film is demonstrated. The film formation (production) of the polyimide film is, for example, a step (1) of obtaining a gel film by cyclizing a polyamic acid solution (converting the polyamic acid or the polyamic acid solution into a gel film), and the obtained gel film. It can be obtained through a step (2) of drying (and solvent removal) and heat treatment. Note that drying and imidization proceed by drying and heat treatment.

  In the step (1), the method for cyclizing the polyamic acid solution is not particularly limited. Specifically, (i) the gel film is obtained by casting the polyamic acid solution into a film and thermally dehydrating it. Or (ii) mixing a catalyst (cyclization catalyst) and a dehydrating agent (converting agent) in a polyamic acid solution and chemically decyclizing to produce a gel film, Examples thereof include a method for obtaining a gel film (chemical ring closure method), and the latter method (chemical ring closure method) is particularly preferable.

  According to the chemical ring closure method (and selecting the chemical ring closure method while selecting the specific diamine component and / or tetracarboxylic acid component as described above), the polyimide film of the present invention is surprisingly required. It seems that it is easy to efficiently obtain physical properties and characteristics (dielectric characteristics, water absorption, CTE, etc.). The chemical ring closure method is also suitable from the viewpoint of mass productivity.

  The polyamic acid solution may contain a gelation retarder and the like. It does not specifically limit as a gel retarder, Acetyl acetone etc. can be used.

  Cyclization catalysts include amines such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), heterocyclic tertiary amines (eg, isoquinoline, pyridine, β-picoline and the like). These may be used individually by 1 type, and 2 or more types may be mixed and used for them. Of these, heterocyclic tertiary amines such as β-picoline are preferred.

  Examples of the dehydrating agent include acid anhydrides such as aliphatic carboxylic acid anhydrides (eg, acetic anhydride, propionic anhydride, butyric anhydride), aromatic carboxylic acid anhydrides (eg, benzoic anhydride, etc.), and the like. . These may be used individually by 1 type, and 2 or more types may be mixed and used for them. Among these, acetic anhydride and / or benzoic anhydride are preferable, and acetic anhydride is particularly preferable.

  Although the usage-amount of a cyclization catalyst and a dehydrating agent is not specifically limited, For example, 1 mol or more (for example, 1.5 mol) with respect to 1 mol of amide groups (or carboxyl groups) of polyamic acid (or polyamic acid), respectively. About 10 mol).

  The gel film is usually obtained by casting (coating) a polyamic acid solution (particularly, a polyamic acid solution in which a cyclization catalyst and a conversion agent are mixed) onto a support, and partially drying and curing (imidizing). Can be obtained.

  More specifically, the polyamic acid solution is cast on a support from a base with a slit and formed into a film, and is heated by receiving heat from the support, heat from a heat source such as hot air or an electric heater. The gel film may be obtained by ring-closing reaction and drying a volatile component such as a free organic solvent, and then peeled off from the support.

  Here, the gel film needs to have a self-supporting property in order to peel off, but usually the gel film obtained by the chemical cyclization method and the gel film obtained by the thermal cyclization method have greatly different modes. . That is, in the chemical ring closure method, gelation (conversion) can be performed by a catalyst, so that a self-supporting gel film (soft or wet gel film) containing a large amount of solvent can be obtained. A large amount of heat treatment is required to give supportability, and as a result, a gel film that is relatively hard (low residual solvent) is obtained.

  Surprisingly, in the present invention, a polyimide film having desired characteristics (low dielectric loss tangent, low dielectric constant, low water absorption, low CTE, etc.) can be efficiently formed by using a gel film that has undergone a chemical ring closure method.

  Although it does not specifically limit as a support body, A metal (for example, stainless steel) rotating drum, an endless belt, etc. are mentioned as an example. The temperature of a support body is not specifically limited, For example, 30-200 degreeC, Preferably it is 40-150 degreeC, More preferably, it may be 50-120 degreeC.

  The temperature of the support can be controlled by (i) a liquid or gas heat medium, (ii) radiant heat from an electric heater or the like.

  In step (2), the gel film is dried (desolvent) and then heat-treated. Usually, the step (2) may include a step of passing through a heating furnace (such as a tenter heating furnace) while drying both ends in the width direction of the gel film, drying, and then performing a heat treatment.

  Specifically, the gel film peeled off from the support is not particularly limited, but usually may be stretched in the transport direction while regulating the running speed with a rotating roll. The stretching in the transport direction may be performed at a predetermined temperature (for example, a temperature of 140 ° C. or lower). The draw ratio (MDX) is usually 1.05 to 1.9 times, preferably 1.1 to 1.6 times, more preferably 1.1 to 1.5 times (for example, 1.15). ~ 1.4 times).

  In the drying, the drying temperature is, for example, 210 ° C. or higher (for example, 213 to 500 ° C.), preferably 215 ° C. or higher (for example, 218 to 400 ° C.), more preferably 220 ° C. or higher (for example, 220 to 300 ° C.). You may go.

  Moreover, you may perform drying, suppressing the drying nonuniformity (variation) in a film width direction. For example, the drying temperature unevenness in the film width direction is, for example, less than 25 ° C. (for example, 0 to 24 ° C.), preferably 22 ° C. or less (for example, 1 to 21 ° C.), more preferably 20 ° C. or less (for example, 2 to 2 ° C.). 19 ° C.), particularly 18 ° C. or lower (eg, 3 to 18 ° C.)

  In addition, the drying temperature unevenness takes, for example, a plurality of points at a predetermined interval (for example, 200 mm) along the film width direction, and the difference (width) between the maximum value and the minimum value of the measured drying temperature is defined as the drying temperature unevenness. It can be measured.

  A gel film (in particular, a gel film stretched in the transport direction) is heat-treated after drying. The heat treatment temperature is not particularly limited, and may be, for example, 200 ° C. or higher (for example, 250 to 600 ° C.), preferably 300 ° C. or higher, more preferably 350 ° C. or higher.

  Moreover, after drying, it may be further stretched in the width direction. The stretching in the width direction may be performed together with the heat treatment.

  In stretching in the width direction, the draw ratio (TDX) is, for example, 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times. Double (for example, 1.15 to 1.4 times) may be sufficient.

  In addition, by such stretching, the dielectric loss tangent, the relative dielectric constant, the CTE, the water absorption rate and the like may be easily reduced (or easily adjusted) in some cases.

  In this way, a polyimide film is obtained. The obtained polyimide film may be further subjected to annealing treatment or easy adhesion treatment (for example, electrical treatment such as corona treatment or plasma treatment or blast treatment).

[Metal laminate]
The polyimide film of the present invention can be suitably used for laminating with a metal layer (metal foil) to form a metal laminate.

  In particular, the polyimide film of the present invention is suitable as a film for a circuit board, particularly a flexible printed circuit board (FPC) (particularly, an insulating film or a coverlay film).

Therefore, the present invention includes a metal laminate including (used) the polyimide film. Such a metal laminate may particularly constitute a flexible printed circuit board (flexible board). In such a metal laminate (or substrate), the polyimide film may be laminated on the metal layer, may constitute a base film in the metal laminate, or may constitute a cover lay (film). Both of these may be configured.
For example, a base film, a metal layer (metal layer on which a wiring or a pattern is formed) laminated (formed) on the base film, and a film (metal layer) laminated (formed) on the metal layer In a metal laminate including a protective film and a cover lay film, at least one of the base film and the cover lay may be formed of the polyimide film.
In particular, the polyimide film of the present invention may be suitably used as at least a base film (base film for forming a metal layer).

  The type of metal constituting the metal layer (metal foil) is not particularly limited. For example, copper (copper alone, copper alloy, etc.), stainless steel and its alloys, nickel (nickel alone, nickel alloy, etc.), aluminum (aluminum) , Aluminum alloy, etc.).

  Copper is preferred. A copper-clad laminate is obtained by laminating such a metal layer and a polyimide film. Moreover, what formed the antirust layer, the heat-resistant layer (for example, plating processing of chromium, zinc, etc.), a silane coupling agent, etc. on these metal surfaces can also be utilized. Preferably, copper and / or nickel, zinc, iron, chromium, cobalt, molybdenum, tungsten, vanadium, beryllium, titanium, tin, manganese, aluminum, phosphorus, silicon, etc. and at least one component and copper are included. These are copper alloys, which are preferred for use in circuit processing. Particularly preferable metal layers include copper formed by rolling or electrolytic plating.

  Although the thickness of a metal layer is not specifically limited, For example, about 1-150 micrometers (for example, 3-50 micrometers) may be sufficient.

  As long as the metal laminate includes a polyimide film and a metal layer, the form of the laminate is not particularly limited, and depends on the purpose of use of the polyimide film (whether it is a substrate film or a coverlay). However, for example, a polyimide film and a metal layer may be directly laminated, or a polyimide film and a metal foil may be laminated (bonded) via an adhesive layer (adhesive layer).

  The adhesive component which comprises an adhesive layer is not specifically limited, For example, any of a thermosetting resin and a thermoplastic resin may be sufficient.

  The metal laminate can be used for a flexible wiring board on which various miniaturized and densified components are mounted if a desired pattern wiring is formed by etching the metal layer. Of course, the application of the present invention is not limited to this, and it is needless to say that a laminated body including a metal layer can be used for various applications.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in more detail, this invention is not limited to these examples.

  About the polyimide film produced by the Example and the comparative example, the following characteristics were measured.

[Evaluation of dielectric properties]
Dielectric characteristics were measured by connecting a perturbation method dielectric constant measuring device CP521 (for 5.8 GHz) manufactured by Agilent Technology Co., Ltd./Kanto Electronics Co., Ltd. to a network analyzer 8722A / C / D with a coaxial cable. Using a Mitutoyo lightmatic (Series 318) thickness gauge, 15 locations were arbitrarily selected from the entire surface of the film, the thicknesses were measured at these 15 locations, and the average was calculated to obtain the thickness.

[Water absorption rate]
It left still in distilled water for 1 day, and evaluated by the weight% increase with respect to the weight at the time of drying. Specifically, the film was cut into a 6 cm diameter circle, and the weight (W0) after heat treatment at 200 ° C. for 1 hour was measured as the weight at the time of drying. The weight of the film (W1) ) Was measured, and the water absorption was determined by the following formula.
Water absorption (%) = (W1-W0) / W0 × 100

[Evaluation of CTE (Linear Expansion Coefficient)]
A TMA-50 thermomechanical analyzer manufactured by Shimadzu Corporation was used, and measurement was performed under the conditions of measurement temperature range: 50 to 200 ° C., temperature increase rate: 10 ° C./min. The load was 0.25 N, and the temperature was first raised from 35 ° C. at 10 ° C./min to 230 ° C. Hold at 230 ° C. for 5 minutes, then lower the temperature at 10 ° C./min to lower the temperature to 35 ° C., hold at 35 ° C. for 30 minutes, then raise the temperature at 10 ° C./min to raise the temperature to 230 ° C. It was. Data at the time of the second temperature increase from 35 ° C. to 230 ° C. was read, and the linear expansion coefficient was calculated from the average of the portion of 50 to 200 ° C.

[Gelification test]
A polymer-cast film on a polyethylene terephthalate (PET) film is immersed in a catalyst / dehydrating agent mixed solution (50/50, v / v), peeled off from the PET film after 2 minutes, and converted into a self-supporting film The polymer that can be pinned to a metal frame with a needle was designated as “◯” (chemically cyclable). On the other hand, a polymer having low self-supporting ability and cannot be pinned was designated as “x” (chemical ring closure impossible, chemical ring closure inappropriate).

[Glass-transition temperature]
Using a dynamic viscoelasticity measuring device DMS6000 manufactured by Hitachi High-Tech Science, measurement temperature range: 25-400 ° C., temperature rising rate: 2 ° C./min, frequency: 5 Hz, measured under nitrogen atmosphere. The temperature at the peak top of the obtained Tan δ was defined as the glass transition temperature.

[Example 1]
In a 500 ml separable flask equipped with a DC stirrer, 36.0 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 33.0 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
To 100 g of the cooled polyamic acid solution, 18 g of β-picoline, 20 g of acetic anhydride, and 10 g of N, N-dimethylacetamide were added and cast into a glass plate using an applicator to obtain a self-supporting gel film. A gel film is pinned to a metal frame with a 10 cm square needle and heat treated under conditions of 200 ° C. for 30 minutes, 300 ° C. for 20 minutes, and 320 ° C. for 5 minutes to obtain a polyimide film (unstretched film) with a thickness of 25 μm. It was.

[Example 2]
In a 500 ml separable flask equipped with a DC stirrer, 33.5 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 21.5 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 13.9 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 3]
The amounts of 2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride added were 37.3 g and 24.0 g, respectively, and 4,4 ′-( A polyimide film having a thickness of 25 μm was obtained by the same method as in Example 2 except that hexafluoroisopropylidene) diphthalic anhydride was changed to 7.6 g of pyromellitic anhydride.

[Example 4]
The amounts of 2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride added were 35.7 g and 22.9 g, respectively, and 4,4 ′-( A polyimide film having a thickness of 25 μm was obtained in the same manner as in Example 2 except that hexafluoroisopropylidene) diphthalic anhydride was changed to 10.4 g of 4,4′-oxydiphthalic anhydride.

[Example 5]
The amount of 2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride added was 32.4 g and 20.8 g, respectively. Hexafluoroisopropylidene) diphthalic anhydride was changed to 15.8 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) A polyimide film with a thickness of 25 μm was obtained by the same method as in Example 2 except that.

[Example 6]
In a 500 ml separable flask equipped with a DC stirrer, 24.1 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 22.1 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 13.2 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 9.5 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 7]
2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added in amounts of 25.5 g and 23.5 g, respectively. 4- (4-Aminophenoxy) phenyl] propane was changed to 10.0 g of 1,3-bis (4-aminophenoxy) benzene, and then 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 10 A polyimide film having a thickness of 25 μm was obtained in the same manner as in Example 6 except that 0.1 g was added.

[Example 8]
2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added in amounts of 25.5 g and 23.5 g, respectively. 4- (4-aminophenoxy) phenyl] propane is changed to 10.0 g of 1,4-bis (4-aminophenoxy) benzene, and then 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 10 A polyimide film having a thickness of 25 μm was obtained in the same manner as in Example 6 except that 0.1 g was added.

[Example 9]
2,2′-bis (trifluoromethyl) benzidine and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added in amounts of 26.7 g and 24.6 g, respectively. 7.2 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) 4- (4-aminophenoxy) phenyl] propane Then, a polyimide film having a thickness of 25 μm was obtained in the same manner as in Example 6 except that 10.5 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added.

[Example 10]
In a 500 ml separable flask equipped with a DC stirrer, 26.7 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 24.5 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 8.6 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 9.3 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 11]
In a 500 ml separable flask equipped with a DC stirrer, 22.5 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 20.7 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 12.4 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 13.4 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 12]
In a 500 ml separable flask equipped with a DC stirrer, 26.1 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 24.0 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 8.4 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. To this, 10.5 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) was added in several portions. The mixture was stirred for a time to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 13]
In a 500 ml separable flask equipped with a DC stirrer, 21.8 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 20.0 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 12.0 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 15.2 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) was added in several portions. The mixture was stirred for a time to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 14]
The polyamic acid solution obtained in Example 1 was cast into a glass plate using an applicator, heat-treated at 90 ° C. for 10 minutes, and a self-supporting gel film was obtained by a thermal ring closure method. The gel film was pinned on a metal frame with a 10 cm square needle, and heat-treated under conditions of 200 ° C. for 30 minutes, 300 ° C. for 20 minutes, and 320 ° C. for 5 minutes to obtain a polyimide film with a thickness of 25 μm.

[Example 15]
In a 500 ml separable flask equipped with a DC stirrer, 15.0 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 13.8 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 19.3 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 20.9 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Example 16]
In a 500 ml separable flask equipped with a DC stirrer, 14.2 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 13.3 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added in several portions and stirred for 1 hour. Thereafter, 18.3 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane was added and stirred for 30 minutes. Thereto, 23.2 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) was added in several portions. The mixture was stirred for a time to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Reference Example 1]
In a 500 ml separable flask equipped with a DC stirrer, 28.9 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 40.1 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The polyamic acid solution was cast into a glass plate using a replicator, heat-treated at 90 ° C. for 10 minutes, and a self-supporting gel film was obtained by a thermal ring closure method. The gel film was pinned on a metal frame with a 10 cm square needle, and heat-treated under conditions of 200 ° C. for 30 minutes, 300 ° C. for 20 minutes, and 320 ° C. for 5 minutes to obtain a polyimide film with a thickness of 25 μm.
In addition, as described in the gelation test described in the table below, the above polyamic acid was not suitable for the chemical ring closure method for producing a gel film.

[Reference Example 2]
A 500 ml separable flask equipped with a DC stirrer was charged with 41.0 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 28.0 g of pyromellitic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.

[Reference Example 3]
In a 500 ml separable flask equipped with a DC stirrer, 35.0 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 34.0 g of 4,4′-oxydiphthalic anhydride was added in several portions and stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Reference Example 1 to obtain a polyimide film having a thickness of 25 μm.
In addition, as described in the gelation test described in the table below, the above polyamic acid was not suitable for the chemical ring closure method for producing a gel film.

[Reference Example 4]
In a 500 ml separable flask equipped with a DC stirrer, 26.3 g of 2,2′-bis (trifluoromethyl) benzidine and 231.0 g of N, N-dimethylacetamide were placed at 40 ° C. using a water bath in a nitrogen atmosphere. Stir. After stirring for 30 minutes, 42.7 g of 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (isobenzofuran-1,3-dione) was added in several portions. And stirred for 1 hour to obtain a polyamic acid.
The obtained polyamic acid was formed into a film by the method described in Example 1 to obtain a polyimide film having a thickness of 25 μm.
In addition, as described in the gelation test described in the table below, the above polyamic acid was not suitable for the chemical ring closure method for producing a gel film.

  Various characteristics of the polyimide film obtained above are shown in the following table together with the polyimide composition and the like.

  In the table, the meanings of various symbols are as follows.

TFMB: 2,2′-bis (trifluoromethyl) benzidine BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane 1,3-APB: 1,3-bis (4-aminophenoxy) Benzene 1,4-APB: 1,4-bis (4-aminophenoxy) benzene ODA: 4,4′-oxydianiline BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 6FDA: 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride PMDA: pyromellitic anhydride ODPA: 4,4′-oxydiphthalic anhydride BPADA: 5,5 ′-[1-methyl-1,1-ethanediylbis (1,4-Phenylene) bisoxy] bis (isobenzofuran-1,3-dione)
CTE: linear expansion coefficient Tg: glass transition temperature

  In this invention, the polyimide film which can be used conveniently for flexible printed circuit boards etc. can be provided.

Claims (12)

  A polyimide film having a dielectric loss tangent of 0.007 or less, a water absorption of 0.8% or less, and a linear expansion coefficient at 50 to 200 ° C. of 30 ppm / ° C. or less.   The polyimide film according to claim 1, which has a relative dielectric constant of 3.3 or less.   The at least 1 sort (s) selected from the diamine component (A) and the tetracarboxylic-acid component (B) which are the polymerization components of the polyimide which comprises a polyimide film contains a fluorine in any one of Claims 1-2. Polyimide film.   The polyimide film of Claim 3 in which a diamine component (A) contains 60 mol% or more of fluorine-containing diamine components (A1).   The polyimide film according to claim 3 or 4, wherein the diamine component (A) contains 65 mol% or more of 2,2'-bis (trifluoromethyl) benzidine.   The polyimide film according to any one of claims 3 to 5, wherein the diamine component (A) includes a fluorine-containing diamine component (A1) and a fluorine-free diamine component (A2).   The polyimide film according to any one of claims 3 to 6, wherein the tetracarboxylic acid component (B) contains 60 mol% or more of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride.   The polyimide film according to any one of claims 1 to 7, which is used for a substrate film of a copper-clad laminate and / or a coverlay.   A method for producing a polyimide film according to any one of claims 1 to 8, wherein a self-supporting gel film is obtained by a chemical ring closure method, and the gel film is used.   The metal laminated body using the polyimide film in any one of Claims 1-8.   The metal laminate according to claim 10, which is a copper-clad laminate using a polyimide film as a base film.   The metal laminate according to claim 10 or 11, wherein the polyimide film constitutes a coverlay for protecting the metal layer.