JP5567283B2 - Polyimide film - Google Patents

Description

  The present invention relates to a polyimide film having a small hygroscopic expansion coefficient, excellent dimensional stability, and suitable for an insulating layer of a wiring board.

  In general, polyimide resins have excellent heat resistance, chemical resistance, electrical properties, and mechanical properties, so they are widely used as materials for electronic and electrical equipment, especially for electrical insulation materials that require heat resistance. Yes. Various flexible copper-clad laminates using polyimide as an insulating layer have been studied so far, and a so-called three-layer type laminate in which a polyimide resin film is laminated with a metal layer using an adhesive such as an epoxy resin, A two-layer type laminate in which an insulating layer and a metal layer are laminated without using an adhesive is known. And the laminated body for 2 layers type flexible wiring boards is used as what shows the outstanding characteristic from surfaces, such as heat resistance and a bending characteristic.

  2. Description of the Related Art In recent years, with higher functionality and lighter, thinner and smaller electronic information equipment, higher wiring board density is required, and the wiring pattern is becoming increasingly narrower. As the wiring pattern becomes narrower, materials with low dimensional stability are likely to cause mounting defects such as misalignment of the wiring during the circuit board processing process, and therefore higher dimensional stability of the board is required. It has been. To date, studies have been made to improve the problem by using a material having a low coefficient of linear thermal expansion (CTE) for the polyimide layer serving as an insulating layer. As a result of lowering the CTE, There has been a problem in that the polyimide resin material expands due to moisture absorption, that is, the dimensional change due to moisture absorption increases, causing the substrate to warp. Further, in COF (chip on film) applications that require fine wiring, high tear strength and heat resistance are also required at the stage of processing and mounting.

  As a resin exhibiting low moisture absorption characteristics, a fluororesin exhibiting unique properties such as water repellency is known. Moreover, the polyimide metal composite film which used the fluorinated polyimide copolymer and the fluorinated polyimide for the insulating layer is reported (refer patent document 1, 2). However, the materials reported in these materials have a problem in that the hygroscopic expansion of polyimide is not sufficiently suppressed and the strength is low, so that breakage and deformation are likely to occur at the stage of processing and mounting. On the other hand, for the purpose of improving the hygroscopic expansion coefficient, a laminate for a flexible wiring board using polyimide having high heat resistance and high strength has also been reported (see Patent Documents 3 and 4). It was insufficient in terms of the hygroscopic expansion coefficient. Accordingly, it has been desired to develop a polyimide film that has sufficient heat resistance, film strength, and other excellent polyimide resin properties, and has low hygroscopic expansion and excellent dimensional stability.

Japanese Patent Laid-Open No. 4-8734 JP-A-4-47933 WO01 / 028767 WO02 / 085616

  The present invention is a polyimide film that takes advantage of the excellent properties of polyimide resin, has low hygroscopic expansion, excellent dimensional stability, high heat resistance, sufficient film strength, and good handling properties during processing and mounting. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have found that the polyimide constituting the polyimide film has a specific structure and can solve the above problems by satisfying a certain relational expression. The present invention has been completed.

（一般式（２）において、Ｒは炭素数１〜６の低級アルキル基、フェニル基又は炭素数１〜６のハロゲン化アルキル基を示すが、一般式（２）で表される構造単位が一般式（１）で表される構造単位と同じとなることはない。一般式（２）及び（３）において、Ar₁は芳香族テトラカルボン酸残基であり、一般式（３）中、Ar₂は下記式（c）及び（d）から選択される芳香族基のいずれかを示し、式（c）及び（d）において、Ar₃は二価の芳香族基である。）

That is, the present invention provides 50 to 95 mol% of the structural unit represented by the following general formula (1), 0 to 45 mol% of the structural unit represented by the following general formula (2), and general formula (3). 5 to 50 mol%, 5 to 50 mol% of the structural unit represented by the general formula (2) and the structural unit represented by the general formula (3) are contained, and the hygroscopic expansion coefficient The polyimide film is characterized in that the main layer is a polyimide resin layer (A) having a content of 9 ppm /% RH or less.

(In the general formula (2), R represents a lower alkyl group having 1 to 6 carbon atoms, a phenyl group, or a halogenated alkyl group having 1 to 6 carbon atoms, but the structural unit represented by the general formula (2) is generally used. It is not the same as the structural unit represented by the formula (1) In the general formulas (2) and (3), Ar ₁ is an aromatic tetracarboxylic acid residue. ₂ represents any one of the aromatic groups selected from the following formulas (c) and (d), and in the formulas (c) and (d), Ar ₃ is a divalent aromatic group.

Here, in the general formulas (2) and (3), Ar ₁ is preferably any one of the following aromatic groups (a) or (b). Ar ₃ is a divalent aromatic group represented by the following formula (e) .

Moreover, it is preferable that the polyimide film of the present invention further satisfies any one or more of the following requirements.
(1) The linear expansion coefficient of the polyimide resin layer (A) is 25 ppm / ° C. or less.
(2) The polyimide resin layer (A) has a thermoplastic polyimide resin layer (B) having a linear expansion coefficient of 30 ppm / ° C. or more on one side or both sides of the polyimide resin layer (A), and the polyimide resin layer (A) and the thermoplastic polyimide resin layer (B ) Thickness ratio (B) / (A) is in the range of 0.02-1.
(3) The glass transition temperature of the insulating layer is 310 ° C. or higher, the tear propagation resistance is 3.0 kN / m or higher, and the moisture absorption is 0.7 wt% or lower.

  According to the present invention, the polyimide film has low moisture absorption and low hygroscopic expansion, so that it has excellent dimensional stability and can be suitably used for an insulating layer of a flexible wiring board that requires high dimensional stability. it can.

  The method for producing the polyimide film of the present invention is not particularly limited. For example, a polyimide precursor (polyamic acid) resin solution, which is a raw material of the polyimide film, is cast on an arbitrary support substrate. After forming into a film and heating and drying on a support to form a gel film having a self-supporting property, it is generally peeled off from the support and then heat-treated at a high temperature to be imidized to form a polyimide film. Is. After polyamic acid is cast-applied on an arbitrary substrate such as copper foil using an applicator and pre-dried, it is further heat-treated for solvent removal and imidization, and the substrate used at the time of imidation is peeled off or The method of removing by etching etc. is also mentioned. At this time, the viscosity of the resin solution is preferably in the range of 500 to 70000 cps. When making a polyimide insulating layer into multiple layers, it can form by coating another polyimide precursor resin sequentially on the polyimide precursor resin which consists of a different structural component. When the polyimide insulating layer is composed of three or more layers, the polyimide precursor resin having the same configuration may be used twice or more. The coating may be carried out after appropriately treating the surface of the metal layer to be the application surface of the resin solution. It is appropriate that the drying conditions are 150 ° C. or lower for 2 to 30 minutes, and the heat treatment for imidization is performed at a temperature of about 130 to 360 ° C. for about 2 to 30 minutes.

  The polyimide film of the present invention has a polyimide resin layer (A) as a main polyimide resin layer. Here, the main means the thickest layer among the polyimide resin layers constituting the polyimide film, preferably 60% or more, particularly preferably 70% or more, most preferably 75% of the total thickness of the polyimide resin layer. Refers to a layer having a thickness of ~ 95%. It is preferable that a polyimide film consists of a polyimide resin layer (A) and a thermoplastic polyimide resin layer (B), and each layer should just have at least 1 layer and may consist of two or more layers. When it consists of a polyimide resin layer (A) and a thermoplastic polyimide resin layer (B), (B) / (A) is the ratio of the thickness of a polyimide resin layer (A) and a thermoplastic polyimide resin layer (B). The range is 02 to 1, preferably 0.05 to 0.4.

  When the polyimide film of the present invention and a metal layer are laminated by heating and pressing in the production of a laminate for a flexible wiring board, advantageously, the polyimide resin layer in contact with the metal layer is a thermoplastic polyimide resin layer (B), The polyimide resin layer (A) may be a polyimide resin layer that is in contact with the thermoplastic polyimide resin layer (B) but not in contact with the metal layer. When the thermoplastic polyimide resin layer (B) has the thermoplastic polyimide resin layer (B) only on one side of the polyimide resin layer (A), the polyimide resin layer (A) and the thermoplastic polyimide resin layer (B) The thickness ratio of (B) / (A) is preferably in the range of 0.05 to 0.2. When the thermoplastic polyimide resin layer (B) is provided on both sides of the polyimide resin layer (A), 0.1% is obtained. A range of ~ 0.4 is preferred.

  The polyimide resin layer (A) is 50 to 95 mol% of the structural unit represented by the general formula (1), and 5 to 50 mol in total of the structural units represented by the general formulas (2) and (3). %, And the hygroscopic expansion coefficient is 9 ppm /% RH or less. Here, 0 may be sufficient as the structural unit represented by General formula (2), and the structural unit represented by General formula (3) contains 5 mol% or more.

  The polyimide resin layer (A) needs to contain the structural unit represented by the general formula (1) in the range of 50 to 95 mol%, but the other structural units are polyimide raw materials. Certain known acid anhydrides and diamines can be appropriately selected and used. In the present invention, it is advantageous that the structural unit represented by the general formulas (2) and (3) together with the structural unit represented by the general formula (1) is contained in a range of 5 to 50 mol%. is there. Here, the preferred ratio of the structural units of the general formulas (1) to (3) is such that l is the molar ratio of the structural units of the general formula (1), m is the molar ratio of the structural units of the general formula (2), When n is the molar ratio of the structural unit of the general formula (3), l is 0.5 to 0.95, m is 0 to 0.45, and n is 0.05 to 0.50, but the total of m and n is 0.05 to 0.50. Range. L is 0.6 to 0.9, m is 0.05 to 0.3, n is 0.05 to 0.3, and the total of m and n is more preferably in the range of 0.1 to 0.4. When the molar ratio is 1.0, the content ratio of the structural unit is calculated as 100%.

  In General formula (2), R shows a C1-C6 lower alkyl group, a phenyl group, or a C1-C6 halogenated alkyl group. Preferably they are a C1-C3 lower alkyl group, a phenyl group, or a C1-C3 halogenated alkyl group. The structural unit represented by the general formula (2) is not the same as the structural unit represented by the general formula (1). That is, the structural unit represented by the general formula (1) is not treated as the structural unit represented by the general formula (2).

In the general formulas (2) and (3), Ar ₁ is preferably any one of aromatic groups selected from the above formulas (a) and (b). In the general formula (3), Ar 1 ₂ is any aromatic group selected from the above formulas (c) and (d). In the formulas (c) and (d), Ar ₃ is preferably any one of aromatic groups selected from the formulas (e) and (f).

Preferable specific examples of the structural unit represented by the general formula (2) include a structural unit represented by the following formula (4).

  The structural unit of the general formula (1) mainly improves properties such as low-humidity expansion and high heat resistance, and the structural unit of the general formula (2) is effective for improving low thermal expansion and high heat resistance. is there. The structural unit of the general formula (3) is considered to improve mainly properties such as toughness and adhesiveness, but is not strict because of synergistic effects and molecular weight effects. However, in order to increase toughness and the like, it is usually effective to increase the structural unit of the general formula (3).

  Examples of the diamine used to give the structural unit of the general formula (3) include 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,3-bis (3-aminophenoxy) benzene (APB). ) Or 4,4'-diaminodiphenyl ether (4,4'-DAPE)

  Examples of the acid anhydride used to give the structural units of the general formula (2) and the general formula (3) include pyromellitic dianhydride (PMDA) and biphenyltetracarboxylic dianhydride (BPDA).

  The diamine and acid anhydride used as the raw material for the polyimide resin layer (A) satisfy the above formula and molar ratio, and a plurality of diamines and acid anhydrides may be used as long as the above resin layer characteristics are satisfied. The diamines and acid anhydrides may be used.

  The thermoplastic polyimide resin layer (B) has a linear expansion coefficient larger than 30 ppm / ° C., and its glass transition temperature is preferably 350 ° C. or less, and more preferably in the range of 250 to 330 ° C. In order to obtain a polyimide resin satisfying such characteristics, a known acid anhydride and diamine can be used as raw materials, and they can be appropriately combined and reacted.

As an acid anhydride used for forming the thermoplastic polyimide resin layer (B), when the acid anhydride is represented by O (OC) ₂ Ar ₄ (CO) ₂ O, Ar ₄ is represented by the following formula. Aromatic dianhydride residues are exemplified.

  Among these, PMDA, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride (BTDA) or 3, 3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA) is exemplified as a suitable one.

As the diamine component that is used to form a thermoplastic polyimide resin layer (B), when representing the diamine _{H 2 N-Ar 5 -NH 2} , diamine exemplary Ar ₅ is represented by the following formula Is done.

  Among these, 4,4′-DAPE, TPE-R, APB or 2,2-bis (4-aminophenoxyphenyl) propane (BAPP) is preferable.

  As described above, the polyimide film of the present invention comprises a single layer or a plurality of polyimide resin layers. In the case of a plurality of layers, the polyimide resin layer (A) is the main layer, and at least one surface thereof is a thermoplastic polyimide resin layer (B ). The total thickness of the polyimide resin layer is preferably 10 to 40 μm, more preferably 15 to 35 μm. Moreover, although the thickness ratio of the polyimide resin layer (A) with respect to the polyimide layer whole thickness is as above-mentioned, especially the thickness ratio (B) / (of a polyimide resin layer (A) and a thermoplastic polyimide resin layer (B). A) can be made into the polyimide film excellent in the balance of tear strength and flexibility especially by setting it as the range of 0.02-1.

  The polyimide film can be produced by polymerizing raw material diamine and acid anhydride in the presence of a solvent to obtain a polyimide precursor resin, and then imidizing by heat treatment. The molecular weight of the polyimide resin can be mainly controlled by changing the molar ratio of the raw material diamine and acid anhydride. The molar ratio is usually 1: 1. Examples of the solvent include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglyme, xylene and the like, and they can be used alone or in combination of two or more.

  In the flexible wiring board using the polyimide film of the present invention, in order to control the peel strength, it is effective that the thermoplastic polyimide resin layer (B) is in contact with the metal layer. In addition, the polyimide film has a glass transition temperature of 310 ° C. or higher, a tear propagation resistance of 3.0 kN / m or higher, and a hygroscopic expansion coefficient of 9 ppm /% RH or lower. This is effective to enable circuit formation. In particular, in order to reduce the curl of the polyimide film, it is effective to have both the polyimide resin layer (A) and the thermoplastic polyimide resin layer (B), and the effect is the same as the polyimide resin layer (A) and the heat. It differs depending on the stacking order and thickness ratio of the plastic polyimide resin layer (B).

  EXAMPLES Hereinafter, although the content of this invention is demonstrated concretely based on an Example, this invention is not limited to the range of these Examples.

Abbreviations used in Examples and the like are shown below.
-PMDA: pyromellitic dianhydride-BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride-TFMB: 2,2'-ditrifluoromethylbenzidine-TPE-R: 1,3- Bis (4-aminophenoxy) benzene / m-TB: 2,2'-dimethylbenzidine / BAPP: 2,2-bis (4-aminophenoxyphenyl) propane / DMAc: N, N-dimethylacetamide

  In addition, measurement methods and conditions for various physical properties in the examples are shown below. In addition, what was expressed as a polyimide film below refers to the polyimide film obtained by carrying out the etching removal of the copper foil of the laminated body which used copper foil as a support base.

[Measurement of tear propagation resistance]
A test piece of polyimide film (63.5 mm × 50 mm) was prepared, a cut of 12.7 mm in length was made in the test piece, and measurement was performed at room temperature using a light load tear tester manufactured by Toyo Seiki.

[Measurement of coefficient of thermal expansion (CTE)]
The polyimide film (3 mm × 15 mm) was subjected to a tensile test in a temperature range from 30 ° C. to 260 ° C. at a constant temperature increase rate while applying a 5 g load with a thermomechanical analysis (TMA) apparatus. The thermal expansion coefficient was measured from the amount of elongation of the polyimide film with respect to temperature.

[Measurement of glass transition temperature (Tg)]
The dynamic viscoelasticity when a polyimide film (10 mm × 22.6 mm) was heated from 20 ° C. to 500 ° C. at a rate of 5 ° C./min was measured by DMA to determine the glass transition temperature Tg (tan δ maximum value). It was.

[Measurement of film curl]
A polyimide film (50 mm × 50 mm) was conditioned under constant temperature and humidity (23 ° C., 50% RH) for 24 hours, and then the curvature radius of the film was measured.

[Measurement of moisture absorption rate]
A polyimide film (4 cm × 20 cm) was dried at 120 ° C. for 2 hours, and then allowed to stand for 24 hours in a constant temperature and humidity chamber of 23 ° C./50% RH.
Moisture absorption rate (%) = [(weight after moisture absorption−weight after drying) / weight after drying] × 100

[Measurement of hygroscopic expansion coefficient (CHE)]
An etching resist layer was provided on a copper foil of a 35 cm × 35 cm copper-clad product, and this was formed into a pattern in which 16 points with a diameter of 1 mm were arranged at intervals of 10 cm on four sides of a square with a side of 30 cm. The exposed portion of the etching resist opening was etched to obtain a CHE measurement polyimide film having 16 copper foil remaining points. After drying this film at 120 ° C. for 2 hours, each film was allowed to stand for 24 hours at 23 ° C./30% RH / 50% RH / 70% RH constant temperature and humidity at 24 ° C. and measured with a two-dimensional measuring machine. The humidity expansion coefficient (ppm /% RH) was determined from the dimensional change between the copper foil points at humidity.

Synthesis example 1
In order to synthesize polyimide precursor resins A to I (polyamic acid), the diamines shown in Table 1 were dissolved in about 250 to 300 g of solvent DMAc while stirring in a 500 ml separable flask under a nitrogen stream. . Subsequently, the tetracarboxylic dianhydride shown in Table 1 was added. Thereafter, the solution was continuously stirred at room temperature for 4 hours to carry out a polymerization reaction, thereby obtaining a yellowish brown viscous solution of polyimide precursor resins A to I. Numerical values in Table 1 represent raw material usage (g).

Examples 1-4
Precursor resin solutions A to D were uniformly applied on a copper foil having a thickness of 12 μm using an applicator, dried at 50 to 130 ° C. for 2 to 60 minutes, and then further 130 ° C., 160 ° C. and 200 ° C. , 230 ° C., 280 ° C., 320 ° C., 360 ° C., each of which was subjected to stepwise heat treatment for 2 to 60 minutes to obtain a laminate having a polyimide resin layer formed thereon. Subsequently, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film.

Example 5
On the electrolytic copper foil having a thickness of 12 μm, the polyimide precursor resin solution A was uniformly applied using an applicator so that the thickness after curing was 23 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Next, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Further, stepwise heat treatment was performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C., and 360 ° C. for 2 to 60 minutes each to obtain a laminate having two polyimide resin layers. Next, the copper foil was removed by etching using an aqueous ferric chloride solution to obtain a polyimide film.

Example 6
On the electrolytic copper foil having a thickness of 12 μm, the polyimide precursor resin solution B was uniformly applied using an applicator so that the thickness after curing was 23 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Next, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Further, stepwise heat treatment was performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C., and 360 ° C. for 2 to 60 minutes each to obtain a laminate having two polyimide resin layers. Next, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film.

Example 7
On the electrolytic copper foil having a thickness of 12 μm, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Next, the precursor resin solution A was uniformly applied using an applicator so that the thickness after curing was 21 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Further, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Thereafter, stepwise heat treatment was performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C., and 360 ° C. for 2 to 60 minutes each to obtain a laminate having three polyimide resin layers. Subsequently, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film.

Example 8
On the electrolytic copper foil having a thickness of 12 μm, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Next, the precursor resin solution D was uniformly applied using an applicator so that the thickness after curing was 21 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Further, the precursor resin solution I was uniformly applied using an applicator so that the thickness after curing was 2 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Thereafter, stepwise heat treatment was performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C., and 360 ° C. for 2 to 60 minutes each to obtain a laminate having three polyimide resin layers. Subsequently, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film.

Comparative Examples 1-4
On the electrolytic copper foil having a thickness of 12 μm, the precursor resin solutions E to H were uniformly applied using an applicator so that the thickness after curing was 25 μm, and dried at 50 to 130 ° C. for 2 to 60 minutes. Thereafter, stepwise heat treatment was further performed at 130 ° C., 160 ° C., 200 ° C., 230 ° C., 280 ° C., 320 ° C., and 360 ° C. for 2 to 60 minutes each to obtain a laminate having a polyimide resin layer formed thereon. Subsequently, the copper foil was etched away using an aqueous ferric chloride solution to obtain a polyimide film.

About the obtained polyimide film, various characteristics were evaluated with the above-mentioned measuring method. The results are shown in Tables 2 and 3. Note that the peel strength in Comparative Example 1 could not be measured because the film was brittle. In the table, tearing means tear propagation resistance.

Claims (5)

The structural unit represented by the following general formula (1) is 50 to 95 mol%, the structural unit represented by the following general formula (2) is 0 to 45 mol%, and the structural unit represented by the general formula (3) 5-50 mol%, the structural unit represented by the general formula (2) and the structural unit represented by the general formula (3) are contained in an amount of 5 to 50 mol%, and the hygroscopic expansion coefficient is 9 ppm /% RH or less. A polyimide film characterized by comprising a polyimide resin layer (A) as a main layer.

(In the general formula (2), R represents a lower alkyl group having 1 to 6 carbon atoms, a phenyl group, or a halogenated alkyl group having 1 to 6 carbon atoms, but the structural unit represented by the general formula (2) is generally used. It is not the same as the structural unit represented by the formula (1) In the general formulas (2) and (3), Ar ₁ is an aromatic tetracarboxylic acid residue. ₂ represents any one of aromatic groups selected from the following formulas (c) and (d), and in formulas (c) and (d), Ar ₃ represents a divalent aromatic represented by the following formula (e) A group.)

2. The polyimide film according to claim 1, wherein in the general formulas (2) and (3), Ar ₁ is an aromatic group of any one of the following (a) or (b).

The polyimide film according to claim 1 or 2, wherein the polyimide film has a glass transition temperature of 310 ° C or higher, a tear propagation resistance of 3.0 kN / m or higher, and a moisture absorption of 0.7 wt% or lower .   The polyimide film according to claim 1, wherein the polyimide resin layer (A) has a linear expansion coefficient of 25 ppm / ° C. or less.   The polyimide film consists of a plurality of layers, and has a thermoplastic polyimide resin layer (B) having a linear expansion coefficient of 30 ppm / ° C. or more on one or both sides of the polyimide resin layer (A), and the polyimide resin layer (A) and the thermoplastic resin. The polyimide film according to any one of claims 1 to 4, wherein a thickness ratio (B) / (A) of the polyimide resin layer (B) is in a range of 0.02-1.