JP2022016735A - Polyimide film having gas barrier layer - Google Patents

Abstract

To provide a polyimide film that inhibits degradation in a metal wire and an adhesive layer even under a high temperature environment and allows the production of a flexible printed wiring board having high durability.SOLUTION: A polyimide film has a metal layer or an inorganic layer as a gas barrier layer formed on one side and/or both sides of a non-thermoplastic polyimide film or a polyimide film having thermoplastic resin layers on both sides.SELECTED DRAWING: None

Description

The present invention relates to a polyimide film suitably used for flexible printed substrates (hereinafter, also referred to as FPC) and the like. More specifically, the present invention relates to a non-thermoplastic polyimide or a polyimide film having a thermoplastic resin layer on both sides and having a gas barrier layer formed on one side and / or both sides.

In recent years, the performance, functionality, and miniaturization of electronic devices have been rapidly advancing, and along with this, there is an increasing demand for miniaturization and thinning of electronic components used in electronic devices. Further, cost reduction is progressing, and the materials constituting the FPC are diversifying according to the demand.

Conventionally, a polyimide film having high heat resistance and insulating properties has been used as an insulating material suitable for a flexible printed wiring board. An adhesive layer is formed on one side or both sides of the polyimide film, and a metal foil is further bonded to produce a single-sided or double-sided metal-clad laminate. By forming a semi-cured adhesive layer on one side of the polyimide film. Coverlay film is manufactured. A flexible printed wiring board is manufactured by using these metal-clad laminates and a coverlay film. Specifically, it is manufactured by adhering a coverlay film to a metal-clad laminate in which wiring is formed and curing it.

In recent years, the digitization of automobiles has progressed, and the application of flexible printed wiring boards to automobiles is also progressing. In automobile applications, durability is required more than that of electronic devices such as smartphones, and the materials used, especially the adhesive layer, are becoming more heat resistant, but metal wiring and adhesives are used after reliability tests such as long-term heat resistance tests. There was a problem that the layer deteriorated. The cause of this is that oxygen and water vapor permeate through the polyimide film. To solve the above problems, in order to reduce the permeability of gas such as oxygen and water vapor of plastic products, silica (CVD) is utilized by vacuum vapor deposition method, sputtering method, or chemical vapor deposition method (CVD). Various films in which a SiOX) or alumina (AlOX) thin film is formed on a polyester film have been proposed (for example, Patent Document 1), and by utilizing such a technique, a metal layer / A material for a flexible circuit board made of a polyimide film / a thin film layer having a low oxygen permeability has also been proposed (for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 5-8318 Japanese Unexamined Patent Publication No. 6-29634

However, in recent years, due to the improvement of quality requirements, the conditions of long-term reliability test have become stricter, and it is required to withstand strict conditions of, for example, 260 ° C. and 3000 hours, but it is difficult to solve by the above method. Met.
The present invention has been made in view of the above problems, and an object thereof relates to a polyimide film preferably used for FPCs that require particularly high durability. More specifically, it is an object of the present invention to provide a non-thermoplastic polyimide or a polyimide film having a thermoplastic resin layer on both sides and having a gas barrier layer formed on one side and / or both sides.

As a result of diligent studies to solve the above problems, the present inventors have found that the desired FPC can be obtained by the following method, and have completed the present invention.

That is, the present invention relates to a polyimide film that is particularly preferably used for a highly durable FPC or the like. More specifically, the present invention relates to a non-thermoplastic polyimide or a polyimide film having a thermoplastic resin layer on both sides and having a gas barrier layer formed on one side and / or both sides.
That is, it has the following configuration.
(1). A polyimide film having an inorganic layer as a gas barrier layer on one side and / or both sides of a non-thermoplastic polyimide film.
(2). The polyimide film according to (1), which has a metal layer as a gas barrier layer.
(3). A polyimide film having an inorganic layer as a gas barrier layer on one side and / or both sides of a polyimide film having a thermoplastic resin layer on both sides.
(4). The polyimide film according to (2), which has a metal layer as a gas barrier layer.
(5). A coverlay film using the polyimide films of (1) to (4).
(6). A single-sided metal-clad laminate made of the polyimide films of (1) to (4).
(7). A double-sided metal-clad laminate made of the polyimide films of (1) to (4).
(8). A flexible printed wiring board using the coverlay film and / or the single-sided metal-clad laminate and / or the double-sided metal-clad laminate according to (5) to (7).
(9). The flexible printed wiring board according to (8), wherein the retention rate of the peel strength between the metal foil and the adhesive layer after heat treatment at 260 ° C. for 3000 hours is 80% or more.

According to the present invention, a remarkable effect is exhibited when a coverlay film preferably used for an FPC that requires particularly durability, such as an FPC for an automobile, or a single-sided or double-sided metal-clad laminate is manufactured.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and can be carried out in a mode in which various modifications are added within the range described.

<Non-thermoplastic polyimide film>
In the present invention, the non-thermoplastic polyimide film needs to be able to withstand use at a heating temperature during thermal laminating. Therefore, the non-thermoplastic polyimide film is not particularly limited as long as it satisfies the above properties.

The non-thermoplastic polyimide film may be formed by containing 80% by weight or more, preferably 90% by weight or more of the non-thermoplastic polyimide, and the molecular structure and thickness of the non-thermoplastic polyimide are not particularly limited. The non-thermoplastic polyimide used for forming a heat-resistant (non-thermoplastic) polyimide film is generally manufactured by using a polyamic acid (also referred to as a polyamic acid) as a precursor, and the non-thermoplastic polyimide is produced. It may be completely imidized, or it may contain a non-imidized precursor, that is, polyamic acid as a part. Here, the non-thermoplastic polyimide generally refers to a polyimide that does not soften or show adhesiveness even when heated. In the present invention, it refers to a polyimide that is heated at 450 ° C. for 2 minutes in a film state and does not wrinkle or stretch and retains its shape, or a polyimide that does not substantially have a glass transition temperature. The glass transition temperature can be obtained from the value of the inflection point of the storage elastic modulus measured by the dynamic viscoelasticity measuring device (DMA). Further, "substantially having no glass transition temperature" means that thermal decomposition starts before the glass transition state is reached.

Generally, a polyimide film can be produced using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid, and it is usually controlled by dissolving an aromatic tetracarboxylic acid dianhydride and an aromatic diamine in a substantially equimolar amount in an organic solvent. It can be produced by stirring under temperature conditions until the polymerization of the aromatic tetracarboxylic acid dianhydride and the aromatic diamine is completed. These polyamic acid solutions are usually obtained in a concentration of 5 to 35% by weight, preferably 10 to 30% by weight. Suitable molecular weights and solution viscosities can be obtained at concentrations in this range.

As the polymerization method, any known method or a method in which they are combined can be used. The characteristic of the polymerization method in the polymerization of polyamic acid lies in the order in which the monomers are added, and various physical properties of the polyimide obtained by controlling the order in which the monomers are added can be controlled. Therefore, in the present invention, any method of adding a monomer may be used for the polymerization of polyamic acid. The following methods can be mentioned as typical polymerization methods. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent, and a substantially equimolar aromatic tetracarboxylic dianhydride is reacted with the aromatic diamine for polymerization.
2) An aromatic tetracarboxylic acid dianhydride is reacted with an aromatic diamine compound in a small molar amount in an organic polar solvent to obtain a prepolymer having an acid anhydride group at both ends. Subsequently, a method of polymerizing using an aromatic diamine compound so that the aromatic tetracarboxylic acid dianhydride and the aromatic diamine compound are substantially equimolar in all steps.
3) Aromatic tetracarboxylic acid dianhydride is reacted with an excess molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, a method of polymerizing using an aromatic tetracarboxylic acid dianhydride so that the aromatic tetracarboxylic acid dianhydride and the aromatic diamine compound are substantially equimolar in all steps.
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent, and then polymerized using an aromatic diamine compound so as to be substantially equimolar.
5) A method of polymerizing a mixture of a substantially equimolar aromatic tetracarboxylic acid dianhydride and an aromatic diamine by reacting them in an organic polar solvent.
And so on. These methods may be used alone or in combination partially.

In the present invention, the polyamic acid obtained by any of the above polymerization methods may be used, and the polymerization method is not particularly limited.

The aromatic diamine is not limited to this, and for example, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2-bis {4. -(4-Aminophenoxy) phenyl} propane, 2,2-bis {4- (4-aminophenoxy) phenyl} hexafluoropropane, bis {4- (3-aminophenoxy) phenyl} sulfone, bis {4- ( 4-Aminophenoxy) phenyl} sulfone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 3, 3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2' -Dimethoxybenzidine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene (m-phenylenediamine), 4,4'-diaminodiphenylsulphon, 3,3'-diaminodiphenylsulphon, 9, 9-bis (4-aminophenyl) fluorene, 4,4'-(1,4-phenylenebis (1-methylethylidene)) bisaniline, 4,4'-(1,3-phenylenebis (1-methylethylidene)) ) Bisaniline, 4,4'-diaminobenzanilide, 2,2'-dimethylbiphenyl-4,4'-diamine, etc., or a combination of two or more thereof can be mentioned.

The aromatic tetracarboxylic acid dianhydride is not limited to, but is not limited to, for example, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3. , 3'-Benzophenone tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 3,4'-oxyphthalic acid dianhydride, ethylene bis (trimellitic acid monoesteric acid anhydride), bisphenol A bis (Trimeric acid monoesteric acid anhydride), pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 3,3', 4,4'-dimethyldiphenylsilanetetracarboxylic acid dianhydride, 3,3', 4,4'-tetra Phenylsilanetetracarboxylic acid dianhydride, 1,2,3,4-frantetracarboxylic acid dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 4,4' -Hexafluoroisopropyridendiphthalic anhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid dianhydride, p-phenylene Examples thereof include bis (trimellitic acid monoester anhydride), aromatic tetracarboxylic acid dianhydride such as p-phenylenediphthalic anhydride, or a combination of two or more thereof.

The aromatic diamine and the aromatic tetracarboxylic dianhydride may be reacted so as to have substantially the same molar amount, and the order of addition, the combination of the monomers and the composition are not particularly limited. do not have.

The organic solvent used as the polymerization solvent for producing the polyamic acid is not particularly limited as long as it dissolves the aromatic diamine, the aromatic tetracarboxylic acid dianhydride, and the obtained polyamic acid. .. As the above-mentioned polymerization solvent, for example, an amide solvent such as N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like is preferable, and if these are used, the obtained solvent can be obtained. The resin solution can be prepared by using the organic solvent solution (polyamic acid solution) of the polyamic acid as it is.

The reaction temperature for producing the polyamic acid is preferably −10 ° C. to 50 ° C. By controlling within such a temperature range, the reaction proceeds at a good reaction rate and the productivity is excellent, which is preferable. The reaction time is not particularly limited, but is usually several minutes to several hours.

In the present invention, the curing agent is intended to include at least one of a dehydrating agent and a catalyst.

Here, the dehydrating agent is not particularly limited as long as the polyamic acid can be dehydrated by the dehydration ring-closing action, but for example, aliphatic acid anhydride, aromatic acid anhydride, N, N'-dialkylcarbodiimide, lower aliphatic. Examples thereof include halides, halogenated lower aliphatic acid anhydrides, aryl sulfonic acid dihalides, and thionyl halides. These may be used alone or in combination of two or more as appropriate. Among these, aliphatic acid anhydrides and aromatic acid anhydrides can be particularly preferably used.

The catalyst is not particularly limited as long as it is a component having an effect of promoting the dehydration ring closing action of the dehydrating agent on the polyamic acid, but specifically, for example, an aliphatic tertiary amine and an aromatic tertiary amine. , Heterocyclic tertiary amine and the like.

A filler may be added to the heat-resistant film (A) for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

<Thermoplastic resin layer>
In the present invention, examples of the thermoplastic resin layer include a polycarbonate resin, an acrylonitrile / styrene copolymer resin, a thermoplastic polyimide resin, and the like, but the thermoplastic polyimide resin is particularly preferably used from the viewpoint of heat resistance. Can be done. If the thermoplastic polyimide resin exhibits desired characteristics such as significant adhesion to a metal foil and a suitable linear expansion coefficient, the content, molecular structure, and thickness of the thermoplastic polyimide resin contained in the layer can be determined. It is not particularly limited. However, in order to exhibit desired properties such as significant adhesive strength and a suitable linear expansion coefficient, it is preferable that the thermoplastic polyimide resin is substantially contained in the thermoplastic resin layer in an amount of 50% by weight or more. Further, the thermoplastic polyimide resins contained in the thermoplastic resin layers facing each other via the polyimide film may be of the same type from the viewpoints of balancing the linear expansion coefficient of the entire adhesive sheet and simplifying the manufacturing process. preferable.

As the thermoplastic polyimide resin contained in the thermoplastic resin layer, for example, a thermoplastic polyamide-imide, a thermoplastic polyetherimide, a thermoplastic polyesterimide, or the like can be preferably used.

The thermoplastic polyimide contained in the thermoplastic resin layer can be obtained by a conversion reaction from its precursor, polyamic acid. As a method for producing the polyamic acid, any known method can be used as in the precursor of the non-thermoplastic polyimide resin that can be used for the polyimide film.

The thermoplastic polyimide resin used in the present invention is in the range of 150 ° C. to 300 ° C. from the viewpoint of exhibiting significant adhesive strength to the metal foil and not impairing the heat resistance of the obtained single-sided metal-clad laminate. It is preferable to have a glass transition temperature (Tg). In addition, Tg can be obtained from the value of the inflection point of the storage elastic modulus measured by the dynamic viscoelasticity measuring device (DMA).

The polyamic acid as a precursor of the thermoplastic polyimide that can be used in the present invention is not particularly limited, and any known polyamic acid can be used. As for the production of the polyamic acid solution, the raw materials exemplified above, the production conditions and the like can be appropriately selected and used in the same manner.

Various characteristics of thermoplastic polyimide can be adjusted by combining various raw materials such as aromatic tetracarboxylic acid dianhydride and aromatic diamine to be used, but in general, the ratio of aromatic diamine having a rigid structure is large. In this case, the glass transition temperature may increase, the storage elastic modulus during heating may increase, and the adhesiveness / processability may decrease. For example, the ratio of the aromatic diamine having the rigid structure to the total amount of the aromatic diamine is preferably 40 mol% or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

As a specific example of the preferable thermoplastic polyimide resin, an aromatic diamine or an aromatic tetracarboxylic acid dianhydride that can be used for the above-mentioned heat-resistant polyimide film can be used. More preferably, an acid dianhydride such as benzophenone tetracarboxylic acid dianhydride, biphenyltetracarboxylic acid dianhydride, oxydiphthalic acid dianhydride, biphenylsulfonetetracarboxylic acid dianhydride and an aromatic diamine having an aminophenoxy group are used. Examples thereof include those that have undergone a polymerization reaction.

Further, for the purpose of controlling the slipperiness of the adhesive sheet according to the present invention, an inorganic or organic filler and other resins may be added, if necessary.

The method for producing a polyimide film having a thermoplastic resin according to the present invention is not particularly limited, and examples thereof include a method of forming a thermoplastic resin on a polyimide film as a core layer on each side or simultaneously on both sides.

Further, for example, a resin solution obtained by dissolving or dispersing the resin composition in an organic solvent may be applied to the surface of the polyimide.

The thickness structure of each layer of the polyimide film in the present invention may be appropriately adjusted so as to have a total thickness according to the intended use.

As the non-thermoplastic polyimide film in the present invention, Apical manufactured by Kaneka Corporation can be used, and as the polyimide having a thermoplastic resin layer in the present invention, Pixio (registered trademark) manufactured by Kaneka Corporation can be used.

<Gas barrier layer>
In the present invention, a gas barrier layer is provided on one side and / or both sides of the polyimide film in order to prevent gas such as oxygen and water vapor from entering.
An inorganic layer is preferably used as the gas barrier layer in order to apply it to the high durability of FPC in recent years. Examples of the inorganic layer include compounds of inorganic substances such as silicon, magnesium, indium, aluminum and titanium, or compounds such as oxides, nitrides, sulfides and fluorides of metals. Silicon oxide and aluminum oxide are more preferably used from the viewpoint of balance between gas barrier performance and cost. It is also preferable to use a metal layer as the gas barrier layer, and examples thereof include tin, nickel, chromium, nichrome, titanium, molybdenum, tungsten, zinc, silicon, gold, silver, and copper.

The thickness to be formed is not particularly limited, but it is preferably formed on the entire surface in order to exhibit the gas barrier performance, and the thickness is preferably 1 nm or more, more preferably 5 nm or more. When a metal layer is used as the gas barrier layer, the gas barrier layer can be formed so as to have a sea-island structure for the purpose of maintaining insulating properties.

Further, for the purpose of improving the gas barrier performance, it can be provided not only on one side of the polyimide film but also on both sides.

For the purpose of changing the crystal state of the formed gas barrier layer and further improving the gas barrier performance, heat treatment can be performed after the gas barrier layer is formed, and it is preferable to perform heat treatment at 100 ° C. for 30 seconds or longer, preferably 150 ° C. for 30 seconds. It is more preferable to perform the above heat treatment.

The gas barrier property can be evaluated by the oxygen permeability, and as a polyimide film applicable to high durability requirements, the oxygen permeability is preferably 10 ml / m 2/24 hours or less, and 5 ml / m ^2/24 hours. The following is more preferable.

The method for forming the gas barrier layer is not particularly limited, and methods such as vapor deposition and sputtering can be applied, but a thin film deposition method is preferable in order to balance gas barrier performance and cost.

<Coverlay film>
In the present invention, the coverlay film can be produced by forming an adhesive layer on one side of the polyimide film having the gas barrier property of the present invention. The adhesive layer is not particularly limited, but an adhesive layer having high heat resistance is preferable in order to maintain high durability. Since the adhesive layer also needs to have a function of embedding the wiring of the inner layer wiring substrate of the FPC, various thermosetting resin systems such as an epoxy resin system and an acrylic resin system are preferably used. The thickness of the adhesive layer is not particularly limited, and the design can be made in consideration of the thickness of the wiring to be embedded and the total thickness of the FPC. The method for forming the adhesive layer is not particularly limited, and various methods such as a method of casting and drying an adhesive solution, a method of laminating an adhesive sheet, and the like can be applied. In order to obtain the function of embedding the wiring as described above, the adhesive layer is preferably in a semi-cured state.

<Metal-clad laminate>
The metal-clad laminate in the present invention can be manufactured on either one side or both sides as long as the polyimide film having the gas barrier property of the present invention is used. When the non-thermoplastic polyimide film of the present invention is used, a metal foil may be formed via an adhesive layer, and when the polyimide film having a thermoplastic resin layer on both sides of the present invention is used, a single plate press is used. The metal foil may be formed by a hot crimping method by batch processing, a hot roll laminating device (also referred to as a hot laminating device), or a hot crimping method by continuous treatment using a double belt press (DBP) device.

The metal foil is not particularly limited, but when the single-sided metal-clad laminate of the present invention is used for electronic equipment / electrical equipment applications, for example, copper or a copper alloy, stainless steel or an alloy thereof, nickel or nickel. Examples include alloys (including 42 alloys), aluminum or foils made of aluminum alloys. In general flexible laminated plates, copper foils such as rolled copper foils and electrolytic copper foils are often used, but they can also be preferably used in the present invention. The surface of these metal foils may be coated with a rust preventive layer, a heat resistant layer, or an adhesive layer. Further, the thickness of the metal foil is not particularly limited, and may be any thickness as long as it can exhibit sufficient functions according to its use. The thickness of the metal foil is, for example, preferably 3 μm to 30 μm, more preferably 5 μm to 20 μm. The surface roughness (Rz) of the metal foil is preferably 0.01 μm to 1 μm. When the surface roughness (Rz) of the metal foil is out of this range, the adhesiveness with the thermoplastic resin layer on the side in contact with the metal foil may be inferior.

<Flexible printed wiring board>
By using the coverlay film, single-sided metal-clad laminate, and / or double-sided metal-clad laminate, a flexible printed wiring board with high durability that does not deteriorate the wiring or adhesive layer even after a long-term reliability test can be obtained. Obtainable.

As a high durability evaluation method, it can be evaluated by the retention rate of the peel strength between the wiring and the adhesive layer after the heat treatment at 260 ° C. for 3000 hours, and the retention rate is preferably 80% or more. As a specific method for evaluating the peel strength retention rate, a wiring having a width of 1 mm is formed on a double-sided metal-clad laminate, and the peel strength (a) at 90 ° is measured. The FPC prepared by laminating the coverlays on both sides is heat-treated at 260 ° C. for 3000 hours, a notch is made for each coverlay along the wiring, and the peel strength (b) at 90 ° is measured. The retention rate of the peel strength is calculated by the formula of 100 (%) × (b) / (a).

Hereinafter, the polyimide film according to the present invention will be described in detail with reference to Examples, but the present invention is not limited to the Examples.

(Example 1)
Silicon oxide was formed on one side of a 50 μm-thick polyimide film (Apical NPI manufactured by Kaneka Corporation) by a thin-film deposition method to obtain a polyimide film having a gas barrier layer on one side. The oxygen permeability of the polyimide film was measured.

Further, an adhesive solution containing an epoxy resin as a main component was applied to one side of the polyimide film with a bar coater and dried at 150 ° C. for 5 minutes to obtain a coverlay film having a semi-curable adhesive layer.

Further, an adhesive solution containing an epoxy resin as a main component is applied to both sides of the polyimide film with a bar coater and dried at 150 ° C. for 5 minutes to obtain a polyimide film having a semi-curable adhesive layer. Rolled copper foil (GHY5-82F-HA manufactured by JX Nikko Nisseki Metal Co., Ltd.) with a thickness of 12 μm, which is a metal foil, is laminated on both sides of the polyimide film, press-laminated at 180 ° C for 3 MPa for 60 minutes, and double-sided copper-clad laminate. Got A wiring having a width of 1 mm was formed on the double-sided metal-clad laminate, and the peel strength (a) at 90 ° was measured.

The above-mentioned coverlay film was laminated on both sides of the double-sided metal-clad laminate having the wiring formed to prepare a laminate. The laminate was heat-treated at 260 ° C. for 3000 hours, a notch was made for each coverlay along the wiring, the peel strength (b) was measured at 90 °, and the formula 100 (%) × (b) / (a) was measured. The retention rate of peel strength was calculated by.

Table 1 shows the results of the oxygen permeability and the peel strength retention rate.

(Example 2)
The oxygen transmittance and the peel strength retention rate were measured in the same manner as in Example 1 except that silicon oxide was vapor-deposited on both sides. The results are shown in Table 1.

(Example 3)
The oxygen transmittance and the peel strength retention rate were measured in the same manner as in Example 1 except that a polyimide film having a thermoplastic resin layer having a thickness of 50 μm (Pixio FRS manufactured by Kaneka Corporation) was used. The results are shown in Table 1.

(Example 4)
The oxygen transmittance and the peel strength retention rate were measured in the same manner as in Example 1 except that silicon oxide was deposited to a thickness of 100 μm. The results are shown in Table 1.

(Example 5)
The oxygen transmittance and the peel strength retention rate were measured in the same manner as in Example 1 except that aluminum oxide was vapor-deposited. The results are shown in Table 1.

(Example 6)
The oxygen transmittance and the peel strength retention rate were measured in the same manner as in Example 1 except that tin was vapor-deposited. The results are shown in Table 1.

(Example 7)
After the silicon oxide was vapor-deposited, the oxygen permeability and the peel strength retention rate were measured in the same manner as in Example 1 except that the heat treatment was performed at 150 ° C. for 1 minute. The results are shown in Table 1.

(Example 8)
After the silicon oxide was vapor-deposited, the oxygen permeability and the peel strength retention rate were measured in the same manner as in Example 1 except that the heat treatment was performed at 200 ° C. for 1 minute. The results are shown in Table 1.

(Comparative Example 1)
The oxygen permeability and the peel strength retention rate were measured in the same manner as in Example 1 except that the gas barrier layer was not formed. The results are shown in Table 1.

(Comparative Example 2)
The oxygen permeability and the peel strength retention rate were measured in the same manner as in Example 3 except that the gas barrier layer was not formed. Oxygen permeability and peel strength retention rate were measured. The results are shown in Table 1.

Claims (9)

A polyimide film having an inorganic layer as a gas barrier layer on one side and / or both sides of a non-thermoplastic polyimide film. The polyimide film according to claim 1, which has a metal layer as a gas barrier layer. A polyimide film having an inorganic layer as a gas barrier layer on one side and / or both sides of a polyimide film having a thermoplastic resin layer on both sides. The polyimide film according to claim 2, which has a metal layer as a gas barrier layer. A coverlay film using the polyimide films of claims 1 to 4. A single-sided metal-clad laminate using the polyimide films of claims 1 to 4. A double-sided metal-clad laminate using the polyimide films of claims 1 to 4. A flexible printed wiring board using the coverlay film and / or the single-sided metal-clad laminate and / or the double-sided metal-clad laminate according to claims 5 to 7. The flexible printed wiring board according to claim 8, wherein the retention rate of the peel strength between the metal foil and the adhesive layer after heat treatment at 260 ° C. for 3000 hours is 80% or more.