JP6777195B2 - Method for manufacturing polyimide film - Google Patents

Description

The present invention relates to a method for producing a polyimide film. More specifically, heat resistance, transparency, and surface smoothness used for various members such as optical members, electrical / electronic members, polyimide members, and mechanical members that require heat resistance, such as electronic information equipment and automobile applications. The present invention relates to a polyimide film manufacturing method having excellent properties, optical properties, and film forming processability.

In general, polyimide resin is widely used as an insulating material for electric and electronic devices because it is excellent in heat resistance, insulating property, chemical resistance and the like, and is also excellent in processability.

Usually, as a method for producing a polyimide film, a dry film forming method consisting of the following steps (1) to (3) is typical.
(1) A polyamic acid solution is applied onto a support such as an endless belt or a drum and dried.
(2) The self-supporting film peels off before sticking to the support.
(3) Further heat treatment is performed to imidize.
For example, in steps (2) to (3), the film is peeled off from the support with a certain solvent left, and the film is heat-treated again while holding both ends of the film by a pin tenter method or the like (Patent Document). 1, 2, 3).

However, since the support such as an endless belt or a drum is usually made of a hard material such as a metal material, the surface property is not always smooth. In addition, scratches and dents are easily formed. Therefore, there is a problem that it is difficult to obtain a polyimide-based film satisfying the surface smoothness by the conventional method of coating on the support and peeling off the film.

Further, in the conventional method of applying a polyimide resin solution on a support such as an endless belt or a drum, drying the coating film, and then peeling the film from the support, the peelability is improved when the applied film thickness is thin. become worse. In addition, there is a problem that the film is easily wrinkled and scratched, and the film forming processability is poor.

Further, a method has been proposed in which a base material having a polyimide resin surface is used as a support, a polyamic acid solution is applied to the surface, and the polyimide film is peeled off from the support base material by drying and imidizing. , Hydrolysis occurs in the imidization step. Due to this hydrolysis, the imide ring is partially cleaved on the peeling surface in contact with the polyamic acid layer, and the wettability of the peeling surface on the support side becomes large (contact angle becomes small), resulting in poor peelability. was there. As a result, when two or more cycles are performed, it is necessary to perform heat treatment again to restore the surface state, resulting in poor production efficiency. In addition to this, since it is necessary to treat the film at a high temperature in the imidization step, the film is easily colored, and it is difficult to obtain a film satisfying transparency, surface smoothness, and optical properties (patented). Documents 4, 5, 6).

As a method for solving the above problem, a metal laminate in which a specific polyamide-imide resin is laminated on the surface of a metal material is used as a support, and another polyamide-imide resin is further laminated to form a film, and then the film is peeled off. Has reported a method for producing a polyamide-imide film having excellent heat resistance, transparency, surface smoothness, and optical properties (Patent Document 7).

Japanese Unexamined Patent Publication No. 09-29852 Japanese Patent No. 4428016 Japanese Patent No. 4253791 Japanese Unexamined Patent Publication No. 2004-322441 Japanese Patent No. 5234642 Japanese Unexamined Patent Publication No. 2010-201890 Japanese Unexamined Patent Publication No. 2012-229402

Although the method is an excellent method for producing a polyamide-imide film, the film-forming processability including the characteristics of the metal material constituting the support is not particularly described.
As described above, the prior art has the following problems.
(1) It is difficult to manufacture a polyimide film that satisfies transparency, surface smoothness, and optical characteristics.
(2) It is difficult to manufacture a thin polyimide film.
(3) In the film forming method using a support such as an endless belt or a drum, the film is easily wrinkled or scratched, which hinders transparency, surface smoothness, and optical characteristics.
(4) In the method of obtaining a film by heat-imidizing polyamic acid on the support, the wettability of the support peeling surface becomes large (contact angle becomes small) after the end of the first cycle, and the temperature is high in order to restore the surface state. The production efficiency is not good because the heat treatment is required.
(5) In the method of obtaining a film by thermally imidizing a polyamic acid, it is necessary to treat the film at a high temperature of 300 ° C. or higher, and transparency and optical characteristics cannot be realized.

With the progress of miniaturization, weight reduction, and high functionality of electronic information devices, films used for electrical / electronic members, opt device members, etc. have better heat resistance, transparency, surface smoothness, and optical properties. Is required. Further, as electronic information devices and the like become smaller and lighter, thinner films are required.

Therefore, an object of the present invention is to provide a method for efficiently producing a polyimide film having excellent heat resistance, transparency, surface smoothness, and optical properties with a high yield.

As a result of diligent research to achieve the above object, the present inventors have found an efficient method for producing a polyimide-based film having excellent heat resistance, transparency, surface smoothness, and optical properties. That is, the present invention has the following configuration.

A method for producing a polyimide film having steps (A) to (C) and having a surface roughness (Rz) of less than 0.08 μm.
Step (A): A solvent-soluble resin A is laminated on a part or all of the surface of a metal material having a mirror surface glossiness of 200 or more and a surface roughness (Rz) of 0.5 μm or less to form a metal laminate. Step of obtaining A Step (B): Step of further laminating a polyimide resin B different from the solvent-soluble resin A on the surface of the solvent-soluble resin A layer of the metal laminate A to obtain the metal laminate B (C). ): A step of peeling the polyimide resin B layer from the metal laminate B to obtain a polyimide film.

The solvent-soluble resin A is preferably a polyamide-imide resin A1 or a polyamide resin A2.

The polyamide-imide resin A1 is preferably the following (i).
(I) The acid components constituting the polyamideimide resin A are trimellitic anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride, and biphenyl-3,3', 4,4'. -The main component is one or more compounds selected from the group consisting of tetracarboxylic dianhydride.

The polyamide resin A2 is preferably the following (iv).
(Iv) The acid component constituting the polyamide resin A2 is mainly composed of one or more compounds selected from the group consisting of terephthalic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid.

It is preferable that the polyamide-imide resin A1 and / or the polyamide resin A2 is (ii) and / or (iii) below.
(Ii) The diamine component constituting the polyamide-imide resin A is 3,3'-dimethyl-4,4'-diaminobiphenyl, or a corresponding diisocyanate, 3,3'-dimethyl-4,4'-di. Isocyanatobiphenyl as the main component (iii) In N-methyl-2-pyrrolidone (polymer concentration 0.5 g / dl), the logarithmic viscosity at 30 ° C. is 0.3 dl / g or more and 3.5 dl / g or less. Must have a molecular weight equivalent to

It is preferable that the polyamide-imide resin A1 contains at least one structure selected from the group consisting of the following formulas (1), (2), and (3) as a constituent unit.

It is preferable that the polyamide resin A2 contains at least one structure selected from the group consisting of the following formulas (4) and (5) as a constituent unit.

It is preferable that the polyamide-imide resin A1 and the polyamide resin A2 are crosslinked with an epoxy resin.

It is preferable that the Young's modulus of the metal material is 50 kN / mm ² or more and the thickness is 30 μm or more.

The acid component constituting the polyimide resin B is cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride. The main component is preferably 1,1'-bicyclohexane-3,3', 4,4'-tetracarboxylic acid-3,3', 4,4'-dianhydride. ..

A polyimide-based film obtained by the production method according to any one of the above, which is one or more selected from the group consisting of the following (a), (b), (c), and (d).
(A) Surface roughness (Rz) is less than 0.08 μm (b) Glass transition point is 180 ° C or higher and 350 ° C or lower (c) Light transmittance at a wavelength of 400 nm is 60% or higher and 90% or lower (d) Haze value Is 0.1 or more and 2.0 or less

A flexible metal-clad laminate using the above-mentioned polyimide film.

By having a specific step, the present invention can efficiently produce a polyimide film having a surface roughness (Rz) of less than 0.08 μm with a good yield. The polyimide film obtained by the production method of the present invention is industrially superior because it is excellent in heat resistance, transparency, surface smoothness, and optical properties.

Hereinafter, a method for producing a polyimide film according to an embodiment of the present invention will be described.

The method for producing a polyimide film of the present invention has steps (A) to (C).
Step (A): A solvent-soluble resin A different from the raw material of the polyimide film on a part or all of the surface of a metal material having a mirror surface glossiness of 200 or more and a surface roughness (Rz) of 0.5 μm or less. Step (B): A step (B): A polyimide resin B, which is a raw material for a polyimide film, is further laminated on the surface of the solvent-soluble resin A of the metal laminate to obtain a metal laminate B. Step (C): A step of peeling only the polyimide resin B layer from the metal laminate B to obtain a polyimide film.

Since it has the above steps, the surface roughness (Rz) of the surface of the polyimide film in contact with the solvent-soluble resin A layer is less than 0.08 μm, which is extremely smooth and has excellent heat resistance, transparency and optical properties. You can get the film.

Hereinafter, the production method of the present invention will be described separately for each step.
<< Process (A) >>
In the step (A), a raw material (acid component and / or) of a polyimide film is applied to a part or all of the surface of a metal material having a mirror surface glossiness of 200 or more and a surface roughness (Rz) of 0.5 μm or less. This is a step of laminating a solvent-soluble resin A having a different composition or physical properties (diamine component) to obtain a metal laminate A.

<Metallic material>
The metal material used in the present invention serves as a support for producing the polyimide-based film of the present invention. Therefore, the surface of the metal material (the surface on which the solvent-soluble resin A is laminated) needs to be smooth. Smoothness can be expressed by mirror glossiness and surface roughness. As the mirror glossiness, it is necessary that the mirror surface glossiness at an incident angle of 20 ° measured according to JIS Z-8741 (1997) is 200 or more, preferably 400 or more, and more preferably 500 or more. Yes, more preferably 600 or more. The upper limit is not particularly limited, but is industrially 1000 or less. Further, as the surface roughness, it is necessary that the surface roughness (Rz) measured according to JIS B-0601 (1994) is 0.5 μm or less. It is preferably 0.45 μm or less, more preferably 0.4 μm or less, and further preferably 0.35 μm or less. The lower limit is not particularly limited, but is industrially 0.001 μm or more. By satisfying the above range, the surface roughness of the metal laminate A on the solvent-soluble resin A surface side becomes 0.2 μm or less, and the surface smoothness, transparency, and optical characteristics of the polyimide film obtained in the present invention are improved. , Easy to apply to optical materials, etc.

Further, the metal material is preferably a metal material having an excellent rigidity having a Young's modulus of 50 kN / mm ² or more. More preferably, it is 60 kN / mm ² or more. The thickness is not particularly limited, but is preferably 1 μm or more and 1000 μm or less, more preferably 5 μm or more and 500 μm or less, further preferably 20 μm or more and 200 μm or less, and particularly preferably 30 μm or more and 150 μm or less. Can be used for. If the rigidity or thickness of the metal material is out of the above range, the base material such as the solvent-soluble resin A or the metal material is deformed due to the influence of the solvent volume shrinkage during the heat treatment of the metal laminate A, and the smoothness cannot be maintained. Sometimes.

The three-dimensional arithmetic mean surface roughness (Sa) on the surface of the metal material (930 μm × 700 μm) is preferably 0.2 μm or less, more preferably 0.15 μm or less, still more preferably 0.1 μm. It is as follows. The lower limit is not particularly limited, but is industrially 0.001 μm or more.

The metal material is not particularly limited, but copper, SUS, aluminum, steel, nickel and the like can be used. Further, a composite metal obtained by combining these, and a metal treated with another metal such as zinc or a chromium compound can also be used. The shape is not particularly limited, but a plate shape, a foil shape, or the like is preferable from the viewpoint of continuous productivity such as roll-to-roll processing.

For example, in the case of foil, copper foil, steel foil, SUS foil, aluminum foil, nickel foil and the like can be used without particular limitation. Further, a composite metal foil obtained by combining these, a metal foil treated with another metal such as zinc or a chromium compound, or the like can also be used. The metal foil can be used in various shapes such as a cut sheet, a roll, and an endless belt. The roll shape is preferable, and the length thereof is not particularly limited. The width of the roll-shaped metal foil is also not particularly limited, but is preferably 10 cm or more and 300 cm or less, preferably 15 cm or more and 250 cm or less, more preferably 20 cm or more and 200 cm or less, and particularly preferably 30 cm or more and 150 cm or less. ..

<Solvent-soluble resin A>
The solvent-soluble resin A used in the present invention is an organic solvent that can withstand the heat history in the step (hereinafter, also referred to as film formation step) for obtaining the polyimide film in the step (C) and has excellent smoothness and peelability. As long as it is a soluble resin, there is no particular limitation. A preferable solvent-soluble resin A is a polyamide-imide resin A1 or a polyamide resin A2, and the polyamide-imide resin A1 is soluble in an organic solvent and has excellent processability, heat resistance, and durability of the metal laminate A and the metal laminate B. Alternatively, the polyamide resin A2 is preferable. When the polyimide resin B is a resin derived from a polyamic acid, it is preferably the polyamide resin A2 that is not affected by the dehydration reaction during imidization.

Solvent-soluble in the solvent-soluble resin A means that it is soluble in an organic solvent. The organic solvent is not particularly limited, but for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, etc. Examples thereof include sulfolane, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and cyclopentanone. Further, the solubility in an organic solvent is preferably 80% by mass or more at 25 ° C., more preferably 90% by mass or more, and further preferably 100% by mass.

The solvent-soluble resin A used in the present invention is preferably a polyamide-imide resin A1 or a polyamide resin A2, and is different in raw material (acid component and / or diamine component), composition or physical properties from the polyimide resin B described later. is there. The acid component and the diamine component when the solvent-soluble resin A is the polyamide-imide resin A1 or the polyimide resin A2 will be described.

<Polyamide-imide resin A1>
The polyamide-imide resin A1 used in the present invention can synthesize an acid component and a diamine component in a solvent by a usual method such as an acid chloride method, a low temperature solution polymerization method, a room temperature solution polymerization method, or an isocyanate method. In particular, a preferred production method is an isocyanate method for obtaining a polymer varnish that can be directly applied to a metal material, which is advantageous from the viewpoint of production cost and the like.

<Acid component of polyamide-imide resin A1>
The "acid component" of the polyamideimide resin A1 is not particularly limited, but is limited to trimellitic anhydride, 1,2,4-naphthalene tricarboxylic acid, diphenyl ether-3,3', 4'-tricarboxylic acid, diphenylsulfon-3, 3', 4'-tricarboxylic acid, benzophenone-3,3', 4,4'-tetracarboxylic acid, biphenyl-3,3', 4,4,'-tetracarboxylic acid, diphenyl ether-3,3', 4 , 4'-tetracarboxylic acid, alkylene glycol bis (trimeritate), bisphenol bis (trimeritate), pyromellitic acid, 3,3', 4,4'-diphenylsulfonetetracarboxylic acid, naphthalene-2,3,6,7 Examples thereof include monoanhydrides, dianhydrides, esters and the like such as −tetracarboxylic acid, naphthalene-1,2,4,5-tetracarboxylic acid, or naphthalene-1,4,5,8-tetracarboxylic acid. In addition, dicarboxylic acid components such as isophthalic acid, terephthalic acid, biphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, and diphenylsulfone dicarboxylic acid can be mentioned. These can be used alone or as a mixture of two or more.

Preferably, trimellitic anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride, biphenyl-3,3', 4,4'-tetracarboxylic dianhydride, pyromellitic acid, Alternatively, it is diphenyl ether-3,3', 4,4'-tetracarboxylic dian, and these can be used alone or a mixture of two or more kinds as an acid component. Among them, selected from the group consisting of trimellitic anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride, and biphenyl-3,3', 4,4'-tetracarboxylic dianhydride. It is preferable that the main component is one or more of the above compounds. Here, the main component is preferably 50 mol% or more, more preferably 70 mol%, still more preferably 90 mol% or more, out of 100 mol% of the total acid component of the polyamide-imide resin A. It may be 100 mol%.

<Diamine component of polyamide-imide resin A1>
The "diamine component" of the polyamideimide resin A1 is not particularly limited, but is p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-. Diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 3,4′-diaminobiphenyl, 3,3′-diaminobiphenyl, 3,3′-diaminobenzanilide, 4,4′-diaminobenzanilide, 4,4 '-Diaminobenzophenylone, 3,3'-diaminobenzophenylone, 3,4'-diaminobenzophenylone, 2,6-tolylene diamine, 2,4-tolylene diamine, 4,4'-diaminodiphenyl Sulphide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, P-xylene diamine, m-xylene diamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, 2,7-naphthalenediamine, 2,2'-bis (4-aminophenyl) propane, 1,3 -Bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, 4,4' -Bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4' -Diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, or 3,3'-diethoxy-4,4'-diaminobiphenyl, or the corresponding diisocyanates can be used alone or as a mixture of two or more.

Preferably, it is 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,4-tolylenediamine, or 4,4'-diaminodiphenylmethane, or the corresponding diisocyanate, which can be used alone. Alternatively, it can be used as a mixture of two or more kinds. Among them, 3,3'-dimethyl-4,4'-diaminobiphenyl, or 3,3'-dimethyl-4,4'-diisocyanatobiphenyl (hereinafter, "o-trizine diisocyanate") which is a diisocyanate corresponding to these. ”) Is preferable. It is preferable that the total amount of 3,3'-dimethyl-4,4'-diaminobiphenyl and / or o-trizine diisocyanate is 50 mol% or more out of 100 mol% of the total diamine component of the polyamide-imide resin A1. It is preferably 70 mol%, more preferably 90 mol% or more, and may be 100 mol%.

Among the above acid components and diamine components, the processability of the metal laminate A and the metal laminate B, the heat resistance and durability in the film forming process, and the transparency, surface smoothness, optical properties, and peeling of the polyimide film. From the viewpoint of sex, the following components are preferably used. That is, as an acid component, from trimellitic anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride, and biphenyl-3,3', 4,4'-tetracarboxylic dianhydride. One or more compounds selected from the above group are used, and 3,3'-dimethyl-4,4'-diaminobiphenyl and / or o-trizinediisocyanate is used as the diamine component.

Below, as an example of a preferable embodiment of the acid component, trimellitic anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride and biphenyl-3,3', 4,4'-tetracarboxylic The mixing ratio of acid dianhydride is disclosed. Since the mixing ratio shown below is basically excellent in solubility in a solvent, a metal laminate A can be obtained simply by applying a polyamide-imide resin A1 solution to a metal material and drying it, which is a precursor of polyimide. It is not necessary to carry out a condensation reaction at a high temperature after laminating. Therefore, the metal laminate A and the metal laminate B are excellent in processability, productivity of the polyimide-based film, surface smoothness, transparency, optical characteristics, and peelability.

First, the ratio of biphenyl-3,3', 4,4'-tetracarboxylic dianhydride to benzophenone-3,3', 4,4'-tetracarboxylic dianhydride is the ratio of biphenyl-3,3', 4,4'-Tetracarboxylic dianhydride / benzophenone-3,3', 4,4'-tetracarboxylic dianhydride = 1/99 to 99/1 (molar ratio) is preferable, and more preferably 30 It is / 70 to 70/30 (molar ratio).

Next, a mixture of {biphenyl-3,3', 4,4'-tetracarboxylic dianhydride and benzophenone-3,3', 4,4'-tetracarboxylic dianhydride} and trimellitic anhydride The acid ratio is {biphenyl-3,3', 4,4'-tetracarboxylic dianhydride + benzophenone-3,3', 4,4'-tetracarboxylic dianhydride} / trimellitic anhydride = It is preferably 50/50 to 5/95 (molar ratio), more preferably 40/60 to 10/90 (molar ratio).

The diamine component is preferably 50 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol% or less, based on 100 mol% of the mixture of the acid components. Within these ranges, the processability of the metal laminate A and the metal laminate B, the heat resistance and durability in the film forming process, and the surface smoothness, transparency, optical properties, and peelability of the polyimide film are improved. Excellent.

Further, as the polyamide-imide resin A1, it is more preferable to use a compound containing at least one structure selected from the group consisting of the following formulas (1), (2) and (3) as a constituent unit.

<Polyamide resin A2>
In the polyamide resin A2 used in the present invention, an acid component and a diamine component can be synthesized in a solvent by a usual method such as an acid chloride method, a low temperature solution polymerization method, a room temperature solution polymerization method, or an isocyanate method. In particular, a preferred production method is an isocyanate method for obtaining a polymer varnish that can be directly applied to a metal material, which is advantageous from the viewpoint of production cost and the like.

<Acid component of polyamide resin A2>
The "acid component" of the polyamide resin A2 is not particularly limited, but a dicarboxylic acid component such as terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, biphenyldicarboxylic acid, diphenyl ether dicarboxylic acid, and diphenylsulfone dicarboxylic acid can be used. Can be mentioned. These can be used alone or as a mixture of two or more.

Preferably, it is terephthalic acid, isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, and these can be used alone or as a mixture of two or more kinds as an acid component. Of these, it is preferable that isophthalic acid is the main component. Here, the main component is preferably 50 mol% or more, more preferably 70 mol%, still more preferably 90 mol% or more, 100 mol% or more, out of 100 mol% of the total acid component of the polyamide resin A. It does not matter if it is mol%.

<Diamine component of polyamide resin A>
The "diamine component" of the polyamide resin A is not particularly limited, but the diamine component mentioned in the polyamide-imide resin A1 or the diisocyanate corresponding thereto may be used alone or as a mixture of two or more kinds. Can be done.

Among the above acid components and diamine components, the processability of the metal laminate A and the metal laminate B, the heat resistance and durability in the film forming process, and the transparency, surface smoothness, optical properties, and peeling of the polyimide film. From the viewpoint of sex, the following components are preferably used. That is, as the acid component, one or more compounds selected from the group consisting of terephthalic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid are used, and as the diamine component, 3,3'-dimethyl-4, 4'-Diaminobiphenyl and / or o-trizine diisocyanate is used.

Below, as an example of a preferable embodiment of the acid component, the mixing ratio of isophthalic acid and 1,4-cyclohexanedicarboxylic acid will be disclosed. Since the mixing ratio shown below is basically excellent in solubility in a solvent, the metal laminate A can be obtained simply by applying the polyamide resin A2 solution to the metal material and drying it, and the condensation reaction occurs at a high temperature. There is no need. Therefore, the metal laminate A and the metal laminate B are excellent in processability, productivity of the polyimide-based film, surface smoothness, transparency, optical characteristics, and peelability.

The ratio of isophthalic acid and 1,4-cyclohexanedicarboxylic acid is preferably isophthalic acid / 1,4-cyclohexanedicarboxylic acid = 1/99 to 99/1 (molar ratio), more preferably 30/70. ~ 90/10 (molar ratio).

The diamine component is preferably 50 mol% or more and 100 mol% or less, preferably 70 mol% or more and 100 mol% or less, based on 100 mol% of the mixture of the acid components. Within these ranges, the processability of the metal laminate A and the metal laminate B, the heat resistance and durability in the film forming process, and the surface smoothness, transparency, optical properties, and peelability of the polyimide film are improved. Excellent.

Further, as the polyamide resin A2, it is more preferable to use a compound containing at least one structure selected from the group consisting of the following formulas (4) and (5) as a constituent unit.

The polyamide-imide resin A1 and the polyamide resin A2 can be obtained by a copolymerization reaction of the acid component and a diamine component in an organic solvent. The organic solvent is not particularly limited, but for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, etc. Examples thereof include sulfolane, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, cyclopentanone and the like, and N-methyl-2-pyrrolidone and N, N-dimethylacetamide are preferable. The reaction temperature is usually preferably 10 ° C. or higher and 200 ° C. or lower, more preferably 50 ° C. or higher and 150 ° C. or lower, and further preferably 100 ° C. or higher and 120 ° C. or lower. The reaction time depends on the reaction temperature and can be appropriately set, but is usually preferably 1 hour or more and 24 hours or less, more preferably 2 hours or more and 15 hours or less, and further preferably 3 hours or more and 10 hours or less. .. Further, the polymerization reaction may be carried out in the presence of a catalyst for the reaction of the isocyanate and the active hydrogen compound, for example, a tertiary amine, an alkali metal compound, an alkaline earth metal compound or the like. For example, it may be carried out in the presence of diazabicycloundecene as a tertiary amine.

The solvent-soluble resin A has a molecular weight corresponding to 0.3 dl / g or more and 3.5 dl / g or less in logarithmic viscosity at 30 ° C. in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / dl). Is preferable. It is more preferably 1.0 dl / g or more and 3.0 dl / g or less, and further preferably has a molecular weight corresponding to 1.7 dl / g or more and 2.5 dl / g or less. When the logarithmic viscosity is 0.3 dl / g or more, the metal laminate A has excellent heat resistance and mechanical properties, and also has good heat resistance and durability in the film forming process, and is a polyimide film. The peelability of the film is also improved. If it exceeds 3.50 dl / g, the viscosity of the solution becomes high, which may make it difficult to mold the metal laminate A itself.

<Varnish of solvent-soluble resin A>
The solvent-soluble resin A described above is laminated on a part or all of the metal material. If it is a part or all, it may be single-sided or may be laminated on both sides. The solvent-soluble resin A may be a solution (varnish-like).

The solvent for producing the solvent-soluble resin A solution (crocodile) is not particularly limited, but the solvent used in the polymerization reaction in the polyamide-imide resin A1 and the polyamide resin A2 may be used as it is. Specifically, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, dimethyl sulfoxide, etc. γ-Butyrolactone, cyclohexanone, cyclopentanone and the like, preferably N-methyl-2-pyrrolidone, N, N-dimethylacetamide.
It is also possible to replace some of these with hydrocarbon-based organic solvents such as toluene and xylene, ether-based organic solvents such as diglyme, triglime and tetrahydrofuran, and ketone-based organic solvents such as methyl ethyl ketone and methyl isobutyl ketone.

If necessary, the solvent-soluble resin A of the present invention is used for the purpose of improving various properties of the metal laminate A and the metal laminate B, for example, mechanical properties, electrical properties, slipperiness, flame retardancy, and the like. Other resins, organic compounds, and inorganic compounds may be mixed or reacted with the solution. For example, lubricants (silica, talc, silicone, etc.), flame retardants (phosphorus, triazine, aluminum hydroxide, etc.), stabilizers (antioxidants, UV absorbers, polymerization inhibitors, etc.), organic and inorganic fillers. (Tark, titanium oxide, fluoropolymer fine particles, pigments, dyes, calcium carbide, etc.), leveling agents (polyester-modified polydimethylsiloxane solution, polyether-modified polydimethylsiloxane solution, etc.), other silicone compounds, fluorine compounds, isocyanate compounds , Blocked isocyanate compounds, acrylic resins, urethane resins, polyester resins, polyamide resins, epoxy resins, phenolic resins and other resins and organic compounds, or their curing agents, silicon oxide, titanium oxide, calcium carbonate, iron oxide and other inorganic substances. The compound can be used in combination as long as the object of the present invention is not impaired.

Further, in addition to the solvent-soluble resin A, a resin capable of withstanding the heat history in the film forming step may be used in combination as long as the effect of the present invention is not impaired. Although not particularly limited, examples thereof include polyimide resin, polyamide-imide resin, polyesterimide resin, polybenzimidazole resin, aromatic polyester resin and polyparavanic acid, and one or more of these can be blended. ..

In particular, when the solvent-soluble resin A is the polyamide-imide resin A1 or the polyamide resin A2, it is preferably crosslinked with a curable resin such as an epoxy resin or an isocyanate resin. By cross-linking with these curable resins, it can be expected that the performance such as peelability of the polyimide film will be improved. Among the curable resins, an epoxy resin is particularly preferable, and commercially available ones are not particularly limited, but brominated epoxy resin Bren (manufactured by Nippon Kayaku Co., Ltd.) and phenol novolac type epoxy resin jER ( A registered trademark) 152 (manufactured by Mitsubishi Chemical Corporation), jER154 (manufactured by Mitsubishi Chemical Corporation), bisphenol A type epoxy resin jER828 (manufactured by Mitsubishi Chemical Corporation), and the like can be preferably used.

When the solvent-soluble resin A is the polyamide-imide resin A1, the amount of the epoxy resin is preferably 1 part by mass or more and 40 parts by mass or less, more preferably 2 parts by mass, based on 100 parts by mass of the polyamide-imide resin A1. It is 10 parts by mass or less, more preferably 3 parts by mass or more and 8 parts by mass or less. When it is 1 part by mass or more, the cross-linking reaction of the polyamide-imide resin A is sufficient, and the effect of improving the peelability of the polyimide film is great. Further, if it is 40 parts by mass or less, it is excellent in heat resistance and mechanical properties.

When the solvent-soluble resin A is the polyimide resin A2, the amount of the epoxy resin blended is preferably 1 equivalent or more and 10 equivalents or less, more preferably 1 equivalent, with respect to 1 acid value of the polyamide resin A2. It is 5 equivalents or less, and more preferably 2 equivalents or more and 3 equivalents or less. When the amount is 1 equivalent or more, the cross-linking reaction of the polyamide resin A2 is sufficient, and the effect of improving the peelability of the polyimide film is great. Further, if the amount is 10 equivalents or less, the heat resistance and mechanical properties are excellent.

Further, a silicone-based surface conditioner such as a polyester-modified polydimethylsiloxane solution, a polyether-polyester-modified polydimethylsiloxane, or a polyether-modified polydimethylsiloxane is added to the solvent-soluble resin A to improve the wettability of the solvent-soluble resin A with a metal material. It is also preferable to mix or react for the purpose of improving fluidity and leveling property. This is expected to improve the performance such as surface smoothness of the metal laminate A. Examples of commercially available polyester-modified polydimethylsiloxane solutions include BYK (registered trademark) -370 and BYK-371, and examples of polyether-polyester-modified polydimethylsiloxane include BYK-375 and the like. Examples of the modified polydimethylsiloxane include BYK-377 (both manufactured by Big Chemie Japan Co., Ltd.). Particularly preferably, BYK-370 or the like can be preferably used.

The solid content concentration of the solvent-soluble resin A solution (varnish) thus obtained can be selected from a wide range, but 5% by weight or more and 40% by weight or less is preferable because it is excellent in processability. More preferably, it is 8% by weight or more and 20% by weight or less.

<Metal laminate A>
The metal laminate A used in the present invention is a laminate of two or more layers in which the solvent-soluble resin A layer is laminated on a part or all of the metal material. To prepare the metal laminate A, it is preferable to directly apply the solvent-soluble resin A solution to a part or all of the metal material and dry it. The coating method is not particularly limited, and a conventionally well-known method can be applied. For example, a roll coater, a knife coater, a doctor, a blade coater, a gravure coater, a die coater, a reverse coater, or the like can be used to adjust the viscosity of the solvent-soluble resin A solution, which is a coating liquid, and then directly apply to a metal material.

The drying conditions after coating are not particularly limited, but the initial drying temperature is 70 ° C. to 130 ° C. lower than the boiling point (Tb (° C.)) of the solvent used in the solvent-soluble resin A solution, preferably 80 ° C. to 120 ° C. Low temperature is good. In other words, the initial drying temperature is preferably (Tb-70) ° C. or lower (Tb-130) ° C., preferably (Tb-80) ° C. or lower (Tb-120) ° C. or higher. When the initial drying temperature is (Tb-70) ° C. or lower (Tb-130) ° C. or higher, foaming is unlikely to occur on the coated surface, and unevenness of the residual solvent in the thickness direction of the solvent-soluble resin A layer is reduced. Drying efficiency in the heat treatment process of.

For example, when the solvent used in the solvent-soluble resin A solution is N-methyl-2-pyrrolidone, the boiling point (Tb (° C.)) of the solvent is 204 ° C., so that it is 74 ° C. or higher and 134 ° C. or lower, preferably. Initial drying is preferable at a temperature of 84 ° C. or higher and 124 ° C. or lower.

When two or more kinds of mixed solvents are used, it is preferable to set the above temperature with reference to the solvent having the highest boiling point.

The time required for the initial drying may be an effective time for the solvent residual ratio in the coating film to be about 5% by weight or more and 40% by weight or less under the above temperature conditions, but it may be about 1 minute or more and 30 minutes or less. Just do it. Preferably, it is about 2 minutes or more and 15 minutes or less.

After the initial drying, it is preferable to further dry (also referred to as heat treatment) at a temperature near or above the boiling point of the solvent.

The heat treatment conditions are not particularly limited, and the solvent may be dried at a temperature near the boiling point or above the boiling point. Although it depends on the resin composition of the solvent-soluble resin A, when the solvent-soluble resin A is the polyamide-imide resin A1, the deterioration reaction is small, the polyamide-imide resin A1 layer is not brittle, and the polyamide-imide resin A1 layer can be dried in a short time and has good productivity. The range is 150 ° C. or higher and 500 ° C. or lower, preferably 250 ° C. or higher and 400 ° C. or lower. When the solvent-soluble resin A is the polyamide resin A2, the temperature range in which the deterioration reaction is small, the polyamide resin A2 layer is not brittle, the layer can be dried in a short time, and the productivity is good is 150 ° C. or higher and 400 ° C. or lower, which is preferable. Is 250 ° C. or higher and 350 ° C. or lower.
The time required for the heat treatment may be an effective time such that the residual ratio of the solvent in the coating film disappears under the above-mentioned temperature conditions, but it is about several minutes to several tens of minutes.

The heat treatment may be carried out under an inert gas atmosphere or under reduced pressure. The inert gas is not particularly limited, and examples thereof include nitrogen, carbon dioxide, helium, and argon, but it is preferable to use easily available nitrogen. It is desirable to reduce the oxygen concentration to 0.5% by volume or less, more preferably 0.1% by volume or less. When it is carried out under reduced pressure, it is preferably carried out under a pressure of about ^10-5 Pa or more and 10 ³ Pa or less, preferably 10 ^-1 Pa or more and 200 Pa or less.

The method for both initial drying and heat treatment is not particularly limited, but continuous processing can be performed by a conventionally known method such as a roll support method or a floating method. In addition, continuous heat treatment in a heating furnace such as a tenter type is also possible.

The thickness of the solvent-soluble resin A layer in the metal laminate A can be selected from a wide range, but the thickness after initial drying and heat treatment (hereinafter, also referred to as absolute drying) is preferably 5 μm or more and 1000 μm or less, preferably 7 μm or more. It is preferably 200 μm or less, and more preferably 10 μm or more and 50 μm or less.
If the thickness after absolute drying is 5 μm or more and 1000 μm or less, the mechanical properties and handleability are good, the surface smoothness and optical properties are also advantageous, and the workability (dryness, coatability, and transportability) is good. Gender, etc.) will also improve. In the present invention, since the specific steps (A) to (C) are provided, a polyimide film having a surface roughness (Rz) of less than 0.08 μm can be obtained even if the solvent-soluble resin A layer is thin. ..
Further, if necessary, surface treatment may be applied. For example, surface treatments such as hydrolysis, corona discharge, low temperature plasma, and physical roughening can be performed.

In this way, the metal laminate A having a smooth surface of the solvent-soluble resin A layer can be obtained. The surface roughness (Rz) of the solvent-soluble resin A layer surface in the metal laminate A is preferably 0.2 μm or less, more preferably 0.15 μm, still more preferably 0.1 μm or less, and particularly preferably 0. It is 05 μm or less. The lower limit is not particularly limited, but is industrially 0.01 μm or more. Further, by increasing the thickness of the solvent-soluble resin A layer (5 μm or more and less than 10 μm), the surface roughness (Rz) can be 0.15 μm or less, and by further increasing the thickness (10 μm or more), 0.11 μm or less can be achieved. When the surface roughness (Rz) of the metal laminate A is 0.2 μm or less, the surface smoothness, transparency, and optical characteristics of the polyimide film obtained by the production method of the present invention are improved, and the application to optical materials and the like is improved. Becomes easier. For example, since the haze value is 1.0 or less, it becomes easy to achieve the object of the present invention. In a general method for producing a polyimide film, the surface roughness (Rz) of a support such as an endless belt or a drum is about 0.5 μm. Therefore, it can be said that the metal laminate A of the present invention is clearly smooth.

<< Process (B) >>
The step (B) is a step of further laminating a polyimide resin B different from the solvent-soluble resin A on the surface of the solvent-soluble resin A layer of the metal laminate A to obtain the metal laminate B.

<Polyimide resin B>
The polyimide-based resin B used in the present invention is different from the solvent-soluble resin A in terms of raw material (acid component and / or diamine component), composition or physical properties. A polyimide resin B which is superior in heat resistance, transparency, surface smoothness, optical properties, and peelability to a conventional polyimide film and can produce a thinner polyimide film will be described.

The polyimide resin B is not particularly limited as long as it has a raw material, composition or physical properties different from those of the solvent-soluble resin A and can withstand heat resistance in the film forming process. Preferably, from the viewpoint of surface smoothness, transparency, optical properties, and peelability of the polyimide film, a polyamide-imide resin, a polyesterimide resin, or a solvent-soluble polyimide resin or an imidization reaction that does not involve an imidization reaction after lamination is used. It is a polyimide resin that is partially imidized and a polyamic acid that is a polyimide precursor.

Similar to the above-mentioned polyamide-imide resin A1 and polyamide resin A2, the polyimide-based resin B is usually produced by using an acid chloride method, a low-temperature solution polymerization method, a room temperature solution polymerization method, an isocyanate method, etc. for the acid component and the diamine component in a solvent. It can be synthesized by the method. In particular, a preferable production method is an isocyanate method for obtaining a polymer varnish that can be directly applied to the metal laminate A, which is advantageous from the viewpoint of production cost and the like.

<Acid component of polyimide resin B>
The "acid component" of the polyimide resin B is not particularly limited, but is 1,2,4-naphthalene tricarboxylic acid, diphenyl ether-3,3', 4'-tricarboxylic acid, diphenylsulfone-3,3', 4'. -Hydrogenates of the above monomers such as tricarboxylic acids, trimellitic acids and other monoanhydrides, dianhydrides, esterifieds, or hexahydrotrimellitic acids; 4,4'-(hexafluoroisopropyridene) diphthalic acid, Benzophenone-3,3', 4,4'-tetracarboxylic acid, biphenyl-3,3', 4,4'-tetracarboxylic acid, diphenyl ether-3,3', 4,4'-tetracarboxylic acid, alkylene glycol Bis (Trimelitate), Bisphenol Bis (Trimelitate), 3,3', 4,4'-diphenylsulfonetetracarboxylic acid, Naphthalene-2,3,6,7-Tetracarboxylic acid, Naphthalene-1,2,4,5 -Tetracarboxylic acid, naphthalene-1, 4, 5, 8-tetracarboxylic acid, pyromellitic acid and other monoanhydrides, dianoxides, esterified products, or hexahydropyromellitic acid and other hydrogenated monomers; Examples thereof include hydrogenated additives of the above-mentioned monomers such as isophthalic acid, terephthalic acid, biphenyldicarboxylic acid, diphenyletherdicarboxylic acid, dicarboxylic acid component of diphenylsulfonedicarboxylic acid, or cyclohexanedicarboxylic acid. These can be used alone or as a mixture of two or more.

Preferably, cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (hereinafter, also referred to as H-TMA), benzophenone-3,3', 4,4'-tetracarboxylic dianhydride. Hydrogen additive (hereinafter, also referred to as H-BPDA), or 1,1'-bicyclohexane-3,3', 4,4'-tetracarboxylic acid-3,3', 4,4'-dianhydride. It is a substance (hereinafter, also referred to as H-BTDA), and these can be used alone or a mixture of two or more kinds as an acid component. Of these, it is preferable that H-TMA, H-BTDA or H-BPDA is the main component. Here, the main component is preferably 50 mol% or more, more preferably 70 mol%, still more preferably 90 mol% or more, out of 100 mol% of the total acid component of the polyimide resin B. It may be 100 mol%.

<Diamine component of polyimide resin B>
The "diamine component" of the polyimide-based resin B is not particularly limited, but is p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-. Diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 3,4′-diaminobiphenyl, 3,3′-diaminobiphenyl, 3,3′-diaminobenzanilide, 4,4′-diaminobenzanilide, 4,4 '-Diaminobenzophenylone, 3,3'-diaminobenzophenylone, 3,4'-diaminobenzophenylone, 2,6-tolylene diamine, 2,4-tolylene diamine, 4,4'-diaminodiphenyl Sulphide, 3,3'-diaminodiphenylsulfide, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, P-xylene diamine, m-xylene diamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, 2,7-naphthalenediamine, 2,2'-bis (4-aminophenyl) propane, 1,3 -Bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] propane, 4,4' -Bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-diethyl-4,4' -Diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-diethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3 , 3'-diethoxy-4,4'-diaminobiphenyl, trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-diaminocyclohexane (trans / cis mixture), 1,3-diamino Cyclohexane, dicyclohexylmethane-4,4'-diamine (trans, cis, trans) Su / cis mixture), isophorone diamine, 1,4-cyclohexanebis (methylamine), norbornenediamine, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantan , 4,4'-Methylenebis (2-methylcyclohexylamine), 4,4'-Methylenebis (2-ethylcyclohexylamine), 4,4'-Methylenebis (2,6-dimethylcyclohexylamine), 4,4' -Methylenebis (2,6-diethylcyclohexylamine), 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1, 4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, or 1,9-nonamethylenediamine, 2,2 '-Bis (trifluoromethyl) benzidine or the corresponding diisocyanate can be used alone or a mixture of two or more kinds can be used as a diamine component.

Preferably, a hydrogenated product of diphenylmethane-4,4'-diisocyanate (hereinafter, also referred to as H-MDI), a hydrogenated product of m-xylene diisocyanate (hereinafter, also referred to as H-XDI), t-1,4-diamino. Examples thereof include alicyclic isocyanates such as cyclohexane, isophorone diisocyanate, and norbornene diisocyanate, and these can be used alone or in admixture of two or more as the diisocyanate component.

When the total diamine component in the polyimide resin B is 100 mol%, the above-exemplified diamine component is preferably contained in an amount of 50 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less. Good. Within these ranges, heat resistance and durability in the film forming process are good, and surface smoothness, transparency, optical properties, and peelability of the obtained polyimide film are improved.

The polyimide resin B can be obtained by a copolymerization reaction of the acid component and the diamine component in an organic solvent. The organic solvent is not particularly limited, but for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, etc. Examples thereof include sulfolane, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, cyclopentanone, etc., which can be used alone or as a mixed solvent of two or more kinds. Preferably, it is 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone, or a combination thereof. The reaction temperature is usually preferably 10 ° C. or higher and 200 ° C. or lower, more preferably 50 ° C. or higher and 150 ° C. or lower, and further preferably 100 ° C. or higher and 120 ° C. or lower. The reaction time depends on the reaction temperature and can be appropriately set, but is usually preferably 1 hour or more and 24 hours or less, more preferably 2 hours or more and 15 hours or less, and further preferably 3 hours or more and 10 hours or less. .. Further, the polymerization reaction may be carried out in the presence of a catalyst for the reaction of the isocyanate and the active hydrogen compound, for example, a tertiary amine, an alkali metal compound, an alkaline earth metal compound or the like. For example, it may be carried out in the presence of triethylenediamine as the tertiary amines.

The polyimide resin B has a molecular weight corresponding to 0.3 dl / g or more and 3.5 dl / g or less in logarithmic viscosity at 30 ° C. in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / dl). Those having a molecular weight corresponding to 1.0 dl / g or more and 3.0 dl / g or less, still more preferably 1.7 dl / g or more and 2.5 dl / g or less. When the logarithmic viscosity is 0.3 dl / g or more, the mechanical properties are excellent and the peelability is also improved. Further, if it is 3.50 dl / g or less, the molding process is easy.

<Varnish of polyimide resin B>
The polyimide resin B used in the present invention is laminated on the surface of the solvent-soluble resin A layer of the metal laminate A. The polyimide resin B may be in the form of a varnish. As the solvent for producing the polyimide resin B solution (varnish), the solvent used in the polymerization reaction may be used as it is. Specifically, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, dimethyl sulfoxide, etc. Examples thereof include γ-butyrolactone, cyclohexanone, cyclopentanone, etc., and these can be used alone or as a mixed solvent. Preferably, it is 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone, or a combination thereof. It is also possible to replace some of these with hydrocarbon-based organic solvents such as toluene and xylene, ether-based organic solvents such as diglyme, triglime and tetrahydrofuran, and ketone-based organic solvents such as methyl ethyl ketone and methyl isobutyl ketone.

More preferred solvents are 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, N, N-dimethylacetamide, or a combination thereof. The combination of 1,3-dimethyl-2-imidazolidinone and γ-butyrolactone is most preferable from the viewpoint of releasability from the metal laminate A, and the mixing ratio (mass ratio) is 1,3-dimethyl-2-imidazolidinone. / Γ-Butyrolactone = 30 to 70/70 to 30, more preferably 40 to 50/60 to 50. By using such a ratio, the adhesion between the solvent-soluble resin A and the polyimide resin B is relaxed, and the peelability is improved. It is also possible to replace some of these with hydrocarbon-based organic solvents such as toluene and xylene, ether-based organic solvents such as diglyme, triglime and tetrahydrofuran, and ketone-based organic solvents such as methyl ethyl ketone and methyl isobutyl ketone.

If necessary, other resins or organic compounds are added to the polyimide resin B solution for the purpose of improving various properties of the polyimide film, such as mechanical properties, electrical properties, slipperiness, and flame retardancy. , And inorganic compounds may be mixed or reacted.
For example, lubricants (silica, talc, silicone, etc.), flame retardants (phosphorus, triazine, aluminum hydroxide, etc.), stabilizers (antioxidants, UV absorbers, polymerization inhibitors, etc.), plating activators, organics, etc. And inorganic fillers (talc, titanium oxide, fluoropolymer fine particles, pigments, dyes, calcium carbide, etc.), leveling agents (polyester-modified polydimethylsiloxane solution, polyether-modified polydimethylsiloxane solution, etc.), and other silicone compounds, Fluorine compounds, isocyanate compounds, blocked isocyanate compounds, acrylic resins, urethane resins, polyester resins, polyamide resins, epoxy resins, phenolic resins and other resins and organic compounds, or their curing agents, silicon oxide, titanium oxide, calcium carbonate, Inorganic compounds such as iron oxide can be used in combination as long as the object of the present invention is not impaired.

The solid content concentration of the polyimide resin B solution (varnish) thus obtained can be selected from a wide range, but 5% by weight or more and 40% by weight or less is preferable because it is excellent in processability. More preferably, it is particularly preferably 8% by weight or more and 20% by weight or less.

<Metal laminate B>
The metal laminate B used in the present invention is a laminate of three or more layers (metal material / solvent-soluble resin A /) in which the polyimide resin B is further laminated on the surface on which the solvent-soluble resin A of the metal laminate A is laminated. Polyimide-based resin B). It is preferable that the metal laminate B is dried by directly applying the polyimide resin B solution to one side or both sides on which the solvent-soluble resin A of the metal laminate A is laminated. The coating method is not particularly limited, and a conventionally well-known method can be applied. For example, a roll coater, a knife coater, a doctor, a blade coater, a gravure coater, a die coater, a reverse coater, or the like can be used to adjust the viscosity of the polyimide resin solution as the coating liquid, and then the coating can be directly applied to the metal laminate.

The drying conditions after coating are not particularly limited, but after initial drying at a temperature 70 ° C. to 130 ° C. lower than the boiling point (Tb (° C.)) of the solvent used in the polyimide resin B solution, it is near the boiling point of the solvent or above the boiling point. It is preferable to further dry (heat heat) at the temperature of. More preferably, it is about 80 to 120 ° C. In other words, the initial drying temperature is preferably (Tb-70) ° C. or lower (Tb-130) ° C. or higher, preferably (Tb-80) ° C. or lower (Tb-120) ° C. or higher. When the initial drying temperature is (Tb-70) ° C. or lower (Tb-130) ° C. or higher, foaming is less likely to occur on the coated surface, and the peelability from the metal laminate B is improved. The time required for the initial drying may be an effective time for the solvent residual ratio in the coating film to be about 5% by weight or more and 40% by weight or less under the above temperature conditions, but it may be about 1 minute or more and 30 minutes or less. Just do it. Preferably, it is about 2 minutes or more and 15 minutes or less.

Further, the heating conditions are not particularly limited, and the solvent may be dried at a temperature near the boiling point or above the boiling point. Although it depends on the resin composition of the polyimide resin B, the releasability from the metal laminate B, the transparency of the polyimide film, the surface smoothness, and the optical properties are good, the deterioration reaction is small, and the polyimide film does not become brittle. The temperature range in which drying can be performed in a short time and the productivity is good is 100 ° C. or higher and 400 ° C. or lower, preferably 150 ° C. or higher and 350 ° C. or lower.
The time required for the heat treatment may be an effective time such that the residual ratio of the solvent in the coating film disappears under the above temperature conditions, but it is about several minutes to several tens of minutes.

For example, it is possible to achieve both peelability, surface smoothness, optical properties, and transparency by drying at 330 to 340 ° C. × 10 to 30 minutes, but when dried at a higher temperature than this, the solvent-soluble resin in the metal laminate B The adhesive force between A and the polyimide resin B coated on the A is strengthened, the peelability is lowered, the transparency is lowered, and the film tends to turn yellow.

Drying may be carried out under an inert gas atmosphere or under reduced pressure. The inert gas is not particularly limited, and examples thereof include nitrogen, carbon dioxide, helium, and argon, but it is preferable to use easily available nitrogen. In order to suppress the coloring of the polyimide film and obtain a colorless and transparent film, it is desirable to reduce the oxygen concentration to 0.5% or less, more preferably 0.1% or less. When it is carried out under reduced pressure, it is preferably carried out under a pressure of about ^10-5 Pa or more and 10 ³ Pa or less, preferably 10 ^-1 Pa or more and 200 Pa or less.

The method for both initial drying and heat treatment is not particularly limited, but continuous processing can be performed by a conventionally known method such as a roll support method or a floating method. In addition, continuous heat treatment in a heating furnace such as a tenter type is also possible.

In the present invention, the thickness of the polyimide resin B layer can be selected from a wide range, but the thickness after absolute drying is about 1 μm or more and 100 μm or less, preferably about 10 μm or more and 50 μm or less. If the thickness is smaller than 1 μm, the mechanical properties such as film strength and handleability are inferior, while if the thickness exceeds 100 μm, the processability (drying property, coatability) and the like may be deteriorated.
Further, if necessary, surface treatment may be applied. For example, surface treatments such as hydrolysis, corona discharge, low temperature plasma, physical roughening, and easy adhesive coating can be applied.

<< Process (C) >>
The step (C) is a step of peeling only the polyimide resin B layer from the metal laminate B to obtain a polyimide film. The peeled polyimide resin B layer becomes a polyimide film.

According to the present invention, a polyimide-based film having excellent transparency, surface smoothness, optical properties, and heat resistance can be easily obtained only by peeling the polyimide-based resin B layer from the metal laminate B. The peeling method is not limited and can be easily peeled by a conventionally known method. For example, it can be manufactured by winding the metal laminate A and the polyimide film on separate rolls while peeling off the polyimide film after continuous heat treatment.
In particular, in the conventional film forming method, the surface smoothness itself is inferior, and scratches, wrinkles, dents derived from the base material, etc. are easily formed, and even a thin film that cannot be used for optical applications can be easily produced. it can.

<< Characteristics of polyimide film >>
The polyimide-based film obtained by the present invention is superior in heat resistance, transparency, surface smoothness, and optical properties to conventional films.

<Heat resistance>
The heat resistance is indicated by the glass transition point, and the glass transition point of the obtained polyimide film is preferably 180 ° C. or higher and 350 ° C. or lower, more preferably 200 ° C. or higher and 330 ° C. or lower, and further preferably 230 ° C. It is ℃ or more and 320 ℃ or less.

<Surface smoothness>
The surface smoothness of the polyimide film can be indicated by the surface roughness (Rz) and the three-dimensional arithmetic mean roughness (Sa), and the surface roughness (Rz) is measured according to JIS B-0601 (1994). The three-dimensional arithmetic mean roughness (Sa) was measured by a non-contact surface / layer cross-sectional shape measurement system.
The surface roughness (Rz) of the surface of the polyimide film in contact with the solvent-soluble resin A layer is less than 0.08 μm. It is preferably 0.07 μm or less, more preferably 0.06 μm or less, further preferably 0.05 μm or less, particularly preferably less than 0.05 μm, and most preferably 0.04 μm or less. The lower limit is not particularly limited, but industrially, it is 0.001 μm or more. By setting the surface roughness (Rz) to less than 0.08 μm, the surface smoothness, transparency, and optical characteristics of the polyimide film are extremely improved, and application to optical materials and the like becomes easy.
Further, the three-dimensional arithmetic mean surface roughness (Sa) in the range of 930 μm × 700 μm of the surface of the polyimide film in contact with the solvent-soluble resin A layer is preferably 0.1 μm or less, more preferably 0. It is 09 μm or less, more preferably 0.08 μm or less, and particularly preferably 0.07 μm or less. The lower limit is not particularly limited, but industrially, it is 0.001 μm or more.

<Transparency and optical characteristics>
Transparency and optical properties are indicated by light transmittance. The light transmittance of the obtained polyimide film is preferably 60% or more and 90% or less, and more preferably 65% or more and 90% or less at a wavelength of 400 nm according to JIS K-7361-1 (1997). The haze value of the obtained polyimide film is preferably 2.0 or less, more preferably 1.0 or less, according to JIS K-7136 (2000). The lower limit is not particularly limited, but is industrially 0.1 or more.

<Peelability>
The peelability when the polyimide resin B layer is peeled from the metal laminate B is indicated by the adhesive strength. The adhesive strength between the obtained polyimide film and the metal laminate is good if it is 1 N / cm or less because it can be easily peeled off, and it is very good if it is 0.5 N / cm or less. The lower limit is not particularly limited, but 0.01 N / cm or more is sufficient.

<Thickness of polyimide film>
The thickness of the polyimide-based film obtained by the present invention can be selected from a wide range, but can be reduced to several μm as long as the mechanical properties such as film strength can be maintained. Specifically, it is preferably 50 μm or less, more preferably 40 μm or less, and further preferably 30 μm or less. Further, 5 μm or more is preferable, 8 μm or more is more preferable, and 10 μm or more is further preferable.

Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not particularly limited by the examples. The evaluation method of the characteristic value in each example is as follows.

(Logarithmic viscosity)
A sample (solvent-soluble resin A or polyimide resin B) is dissolved in N-methyl-2-pyrrolidone so that the polymer concentration becomes 0.5 g / dl, and the solution viscosity and solvent viscosity of the solution are adjusted to Ubbelohde at 30 ° C. It was measured with a viscosity tube of the mold and calculated by the following formula. V1 represents the solution viscosity, V2 represents the solvent viscosity, and V3 represents the concentration of the sample solution (0.5 g / dl).
Logarithmic viscosity (dl / g) = [ln (V1 / V2)] / V3

(Glass transition point (Tg), coefficient of thermal expansion (CTE))
The polyimide film obtained by TMA (thermomechanical analysis) (trade name "EXSTAR TMA / SS 6000", manufactured by Seiko Instruments Inc.) was measured under the following conditions. The inflection point of the obtained curve was defined as the glass transition temperature (Tg), and tangents were drawn in each of the low temperature region (glass region) and the high temperature region (rubber region) from Tg, and the temperature was calculated as the intersection of these tangents. The coefficient of thermal expansion (CTE) is a value indicating the rate of thermal expansion of the length and volume of an object due to an increase in temperature per 1 K (° C.), and is an average value from 100 ° C. to 200 ° C.
Load: 1g
Sample size: 4 (width) x 20 (length) mm
Temperature rise rate: 10 ° C / min Atmosphere: Nitrogen

(Surface roughness (Rz))
According to JIS B 0601: 1994, the ten-point average roughness (Rz) was measured using a surface roughness measuring machine (trade name "E-35B", manufactured by Tokyo Seimitsu Co., Ltd.).

(3D Arithmetic Mean Roughness (Sa))
The three-dimensional arithmetic mean roughness (Sa) was measured using a non-contact surface / layer cross-sectional shape measurement system (trade name "VertScan 2.0", manufactured by Ryoka System Co., Ltd.).

(Mirror gloss)
According to JIS Z 8741: 1997, (trade name "Gloss Meter VG2000", manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used to measure the mirror glossiness at an incident angle of 20 °.

(Residual solvent ratio)
Determine the residual solvent concentration in the polyimide film by reducing the weight from 100 ° C to 350 ° C using a differential thermal weight simultaneous measuring device (trade name "EXSTAR TG / DTA 6000", manufactured by Seiko Instruments Co., Ltd.). It was. All weight loss from 100 ° C. to 350 ° C. was regarded as solvent volatilization.

(Removability (adhesive strength))
A metal laminate in which a solvent-soluble resin A is laminated on at least one surface of a metal material, and a polyimide resin B varnish is further applied to, dried, and filmed on the surface in which the solvent-soluble resin A is laminated. A test sample of B (length 150 mm × width 5 mm) was prepared. Next, the test sample was laminated on a stainless steel plate (SUS plate) by using a double-sided tape (trade name "NW-K10", manufactured by Nichiban Co., Ltd.) in a reciprocating manner with a 1 kg roller. The peelability (adhesive strength) was measured by peeling the above-mentioned polyimide film at a tensile speed of 50 mm / min at an angle of 90 ° and measuring the stress at that time as the adhesive force (N / cm).

(Light transmittance)
According to JIS K-7361-1: 1997, the light transmittance of a wavelength of 200 nm to 800 nm was measured with a spectrophotometer (trade name "UV-3150", manufactured by Shimadzu Corporation), and the light transmittance of 400 nm was measured. Compared.

(Haze)
Measurement was performed using a haze meter (trade name "NDH2000", manufactured by Nippon Denshoku Kogyo Co., Ltd.) according to JIS K 7136: 2000.
In the evaluation, a haze value of 0.5 or less was evaluated as ⊚, a haze value of more than 0.5 and 1.0 or less was evaluated as ◯, more than 1.0 and 2.0 or less was evaluated as Δ, and more than 2.0 was evaluated as x.

[Synthesis Example 1] Synthesis of Polyamide-imide Resin A1 (Resin A1-1)
The following composition was added to the reaction vessel, the temperature was raised to 100 ° C. under a nitrogen stream, and the reaction was carried out at 100 ° C. for 8 hours.
1) Trimellitic anhydride: 153.7 g (80 mol%)
2) Benzophenone-3,3', 4,4'-tetracarboxylic dianhydride: 40.3 g (12.5 mol%)
3) Biphenyl-3,3', 4,4'-tetracarboxylic dianhydride: 22.1 g (7.5 mol%)
4) 3,3'-dimethyl-4,4'-diisocyanate Biphenyl (o-trizine diisocyanate): 264.3 g (100 mol%)
5) Diazabicycloundecene (catalyst): 1.0 g
6) N-methyl-2-pyrrolidone (purity 99.9%): 2500 g
Then, 1031 g of N-methyl-2-pyrrolidone (polymer concentration: 10% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 1.9 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 250 poise.

[Synthesis Example 2] Synthesis of Polyamide-imide Resin A1 (Resin A1-2)
The following composition was added to the reaction vessel, the temperature was raised to 100 ° C. under a nitrogen stream, and the reaction was carried out at 100 ° C. for 8 hours.
1) Trimellitic anhydride: 96.1 g (50 mol%)
2) Biphenyl-3,3', 4,4'-tetracarboxylic dianhydride: 147.1 g (50 mol%)
3) 3,3'-dimethyl-4,4'-diisocyanate Biphenyl (o-trizine diisocyanate): 264.3 g (100 mol%)
4) Diazabicycloundecene (catalyst): 1.5 g
5) N-methyl-2-pyrrolidone (purity 99.9%): 2377 g
Then, 430 g of N-methyl-2-pyrrolidone (polymer concentration 13% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 2.0 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 300 poise.

[Synthesis Example 3] Synthesis of Polyamide Resin A2 (Resin A2-1)
The following composition was added to the reaction vessel, the temperature was raised to 100 ° C. under a nitrogen stream, and the reaction was carried out at 100 ° C. for 8 hours.
1) Isophthalic acid: 156.7 g (90 mol%)
2) 1,4-Cyclohexanedicarboxylic acid: 18.0 g (10 mol%)
3) 3,3'-dimethyl-4,4'-diisocyanate Biphenyl (o-trizine diisocyanate): 263.1 g (100 mol%)
4) Diazabicycloundecene (catalyst): 1.6 g
5) N-methyl-2-pyrrolidone (purity 99.9%): 650 g
Then, 166.8 g of N-methyl-2-pyrrolidone (polymer concentration 30% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 0.4 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 400 poise.

[Synthesis Example 4] Synthesis of Polyamide Resin A2 (Resin A2-2)
The following composition was added to the reaction vessel, the temperature was raised to 100 ° C. under a nitrogen stream, and the reaction was carried out at 100 ° C. for 8 hours.
1) Isophthalic acid: 145.6 g (100 mol%)
2) 3,3'-dimethyl-4,4'-diisocyanate Biphenyl (o-trizine diisocyanate): 231.7 g (100 mol%)
3) Diazabicycloundecene (catalyst): 1.3 g
4) N-methyl-2-pyrrolidone (purity 99.9%): 557.4 g
Then, 142.9 g of N-methyl-2-pyrrolidone (polymer concentration: 30% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 0.5 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 500 poise.

[Synthesis Example 5] Synthesis of Polyimide-based Resin B (Resin B1)
The following composition was added to the reaction vessel, the temperature was raised to 150 ° C. under a nitrogen stream, and the reaction was carried out at 150 ° C. for 6 hours.
1) Cyclohexane-1,2,4-tricarboxylic acid-1,2 monoanhydride (H-TMA): 198.2 g (100 mol%)
2) 3,3'-dimethyl-4,4'-diisocyanate biphenyl: 264.3 g (100 mol%)
3) Triethylenediamine (catalyst): 2.2 g
4) 1,3-Dimethyl-2-imidazolidinone (purity 99.9%): 795.7 g
Then, 702.1 g of γ-butyrolactone (polymer concentration 20% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 0.8 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 500 poise.

[Synthesis Example 6] Synthesis of Polyimide-based Resin B (Resin B2)
66.7 g (100 mol%) of isophorone diisocyanate is placed in a reaction vessel, dissolved in 246 g of 1,3-dimethyl-2-imidazolidinone (purity 99.9%), and then 1,1 with stirring under a nitrogen stream. Gradually add 91.9 g (100 mol%) of powder of'-bicyclohexane-3,3', 4,4'-tetracarboxylic dian-3,3', 4,4'-dianhydride (H-BPDA). In addition, the reaction was carried out at 80 ° C. to 190 ° C. for 8 hours with stirring. Then, 283.2 g of γ-butyrolactone (polymer concentration 20% by weight) was added, and the mixture was cooled to room temperature. The logarithmic viscosity of the obtained polymer was 0.5 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 300 poise.

[Synthesis Example 7] Synthesis of Polyimide-based Resin B (Resin B3)
95.22 g of diestertetracarboxylic dianhydride obtained by reacting PTMG1000 (manufactured by Sanyo Kasei Kogyo Co., Ltd., molecular weight 1000) with cyclohexane-1,2,4-tricarboxylic acid-1,2-hydride in a reaction vessel ( 0.07 mol), 5.95 g (0.03 mol) of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, 25.03 g (0.1 mol) of 4,4′-diphenylmethanediisocyanate, Add 0.1 g of potassium fluoride, dissolve in 249.46 g of 1,3-dimethyl-2-imidazolidinone, and then react with stirring at 80 ° C to 190 ° C for 8 hours under a nitrogen stream to make it transparent. To obtain a viscous polyesterimide solution. The logarithmic viscosity of the obtained polymer was 0.95 dl / g.

[Synthesis Example 8] Synthesis of Polyimide-based Resin B (Resin B4)
24.8 g (100 mol%) of bis (3-aminophenyl) sulfone was placed in a reaction vessel, dissolved in 222 g of N-methyl-2-pyrrolidone, and then 1,1'-bicyclohexane under a nitrogen stream with stirring. Gradually add 30.6 g (100 mol%) of powder of -3,3'-4,4'-tetracarboxylic acid-3,3'-4,4'-dianhydride (H-BPDA) and at room temperature. The reaction for 15 hours gave a clear and viscous polyamic acid solution. The logarithmic viscosity of the obtained polyamic acid was 0.6 dl / g, and the solution viscosity at 25 ° C. (measured at 10 rotations with a B-type viscometer) was 300 poise.

[Production Example 1]
The resin solution of the resin A1-1 obtained in Synthesis Example 1 was applied to the treated surface (M surface) of an aluminum foil (3003 / H18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror gloss 447) having a thickness of 50 μm and a width of 540 mm. It was continuously coated with a tar so that the thickness after removing the solvent was 30 μm. Then, it was continuously passed through a floating drying oven having a length of 20 m set at 100 ° C. at a speed of 5 m / min and wound. The residual solvent ratio of the obtained metal laminate A1-1 was 25% by weight.
The metal-clad laminate A1-1 thus obtained was further continuously heat-treated under nitrogen at an oxygen concentration of 100 ppm under heating conditions of 200 ° C. for 30 minutes, 250 ° C. for 30 minutes, and 300 ° C. for 30 minutes.

[Production Example 2]
A treated surface of an electrolytic copper foil (CF-T9DA-SV manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 20 ° mirror gloss 660) having a thickness of 11 μm and a width of 540 mm from the resin solution of the resin A1-1 obtained in Synthesis Example 1. A metal laminate A1-2 to be a support was produced in the same manner as in Production Example 1 except that (M surface) was used.

[Production Example 3]
The treated surface of the electrolytic copper foil (SH Copper Products Co., Ltd. tough pitch copper foil OFC-HX, 20 ° mirror gloss 247) having a thickness of 15 μm and a width of 540 mm was prepared by applying the resin solution of the resin A1-1 obtained in Synthesis Example 1 A metal laminate A1-3 to be a support was produced in the same manner as in Production Example 1 except that the M surface) was used.

[Production Example 4]
Except for using the treated surface (M surface) of the resin solution of the resin A1-1 obtained in Synthesis Example 1 with a SUS foil (HA manufactured by Nippon Metal Co., Ltd., 20 ° mirror glossiness 287) having a thickness of 30 μm and a width of 540 mm. Made a metal laminate A1-4 as a support in the same manner as in Production Example 1.

[Production Examples 5 to 7]
The treated surface (M surface) of the resin solution of the resin A1-1 obtained in Synthesis Example 1 on a SUS foil (SHE-TA (BS) manufactured by Nippon Metal Co., Ltd., 20 ° mirror glossiness 687) having a thickness of 50 μm and a width of 540 mm. ) Was coated with a die coater so that the thickness after solvent removal was 10 μm (metal laminate A1-5), 20 μm (metal laminate A1-6), and 30 μm (metal laminate A1-7), respectively. Metal laminates A1-5 to A1-7 serving as a support were produced in the same manner as in Production Example 1 except for the above.

[Creation example 8]
The treated surface (M surface) of the resin solution of the resin A1-2 obtained in Synthesis Example 2 on a SUS foil (SHE-TA (BS) manufactured by Nippon Metal Co., Ltd., 20 ° mirror glossiness 687) having a thickness of 50 μm and a width of 540 mm. ) Was coated with a die coater so that the thickness after solvent removal was 20 μm, respectively, to prepare a metal laminate A1-8 to be a support in the same manner as in Production Example 1.

[Production Example 9]
A treated surface (USLP-SE-18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror glossiness 0.3) of an electrolytic copper foil having a thickness of 18 μm and a width of 540 mm was prepared by using the resin solution of the resin A1-1 obtained in Synthesis Example 1 A metal laminate A1-9 to be a support was produced in the same manner as in Production Example 1 except that the M surface) was used.

[Production Example 10]
A die coater was applied to the treated surface (M surface) of the resin solution of the resin A2-1 obtained in Synthesis Example 3 on a SUS foil (304 nanoBA manufactured by Nippon Kinzoku Co., Ltd., 20 ° mirror gloss 1000) having a thickness of 120 μm and a width of 540 mm. It was continuously coated so that the thickness after removing the solvent was 30 μm. Then, it was continuously passed through a floating drying oven having a length of 20 m set at 100 ° C. at a speed of 5 m / min and wound. The residual solvent ratio of the obtained metal laminate A2-1 was 25% by weight.
The metal-clad laminate A2-1 thus obtained was further continuously heat-treated under nitrogen at an oxygen concentration of 100 ppm under heating conditions of 200 ° C. for 30 minutes, 250 ° C. for 30 minutes, and 300 ° C. for 30 minutes.

[Production Example 11]
Same as Production Example 10 except that the resin solution of the resin A2-1 obtained in Synthesis Example 3 was applied to a SUS foil (304BA2 manufactured by Nippon Metal Co., Ltd., 20 ° mirror gloss 310) having a thickness of 50 μm and a width of 540 mm. A2-2 metal laminate to be used as a support was produced.

[Production Example 12]
Production Example 10 except that the resin solution of the resin A2-1 obtained in Synthesis Example 3 was applied to an aluminum foil (3003 / H18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror gloss 447) having a thickness of 50 μm and a width of 540 mm. In the same manner as above, a metal laminate A2-3 serving as a support was produced.

[Production Example 13]
The treated surface of the electrolytic copper foil (CF-T9DA-SV manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., 20 ° mirror gloss 660) having a thickness of 11 μm and a width of 540 mm from the resin solution of the resin A2-1 obtained in Synthesis Example 3. A metal laminate A2-4 to be a support was produced in the same manner as in Production Example 10 except that the surface (M surface) was coated.

[Production Example 14]
The resin solution of the resin A2-2 obtained in Synthesis Example 4 was applied to the treated surface (M surface) of a SUS foil (304 nanoBA manufactured by Nippon Metal Co., Ltd., 20 ° mirror gloss 1000) having a thickness of 120 μm and a width of 540 mm. A metal laminate A2-5 to be a support was produced in the same manner as in Production Example 10 except for the above.

[Production Example 15]
A treated surface (USLP-SE-18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror glossiness 0.3) of an electrolytic copper foil having a thickness of 18 μm and a width of 540 mm was prepared by applying the resin solution of the resin A2-1 obtained in Synthesis Example 3 A metal laminate A2-6 to be a support was produced in the same manner as in Production Example 10 except that the surface (M surface) was coated.

[Example 1] Polyimide-based film B1-1
As a supporting base material, the resin B1 obtained in Synthesis Example 5 is uniformly applied to the resin surface of the metal laminate A1-1 of Production Example 1 so that the thickness after drying becomes 30 μm, and heated at a temperature of 100 ° C. or lower. It was dry. After that, it was continuously conveyed in the heating furnace of the far infrared method (RtoR type heat treatment apparatus heat manufactured by Noritake Engineering Co., Ltd.). The temperature inside the heating furnace (metal laminate B1-1 surface temperature) is 180 ° C in the first, second and third zones, 250 ° C in the fourth zone, and 330 ° C in the fifth, sixth and seventh zones (nitrogen). Flow rate 500 L / min, oxygen concentration 100 ppm, far infrared plate heater top and bottom arrangement, irradiation distance 100 mm, wavelength 5.6 to 1000 μ, capacity 225 kW, heater size 150 mm x 700 mm), and the transport speed is 10 minutes each. The metal laminate B1-1 was obtained in 5 minutes and 10 minutes. Then, only the polyimide resin B1 layer of the metal laminate B1-1 was peeled off to obtain a polyimide film B1-1. The results are shown in Table 1. The haze value was 0.41.

[Example 2] Polyimide-based film B1-2
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-2 of Production Example 2 was used as the supporting base material. The results of the obtained polyimide film B1-2 are shown in Table 1. The haze value was 0.45.

[Example 3] Polyimide-based film B1-3
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-3 of Production Example 3 was used as the supporting base material. The results of the obtained polyimide film B1-3 are shown in Table 1. The haze value was 0.51.

[Example 4] Polyimide-based film B1-4
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-4 of Production Example 4 was used as the supporting base material. The results of the obtained polyimide film B1-4 are shown in Table 1. The haze value was 0.55.

[Example 5] Polyimide-based film B1-5
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-5 (thickness of the resin A1 was 10 μm) of Production Example 5 was used as the supporting base material. The results of the obtained polyimide film B1-5 are shown in Table 1. The haze value was 0.46.

[Example 6] Polyimide-based film B1-6
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-6 (thickness of the resin A1 was 20 μm) of Production Example 6 was used as the support base material. The results of the obtained polyimide film B1-6 are shown in Table 1. The haze value was 0.57.

[Example 7] Polyimide-based film B1-7
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-7 (thickness of the resin A1 was 30 μm) of Production Example 7 was used as the support base material. The results of the obtained polyimide film B1-7 are shown in Table 1. The haze value was 0.37.

[Example 8] Polyimide-based film B1-8
The polyimide resin B1 was formed in the same manner as in Example 1 except that the metal laminate A1-8 of Production Example 8 (thickness of the resin A1 was 20 μm) was used as the supporting base material. The results of the obtained polyimide film B1-8 are shown in Table 1. The haze value was 0.55.

[Example 9] Polyimide-based film B2-1
As a supporting base material, the resin B2 obtained in Synthesis Example 6 is uniformly applied to the resin surface of the metal laminate A1-1 of Production Example 1 so that the thickness after drying becomes 30 μm, and heated at a temperature of 100 ° C. or lower. The polyimide resin B2 was formed in the same manner as in Example 1 except that it was dried. The results of the obtained polyimide film B2-1 are shown in Table 1. The haze value was 0.42.

[Example 10] Polyimide-based film B3-1
As a supporting base material, the resin B3 obtained in Synthesis Example 4 is uniformly applied to the resin surface of the metal laminate A1-1 of Production Example 1 so that the thickness after drying becomes 30 μm, and heated at a temperature of 100 ° C. or lower. A polyimide resin B3 (polyesterimide) was formed in the same manner as in Example 1 except that it was dried. The results of the obtained polyimide film B3-1 are shown in Table 1. The haze value was 0.7.

[Example 11] Polyimide-based film B1-9
The resin B1 obtained in Synthesis Example 5 was continuously coated on the resin surface of the metal laminate A2-1 of Production Example 10 using a die coater so that the thickness after solvent removal was 30 μm. Next, the metal laminate B1-9 was obtained by continuously passing it through a floating type drying oven having a length of 20 m set at 100 ° C. at a speed of 5 m / min and winding it. The metal-clad laminate B1-9 thus obtained was further heat-treated continuously under nitrogen at an oxygen concentration of 100 ppm under heating conditions of 200 ° C. for 30 minutes, 250 ° C. for 30 minutes, and 300 ° C. for 30 minutes.
Then, only the polyimide resin B1 layer of the metal laminate B1-9 was peeled off to obtain a polyimide film B1-9. The results are shown in Table 2. The haze value was 0.35.

[Example 12] Polyimide-based film B1-10
The polyimide resin B1 was formed in the same manner as in Example 11 except that the metal laminate A2-2 of Production Example 11 was used as the supporting base material. The results of the obtained polyimide film B1-10 are shown in Table 2. The haze value was 0.37.

[Example 13] Polyimide-based film B1-11
The polyimide resin B1 was formed in the same manner as in Example 11 except that the metal laminate A2-3 of Production Example 12 was used as the supporting base material. The results of the obtained polyimide film B1-11 are shown in Table 2. The haze value was 0.41.

[Example 14] Polyimide-based film B1-12
The polyimide resin B1 was formed in the same manner as in Example 11 except that the metal laminate A2-4 of Production Example 13 was used as the supporting base material. The results of the obtained polyimide film B1-12 are shown in Table 2. The haze value was 0.45.

[Example 15] Polyimide-based film B1-13
The polyimide resin B1 was formed in the same manner as in Example 11 except that the metal laminate A2-5 of Production Example 14 was used as the supporting base material. The results of the obtained polyimide film B1-13 are shown in Table 2. The haze value was 0.35.

[Example 16] Polyimide-based film B2-2
The same as in Example 11 except that the resin B2 obtained in Synthesis Example 6 was uniformly applied to the resin surface of the metal laminate A2-1 of Production Example 10 as a supporting base material so that the thickness after drying was 30 μm. The polyimide resin B2 was formed into a film. The results of the obtained polyimide film B2-2 are shown in Table 2. The haze value was 0.36.

[Example 17] Polyimide-based film B3-2
The same as in Example 11 except that the resin B3 obtained in Synthesis Example 7 was uniformly applied to the resin surface of the metal laminate A2-1 of Production Example 10 as a supporting base material so that the thickness after drying was 30 μm. The polyimide resin B3 was formed into a film. The results of the obtained polyimide film B3-2 are shown in Table 2. The haze value was 0.36.

[Example 18] Polyimide-based film B4-1
The same as in Example 11 except that the resin B4 obtained in Synthesis Example 8 was uniformly applied to the resin surface of the metal laminate A2-1 of Production Example 10 as a supporting base material so that the thickness after drying was 30 μm. The polyimide resin B4 was formed into a film. The results of the obtained polyimide film B4-1 are shown in Table 2. The haze value was 0.6.

[Comparative Example 1] Polyimide-based film B1-14
As a supporting base material, an aluminum foil having a thickness of 50 μm and a width of 540 mm (3003 / H18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror gloss 447) was used, and the untreated surface (S surface) was the resin obtained in Synthesis Example 5. The polyimide resin B1 was formed in the same manner as in Example 1 except that B1 was uniformly applied. The polyimide resin B1 layer could not be peeled off from the metal laminate B1-14. The results are shown in Table 1. In Table 1, "-" means that it could not be measured because it could not be peeled off. The polyamide-imide resin A1 layer does not exist on the untreated surface (S surface) of the aluminum foil.

[Comparative Example 2] Polyimide-based film B1-15
As a supporting base material, a SUS foil (SHE-TA (BS) manufactured by Nippon Kinzoku Co., Ltd., 20 ° mirror gloss 687) having a thickness of 50 μm and a width of 540 mm was used, and the untreated surface (S surface) was treated with Synthesis Example 5. The polyimide resin B1 was formed in the same manner as in Example 1 except that the obtained resin B1 was uniformly applied. The results of the obtained polyimide film B1-15 are shown in Table 1. The haze value was 2.5. The polyamide-imide resin A1 layer does not exist on the untreated surface (S surface) of the SUS foil.

[Comparative Example 3] Polyimide-based film B1-16
The polyimide resin B1 was formed in the same manner as in Example 1 except that the resin B1 obtained in Synthesis Example 5 was uniformly applied to the resin surface of the metal laminate A1-9 of Production Example 9 as a supporting base material. The results of the obtained polyimide film B1-16 are shown in Table 1. The haze value was 0.9.

[Comparative Example 4] Polyimide-based film B4-2
As a supporting base material, the resin B4 obtained in Synthesis Example 8 was uniformly applied to the resin surface of the metal laminate A1-1 of Production Example 1 so that the thickness after drying was 30 μm, and dried by heating at a temperature of 100 ° C. or lower. did. After that, it was continuously conveyed in the heating furnace of the far infrared method (RtoR type heat treatment apparatus heat manufactured by Noritake Engineering Co., Ltd.). The temperature inside the heating furnace (metal laminate B4-2 surface temperature) is 180 ° C in the first, second, and third zones, 250 ° C in the fourth zone, and 330 ° C in the fifth, sixth, and seventh zones (N). ₂ Flow rate 500 L / min, oxygen concentration 100 ppm, far infrared plate heater upper surface, lower surface arrangement, irradiation distance 100 mm, wavelength 5.6 to 1000 μ, capacity 225 kW, heater size 150 mm × 700 mm), and the transport speed is 10 for each. The metal laminate B4-2 was obtained in 5 minutes and 10 minutes. The polyimide resin B4 layer could not be peeled off from the metal laminate B4-2. The results are shown in Table 1. In Table 1, "-" means that it could not be measured because it could not be peeled off. It is considered that the reason why the metal laminate A could not be peeled off was that the resin A of the metal laminate A was a polyamide-imide resin. That is, it is probable that the imide group of the resin A was ring-opened by the dehydration reaction when the polyamic acid of the resin B4 was imidized, causing a deterioration phenomenon of peeling. On the other hand, in Example 18, since the resin A of the metal laminate A was a polyamide resin, the imide group did not exist and the peelability did not deteriorate.

[Comparative Example 5] Polyimide-based film B1-17
As a supporting base material, a SUS foil having a thickness of 120 μm and a width of 540 mm (304 nanoBA manufactured by Nippon Kinzoku Co., Ltd., 20 ° mirror gloss 1000) was used, and the resin B1 obtained in Synthesis Example 5 was applied to the untreated surface (S surface). The polyimide resin B1 was formed in the same manner as in Example 11 except that it was applied uniformly. The polyimide resin B1 layer could not be peeled off from the metal laminate B1-17. The results are shown in Table 2. In Table 2, "-" means that it could not be measured because it could not be peeled off. The polyamide resin A2 layer does not exist on the untreated surface (S surface) of the SUS foil.

[Comparative Example 6] Polyimide-based film B1-18
As a supporting base material, a SUS foil having a thickness of 50 μm and a width of 540 mm (304BA2 manufactured by Nippon Kinzoku Co., Ltd., 20 ° mirror gloss 1000) was used, and the resin B1 obtained in Synthesis Example 5 was applied to the untreated surface (S surface). The polyimide resin B1 was formed in the same manner as in Example 11 except that it was applied uniformly. The results of the obtained polyimide film B1-18 are shown in Table 2. The haze value was 2.0. The polyamide resin A2 layer does not exist on the untreated surface (S surface) of the SUS foil.

[Comparative Example 7] Polyimide-based film B1-19
As a supporting base material, an aluminum foil having a thickness of 50 μm and a width of 540 mm (3003 / H18 manufactured by Nippon Denki Co., Ltd., 20 ° mirror gloss 447) was used, and the untreated surface (S surface) was the resin obtained in Synthesis Example 5. The polyimide resin B1-19 was formed in the same manner as in Example 11 except that B1 was uniformly applied. The polyimide resin B1 layer could not be peeled off from the metal laminate B1-19. The results are shown in Table 2. In Table 1, "-" means that it could not be measured because it could not be peeled off. The polyamide resin A2 layer does not exist on the untreated surface (S surface) of the aluminum foil.

[Comparative Example 8] Polyimide-based film B1-20
The same as in Example 11 except that the resin B1 obtained in Synthesis Example 5 was uniformly applied to the resin surface of the metal laminate A2-6 of Production Example 15 as a support base material so that the thickness after drying was 30 μm. The polyimide resin B1 was formed into a film. The results of the obtained polyimide film B1-20 are shown in Table 2. The haze value was 2.20.

A metal laminate A1 or A2 in which the polyamide imide resin A1 or the polyamide resin A2 of the present invention is laminated on at least one surface of a metal material is used, and the polyimide resin of the present invention is laminated on the surface on which the polyamide imide resin A1 or the polyamide resin A2 is laminated. In Examples 1 to 18 in which the solution B (crocodile) was applied, dried, and formed into a film, peeling from the base material (metal laminate A) was easy, and heat resistance, surface smoothness, optical properties, and transparency were achieved. A thinner polyimide film was obtained.

When a metal material having a high mirror gloss at an incident angle of 20 ° was used (Examples 1 to 18), a polyimide film having good surface smoothness was obtained, but the mirror gloss at an incident angle of 20 ° was obtained. When a low metal was used (Comparative Examples 3 and 8), the low glossiness of the metal material was transferred to the polyimide film, and only a film having high surface roughness (Rz) and haze value was obtained.

Further, when the metal material is used as it is instead of the metal laminate A (the polyamide-imide resin A1 and the polyamide resin A2 are not laminated), the aluminum foil of Comparative Example 1 and the SUS foil of Comparative Example 5 are treated with a polyimide-based material. Since the adhesiveness to the resin B was high, good peelability could not be obtained. On the other hand, in the cases of Comparative Example 2 and Comparative Example 6 using the SUS foil having high mirror gloss, the polyimide film could be peeled off, but the surface state of the metal material was transferred to the film, and a film having good surface properties was obtained. I couldn't. In the case of the aluminum foil of Comparative Example 7, the adhesiveness to the polyimide resin B to be coated in the same manner was high, and good peelability could not be obtained.

According to the present invention, a thinner polyimide film having excellent heat resistance, transparency, surface smoothness, and optical properties can be produced efficiently with good yield. Therefore, it is expected that it will greatly contribute to the industrial world because it will be very easy to reduce the size and weight of electronic information devices and to improve their functions.

Claims (4)

A method for producing a polyimide film having steps (A) to (C) and having a surface roughness (Rz) of less than 0.08 μm.
Step (A): A part of the surface of the metal material having a mirror surface glossiness of 200 or more, a surface roughness (Rz) of 0.5 μm or less, and a young ratio of the metal material of 50 kN / mm ² or more. In the step of laminating the polyamide-imide resin A1 on all of them and cross-linking the polyamide-imide resin A1 with an epoxy resin to obtain a metal laminate A, (i) the acid component constituting the polyamide-imide resin A1 is an anhydrous polyimide. One or more selected from the group consisting of acid, benzophenone-3,3', 4,4'-tetracarboxylic acid dianhydride, and biphenyl-3,3', 4, 4'-tetracarboxylic acid dianhydride. The diamine component constituting (ii) polyamide-imide resin A1 is 3,3'-dimethyl-4,4'-diaminobiphenyl, or 3,3'-dimethyl, which is a corresponding diisocyanate. A polyamide-imide resin A1 containing -4,4'-diisosianatobiphenyl as a main component has one or more structures selected from the group consisting of the following formulas (1), (2), and (3). Step of obtaining the metal laminate (A) included as a structural unit Step (B): A solvent that does not undergo an imidization reaction on the surface of the polyamide-imide resin A1 layer of the metal laminate A after being laminated differently from the polyamide-imide resin A1. Step of further laminating the soluble polyimide resin B to obtain the metal laminate B Step (C): Step of peeling the polyimide resin B layer from the metal laminate B to obtain a polyimide film.
The method for producing a polyimide film according to claim 1, wherein the polyamide-imide resin A1 is further (iii) below.
(Iii) The molecular weight in N-methyl-2-pyrrolidone (polymer concentration 0.5 g / dl) corresponds to 0.3 dl / g or more and 3.5 dl / g or less in logarithmic viscosity at 30 ° C. The acid component constituting the polyimide resin B is cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, benzophenone-3,3', 4,4'-tetracarboxylic dianhydride. Claim 1 or claim 1 or which contains a hydrogenated additive or 1,1'-bicyclohexane-3,3', 4,4'-tetracarboxylic acid-3,3', 4,4'-dianhydride as a main component. 2. The method for producing a polyimide film according to 2. The method for producing a polyimide film according to any one of claims 1 to 3, which is one or more selected from the group consisting of the following (a), (b), (c), and (d).
(A) Surface roughness (Rz) is less than 0.08 μm (b) Glass transition point is 180 ° C or higher and 350 ° C or lower (c) Light transmittance at a wavelength of 400 nm is 60% or higher and 90% or lower (d) Haze value Is 0.1 or more and 2.0 or less