JP7839330B2 - Polyimide film - Google Patents

Description

This invention relates to polyimide films, etc.

Due to its excellent heat resistance, chemical resistance, and electrical properties, polyimide film is widely used as an electrical insulation material for electric wires, chip-on film (COF), base film for flexible printed circuit boards (FPC), carrier tape film for tape-automated bonding (TAB) of ICs, and tape for fixing IC lead frames.

With the miniaturization, weight reduction, increased functionality, multi-functionality, and high-density mounting of electronic devices, the printed circuit boards used in these devices are rapidly becoming more densely packed through narrower conductor widths and spacing, multi-layering, flexibility, and thinner substrates.

A three-layer flexible printed circuit board has been known for its construction, in which a conductive layer (such as a copper layer) is bonded to a polyimide film via an adhesive layer (Patent Document 1).

On the other hand, when a polyimide film is bonded to a conductive layer via an adhesive layer, sufficient adhesion (tightness) may not be obtained between the polyimide film and the metal layer.
In this context, it is known that when manufacturing polyimide films, a solution containing a heat-resistant surface treatment agent is applied to the surface of a polyamic acid solidified film (self-supporting film), and the solidified film is heat-treated to imidize it, thereby obtaining a polyimide film with improved adhesion (Patent Document 2).

Patent No. 2680816 Japanese Unexamined Patent Publication No. 62-267330

The object of the present invention is to provide a polyimide film suitable for use in metal lamination (for lamination of metal layers), etc.

As described above, it is known that polyimide films can be manufactured by applying a surface treatment agent to the surface of a self-supporting polyamic acid film and then heat-treating it.

However, the inventors have found that while the adhesion between the polyimide film and the metal layer is improved immediately after lamination of the metal layer, this adhesion may decrease when the metal layer laminated film is exposed to high temperatures.

Therefore, the inventors investigated polyimide films for metal lamination from a perspective completely different from that of conventional polyimide films.
Surprisingly, the inventors then considered applying the surface treatment agent not to the self-supporting polyamic acid film, but to the polyimide film after imidization.
However, when applying a surface treatment agent to a polyimide film after imidization, unlike when applying it to a self-supporting polyamic acid film, it was difficult to form a layer containing hydrolysis condensates of the surface treatment agent on the polyimide film, possibly because the polyimide and the surface treatment agent did not react much (i.e., not many chemical bonds were formed between the polyimide and the surface treatment agent).
Furthermore, depending on the type of surface treatment agent, it was difficult to efficiently form such a layer, and forming a layer containing hydrolysis condensates of the surface treatment agent on the polyimide film after imidization proved extremely challenging.

In this context, the inventors, after further intensive research, have discovered that a polyimide film having a layer containing a hydrolysis condensate of a surface treatment agent can be efficiently obtained by treating a specific surface treatment agent (particularly a coupling agent such as a silane coupling agent) under specific conditions [for example, the concentration of the coupling agent in the coupling agent-containing solution, and the drying conditions after coating the coupling agent (for example, drying temperature, drying time, etc.)].
The inventors have found that such a polyimide film is suitable for laminating a metal layer, that sufficient adhesion can be achieved without providing an adhesive layer (in particular, even thin metal layers can be laminated with sufficient adhesion), and that the metal layer laminated polyimide film, in which a metal layer is laminated onto the film, can suppress the decrease in the above-mentioned adhesion even when exposed to high-temperature conditions.
Furthermore, the inventors discovered that when the film is a metal-layered polyimide film in which a metal layer is laminated, the decrease in adhesion when exposed to high-temperature conditions can be suppressed more effectively than when a polyimide film obtained by applying a surface treatment agent to a self-supporting polyamic acid film is used. Further research led to the completion of the present invention.

In other words, the present invention relates to the following inventions, etc.
[1]
A polyimide film (particularly a polyimide film for metal lamination) having a layer (A) on one or both sides containing (or formed from) a hydrolysis condensate of a coupling agent (e.g., a silane coupling agent).
[2]
A polyimide film (particularly a polyimide film for metal lamination) in which a copper layer (for example, a copper layer with a thickness of 8.5 μm, or a copper layer with a thickness of 8.5 μm via a metal layer (copper layer) formed by sputtering) is directly laminated, and T1 is the peel strength (e.g., 90° peel strength) between the copper layer and the polyimide film, and T2 is the peel strength (e.g., 90° peel strength) between the copper layer and the polyimide film after heating at 150°C for 168 hours, wherein T1 is 0.4 kN/m or more and T2/T1 is 0.7 or more.
Such polyimide films may also be manufactured, for example, by applying a coupling agent-containing solution to one or both sides of an (imidized) polyimide film and drying it (hydrolysis condensation), as described later. In other words, such polyimide films may be polyimide films obtained by applying a coupling agent-containing solution to one or both sides of an (imidized) polyimide film and drying it (hydrolysis condensation).
[3]
The polyimide film according to [1], wherein the coupling agent has an amino group.
[4]
A polyimide film according to [1] or [3], wherein the coupling agent comprises a silane coupling agent.
[5]
A polyimide film according to any one of [1] and [3] to [4], wherein the coupling agent comprises an amino-based silane coupling agent.
[6]
A polyimide film according to any one of [1] and [3] to [5], wherein the thickness of layer (A) is 100 to 400 nm.
[7]
A polyimide film according to any one of [1] and [3] to [6], wherein layer (A) comprises a layer (or film) (1) of a hydrolyzed condensate of a coupling agent (on the surface side).
[8]
A polyimide film according to any one of [1] and [3] to [7], comprising layer (A) and layer (2) containing a hydrolysis condensate of a coupling agent and a component derived from polyimide.
[9]
The polyimide film according to [8], wherein the thickness of layer (2) is 300 nm or less.
[10]
A polyimide film according to any one of [1] and [3] to [9], wherein the coupling agent comprises 3-aminopropyltrimethoxysilane.
[11]
A polyimide film according to any one of [1] to [10], wherein, when the coefficient of linear expansion in the mechanical transport direction (MD) of the film is αMD and the coefficient of linear expansion in the width direction (TD) is αTD, the value of (|αMD| + |αTD|)/2 is 15 ppm/K or less.
[12]
A polyimide film according to any one of [1] to [11], wherein the αTD is -5 to +10 ppm/K.
[13]
A polyimide film according to any one of [1] to [12], wherein the polyimide constituting the polyimide film comprises an aromatic diamine component containing at least one selected from paraphenylenediamine and 4,4'-diaminodiphenyl ether, and an aromatic acid anhydride component containing at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride as polymerization components.
[14]
A polyimide film containing inorganic particles, as described in any one of [1] to [13].
[15]
A polyimide film in roll form, as described in any of [1] to [14].
[16]
A polyimide film according to any one of [1] to [15], which contains inorganic particles in a proportion of 0.01 to 5% by mass and is in the form of a roll with a length of 5 m or more.
[17]
A polyimide film for metallizing (e.g., plating), as described in any of [1] to [16].
[18]
A polyimide film according to any one of [1] to [17] for directly laminating a metal layer (or without an adhesive layer) (for example, directly laminating a copper layer with a thickness of 20 μm or less).
[19]
A laminated film comprising a polyimide film and a metal layer laminated directly on the film (or without an adhesive layer), wherein the polyimide film is a polyimide film according to any one of [1] to [18].
[20]
The laminated film according to [19], wherein the metal layer is a copper layer with a thickness of 20 μm or less.
[21]
The laminated film according to [19] or [20], wherein the peel strength (e.g., 90° peel strength) T1 between the metal layer and the polyimide film is 0.5 kN/m or more.
[22]
A laminated film according to any one of [19] to [21], wherein T1 is the peel strength between the metal layer and the polyimide film (e.g., 90° peel strength), and T2 is the peel strength between the metal layer and the polyimide film after heating at 150°C for 168 hours (e.g., 90° peel strength), and T1 is 0.4 kN/m or more, and T2/T1 is 0.7 or more.
[23]
A method for producing a polyimide film (particularly a polyimide film for metal lamination, or a polyimide film according to any one of [1] to [18]), comprising the step of applying a solution containing a coupling agent (e.g., a silane coupling agent) to one or both sides of the polyimide film, and then drying it.
[24]
The manufacturing method according to [23], wherein the coupling agent (e.g., silane coupling agent) containing solution contains 0.1 to 5% by mass of the coupling agent (e.g., silane coupling agent).
[25]
The manufacturing method according to [23] or [24], wherein drying is performed at a drying temperature of 130 to 200°C and a drying time of 40 to 100 seconds.

According to the present invention, a polyimide film can be provided. Such a polyimide film is suitable for applications such as metal lamination (metal layer lamination, metal layer formation, etc.).

For example, in one embodiment of a polyimide film, a metal layer (e.g., a copper layer) can be laminated (formed) with sufficient adhesion. Since such adhesion can be ensured even without an adhesive layer (by directly forming the metal layer), the metal layer can also be suitably formed by metallizing [or a metallizing method or metallizing treatment, such as a plating method (wet or dry plating method, e.g., vacuum deposition, sputtering, ion plating)].

Therefore, with such a polyimide film, sufficient adhesion can be achieved even with thin metal layers (for example, thicknesses of 30 μm or less, 20 μm or less, 10 μm or less, etc.).

In another embodiment of the polyimide film of the present invention, the above-described sufficient adhesion can be efficiently maintained even when exposed to conditions such as high temperatures.

In another embodiment of the polyimide film of the present invention, it is possible to achieve sufficient adhesion to the metal layer while possessing useful or effective functions as a base film (substrate film) {for example, heat resistance, dimensional stability (e.g., dimensional stability during metal layer formation, dimensional stability after metal layer formation (e.g., during processing))} as described above.

In another embodiment of the polyimide film of the present invention, a high dielectric breakdown voltage can be achieved.
Therefore, such polyimide films can provide high insulation properties.

[Polyimide film]
The polyimide film of the present invention may have a layer (A) on its surface that contains (or is formed from) a hydrolyzed condensate of a coupling agent (hereinafter sometimes simply referred to as "layer (A)").
Layer (A) may be a layer containing an element corresponding to the coupling agent [for example, silicon (corresponding to the silane coupling agent)].
Layer (A) may be formed on one side (or one side) of the polyimide film, or on both sides (or both sides).
Such polyimide films can be formed, for example, by applying a coupling agent-containing solution to one or both sides of an (imidized) polyimide film and drying it (causing hydrolysis condensation).

(Layer (A))
The coupling agent may, for example, have a hydrolyzable (condensable) group (e.g., an alkoxy group, a halogen atom, etc.) and a reactive functional group [e.g., an amino group, an epoxy group, a mercapto group, a (meth)acryloyl group, a vinyl group, etc.].

Examples of coupling agents include silane coupling agents, titanium coupling agents, and aluminum coupling agents, and preferably, silane coupling agents.
Coupling agents may be used individually or in combination of two or more types.

Examples of silane coupling agents include those having a silyl group to which a hydrolyzable (condensable) group (e.g., an alkoxy group, a halogen atom, etc.) is bonded.
In a silane coupling agent, the number of silicon atoms may be one or more, or two or more (for example, oligomer or polymer-type silane coupling agents).

Specific silane coupling agents are not particularly limited, but examples include amino-based silane coupling agents (silane coupling agents containing amino groups), epoxy-based silane coupling agents (silane coupling agents containing epoxy groups), mercapto-based silane coupling agents (silane coupling agents containing mercapto groups), (meth)acryloxy-based silane coupling agents (silane coupling agents containing (meth)acryloxy groups), vinyl-based silane coupling agents (silane coupling agents containing vinyl groups), and preferably, amino-based silane coupling agents or the like.
One or more types of silane coupling agents may be used.

Examples of amino-based silane coupling agents include alkoxysilanes having an amino group [for example, aminoalkylalkoxysilanes (e.g., aminoalkyl mono to trialkoxysilanes such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane, preferably aminoC1-4 alkyl mono to triC1-4 alkoxysilanes), (aminoalkylamino)alkylalkoxysilanes (e.g., (aminoalkylamino)alkyl mono to trialkoxysilanes such as 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propylmethyldimethoxysilane, and 3-(2-aminoethylamino)propyltriethoxysilane, preferably (aminoC1-4 amino)C1-4 alkyl mono to triC1-4 alkoxysilanes), phenylaminoalkylalkoxysilanes (e.g., phenylaminoalkyl mono to trialkoxysilanes such as N-phenyl-3-aminopropyltrimethoxysilane, preferably phenylaminoC1-4 alkyl mono to triC1-4 alkoxysilanes), etc.].

Examples of epoxy-based silane coupling agents include alkoxysilanes having epoxy groups [for example, glycidoxyalkylalkoxysilanes (e.g., glycidoxyalkyl mono to trialkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, etc., preferably glycidoxy C1-4 alkyl mono to tri C1-4 alkoxysilanes), epoxycycloalkylalkoxysilanes (e.g., epoxycycloalkyl mono to trialkoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, preferably epoxy C3-10 cycloalkyl mono to tri C1-4 alkoxysilanes), etc.].

Examples of mercapto-silane coupling agents include alkoxysilanes having a mercapto group [for example, mercaptoalkylalkoxysilanes (e.g., mercaptoalkyl mono to trialkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane, preferably mercapto C1-4 alkyl mono to triC1-4 alkoxysilanes)].

Examples of (meth)acryloxy silane coupling agents include alkoxysilanes having a (meth)acryloyl group [for example, (meth)acryloxyalkyl mono to trialkoxysilanes such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, preferably (meth)acryloxy C2-4 alkyl mono to triC1-4 alkoxysilanes, etc.].

Examples of vinyl-based silane coupling agents include vinyl group-containing silanes {e.g., halosilanes having a vinyl group (e.g., vinyl mono to trihalosilanes such as vinyltrichlorosilane), alkoxysilanes having a vinyl group [e.g., vinyl alkoxysilanes (e.g., vinyl mono to trialkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane, preferably vinyl mono to triC1-4 alkoxysilanes), vinyl alkoxyalkoxysilanes (e.g., vinyl tri(methoxyethoxy)silane, vinyltris(β-methoxyethoxy)silane, etc., vinyl mono to tri(C1-4 alkoxyC1-4 alkoxy)silanes), styryl group-containing silanes (e.g., styryl mono to trialkoxysilanes such as p-styryltrimethoxysilane, preferably styryl mono to triC1-4 alkoxysilanes), etc.]}.

Examples of titanium coupling agents include isostearoyl titanates (e.g., mono- or triisostearoyl titanates such as isopropyltriisostearoyl titanate, isopropyldimethacryloylisostearoyl titanate, isopropylisostearoyldiacrylic titanate, etc.), amino group-containing titanates (e.g., isopropyltri(N-aminoethyl-aminoethyl) titanate), isopropyltridecylbenzenesulfonyl titanate, isopropyl Examples include pyrtris(dioctyl pyrophosphate) titanate, tetraisopropylbis(dioctyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, isopropyltrioctanoyl titanate, and isopropyltricumylphenyl titanate.

Examples of aluminum coupling agents include alkylacetacetate aluminum diisopropylate.

From the viewpoint of adhesion between the polyimide film and the metal layer of the present invention (particularly adhesion when exposed to high-temperature conditions), the coupling agent may preferably be one having an amino group (for example, an amino-based silane coupling agent).
When using a coupling agent containing amino groups, although not certain, it is thought that the reaction between the polyimide film to which the coupling agent is applied and the coupling agent can be suppressed to some extent, and therefore amino groups remain on the surface of the polyimide film of the present invention [for example, the surface of layer (A)]. In other words, when using a coupling agent containing amino groups, it is thought that the surface of the polyimide film of the present invention contains amino groups.
Furthermore, although not certain, it is thought that when a metal layer is laminated on such a polyimide film of the present invention, coordination bonds are formed between the amino groups and metal atoms (for example, copper atoms, etc.), which makes it easier to stabilize the metal layer, and thus easier to obtain good adhesion between the metal layer and the polyimide film of the present invention even when exposed to high-temperature conditions.

Furthermore, layer (A) may contain hydrolysis condensates of surface treatment agents other than coupling agents {for example, silane compounds [e.g., mono- to tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, preferably mono- to tetraC1-4 alkoxysilanes]}.

Layer (A) may have a layer (or film) (1) of a hydrolysis condensate of a coupling agent.
Layer (1) may be formed on the surface side of layer (A).
Layer (1) may be formed substantially solely from hydrolyzed condensates of coupling agents and may not contain polyimide (or polyimide-derived components).
Furthermore, if the polyimide film of the present invention has layers (A) on both sides (or both sides), layer (1) may be formed on both sides (or both sides) of the polyimide film, or on one side (or one side).

Layer (A) may have a layer (2) containing a hydrolysis condensate of the coupling agent and a component derived from polyimide.
Layer (2) may be formed on the polyimide film side of layer (A).
If layer (A) has layer (1) and layer (2), the layers may be formed in the order of layer (2) and layer (1) from the polyimide film (surface) side.
Furthermore, if the polyimide film of the present invention has layer (A) on both sides (or both sides), layer (2) may be formed on both sides (or both sides) of the polyimide film, or on one side (or one side).

The thickness of layer (A) is not particularly limited, but from the viewpoint of adhesion between the polyimide film and the metal layer of the present invention, it may be, for example, 50 nm or more (e.g., 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more), preferably 100 nm or more (e.g., 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, 200 nm or more).

The thickness (upper limit) of layer (A) is not particularly limited, but may be, for example, 500 nm or less (e.g., 480 nm or less, 450 nm or less, 430 nm or less), preferably 400 nm or less (e.g., 390 nm or less, 380 nm or less, 370 nm or less, 360 nm or less, 350 nm or less, 330 nm or less, 300 nm or less, 280 nm or less, 250 nm or less, 230 nm or less, 200 nm or less).

The method for measuring the thickness of layer (A) may be a known method and is not particularly limited; for example, it may be measured by the method for measuring the thickness of layer (1) or layer (2) described in the embodiments below.

The thickness of layer (1) is not particularly limited, but from the viewpoint of adhesion between the polyimide film and the metal layer of the present invention, it may be, for example, 5 nm or more (e.g., 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more), preferably 10 nm or more (e.g., 11 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, 15 nm or more).

The thickness (upper limit) of layer (1) is not particularly limited, but may be, for example, 150 nm or less (e.g., 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less), preferably 100 nm or less (e.g., 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less).

The method for measuring the thickness of layer (1) may be a known method and is not particularly limited; for example, it may be measured by the method described in the examples below.

The thickness of layer (2) is not particularly limited, but may be, for example, 50 nm or more (e.g., 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more), preferably 100 nm or more (e.g., 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more).

The thickness (upper limit) of layer (2) is not particularly limited, but may be, for example, 350 nm or less (e.g., 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less), preferably 300 nm or less (e.g., 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less), and more preferably 250 nm or less (e.g., 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less).

The method for measuring the thickness of layer (2) may be a known method and is not particularly limited; for example, it may be measured by the method described in the examples below.

(Polyimide film to which the coupling agent will be applied)
The following describes the polyimide film on which the coupling agent is applied to the surface (i.e., the film to which the coupling agent is applied).

The thickness of the polyimide film can be appropriately selected depending on the application, but from the viewpoint of suitably using it as a base film for laminated films, for example, it may be 1 μm or more (e.g., 2 μm or more), preferably 3 μm or more (e.g., 4 μm or more), and more preferably 5 μm or more (e.g., 6 μm or more), and may also be 7 μm or more (e.g., 8 μm or more, 10 μm or more, 12 μm or more, 15 μm or more, 18 μm or more, 20 μm or more, 22 μm or more, 25 μm or more, 28 μm or more, 30 μm or more, 32 μm or more, 35 μm or more).

The thickness (upper limit) of such polyimide film is not particularly limited, but may be, for example, 300 μm or less (e.g., 250 μm or less), preferably 200 μm or less (e.g., 150 μm or less), and more preferably 100 μm or less (e.g., 80 μm or less), or 70 μm or less (e.g., 60 μm or less, 55 μm or less, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less).

Specific examples of polyimide film thicknesses include, for instance, 1 to 200 μm, preferably 3 to 100 μm, and more preferably 5 to 80 μm.

A polyimide film may be a laminate of multiple polyimide films, but it is usually a single polyimide film.

The polyimide film may be an unstretched film or a stretched film (uniaxial or biaxially oriented film). In such a stretched film, the stretching conditions (e.g., stretching ratio in the TD and/or MD directions) may be those described later.

In this invention, sufficient adhesion and other properties can be efficiently achieved even in stretched films.

Composition, manufacturing method, etc. Polyimide films (or polyimides or polyamic acids that constitute polyimide films) typically contain aromatic diamine components and aromatic acid anhydride components as raw materials (these are the polymerization components).

Aromatic diamine components include, for example, paraphenylenediamine, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, metaphenylenediamine, diaminodiphenylpropane (e.g., 4,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, etc.), diamino Diphenylmethane (e.g., 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, etc.), benzidine, diaminodiphenyl sulfide (e.g., 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, etc.), diaminodiphenyl sulfone (e.g., 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, etc.), 2 ,6-diaminopyridine, bis-(4-aminophenyl)diethylsilane, 3,3'-dichlorobenzidine, bis-(4-aminophenyl)ethylphosphinoxide, bis-(4-aminophenyl)phenylphosphinoxide, bis-(4-aminophenyl)-N-phenylamine, bis-(4-aminophenyl)-N-methylamine, 1,5-diaminonaphthalene, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,4'-dimethyl-3',4-diaminobiphenyl, 3,3'-dimethoxybenzidine, 2,4-bi Examples include p-β-amino-t-butylphenyl ether, bis(p-β-amino-t-butylphenyl) ether, p-bis(2-methyl-4-aminopentyl)benzene, p-bis-(1,1-dimethyl-5-aminopentyl)benzene, m-xylylenediamine, p-xylylenediamine, 2,5-diamino-1,3,4-oxadiazole, 2,2-bis(4-aminophenyl)hexafluoropropane, N-(3-aminophenyl)-4-aminobenzamide, and 4-aminophenyl-3-aminobenzoate. These can be used individually or in combination of two or more.

The aromatic diamine component may preferably contain at least one selected from paraphenylenediamine and 4,4'-diaminodiphenyl ether, and more preferably, both paraphenylenediamine and 4,4'-diaminodiphenyl ether, from the viewpoint of efficiently achieving adhesion to the metal layer, heat resistance, dimensional stability, etc.

When the aromatic diamine component includes paraphenylenediamine and 4,4'-diaminodiphenyl ether, the molar ratio of paraphenylenediamine to 4,4'-diaminodiphenyl ether may be, for example, 60/40 to 1/99 (e.g., 55/45 to 5/95), preferably 50/50 to 10/90 (e.g., 45/55 to 15/85).

Examples of aromatic acid anhydride components (aromatic tetracarboxylic acid components) include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid anhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenedicarboxylic acid dianhydride, and 2,2-bis(3,4-dicarboxyphenyl) ether. Pyridine-2,3,5,6-tetracarboxylic acid dianhydride, naphthalenetetracarboxylic acid dianhydride (e.g., 1,2,4,5-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-decahydronaphthalenetetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,5,6-hexahydronaphthalenetetracarboxylic acid dianhydride, 2,6-dichloro-1,4,5,8-naphthalenetetracarboxylic acid dianhydride) Dianhydride, 2,7-dichloro-1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-tetrachloro-1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 1,8,9,10-phenanthrenetetracarboxylic acid dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane Examples include dianhydrides, bis(2,3-dicarboxyphenyl)methane dianhydrides, bis(3,4-dicarboxyphenyl)methane dianhydrides, bis(3,4-dicarboxyphenyl)sulfone dianhydrides, benzene-1,2,3,4-tetracarboxylic acid dianhydrides, 3,4,3',4'-benzophenonetetracarboxylic acid dianhydrides, etc. Preferably, pyromellitic acid dianhydrides, 3,3',4,4'-biphenyltetracarboxylic acid dianhydrides, etc. These can be used individually or in combination of two or more.

The aromatic acid anhydride component, in combination with the aromatic diamine component as described above, preferably contains at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, from the viewpoint of efficiently achieving adhesion to the metal layer, heat resistance, dimensional stability, etc., and more preferably contains both pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride.

When the aromatic acid anhydride component includes at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, the proportion of at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride to the total aromatic acid anhydride component (or total acid anhydride component) may be selected from a range of 30 mol% or more (for example, 40 to 100 mol%), for example, 50 mol% or more (for example, 60 mol% or more), preferably 70 mol% or more (for example, 80 mol% or more), and more preferably 90 mol% or more (for example, 95 mol% or more, 97 mol% or more, 98 mol% or more, 99 mol% or more, 100 mol%).

When the aromatic acid anhydride component includes pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, the molar ratio of pyromellitic dianhydride to 3,3',4,4'-biphenyltetracarboxylic acid dianhydride may be, for example, 95/5 to 40/60 (e.g., 90/10 to 45/55), preferably around 85/15 to 50/50 (e.g., 80/20 to 55/45).

The raw material components of the polyimide film (polymerization components, diamine components, and acid anhydride components) may also include other polymerization components (e.g., other acid anhydride components, other diamine components) other than the above-mentioned aromatic acid anhydride components and aromatic diamine components, to the extent that they do not hinder the effects of the present invention.
Other diamine components (non-aromatic diamine components) include, for example, diaminoadamantanes (e.g., 1,3-diaminoadamantan, 3,3'-diamino-1,1'-diaminoadamantan, 3,3'-diaminomethyl-1,1'-diadamantane, etc.) and diaminoalkanes (e.g., hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 3-methylheptamethylenediamine, 4,4'-dimethylheptamethylenediamine, 2,11-diaminododecane, 2,2-dimethylp Examples include propyldiamine, 3-methoxyhexaethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, etc.), 1,2-bis(3-aminopropoxy)ethane, 2,5-diamino-1,3,4-oxadiazole, 2,2-bis(4-aminophenyl)hexafluoropropane, N-(3-aminophenyl)-4-aminobenzamide, 4-aminophenyl-3-aminobenzoate, etc. These can be used individually or in combination of two or more.

Furthermore, if the polymerization component contains other polymerization components (such as other diamine components), the proportion of the other polymerization components to the total polymerization component may be small, for example, 20 mol% or less (for example, 15 mol% or less, 10 mol% or less, 5 mol% or less, 3 mol% or less, or 1 mol% or less).

Polyimide films may contain components other than polyimide (the resin component). For example, polyimide films may contain inorganic particles from the viewpoint of handling (ease of handling), etc. The other components may be present in one or more types.

When inorganic particles are present, they are typically dispersed within the polyimide film.
Examples of inorganic particles include oxides {e.g., _SiO₂ (silica), _TiO₂ (titanium(IV) oxide), etc.}, inorganic salts {e.g., phosphate _{(hydrogen) salts such as CaHPO₄ (calcium hydrogen phosphate), CaPO₄ (calcium phosphate), Ca₂P₂O₃ ( dicalcium phosphate} ), _etc. , and carbonates such as _CaCO₃ (calcium carbonate)}.
Inorganic particles may be used individually or in combination of two or more types.

The average particle size of the inorganic particles used for dispersion may be, for example, 0.1 to 3.5 μm (for example, 0.2 to 3 μm), preferably 0.3 to 2.5 μm, etc.
Furthermore, the method for measuring the average particle size of inorganic particles is not particularly limited, and known methods may be used.

Regarding the particle size distribution of inorganic particles (inorganic particles used for dispersion), a narrow distribution is preferable; that is, a high proportion of inorganic particles of similar size is desirable. Specifically, it is preferable that inorganic particles of a specific particle size (e.g., 0.5 to 2.5 μm, 1 to 3.5 μm, etc.) account for 80% or more (e.g., 80 to 100% by volume) of the total inorganic particles.

When inorganic particles are included, the proportion of inorganic particles in the polyimide film may be, for example, 0.01% by mass or more (e.g., 0.02% by mass or more), preferably 0.03% by mass or more (e.g., 0.04% by mass or more), and more preferably 0.05% by mass or more.

The upper limit of the inorganic particle ratio in the polyimide film may be selected from a range of approximately 5% by mass or less (for example, 3% by mass or less, 2% by mass or less, 1.5% by mass or less), preferably 1% by mass or less (for example, 0.9% by mass or less), preferably 0.8% by mass or less (for example, 0.7% by mass or less), and more preferably 0.6% by mass or less (for example, 0.55% by mass or less, 0.5% by mass or less, 0.45% by mass or less, 0.4% by mass or less, 0.3% by mass or less), etc.

The polyimide film may be in a laminated state, and in particular, it may be in a wound state, that is, in the form of a roll.
The width of the polyimide film (for example, a roll of polyimide film) is not particularly limited, but may be, for example, 30 mm or more, 45 mm or more, 50 mm or more, 75 mm or more, 100 mm or more, 150 mm or more, 200 mm or more, 300 mm or more, 500 mm or more, etc., or it may be 3000 mm or less, 2000 mm or less, 1000 mm or less, etc.
The polyimide film may have a relatively large size. The length of such a polyimide film (for example, a roll of polyimide film) may be, for example, 1 m or more (for example, 5 m or more), 10 m or more (for example, 20 m or more), preferably 30 m or more (for example, 40 m or more), and more preferably 50 m or more (for example, 100 m or more), and may also be 200 m or more, 300 m or more, 500 m or more, 1000 m or more, 2000 m or more, 3000 m or more, 5000 m or more, and so on.

The polyimide film may be surface-treated (e.g., by electrolytic treatment such as corona treatment or plasma treatment, or by blast treatment). Such surface treatment may be applied to one side or both sides.
Furthermore, depending on the surface treatment (such as plasma treatment) and its degree, it may be a factor that reduces adhesion (for example, the values embodied in T2 or T2/T1 mentioned above) when exposed to conditions such as high temperatures.
On the other hand, the present invention can achieve sufficient adhesion without surface treatment.
Therefore, while the polyimide film may be plasma-treated, it may also be preferable to select a film that is not plasma-treated, or one that is treated to a minimal degree.

The method for producing polyimide films is not particularly limited, but representative methods are described below.
To obtain a polyimide film, a polyamic acid solution (hereinafter also referred to as a polyamic acid solution) is first obtained by polymerizing the polymerization components (components including aromatic diamine components and aromatic acid anhydride components) in an organic solvent.

Specific examples of organic solvents used in the formation of polyamic acid solutions include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N,N-dimethylformamide and N,N-diethylformamide; acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenolic solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenols, and catechol; and aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone. These can be used individually or in combination of two or more. Furthermore, they may be used in combination with aromatic hydrocarbons such as xylene and toluene.

The polymerization method for the polyamic acid solution may be any known method, for example,
(1) A method of polymerization in which the entire amount of the diamine component (aromatic diamine component) is first placed in the solvent, and then the acid anhydride component (aromatic acid anhydride component) is added in an amount equivalent to the total amount of the diamine component (aromatic diamine component),
(2) A method in which the entire amount of the acid anhydride component (aromatic acid anhydride component) is first placed in the solvent, and then the diamine component (aromatic diamine component) is added in an equivalent amount to the acid anhydride component (aromatic acid anhydride component) to polymerize.
(3) A method of polymerization in which one diamine component (aromatic diamine component) is placed in a solvent, one acid anhydride component (aromatic acid anhydride component) is mixed for the time required for the reaction in a ratio of 95 to 105 mol% relative to the reaction components, the other aromatic diamine component is added, and then the other acid anhydride component (aromatic acid anhydride component) is added so that the total diamine component (aromatic diamine component) and the total acid anhydride component (aromatic acid anhydride component) are approximately equivalent in amount.
(4) A method of polymerization in which one acid anhydride component (aromatic acid anhydride component) is placed in a solvent, one diamine component (aromatic diamine component) is mixed for the time required for the reaction in a ratio of 95 to 105 mol% relative to the reaction components, the other acid anhydride component (aromatic acid anhydride component) is added, and then the other diamine component (aromatic diamine component) is added so that the total diamine component (aromatic diamine component) and the total acid anhydride component (aromatic acid anhydride component) are approximately equivalent in amount.
(5) A polyamic acid solution (A) is prepared by reacting one diamine component (aromatic diamine component) and an acid anhydride component (aromatic acid anhydride component) in a solvent such that one is in excess, and a polyamic acid solution (B) is prepared by reacting the other diamine component (aromatic diamine component) and an acid anhydride component (aromatic acid anhydride component) in a separate solvent such that one is in excess. The obtained polyamic acid solutions (A) and (B) are then mixed to complete the polymerization. When preparing polyamic acid solution (A), if there is an excess of diamine component (aromatic diamine component), polyamic acid solution (B) may contain an excess of acid anhydride component (aromatic acid anhydride component). Conversely, if there is an excess of acid anhydride component (aromatic acid anhydride component) in polyamic acid solution (A), polyamic acid solution (B) may contain an excess of diamine component (aromatic diamine component). By mixing polyamic acid solutions (A) and (B), the total amount of diamine component (aromatic diamine component) and total amount of acid anhydride component (aromatic acid anhydride component) used in these reactions may be adjusted to be approximately equivalent.
The polymerization method is not limited to these methods, and other known methods may also be used.

The acid anhydride component (aromatic acid anhydride component) and the diamine component (aromatic diamine component) constituting the polyamic acid are polymerized in a ratio where the number of moles of each is approximately equal. However, one component may be added in excess of the other, within a range of 10 mol%, preferably 5 mol%.

The polymerization reaction is preferably carried out in an organic solvent with stirring. The polymerization temperature is not particularly limited, but is usually carried out at an internal temperature of 0 to 80°C in the reaction solution. The polymerization time is not particularly limited, but is preferably carried out continuously for 10 minutes to 30 hours. The polymerization reaction may be divided into stages or the temperature may be raised or lowered as needed. There are no particular restrictions on the order in which the two reactants are added, but it is preferable to add the aromatic acid anhydride to the solution of the aromatic diamine component. Vacuum degassing during the polymerization reaction is an effective method for producing a high-quality organic solvent solution of polyamic acid. Furthermore, the polymerization reaction may be controlled by adding a small amount of end-capping agent to the aromatic diamines before the polymerization reaction. The end-capping agent is not particularly limited, and known agents can be used.

The resulting polyamic acid solution may contain a solid content of typically 5 to 40% by mass, preferably 10 to 30% by mass. Its viscosity is not particularly limited, but the measurement using a Brookfield viscometer is typically 10 to 2000 Pa·s, and preferably 100 to 1000 Pa·s for stable liquid delivery. Furthermore, the polyamic acid in the organic solvent solution may be partially imidized.

When obtaining a polyimide film containing inorganic particles, the inorganic particles may be included in the polyamic acid solution. To obtain a polyamic acid solution containing inorganic particles, the inorganic particles may be added to a pre-polymerized polyamic acid solution, or the polyamic acid solution may be polymerized in the presence of the inorganic particles.

It is preferable to use inorganic particles as a slurry (inorganic particle slurry) dispersed in a solvent (for example, polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone) because this prevents aggregation.

The method for producing the inorganic particle slurry is not particularly limited and may follow conventionally known methods. Examples of methods for producing the inorganic particle slurry include mixing inorganic particles with a solvent using a mixer. It is preferable to use a mixer with high shear force, such as a high-speed disperser, homomixer, ball mill, coreless mixer, or agitated disperser. Furthermore, wet grinding may be performed to refine the average particle size. For wet grinding, for example, a bead mill or sand mill can be used.

As the inorganic particle slurry, a commercially available product in which inorganic particles are pre-dispersed in a solvent may be used. Furthermore, the inorganic particle slurry may contain other organic solvents or compounding agents as needed.

The concentration of inorganic particles in the inorganic particle slurry is not particularly limited, but is, for example, 1 to 80% by mass, preferably 1 to 60% by mass, and more preferably 1 to 40% by mass.

Furthermore, filtering the inorganic particle slurry through a filter having a predetermined pore size (for example, a cut filter with a pore size of 15 μm or less, preferably 13 μm or less, more preferably 11 μm or less, even more preferably 5 μm or less, and particularly preferably 3 μm or less) is preferable from the viewpoint of suppressing aggregation of inorganic particles and removing inorganic particles of a predetermined particle size (for example, inorganic particles of 15 μm or larger) from the polyimide film.

The material of the filter is not particularly limited and may include, for example, polymer materials (e.g., polyethylene, polypropylene, polytetrafluoroethylene, etc.) or metals (e.g., stainless steel, etc.).

The amount of inorganic particles added should be appropriately selected to correspond to the desired content in the polyimide film (for example, so that when the polyimide is formed, the amount is 0.03 to 0.8 parts by mass per 100 parts by mass of polyimide).

Next, a method for manufacturing polyimide films will be described. Polyimide films can be produced (manufactured) by, for example, a step (1) of cyclizing a polyamic acid solution to obtain a gel film (converting polyamic acid or a polyamic acid solution into a gel film), and a step (2) of drying (and desolvation) the obtained gel film and then heat-treating it. Note that drying and imidization proceed during the drying and heat treatment.

In step (1), the method for cyclizing the polyamic acid solution is not particularly limited, but specifically, examples include (i) a method of casting the polyamic acid solution into a film and obtaining a gel film by thermal dehydration and cyclization (thermal cyclization method), or (ii) a method of mixing a catalyst (cyclization catalyst) and a dehydrating agent (converter) with the polyamic acid solution, chemically decyclizing it to produce a gel film, and then obtaining the gel film by heating (chemical cyclization method). The latter method (chemical cyclization method) is particularly preferred.

The chemical cyclization method (and moreover, the selection of the polymerization components as described above while simultaneously selecting the chemical cyclization method) surprisingly appears to efficiently yield the physical properties (characteristics) required for the polyimide film of the present invention. Furthermore, the chemical cyclization method is also suitable from the viewpoint of mass production.

Furthermore, the above polyamic acid solution may contain a gelation retarder, etc. The gelation retarder is not particularly limited, and acetylacetone, for example, can be used.

Examples of cyclization catalysts include amines, such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), and heterocyclic tertiary amines (e.g., isoquinoline, pyridine, β-picoline, etc.). These may be used individually or in combination of two or more. Of these, heterocyclic tertiary amines such as β-picoline are preferred.

Examples of dehydrating agents include acid anhydrides, such as aliphatic carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, butyric anhydride, etc.) and aromatic carboxylic acid anhydrides (e.g., benzoic anhydride, etc.). These may be used individually or in combination of two or more. Among these, acetic anhydride and/or benzoic anhydride are preferred, with acetic anhydride being particularly preferred.

The amounts of cyclization catalyst and dehydrating agent used are not particularly limited, but for example, they may be 1 mole or more (for example, about 1.5 to 10 moles) per mole of amide groups (or carboxyl groups) of polyamic acid (or polyamic acid).

Gel films can typically be obtained by casting (coating) a polyamic acid solution (particularly a polyamic acid solution mixed with a cyclization catalyst and a converter) onto a support, followed by partial drying and curing (imidization).

More specifically, the polyamic acid solution may be cast onto a support using a slit nozzle to form a film, heated by heat from the support, hot air, or an electric heater to induce a ring-closing reaction, and then dried to form a gel film. The gel film is then peeled off the support.

Here, the gel film needs to possess self-supporting properties for peeling, but typically, gel films obtained by chemical cyclization and those obtained by thermal cyclization differ significantly in their characteristics. Specifically, chemical cyclization allows for gelation (conversion) using a catalyst, resulting in a self-supporting gel film (flexible or wet gel film) containing a large amount of solvent. In contrast, thermal cyclization requires significant heat treatment for gelation (to impart self-supporting properties), resulting in a relatively hard gel film (with less residual solvent).

The support is not particularly limited, but examples include a rotating drum made of metal (e.g., stainless steel), an endless belt, etc. The temperature of the support is not particularly limited, and may be, for example, 30 to 200°C, preferably 40 to 150°C, and more preferably 50 to 120°C.
The temperature of the support can be controlled by (i) a liquid or gaseous heat transfer medium, (ii) radiant heat from an electric heater, etc.

In step (2), the gel film is dried (solvent removed) and then heat-treated. Typically, step (2) may include a step in which the gel film is held at both ends in the width direction and passed through a heating furnace (such as a tenter heating furnace) to dry it, followed by heat treatment.

Specifically, the gel film peeled from the support is not particularly limited, but it may typically be stretched in the transport direction while its travel speed is regulated by a rotating roll. The thickness of the polyimide film may be adjusted according to the travel speed.

Stretching in the conveying direction may be carried out at a predetermined temperature (for example, a temperature of 140°C or lower). The stretching ratio (MDX) is typically 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times (for example, 1.15 to 1.4 times).

During drying, the drying temperature may be, for example, 210°C or higher (e.g., 213 to 500°C), preferably 215°C or higher (e.g., 218 to 400°C), and more preferably 220°C or higher (e.g., 220 to 300°C).

Furthermore, drying may be carried out while suppressing uneven drying (variation) in the film width direction. For example, the uneven drying temperature in the film width direction may be less than 25°C (e.g., 0 to 24°C), preferably 22°C or less (e.g., 1 to 21°C), more preferably 20°C or less (e.g., 2 to 19°C), and particularly 18°C or less (e.g., 3 to 18°C).

Furthermore, temperature unevenness in drying can be measured by taking multiple points at predetermined intervals (e.g., 200 mm) along the film width direction and determining the difference (width) between the maximum and minimum measured drying temperatures.

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

As mentioned above, the L value can be efficiently adjusted by adjusting or setting the heat treatment temperature (for example, setting the maximum heating temperature) (and furthermore, by combining it with other conditions).

Furthermore, after drying, the material may be stretched in the width direction. This stretching in the width direction may be performed in conjunction with heat treatment.

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

Furthermore, the physical properties (characteristics) required for polyimide films (and more specifically, the polyimide films of the present invention) can sometimes be efficiently adjusted through stretching and its conditions (and even combinations with other conditions).

A polyimide film is obtained in this manner. The obtained polyimide film may be further subjected to annealing.

The annealing method is not particularly limited, and known methods may be used.
The temperature of the annealing process is not particularly limited, but may be, for example, 200 to 500°C, preferably 200 to 370°C, and more preferably 210 to 350°C. Specifically, the annealing process may be carried out by running the film through a furnace heated to the above temperature range under low tension. The film tension during running may be, for example, 10 to 50 N/m, more preferably 20 to 30 N/m.

Plasma treatment may be performed on the polyimide film (or its surface) obtained as described above. Plasma treatment may be performed on both sides of the polyimide film or on one side.
Furthermore, as mentioned above, when considering adhesion when exposed to conditions such as high temperatures, it is sometimes preferable not to perform plasma treatment on polyimide films, or to perform plasma treatment to a small extent.

The plasma treatment method is not particularly limited, and known methods may be used.
The processing gas for plasma treatment is not particularly limited, but examples include inert gases (e.g., He, Ar, Kr, Xe, Ne, Rn, _N2, etc.), _O2 , _H2O , air, _CO2, etc. The processing gas may be used individually or in combination of two or more types.

The processing pressure for plasma treatment is not particularly limited, but may be, for example, 0.1 Pa to 1330 kPa.
The processing intensity (E value) of the plasma treatment is not particularly limited, but may be, for example, ⁵⁰ W・min/m² or more, 75 W・min/ ^m² or more, or 2000 W・min/ ^m² or less, 1800 W・min/ ^m² or less.
The processing time for plasma treatment is not particularly limited, but may be, for example, 1 second to 10 minutes.

The physical properties (characteristics) of the polyimide film to be coated with the coupling agent (e.g., glass transition temperature, coefficient of linear expansion, etc.) may correspond to the physical properties (characteristics) of the polyimide film of the present invention (hereinafter sometimes simply referred to as "polyimide film 1").
In other words, the physical properties (characteristics) of the polyimide film to be coated with the coupling agent (e.g., glass transition temperature, coefficient of linear expansion, etc.) may be the same as the physical properties (characteristics) of polyimide film 1 described later.

(Method for producing the polyimide film of the present invention)
The method for producing the polyimide film (polyimide film 1) of the present invention will be described below.

The method for producing the polyimide film 1 includes the step of applying a coupling agent-containing solution to one or both sides of the polyimide film, and then drying it.
As the polyimide film to which the coupling agent-containing solution is applied, a polyimide film may be used instead of a polyamic acid gel film.

The coupling agent-containing solution may typically contain the coupling agent and the solvent, and may optionally contain other components {for example, surface treatment agents other than the coupling agent {for example, silane compounds [e.g., mono- to tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, preferably mono- to tetraC1-4 alkoxysilanes]}}.

A coupling agent-containing solution can be prepared, for example, by mixing the coupling agent and a solvent (and other components as needed).

The solvent is not particularly limited and includes, for example, water, alcohols (e.g., methanol, ethanol, etc.), esters (e.g., organic acid esters such as ethyl lactate and ethyl acetate), and from the viewpoint of the reactivity of the coupling agent (e.g., the reactivity between the reactive functional group and the polyimide), esters, alcohols, etc. may be preferred. One or more solvents may be used.
Furthermore, it is preferable to use a solvent different from the one used to form the polyamic acid solution (for example, a solvent other than N,N-dimethylacetamide) as the solvent.

The content of the coupling agent in the coupling agent-containing solution may be, for example, 0.05% by mass or more (e.g., 0.1% by mass or more), preferably 0.5% by mass or more (e.g., 1% by mass or more), from the viewpoint of the reactivity of the coupling agent and the formation of layer (A) on the polyimide film surface, and may also be, for example, 10% by mass or less (e.g., 7% by mass or less), preferably 5% by mass or less (e.g., 3% by mass or less).

When the solvent contains an organic acid ester (e.g., ethyl lactate), the proportion of the organic acid ester (e.g., ethyl lactate) to the total solvent may be, for example, 30 parts by mass or more (e.g., 40 parts by mass or more), preferably 50 parts by mass or more (e.g., 60 parts by mass or more, 70 parts by mass or more), and more preferably 80 parts by mass or more (e.g., 90 parts by mass or more), from the viewpoint of the reactivity of the coupling agent (e.g., the reactivity between the reactive functional group and the polyimide).

When the solvent contains an organic acid ester (e.g., ethyl lactate), the proportion (upper limit) of the organic acid ester (e.g., ethyl lactate) to the total solvent is not particularly limited, but may be, for example, 99 parts by mass or less (e.g., 98 parts by mass or less, 97 parts by mass or less, 96 parts by mass or less, 95 parts by mass or less).

During drying, the drying temperature may be, for example, 100°C or higher (e.g., 110°C or higher, 120°C or higher), preferably 130°C or higher (e.g., 140°C or higher), from the viewpoint of forming layer (A) on the surface of the polyimide film and ensuring good adhesion between the polyimide film and the metal layer of the present invention. It may also be, for example, 280°C or lower (e.g., 250°C or lower), 220°C or lower (e.g., 210°C or lower), preferably 200°C or lower (e.g., 190°C or lower).

During drying, the drying time depends on the drying temperature and other factors, but from the viewpoint of forming layer (A) on the surface of the polyimide film and ensuring good adhesion between the polyimide film and the metal layer of the present invention, it may be, for example, 20 seconds or more (e.g., 30 seconds or more), preferably 40 seconds or more (e.g., 50 seconds or more, 60 seconds or more), or for example, 150 seconds or less (e.g., 140 seconds or less, 130 seconds or less), preferably 120 seconds or less (e.g., 110 seconds or less, 100 seconds or less).

(Polyimide film of the present invention)
The polyimide film of the present invention (polyimide film 1) typically possesses certain physical properties.

Polyimide film 1 often satisfies at least one of the following physical properties, and typically, it may satisfy at least adhesion (peel strength to the metal layer) [in particular, adhesion and one or more of the other physical properties]. The following physical properties can be efficiently satisfied, for example, by the composition of the polyimide (of the polyimide film to be coated with the coupling agent), the thickness of the film, the manufacturing conditions of the film, and combinations of these (selection and adjustment).
Furthermore, polyimide film 1 is more likely to maintain the physical properties (characteristics) (e.g., glass transition temperature, coefficient of thermal expansion, etc.) of the polyimide film to which the coupling agent is applied.

The polyimide film 1 can achieve sufficient adhesion to the metal layer. Examples of such polyimide films 1 include those in which, when the metal layer is directly laminated (laminated without an adhesive layer), the peel strength (adhesion, peel strength, 90° peel strength) (T1) between the metal layer and the polyimide film 1 is greater than 0.3 kN/m (e.g., 0.35 kN/m or more), preferably 0.4 kN/m or more (e.g., 0.45 kN/m or more), and more preferably 0.5 kN/m or more.

The upper limit of T1 is not particularly limited, but it may be, for example, 5 kN/m or less, 4 kN/m or less, 3 kN/m or less, 2.5 kN/m or less, 2 kN/m or less, 1.5 kN/m or less, 1.2 kN/m or less, 1 kN/m or less, etc.

Such adhesion can be maintained at a relatively high level even when subjected to conditions such as high temperatures (e.g., harsh conditions). Examples of such polyimide films 1 include those where, when the peel strength (adhesion, tear strength) between the metal layer and the polyimide film 1 is T1 (laminated directly on the polyimide film 1 without an adhesive layer), and T2 is the peel strength (adhesion, tear strength) between the metal layer and the polyimide film 1 after heating at 150°C for 168 hours, T2/T1 is 0.3 or higher (e.g., 0.4 or higher), preferably 0.5 or higher (e.g., greater than 0.5, 0.55 or higher), more preferably 0.6 or higher (e.g., 0.65 or higher), particularly 0.7 or higher (e.g., 0.72 or higher), and particularly preferably 0.75 or higher (e.g., greater than 0.75, 0.78 or higher, 0.8 or higher).

Note that the upper limit of T2/T1 may be 1, or less than 1 (for example, 0.99 or less, 0
(It may also be 98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, or 0.9 or less.)

Furthermore, the value of T2 may be, for example, greater than 0.2 kN/m (e.g., 0.25 kN/m or more), preferably 0.3 kN/m or more (e.g., 0.35 kN/m or more), and even more preferably 0.4 kN/m or more.

The upper limit of T2 is not particularly limited, but for example, it may be 5 kN/m or less, 4 kN/m or less, 3 kN/m or less, 2.5 kN/m or less, 2 kN/m or less, 1.5 kN/m or less, 1.2 kN/m or less, 1 kN/m or less, 0.9 kN/m or less, 0.8 kN/m or less, etc.

Furthermore, in the measurement of T1 (and even T2), the metal layer is not particularly limited, but may be a specific metal layer {for example, one corresponding to the embodiment described later, i.e., a copper layer with a thickness of 8.5 μm [for example, a copper layer with a thickness of 8.5 μm (for example, a layer formed by plating) laminated via a 25 nm thick nickel/chromium alloy (nickel/chromium = 80/20) layer (for example, a layer formed by sputtering) and a 100 nm thick copper layer (for example, a layer formed by sputtering) formed on this layer]}.

The measurement method for T1 (and even T2) may be, for example, one that conforms to Method A in the test method for the peel strength of copper foil described in JIS C 6471 (for example, a tensile angle of 90° and a tensile speed of 50 mm/min).
More specifically, T1 (and even T2) may be measured by the method described in the examples below.

In the polyimide film 1, the coefficient of linear expansion αMD in the MD direction (direction perpendicular to the machine transport direction, longitudinal direction, length direction, longitudinal direction, and width direction (TD direction)) may be selected from a range of approximately 50 ppm/K or less (for example, 40 ppm/K or less, 35 ppm/K or less, 30 ppm/K or less, 25 ppm/K or less). From the viewpoint of dimensional stability (for example, dimensional stability when laminating metal layers such as copper), it may be, for example, approximately 20 ppm/K or less (for example, 18 ppm/K or less), preferably 16 ppm/K or less (for example, 15 ppm/K or less), and even more preferably approximately 14 ppm/K or less (for example, 13 ppm/K or less), or 12 ppm/K or less (for example, 11 ppm/K or less, 10 ppm/K or less), etc.

The lower limit of αMD may be 0 ppm/K, greater than 0 ppm/K [for example, from the viewpoint of dimensional stability (e.g., dimensional stability when laminating metal layers such as copper), 1 ppm/K or more (e.g., 1.5 ppm/K or more), preferably 2 ppm/K or more (e.g., 2.5 ppm/K or more), and more preferably 3 ppm/K or more (e.g., 3.5 ppm/K or more)], or 4 ppm/K or more (e.g., 4.5 ppm/K or more, 5 ppm/K or more, 5.5 ppm/K or more, 6 ppm/K or more, 6.5 ppm/K or more, 7 ppm/K or more].

Specific αMD values may include, for example, 0 to 30 ppm/K, and from the viewpoint of dimensional stability (e.g., dimensional stability when laminating metal layers such as copper), preferably 1 to 20 ppm/K (e.g., 2 to 18 ppm/K), and more preferably 3 to 17 ppm/K (e.g., 4 to 16 ppm/K, 5 to 15 ppm/K, 6 to 14 ppm/K, 6 to 12 ppm/K, 6 to 10 ppm/K), etc.

In the polyimide film 1, the coefficient of linear expansion αTD in the TD direction (width direction, transverse direction, perpendicular direction, and direction perpendicular to the longitudinal direction (MD)) may be selected from a range of approximately 50 ppm/K or less (for example, 40 ppm/K or less, 35 ppm/K or less, 30 ppm/K or less, 25 ppm/K or less), and from the viewpoint of dimensional stability (for example, dimensional stability when laminating metal layers such as copper), it may be set to, for example, 20 ppm/K or less. (For example, 18 ppm/K or less), preferably 16 ppm/K or less (for example, 15 ppm/K or less), and even more preferably around 14 ppm/K or less (for example, 13 ppm/K or less). It may also be 12 ppm/K or less (for example, 11 ppm/K or less, 10 ppm/K or less, 9 ppm/K or less, 8 ppm/K or less, 7 ppm/K or less, 6 ppm/K or less, 5 ppm/K or less), etc.

The lower limit of αTD may be, for example, -10 ppm/K or higher (e.g., -9 ppm/K or higher, -8 ppm/K or higher, -7 ppm/K or higher, -6 ppm/K or higher), -5 ppm/K or higher (e.g., -4 ppm/K or higher, -3 ppm/K or higher, -2 ppm/K or higher, -1 ppm/K or higher), 0 ppm/K or higher, or greater than 0 ppm/K [e.g., 1 ppm/K or higher (e.g., 1.5 ppm/K or higher)], and preferably 2 ppm/K or higher.

Specific αTD values may include, for example, -10 to 30 ppm/K, preferably -10 to 20 ppm/K (e.g., -8 to 18 ppm/K), and more preferably -5 to 17 ppm/K (e.g., -5 to 15 ppm/K, -5 to 10 ppm/K, -5 to 8 ppm/K), from the viewpoint of dimensional stability (e.g., dimensional stability when laminating metal layers such as copper).

In the polyimide film 1, the value of (|αMD| + |αTD|)/2 may be selected from a range of approximately 50 ppm/K or less (for example, 40 ppm/K or less, 35 ppm/K or less, 30 ppm/K or less, 25 ppm/K or less). From the viewpoint of dimensional stability (for example, dimensional stability when laminating a metal layer such as copper), it may be, for example, approximately 20 ppm/K or less (for example, 18 ppm/K or less), preferably 16 ppm/K or less (for example, 15 ppm/K or less), and even more preferably approximately 14 ppm/K or less (for example, 13 ppm/K or less), or 12 ppm/K or less (for example, 11 ppm/K or less, 10 ppm/K or less), etc.

The lower limit of (|αMD| + |αTD|)/2 may be 0 ppm/K, greater than 0 ppm/K [for example, from the viewpoint of dimensional stability (e.g., dimensional stability when laminating metal layers such as copper), 1 ppm/K or more (e.g., 1.5 ppm/K or more), preferably 2 ppm/K or more (e.g., 2.5 ppm/K or more), and more preferably 3 ppm/K or more (e.g., 3.5 ppm/K or more)], and may also be 4 ppm/K or more (e.g., 4.5 ppm/K or more, 5 ppm/K or more).

The specific value of (|αMD| + |αTD|)/2 may be, for example, 0 to 30 ppm/K. From the viewpoint of dimensional stability (e.g., dimensional stability when laminating metal layers such as copper), it may preferably be 1 to 20 ppm/K (e.g., 2 to 18 ppm/K), and more preferably 3 to 17 ppm/K (e.g., 4 to 16 ppm/K, 4 to 15 ppm/K, 5 to 14 ppm/K), etc.

In polyimide film 1, the absolute value of the difference between |αMD| and |αTD| (|αMD| - |αTD|) may be selected from a range of approximately 30 ppm/K or less (for example, 25 ppm/K or less, 20 ppm/K or less). From the viewpoint of dimensional stability (for example, dimensional stability when laminating a metal layer such as copper), it may be, for example, 15 ppm/K or less (for example, 12 ppm/K or less), preferably 10 ppm/K or less (for example, 8 ppm/K or less), and more preferably 7 ppm/K or less (for example, 6 ppm/K or less). It may also be 5 ppm/K or less (for example, 4.5 ppm/K or less, 4 ppm/K or less, 3.5 ppm/K or less, 3 ppm/K or less, 2.5 ppm/K or less, 2 ppm/K or less, 1.5 ppm/K or less, 1 ppm/K or less), etc.

The absolute value (lower limit) of the difference between |αMD| and |αTD| (|αMD| - |αTD|) may be 0 ppm/K, or it may be greater than 0 ppm/K (for example, 0.1 ppm/K or more, 0.2 ppm/K or more, 0.3 ppm/K or more, 0.4 ppm/K or more, 0.5 ppm/K or more).

Furthermore, αMD and αTD are not particularly limited, but may be measured within a specific temperature range (e.g., 50 to 200°C) or under specific conditions (e.g., a heating rate of 10°C/min). Specifically, they may be measured using the method described in the examples below.

The glass transition temperature (Tg) of the polyimide film 1 (or the polyimide constituting the polyimide film, hereinafter the same) may be selected from a range of approximately 400°C or less (for example, 395°C or less), preferably 390°C or less (for example, 385°C or less), and more preferably 380°C or less (for example, 375°C or less), from the viewpoint of adhesion with the metal layer.

The Tg (lower limit of Tg) of the polyimide film 1 may be selected from a range of approximately 150°C or higher (for example, 160°C or higher, 170°C or higher), from the viewpoint of heat resistance, dimensional stability, etc. (and further, balance or compatibility with adhesion to the metal layer), for example, 180°C or higher (for example, 190°C or higher), preferably 200°C or higher (for example, 210°C or higher), and even more preferably 220°C or higher (for example, 22 It may be 5°C or higher, or 230°C or higher (for example, 235°C or higher, 240°C or higher, 245°C or higher, 250°C or higher, 255°C or higher, 260°C or higher, 265°C or higher, 270°C or higher, 275°C or higher, 280°C or higher, 285°C or higher, 290°C or higher, 295°C or higher, 300°C or higher, 305°C or higher, 310°C or higher, 315°C or higher, 320°C or higher, 325°C or higher, 330°C or higher), etc.

Furthermore, you may choose a range by appropriately combining these ranges (upper and lower limits) (for example, 200-400°C, 230-390°C, etc.; the same applies to the range descriptions below).

Specific Tg values for the polyimide film 1 include, for example, 180 to 400°C, preferably 200 to 390°C, and more preferably 220 to 380°C.

The method for measuring Tg may be any known method and is not particularly limited; for example, the tanδ method (i.e., using the peak intensity of tanδ as the Tg value) may be used.

In polyimide film 1, the thickness ratio between the polyimide film (polyimide film to be coated with coupling agent) and layer (A) can be selected according to the application, etc. For example, the thickness ratio of polyimide film to be coated with coupling agent/layer (A) (thickness ratio) may be selected from a range of approximately 30000/1 to 10/1 (e.g., 20000/1 to 30/1), or 10000/1 to 40/1 (e.g., 8000/1 to 50/1), preferably 6000/1 to 60/1 (e.g., 5000/1 to 50/1), and even more preferably 3000/1 to 70/1 (e.g., 2900/1 to 80/1, 2800/1 to 100/1, 2700/1 to 200/1).

The dielectric breakdown voltage of the polyimide film 1 may be, for example, 445 kV/mm or more (e.g., 448 kV/mm or more), preferably 450 kV/mm or more (e.g., 453 kV/mm or more), and more preferably 455 kV/mm or more (e.g., 458 kV/mm or more, 460 kV/mm or more).
The upper limit of the dielectric breakdown voltage of the polyimide film 1 is not particularly limited, but may be, for example, 700 kV/mm or less (e.g., 650 kV/mm or less), preferably 630 kV/mm or less (e.g., 600 kV/mm or less, 580 kV/mm or less, 550 kV/mm or less).
Although it was expected that the dielectric breakdown voltage of polyimide film 1 would be lower due to the decomposition of hydrolyzed condensates of the coupling agent, etc., because polyimide film 1 has layer (A), the high dielectric breakdown voltage of polyimide film 1 was an unexpected effect.
The reason why polyimide film 1 has a high dielectric breakdown voltage is not clear, but it is thought that the presence of layer (A) in polyimide film 1 forms chemical bonds on the surface of the polyimide film, reducing the non-uniformity (roughness) of the polyimide film surface, which increases the number of contact points with the electrode and hinders localized conductivity, or that layer (A) prevents conductivity due to moisture.

Furthermore, the dielectric breakdown voltage of polyimide film 1 may be selected by appropriately combining these ranges (upper and lower limits) (for example, 450 to 600 kV/mm).

The method for measuring the dielectric breakdown voltage is not particularly limited, but for example, it may be measured by a method conforming to the flat-plate electrode method of JIS C 2151.

[Applications of polyimide films, such as metal laminated films]
The polyimide film of the present invention is suitable for use in lamination of metals (metal layers).

Such polyimide films can also be laminated with metal (metal layers) directly, without the need for an adhesive layer. Therefore, they are also suitable as polyimide films for laminating metal (metal layers) directly, without the need for an adhesive layer.

Furthermore, polyimide films can be efficiently laminated (formed) with metal (metal layers) through metallization (plating, etc.). Therefore, the polyimide film of the present invention is also suitable for metallization.

The following describes suitable uses of such polyimide films.

As described above, polyimide films can be laminated films in which metal (metal layers) are laminated.

Such a laminated film can be described as a laminated film (metal-laminated polyimide film, metal-laminated film) composed of a polyimide film and a metal layer (metal) laminated on this film.

In a laminated film, the metal layer may typically be laminated (formed) on the polyimide film without an adhesive layer (or directly).

In such a laminated film, the metal layer may be a metal foil or the like, or it may be formed by metallization, but it is preferably formed by metallization.

Metallizing (metallizing methods) are not particularly limited, but typical examples include plating (plating methods). Specific examples of metallizing include wet plating (e.g., electroplating) and dry plating (e.g., vacuum deposition, sputtering, ion plating, etc.).

These methods may be used individually or in combination of two or more. An example of combining two or more methods is, for instance, when a metal layer is composed of a base layer and an upper layer, as described later, the base layer may be formed using a dry plating method (e.g., relatively thinly), and the upper layer may be formed using a wet plating method.

The metals constituting the metal layer are not particularly limited, but examples include copper, nickel, chromium, manganese, aluminum, iron, molybdenum, cobalt, tungsten, vanadium, titanium, talc, alloys of these metals, oxides of these metals, and carbides of these metals.

The metal layers may consist of one or more metals.

The metal layer may be a single layer or multiple layers (for example, two to three layers).

For example, a metal layer may consist of a base layer (underlying metal layer, base metal layer) and an upper layer (upper metal layer, wiring layer) laminated (formed) on this base layer. Furthermore, the base layer and upper layer (for example, the base layer) may also be multi-layered.

Furthermore, in the case of a multi-layered metal structure, the metals constituting each layer may be the same or different.

Taking a copper laminated film as an example, the metal layer in the copper laminated film may consist solely of a copper layer, or a copper layer (upper layer) may be formed via a base layer (underlying metal layer). In this case, the base layer may consist of one or more layers, and may be composed of at least one selected from copper and non-copper metals.

Specific examples of metal layers with a copper layer as the upper layer include an underlayer (e.g., a sputtering layer) consisting of at least one layer selected from a copper layer, a non-copper metal layer (e.g., a nickel/chromium layer), and combinations thereof, and a copper layer (e.g., a plating layer) laminated on top of this underlayer.

The metal layer may be formed on one side of the polyimide film, or on both sides. Furthermore, when using a plasma-treated polyimide film, the metal layer may be formed on the plasma-treated side of the polyimide film.

The thickness of the metal layer (total thickness in the case of a multilayer structure, or the thickness of each metal layer if it is provided on both sides) can be appropriately selected depending on the application and the characteristics of the metal layer, and may be 1 nm or more (e.g., 2 nm to 100 μm), 3 nm or more (e.g., 5 nm to 50 μm), etc.

In particular, in printed circuit boards (PCBs), the thickness of the metal layer [for example, a copper layer (including a metal layer with a copper layer as the base layer)] may be 1 μm or more (for example, 1 to 50 μm, 2 to 40 μm), preferably 3 μm or more (for example, 3 to 30 μm, 4 to 25 μm, 3 to 20 μm), and more preferably 5 μm or more (for example, 5 to 30 μm, 5 to 20 μm, 5 to 15 μm), etc.

When the metal layer includes an underlying layer, the thickness of the underlying layer is not particularly limited, but may be, for example, 1 to 500 nm (e.g., 5 to 200 nm).

When the metal layer includes the underlying layer, the ratio of the underlying layer's thickness to the total thickness of the metal layer may be selected from a range of, for example, 30% or less, or 20% or less (for example, 15% or less, 10% or less, 5% or less, 3% or less, 2% or less), etc.

In particular, the thickness of the metal layer may be relatively small (thin), for example, 50 μm or less (e.g., 40 μm or less), preferably 30 μm or less (e.g., 25 μm or less), and even more preferably 20 μm or less (e.g., 15 μm or less, 12 μm or less, 10 μm or less).

According to the polyimide film of the present invention (the laminated film of the present invention), even with a relatively small (thin, low-proportion) metal layer, sufficient adhesion can be achieved.

In a laminated film, the thickness ratio of the polyimide film to the metal layer can be selected according to the application, etc. For example, the polyimide film/metal layer (thickness ratio) may be selected from a range of about 1/0.001 to 1/100 (for example, 1/0.01 to 1/50), preferably 1/0.02 to 1/10 (for example, 1/0.03 to 1/8), preferably 1/0.05 to 1/5 (for example, 1/0.07 to 1/3), and even more preferably 1/0.1 to 1/2 (for example, 1/0.15 to 1/1, 1/0.2 to 1/0.8).
According to the polyimide film of the present invention (the laminated film of the present invention), even with such a thickness ratio, the polyimide film can fully exhibit its function as a base film.

Taking copper laminated films (for example, copper laminated films suitable for printed circuit boards, etc.) as an example, a more specific example of a manufacturing method would involve forming a thin copper film on the surface of a polyimide film under vacuum conditions by surface treatment (for example, surface treatment with nickel/chromium by sputtering, followed by sputtering with copper), and then laminating the copper layer by electroplating using a copper sulfate bath or the like.

Furthermore, the metal layer (such as a copper plating layer) may be patterned by etching or other methods. The etching method is not particularly limited, and conventionally known methods may be used.

In a laminated film, the metal layer and the polyimide film may be firmly adhered to each other.

Examples of such laminated films include those with a peel strength (adhesion, tear strength) value (T1) between the metal layer and the polyimide film of more than 0.3 kN/m (for example, 0.35 kN/m or more), preferably 0.4 kN/m or more (for example, 0.45 kN/m or more), and more preferably 0.5 kN/m or more.

The upper limit of T1 is not particularly limited, but it may be, for example, 5 kN/m or less, 4 kN/m or less, 3 kN/m or less, 2.5 kN/m or less, 2 kN/m or less, 1.5 kN/m or less, 1.2 kN/m or less, 1 kN/m or less, etc.

Such adhesion can be maintained at a relatively high level even when subjected to conditions such as high temperatures (e.g., harsh conditions). Examples of such laminated films include those where, when T1 is the peel strength (adhesion, tear resistance) between the metal layer and the polyimide film, and T2 is the peel strength (adhesion, tear resistance) between the metal layer and the polyimide film after heating at 150°C for 168 hours, T2/T1 is 0.3 or higher (e.g., 0.4 or higher), preferably 0.5 or higher (e.g., greater than 0.5, 0.55 or higher), more preferably 0.6 or higher (e.g., 0.65 or higher), particularly 0.7 or higher (e.g., 0.72 or higher), and particularly preferably 0.75 or higher (e.g., greater than 0.75, 0.78 or higher, 0.8 or higher).

Furthermore, the upper limit of T2/T1 may be 1, or it may be less than 1 (for example, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.9 or less).

Furthermore, the value of T2 may be, for example, greater than 0.2 kN/m (e.g., 0.25 kN/m or more), preferably 0.3 kN/m or more (e.g., 0.35 kN/m or more), and even more preferably 0.4 kN/m or more.

The upper limit of T2 is not particularly limited, but for example, it may be 5 kN/m or less, 4 kN/m or less, 3 kN/m or less, 2.5 kN/m or less, 2 kN/m or less, 1.5 kN/m or less, 1.2 kN/m or less, 1 kN/m or less, 0.9 kN/m or less, 0.8 kN/m or less, etc.

The measurement method for T1 (and even T2) may be, for example, one that conforms to Method A in the test method for the peel strength of copper foil described in JIS C 6471 (for example, a tensile angle of 90° and a tensile speed of 50 mm/min).
More specifically, T1 (and even T2) may be measured by the method described in the examples below.

Laminated films can be used in a variety of applications, such as COF (Chip-on-Film), flexible printed circuit boards (FPCs), and other circuit boards (especially those using fine-pitch wiring circuits).

Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited in any way by these examples, and many modifications are possible within the technical concept of the present invention by those with ordinary skill in the art.

In the examples, the following compounds will be referred to by the following abbreviations.
Paraphenylenediamine: PPD
4,4'-diaminodiphenyl ether: 4,4'-ODA
Pyromellitic dianhydride: PMDA
3,3',4,4'-biphenyltetracarboxylic acid dianhydride: BPDA
N,N-dimethylacetamide:DMAc

Each characteristic was evaluated using the following method:

• Coefficient of thermal expansion (CTE)
Equipment: The TMA-50 (product name, manufactured by Shimadzu Corporation) was used for measurement under the following conditions: measurement temperature range: 50 to 200°C, heating rate: 10°C/min. The thermal expansion coefficient α was defined as α = (|αMD| + |αTD|)/2, using the linear expansion coefficient αMD in the mechanical transport direction (MD) and the linear expansion coefficient αTD in the width direction (TD).

• Glass transition temperature (Tg)
Equipment: A DMS6100 (product name: Hitachi High-Tech Science) was used, and measurements were taken in the temperature range of 25 to 420°C while infusing 50 mL/min of nitrogen at a heating rate of 2°C/min and a measurement frequency of 5 Hz. The temperature at which the loss tangent tanδ(E''/E'), which is the ratio of the loss modulus (E'') to the storage modulus (E'), showed a maximum was defined as the glass transition temperature (Tg).

- Adhesion strength between copper and polyimide laminated film (90° peel strength)
The adhesion strength between copper and polyimide laminated film was evaluated according to Method A of the test method for peel strength of copper foil described in JIS C 6471, measured under conditions of a tensile angle of 90° and a tensile speed of 50 mm/min.
The adhesion strength measured immediately after fabrication of the copper-laminated polyimide film was defined as the normal adhesion strength (T1), and the adhesion strength measured after heating at 150°C for 168 hours was defined as the heat-resistant adhesion strength (T2).

- Using a Mitutoyo Lightmatic (Series 318) thickness gauge, 15 locations were arbitrarily selected from the entire surface of the polyimide film (to be coated with the coupling agent). The thickness of these 15 locations was measured, and the average was calculated to determine the film thickness.

- Thickness of layer (1): Using an ULVAC-FI X-ray photoelectron spectrometer, the Si intensity was measured in the depth direction from the film surface. The point where the slope of the relationship between Si intensity and depth (linear graph) changes was defined as the displacement point, and the depth from the film surface to this displacement point was defined as the thickness of layer (1).

- Thickness of layer (2): Using an ULVAC-FI secondary ion mass spectrometer, the Si intensity was measured in the depth direction from the film surface, and the thickness of layer (2) was defined as the depth from the displacement point to where the Si intensity became 0.

- Evaluation of inorganic particles: Using the LA-910 laser diffraction/scattering particle size distribution analyzer manufactured by Horiba, Ltd., samples dispersed in a polar solvent were measured, and the average particle diameter was read as the volume-averaged diameter from the results of the analysis of the laser diffraction and scattered light intensity patterns.

- Dielectric breakdown voltage was measured according to the flat electrode method of JIS C 2151, with an input voltage of 100V ±10% at 50/60Hz, an output voltage of DC 0 to +50kV/5Ma, and a variable boost time of 40 to 800 seconds.
The film test pieces were dried at 200°C for 30 minutes before measurement.
The dimensions of the film test specimen were 200 mm x 200 mm, and the measurement atmosphere was 25°C x 60% RH.

(Preparation of polyamic acid solution)
[Synthesis Example 1]
25.7 g of PPD was placed in a 2000 mL separable flask, and 960 g of DMAc was added. The mixture was stirred until completely dissolved. Subsequently, 50.2 g of PMDA was added, and the mixture was stirred for 1 hour. After that, 71.3 g of 4,4'-ODA was added, and after confirming that it was completely dissolved, 52.4 g of BPDA and 39.1 g of PMDA were added, and the mixture was stirred for 3 hours to obtain a 3000 poise polyamic acid solution (20% solids by mass). To this, a silica DMAc slurry with an average particle size of 0.3 μm was added at a concentration of 0.3% by mass per weight of the polyamic acid resin, and the mixture was thoroughly stirred and dispersed.

(Preparation of coating solution)
The coating solution (silane coupling agent-containing solution) was prepared as follows.
[Coating Liquid 1]
Coating solution 1 was prepared by mixing 90 parts by mass of ethyl lactate (Musashino Scientific Research Institute), 10 parts by mass of ethanol, and 1 part by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.).
[Coating liquid 2]
Coating solution 2 was prepared by mixing 90 parts by mass of ethyl lactate (Musashino Scientific Research Institute), 10 parts by mass of ethanol, and 2 parts by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.).
[Coating liquid 3]
Coating solution 3 was prepared by mixing 90 parts by mass of ethyl lactate (Musashino Scientific Research Institute), 10 parts by mass of ethanol, and 3 parts by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.).

[Example 1]
(Preparation of polyimide film)
After cooling the polyamic acid solution obtained in Synthesis Example 1 to -5°C, a mixture was obtained by mixing 21 parts by mass of DMAc, 16 parts by mass of acetic anhydride, and 14 parts by mass of 3-methylpyridine with 100 parts by mass of the solid content of the polyamic acid.
This mixture was passed through a rotating drum at 85°C for 30 seconds using a T-type slit die. The resulting self-supporting film was then heated at 100°C for 5 minutes while being stretched 1.23 times in the running direction. Next, both ends in the width direction were grasped, and the film was stretched 1.4 times in the width direction while being heated at 270°C for 2 minutes. Finally, it was heated at 380°C for 90 seconds to obtain a polyimide film with a width of 500 mm, a thickness of 25 μm, and a length of 500 m.
The coating solution 1 was applied to one side of the polyimide film, and the polyimide film 1 was dried at 130°C for 60 seconds. In the polyimide film 1, the thickness of layer (1) was 20 nm, and the thickness of layer (2) was 180 nm.

(Fabrication of copper-laminated polyimide film)
Plasma treatment was performed on one side of polyimide film 1, and then a 25 nm thick nickel/chromium alloy (nickel/chromium = 80/20) layer was formed by sputtering. Next, a 100 nm thick copper layer was formed on this nickel/chromium alloy layer, also by sputtering. Then, the copper layer thickness was reduced to 8.5 μm by electrolytic copper plating. Finally, a copper laminated polyimide film 1 was obtained by copper etching to pattern the film so that the wiring width was 1 mm.
The adhesion strength of this copper-laminated polyimide film 1 was evaluated. The results are shown in Table 1.

[Example 2]
A polyimide film 2 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating solution was 200°C. Furthermore, a copper-laminated polyimide film 2 was obtained using this polyimide film 2, following the same procedure as in Example 1.
The adhesion strength of this copper-laminated polyimide film 2 was evaluated. The results are shown in Table 1.

[Example 3]
A polyimide film 3 was obtained in the same manner as in Example 1, except that the drying time after application of the coating solution was 90 seconds. Furthermore, a copper-laminated polyimide film 3 was obtained using this polyimide film 3 in the same manner as in Example 1.
The adhesion strength of this copper-laminated polyimide film 3 was evaluated. The results are shown in Table 1.

[Example 4]
A polyimide film 4 was obtained in the same manner as in Example 3, except that coating solution 2 was used instead of coating solution 1. Furthermore, a copper-laminated polyimide film 4 was obtained using this polyimide film 4 in the same manner as in Example 1.
The adhesion strength of this copper-laminated polyimide film 4 was evaluated. The results are shown in Table 1.

[Example 5]
A polyimide film 5 was obtained in the same manner as in Example 3, except that coating solution 3 was used instead of coating solution 1. Furthermore, a copper-laminated polyimide film 5 was obtained using this polyimide film 5 in the same manner as in Example 1.
The adhesion strength of this copper-laminated polyimide film 5 was evaluated. The results are shown in Table 1.

[Comparative Example 1]
A polyimide film 6 was obtained in the same manner as in Example 1, except that the coating solution of Example 1 was not applied. Furthermore, a copper-laminated polyimide film 6 was obtained using this polyimide film 6 in the same manner as in Example 1.
The adhesion strength of this copper-laminated polyimide film 6 was evaluated. The results are shown in Table 1.

[Comparative Example 2]
After cooling the polyamic acid solution obtained in Synthesis Example 1 to -5°C, a mixture was obtained by mixing 21 parts by mass of DMAc, 16 parts by mass of acetic anhydride, and 14 parts by mass of 3-methylpyridine with 100 parts by mass of the solid content of the polyamic acid.
The mixture was passed through a rotating drum at 85°C for 30 seconds using a T-type slit die. The coating liquid 3 was then applied to one side of the resulting self-supporting film and dried at 120°C for 150 seconds. Next, it was stretched 1.23 times in the running direction while being heated at 100°C for 5 minutes. Then, both ends in the width direction were grasped, and it was stretched 1.4 times in the width direction while being heated at 270°C for 2 minutes, and then heated at 380°C for 90 seconds to obtain a polyimide film 7 with a width of 500 mm, a thickness of 25 μm, and a length of 500 m.
Furthermore, regarding the polyimide film 7, the Si intensity was measured in the depth direction from the film surface using an ULVAC-FI secondary ion mass spectrometer, similar to the method used to measure the thickness of layer (2) described above. The depth at which the Si intensity became zero was measured and found to be 390 nm.
Using the polyimide film 7, a copper-laminated polyimide film 7 was obtained using the same procedure as in Example 1.
The adhesion strength of this copper-laminated polyimide film 7 was evaluated. The results are shown in Table 1.

Note that in Table 1, αMD, αTD, α, Tg, and dielectric breakdown voltage are the values for polyimide films 1 to 7.

As shown in Table 1, the polyimide films of Examples 1 to 5 maintained better adhesion to the metal layer when exposed to high-temperature conditions compared to Comparative Examples 1 and 2.
Furthermore, the polyimide films of Examples 1 to 5 showed a higher dielectric breakdown voltage compared to Comparative Examples 1 and 2.

[Example 6]
A polyimide film 8 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating solution was 170°C. Furthermore, a copper-laminated polyimide film 8 was obtained using this polyimide film 8 in the same manner as in Example 1.
The adhesion strength of this copper-laminated polyimide film 8 was evaluated. The results are shown in Table 2.

[Example 7]
A polyimide film 9 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating solution was 250°C. Furthermore, a copper-laminated polyimide film 9 was obtained using this polyimide film 9 in the same procedure as in Example 1.
The adhesion strength of this copper-laminated polyimide film 9 was evaluated. The results are shown in Table 2.

[Example 8]
A polyimide film 10 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating solution was 280°C. Furthermore, a copper-laminated polyimide film 10 was obtained using this polyimide film 10 in the same procedure as in Example 1.
The adhesion strength of this copper-laminated polyimide film 10 was evaluated. The results are shown in Table 2.

The polyimide film of the present invention is useful for applications such as metal lamination.

Claims (23)

The polyimide film has a layer (A) containing a hydrolysis condensate of a coupling agent on one or both sides, and the polyimide constituting the polyimide film has an aromatic diamine component and an aromatic acid anhydride component as polymerization components, and the polymerization components do not contain any other polymerization components other than the aromatic acid anhydride component and the aromatic diamine component, or the proportion of other polymerization components other than the aromatic acid anhydride component and the aromatic diamine component to the total polymerization components is 20 mol% or less.
Layer (A) comprises a layer (1) which is substantially composed solely of hydrolyzed condensates of a coupling agent, and a layer (2) which contains hydrolyzed condensates of a coupling agent and components derived from polyimide.
A polyimide film for metal lamination in which layer (A) is formed in the order of layer (2) and layer (1) from the surface side of the polyimide film, with a thickness of layer (1) of 5 nm or more and a thickness of layer (A) of 100 to 400 nm . The polyimide film according to claim 1, wherein when the peel strength between the copper layer and the polyimide film when the copper layer is directly laminated is T1, and the peel strength between the copper layer and the polyimide film after heating at 150°C for 168 hours is T2, T1 is 0.4 kN/m or more, and T2/T1 is 0.7 or more. The polyimide film according to claim 1, wherein the coupling agent has an amino group. The polyimide film according to claim 1 or 3, wherein the coupling agent comprises a silane coupling agent. The polyimide film according to claim 1 or 3, wherein the coupling agent comprises an amino-based silane coupling agent. The polyimide film according to claim 1 , wherein the thickness of layer (2) is 300 nm or less. The polyimide film according to claim 1 or 3, wherein the coupling agent comprises 3-aminopropyltrimethoxysilane. The polyimide film according to claim 1 or 2, wherein, when the linear expansion coefficient in the mechanical transport direction of the film is αMD and the linear expansion coefficient in the width direction is αTD, the value of (|αMD| + |αTD|)/2 is 15 ppm/K or less. A polyimide film according to claim 1 or 2, wherein the αTD is -5 to +10 ppm/K. A polyimide film according to claim 1 or 2, wherein the polymerization components consist of an aromatic diamine component comprising at least one selected from paraphenylenediamine and 4,4'-diaminodiphenyl ether, and an aromatic acid anhydride component comprising at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride. A polyimide film according to claim 1 or 2, containing inorganic particles. A polyimide film according to claim 1 or 2, which is in roll form. A polyimide film according to claim 1 or 2, containing inorganic particles in a proportion of 0.01 to 5% by mass and in the form of a roll with a length of 5 m or more. A polyimide film according to claim 1 or 2, for metallizing purposes. A polyimide film according to claim 1 or 2 for directly laminating a copper layer with a thickness of 20 μm or less. A polyimide film according to claim 1 or 2, wherein the glass transition temperature is 285°C or higher. A laminated film comprising a polyimide film and a metal layer directly laminated on the film, wherein the polyimide film is the polyimide film described in claim 1 or 2. The laminated film according to claim 17 , wherein the metal layer is a copper layer with a thickness of 20 μm or less. The laminated film according to claim 17 , wherein the peel strength T1 between the metal layer and the polyimide film is 0.5 kN/m or more. The laminated film according to claim 17, wherein when T1 is the peel strength between the metal layer and the polyimide film, and T2 is the peel strength between the metal layer and the polyimide film after heating at 150°C for 168 hours, T1 is 0.4 kN/m or more, and T2/T1 is 0.7 or more. A method for producing a polyimide film for metal lamination, comprising the step of applying a coupling agent-containing solution to one or both sides of a polyimide film and then drying it,
A method for producing a polyimide film, wherein the polyimide film has a layer (A) on one or both sides containing a hydrolysis condensate of a coupling agent, the polyimide constituting the polyimide film has an aromatic diamine component and an aromatic acid anhydride component as polymerization components, the polymerization components do not contain other polymerization components other than the aromatic acid anhydride component and the aromatic diamine component, or the proportion of other polymerization components other than the aromatic acid anhydride component and the aromatic diamine component to the total polymerization components is 20 mol% or less, and layer (A) comprises a layer (1) substantially formed only of a hydrolysis condensate of a coupling agent and a layer (2) containing a hydrolysis condensate of a coupling agent and components derived from polyimide, the layers (A) are formed in the order of layer (2) and layer (1) from the surface side of the polyimide film, the thickness of layer (1) is 5 nm or more, and the thickness of layer (A) is 100 to 400 nm . The manufacturing method according to claim 21 , wherein the coupling agent-containing solution contains 0.1 to 5% by mass of the coupling agent. The manufacturing method according to claim 21 or 22 , wherein drying is performed at a drying temperature of 130 to 200°C and a drying time of 40 to 100 seconds.