Polyimide Film

Abstract

Provided is a polyimide film that is useful for metal lamination and the like. The polyimide film has a layer (A) containing a hydrolysis condensate of a coupling agent on one or both sides.

Description

[Technical Field]

[0001] The present invention relates to a polyimide film and the like. [Background technology]

[0002] Due to its excellent heat resistance, chemical resistance, and electrical properties, polyimide film is widely used as an electrical insulating material for electrical 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.

[0003] As electronic devices become smaller, lighter, more functional, multifunctional and densely packed, the printed wiring boards used in these electronic devices are rapidly becoming denser due to narrower conductor widths and conductor spacing, more multilayering, flexibility and thinner substrates.

[0004] BACKGROUND ART Conventionally, a flexible printed wiring board having a three-layer structure in which a conductor layer (a metal layer such as a copper layer) is bonded to a polyimide film via an adhesive layer has been known (Patent Document 1).

[0005] On the other hand, when a polyimide film is bonded to a conductor layer via an adhesive layer, sufficient adhesiveness (adhesion) may not be obtained between the polyimide film and the metal layer. Under these circumstances, it is known that, when producing a polyimide film, a solution containing a heat-resistant surface treatment agent is applied to the surface of a solidified film (self-supporting film) of polyamic acid, and the solidified film is heat-treated to imidize it, thereby obtaining a polyimide film with improved adhesion (Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 2680816 [Patent Document 2] Japanese Patent Application Publication No. 62-267330 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a polyimide film suitable for use in metal lamination (lamination of metal layers), etc. [Means for solving the problem]

[0008] As mentioned above, it is known to produce a polyimide film by applying a surface treatment agent to the surface of a self-supporting film of polyamic acid and then heat treating the film.

[0009] However, the present inventors have found that although the polyimide film obtained in this manner exhibits improved adhesion between the polyimide film and the metal layer immediately after lamination of the metal layer, the adhesion may be prone to decrease when the metal layer laminated film is exposed to high temperatures.

[0010] Therefore, the present inventors have investigated polyimide films for metal lamination from a perspective that is completely different from that of conventional polyimide films. Surprisingly, the present inventors have investigated the application of a surface treatment agent not to a self-supporting film of polyamic acid but to a polyimide film after imidization. However, when a surface treatment agent is applied to a polyimide film after imidization, unlike when the agent is applied to a self-supporting polyamic acid film, the polyimide and the surface treatment agent do not react very well (i.e., chemical bonds are not formed very well between the polyimide and the surface treatment agent), making it difficult to form a layer containing a hydrolysis condensate of the surface treatment agent on the polyimide film. Furthermore, depending on the type of surface treatment agent, it can be difficult to efficiently form such a layer, and it has been extremely difficult to form a layer containing a hydrolysis condensate of a surface treatment agent on a polyimide film after imidization.

[0011] Under these circumstances, the present inventors have conducted further intensive research and have found that a polyimide film having a layer containing a hydrolysis condensate of a surface treatment agent can be efficiently obtained by treating the film with a specific surface treatment agent (particularly, a coupling agent such as a silane coupling agent) under specific conditions [e.g., coupling agent concentration in a coupling agent-containing solution, drying conditions after application of the coupling agent (e.g., drying temperature, drying time, etc.)]. The inventors have also found that such a polyimide film is suitable for laminating a metal layer, and that sufficient adhesion can be achieved even without providing an adhesive layer (particularly, even a thin metal layer can be laminated with sufficient adhesion), and that a metal layer-laminated polyimide film in which a metal layer is laminated on the film can suppress the above-mentioned decrease in adhesion even when exposed to high-temperature conditions. Furthermore, the present inventors have found that when the film is laminated with a metal layer to form a metal layer-laminated polyimide film, 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 film of polyamic acid is used, and have conducted further research, leading to the completion of the present invention.

[0012] That is, the present invention relates to the following inventions. [1] A polyimide film (particularly a polyimide film for metal lamination) having a layer (A) containing (or formed of) a hydrolysis condensation product of a coupling agent (e.g., a silane coupling agent) on one or both sides. [2] A polyimide film (particularly, a polyimide film for metal lamination) in which T1 is the peel strength (e.g., 90° peel strength) between a copper layer (e.g., an 8.5 μm-thick copper layer, or an 8.5 μm-thick copper layer via a metal layer (copper layer) formed by a sputtering method) and the polyimide film when the copper layer is directly laminated thereon, 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, T1 is 0.4 kN / m or more, and T2 / T1 is 0.7 or more. Such a polyimide film may be produced, for example, by applying a coupling agent-containing solution to (one or both sides of) an (imidized) polyimide film and drying (hydrolysis and condensation), as described below. That is, such a polyimide film may be a polyimide film obtained by applying a coupling agent-containing solution to (one or both sides of) an (imidized) polyimide film and drying (hydrolysis and condensation). [3] The polyimide film according to [1], wherein the coupling agent has an amino group. [4] The polyimide film according to [1] or [3], wherein the coupling agent comprises a silane coupling agent. [5] The polyimide film according to any one of [1] and [3] to [4], wherein the coupling agent comprises an amino-silane coupling agent. [6] The polyimide film according to any one of [1] and [3] to [5], wherein the layer (A) has a thickness of 100 to 400 nm. [7] The polyimide film according to any one of [1] and [3] to [6], wherein the layer (A) comprises (on the surface side) a layer (or film) (1) of a hydrolysis condensate of a coupling agent. [8] The polyimide film according to any one of [1] and [3] to [7], wherein the layer (A) includes a layer (2) containing a hydrolysis condensate of a coupling agent and a component derived from a polyimide. [9] The polyimide film according to [8], wherein the layer (2) has a thickness of 300 nm or less.

[10] The polyimide film according to any one of [1] and [3] to [9], wherein the coupling agent comprises 3-aminopropyltrimethoxysilane.

[11] The polyimide film according to any one of [1] to

[10] , wherein the value of (|αMD|+|αTD|) / 2 is 15 ppm / K or less, where αMD is the linear expansion coefficient of the film in the machine direction (MD) and αTD is the linear expansion coefficient of the film in the width direction (TD).

[12] The polyimide film according to any one of [1] to

[11] , wherein αTD is −5 to +10 ppm / K.

[13] The polyimide film according to any one of [1] to

[12] , wherein the polyimide constituting the polyimide film comprises, as polymerization components, 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 dianhydride.

[14] The polyimide film according to any one of [1] to

[13] , which contains inorganic particles.

[15] The polyimide film according to any one of [1] to

[14] , which is in a roll form.

[16] The 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 having a length of 5 m or more.

[17] The polyimide film according to any one of [1] to

[16] , which is for metallizing (for plating, etc.).

[18] The polyimide film according to any one of [1] to

[17] , for laminating a metal layer directly (or without an adhesive layer) (for example, laminating a copper layer having a thickness of 20 μm or less directly).

[19] A laminated film composed of a polyimide film and a metal layer laminated directly (or without an adhesive layer) on the polyimide film, wherein the polyimide film is the polyimide film according to any one of [1] to

[18] .

[20]

[19] The laminated film according to

[19] , wherein the metal layer is a copper layer having a thickness of 20 μm or less. [twenty one] The laminated film according to

[19] or

[20] , wherein the peel strength (for example, 90° peel strength) T1 between the metal layer and the polyimide film is 0.5 kN / m or more. [twenty two] The laminated film according to any one of

[19] to

[21] , wherein T1 is the peel strength (e.g., 90° peel strength) between the metal layer and the polyimide film, and T2 is the peel strength (e.g., 90° 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. [twenty three] 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 (or including) a step of applying a solution containing a coupling agent (e.g., a silane coupling agent) to one or both sides of a polyimide film, and then drying the solution. [twenty four] The production method according to

[23] , wherein the solution containing a coupling agent (for example, a silane coupling agent) contains 0.1 to 5 mass % of the coupling agent (for example, a silane coupling agent). [twenty five] The method according to

[23] or

[24] , wherein the drying is carried out at a drying temperature of 130 to 200°C for a drying time of 40 to 100 seconds. [Effects of the Invention]

[0013] The present invention provides a polyimide film, which is suitable for use in metal lamination (for laminating metal layers, for forming metal layers), etc.

[0014] For example, in one embodiment of the polyimide film, a metal layer (e.g., a copper layer) can be laminated (formed) with sufficient adhesion. Such adhesion can be ensured even without providing an adhesive layer (even if the metal layer is directly formed), so the metal layer can also be suitably formed by metallizing (or a metallizing method or metallizing treatment, for example, a plating method (wet or dry plating method, for example, a vacuum deposition method, a sputtering method, or an ion plating method)).

[0015] Therefore, such a polyimide film can achieve sufficient adhesion even with a thin metal layer (for example, 30 μm or less, 20 μm or less, 10 μm or less, etc.).

[0016] 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.

[0017] In another embodiment of the polyimide film of the present invention, the polyimide film can be realized while simultaneously having useful or effective functions as a base film (substrate film) {e.g., heat resistance, dimensional stability (e.g., dimensional stability during metal layer formation, dimensional stability after metal layer formation (e.g., during processing)), etc.} and achieving sufficient adhesion to the metal layer as described above.

[0018] In another embodiment of the polyimide film of the present invention, a high breakdown voltage can be achieved. Therefore, such a polyimide film can exhibit high insulating properties. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Polyimide film] The polyimide film of the present invention may have, on its surface, a layer (A) (hereinafter sometimes simply referred to as "layer (A)") containing (or formed of) a hydrolysis condensation product of a coupling agent. The layer (A) may be a layer containing an element corresponding to the coupling agent [for example, silicon (corresponding to a silane coupling agent)]. The layer (A) may be formed on one surface (or one side) of the polyimide film, or on both surfaces (or both sides). Such a polyimide film can be formed, for example, by applying a solution containing a coupling agent to (one or both sides of) an (imidized) polyimide film, and drying it (to cause hydrolysis and condensation).

[0020] (Layer(A)) The coupling agent may be, for example, one having 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.).

[0021] Examples of the coupling agent include a silane coupling agent, a titanium coupling agent, and an aluminum coupling agent, and preferably a silane coupling agent. The coupling agents may be used alone or in combination of two or more.

[0022] Examples of silane coupling agents include those having a silyl group to which a hydrolyzable (condensable) group (such as an alkoxy group or a halogen atom) is bonded. In the silane coupling agent, the number of silicon (atoms) may be one or more, or may be two or more (for example, an oligomeric or polymeric silane coupling agent).

[0023] Specific silane coupling agents are not particularly limited, but examples thereof include amino-based silane coupling agents (amino group-containing silane coupling agents), epoxy-based silane coupling agents (epoxy group-containing silane coupling agents), mercapto-based silane coupling agents (mercapto group-containing silane coupling agents), (meth)acryloxy-based silane coupling agents ((meth)acryloxy group-containing silane coupling agents), and vinyl-based silane coupling agents (vinyl group-containing silane coupling agents), and preferably amino-based silane coupling agents, etc. The silane coupling agent may be used alone or in combination of two or more.

[0024] 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 amino C1-4 alkyl mono- to tri-C1-4 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 (amino C1-4 amino)C1-4 alkyl mono- to tri-C1-4 alkoxysilanes), and phenylaminoalkylalkoxysilanes (e.g., phenylaminoalkyl mono- to trialkoxysilanes such as N-phenyl-3-aminopropyltrimethoxysilane, preferably phenylamino C1-4 alkyl mono- to tri-C1-4 alkoxysilanes)].

[0025] Examples of epoxy-based silane coupling agents include alkoxysilanes having an epoxy group [for example, glycidoxyalkylalkoxysilanes (for example, glycidoxyalkyl mono- to trialkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane, preferably glycidoxy C1-4 alkyl mono- to tri-C1-4 alkoxysilanes), and epoxycycloalkylalkoxysilanes (for example, epoxycycloalkyl mono- to trialkoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, preferably epoxy C3-10 cycloalkyl mono- to tri-C1-4 alkoxysilanes)].

[0026] Examples of mercapto-based silane coupling agents include alkoxysilanes having a mercapto group [e.g., mercaptoalkylalkoxysilanes (e.g., mercaptoalkyl mono- to trialkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane, preferably mercaptoC1-4 alkylmono- to triC1-4 alkoxysilanes)].

[0027] Examples of (meth)acryloxy-based 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, and 3-(meth)acryloxypropylmethyldiethoxysilane, preferably (meth)acryloxyC2-4 alkylmono- to triC1-4 alkoxysilanes].

[0028] 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., vinylalkoxysilanes (e.g., vinyl mono- to trialkoxysilanes such as vinyltrimethoxysilane and vinyltriethoxysilane, preferably vinyl mono- to tri-C1-4 alkoxysilanes), vinylalkoxyalkoxysilanes (e.g., vinyl mono- to tri-(C1-4 alkoxyC1-4 alkoxy)silanes such as vinyltri(methoxyethoxy)silane and vinyltris(β-methoxyethoxy)silane), and styryl group-containing silanes (e.g., styryl mono- to trialkoxysilanes such as p-styryltrimethoxysilane, preferably styryl mono- to tri-C1-4 alkoxysilanes), etc.].

[0029] Examples of titanium coupling agents include isostearoyl titanates (e.g., mono- or triisostearoyl titanates such as isopropyl triisostearoyl titanate, isopropyl dimethacryloyl isostearoyl titanate, and isopropyl isostearoyl diacryl titanate), amino group-containing titanates (e.g., isopropyl tri(N-aminoethyl-aminoethyl) titanate), isopropyl tridecylbenzenesulfonyl titanate, and isopropyl Examples of the phosphate-soluble polymers include pyritris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)phosphite titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl trioctanoyl titanate, and isopropyl tricumyl phenyl titanate.

[0030] Examples of aluminum coupling agents include alkylacetoacetate aluminum diisopropylate.

[0031] From the viewpoint of adhesion between the polyimide film of the present invention and the metal layer (particularly adhesion when exposed to high temperature conditions), the coupling agent may preferably have an amino group (e.g., an amino-based silane coupling agent, etc.). When a coupling agent having an amino group is used, although it is not clear, it is thought that the reaction between the coupling agent and the polyimide film to which the coupling agent is applied is 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 a coupling agent having an amino group is used, it is thought that the surface of the polyimide film of the present invention contains amino groups. Furthermore, although it is not certain, it is thought that when a metal layer is laminated on such a polyimide film of the present invention, a coordinate bond is formed between the amino group and a metal atom (e.g., a copper atom, etc.), which tends to stabilize the metal layer, making it easier to obtain adhesion between the metal layer and the polyimide film of the present invention even when exposed to high-temperature conditions.

[0032] The layer (A) may contain a surface treatment agent other than the coupling agent {for example, a hydrolysis condensate of a silane compound [for example, a mono- to tetraalkoxysilane such as tetramethoxysilane or tetraethoxysilane, preferably a mono- to tetra-C1-4 alkoxysilane], etc.}.

[0033] The layer (A) may have a layer (or film) (1) of a hydrolysis condensate of a coupling agent. The layer (1) may be formed on the surface side of the layer (A). The layer (1) may be formed substantially only from a hydrolysis condensate of a coupling agent, and may not contain polyimide (or a component derived from polyimide). When the polyimide film of the present invention has layer (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).

[0034] The layer (A) may have a layer (2) containing a hydrolysis condensate of a coupling agent and a component derived from a polyimide. The layer (2) may be formed on the polyimide film side of the layer (A). When the layer (A) has a layer (1) and a layer (2), the layers may be formed in the order of layer (2) and layer (1) from the polyimide film (surface) side. When 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).

[0035] The thickness of layer (A) is not particularly limited, but from the viewpoint of adhesion between the polyimide film of the present invention and the metal layer, 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).

[0036] The thickness (upper limit) of layer (A) is not particularly limited, but may be, for example, about 500 nm or less (e.g., 480 nm or less, 450 nm or less, 430 nm or less), preferably about 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).

[0037] The method for measuring the thickness of layer (A) may be any known method, and is not particularly limited. For example, the thickness of layer (A) may be measured by the method for measuring the thickness of layer (1) or layer (2) described in the Examples below.

[0038] The thickness of layer (1) is not particularly limited, but 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) from the viewpoint of adhesion between the polyimide film of the present invention and the metal layer.

[0039] The thickness (upper limit) of layer (1) is not particularly limited, but may be, for example, about 150 nm or less (e.g., 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less), preferably about 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).

[0040] The thickness of the layer (1) may be measured by any known method without any particular limitation, and may be measured, for example, by the method described in the examples below.

[0041] 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).

[0042] The thickness (upper limit) of layer (2) is not particularly limited, but may be, for example, about 350 nm or less (e.g., 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less), preferably about 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 about 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).

[0043] The thickness of the layer (2) may be measured by any known method without any particular limitation, and may be measured, for example, by the method described in the examples below.

[0044] (Polyimide film (to be coated with coupling agent)) Hereinafter, a polyimide film to be coated with a coupling agent (i.e., a target for coating with a coupling agent) will be described.

[0045] The thickness of the polyimide film can be selected appropriately depending on the application, etc., but from the viewpoint of suitable use (functioning) as a substrate (base film) of a laminate film, for example, it may be about 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), or may be about 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).

[0046] The thickness (upper limit) of such a 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 about 100 μm or less (e.g., 80 μm or less), or may be 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).

[0047] Specific examples of the thickness of the polyimide film include 1 to 200 μm, preferably 3 to 100 μm, and more preferably 5 to 80 μm.

[0048] The polyimide film may be a laminate of a plurality of polyimide films, but usually may be a single polyimide film.

[0049] The polyimide film may be an unstretched film or a stretched film (uniaxially or biaxially stretched film). In such a stretched film, the stretching conditions (e.g., the stretch ratio in the TD direction and / or the MD direction) may be the conditions described below.

[0050] In the present invention, sufficient adhesion and the like can be easily and efficiently achieved even in a stretched film.

[0051] Composition, manufacturing method, etc. A polyimide film (or a polyimide or polyamic acid constituting the polyimide film) usually contains an aromatic diamine component and an aromatic acid anhydride component as raw materials (as polymerization components).

[0052] Examples of the aromatic diamine component include 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.), ... 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-biphenyl Examples thereof include bis(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, 4-aminophenyl-3-aminobenzoate, etc. These can be used alone or in combination of two or more.

[0053] From the viewpoint of easily and efficiently realizing adhesion to the metal layer, heat resistance, dimensional stability, etc., the aromatic diamine component may preferably contain at least one selected from paraphenylenediamine and 4,4'-diaminodiphenyl ether, and more preferably may contain paraphenylenediamine and 4,4'-diaminodiphenyl ether.

[0054] When the aromatic diamine component contains paraphenylenediamine and 4,4'-diaminodiphenyl ether, the molar ratio of paraphenylenediamine to 4,4'-diaminodiphenyl ether may be, for example, about 60 / 40 to 1 / 99 (e.g., 55 / 45 to 5 / 95), preferably about 50 / 50 to 10 / 90 (e.g., 45 / 55 to 15 / 85).

[0055] Examples of aromatic acid anhydride components (aromatic tetracarboxylic acid components) include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3,6,7-naphthalenedicarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)ether, Pyridine-2,3,5,6-tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride (e.g., 1,2,4,5-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,4,5,8-decahydronaphthalene tetracarboxylic dianhydride, 4,8-dimethyl-1,2,5,6-hexahydronaphthalene tetracarboxylic dianhydride, 2,6-dichloro-1,4,5,8-naphthalene tetracarboxylic dianhydride, carboxylic acid 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 dianhydride Examples of suitable dianhydrides include benzene-1,2,3,4-tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, benzene-1,2,3,4-tetracarboxylic acid dianhydride, and 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride, and preferably, pyromellitic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, etc. These may be used alone or in combination of two or more.

[0056] From the viewpoint of easily and efficiently achieving adhesion to the metal layer, heat resistance, dimensional stability, etc., in combination with the aromatic diamine component, the aromatic acid anhydride component preferably contains at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and more preferably contains pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0057] When the aromatic acid anhydride component contains at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, the proportion of at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride relative to the entire aromatic acid anhydride component (or all acid anhydride components) may be selected from a range of about 30 mol% or more (e.g., 40 to 100 mol%), for example, 50 mol% or more (e.g., 60 mol% or more), preferably 70 mol% or more (e.g., 80 mol% or more), and more preferably 90 mol% or more (e.g., 95 mol% or more, 97 mol% or more, 98 mol% or more, 99 mol% or more, 100 mol%).

[0058] When the aromatic acid anhydride component contains pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, the molar ratio of pyromellitic dianhydride to 3,3',4,4'-biphenyltetracarboxylic dianhydride may be, for example, about 95 / 5 to 40 / 60 (e.g., 90 / 10 to 45 / 55), preferably about 85 / 15 to 50 / 50 (e.g., 80 / 20 to 55 / 45).

[0059] The raw material components of the polyimide film (polymerization component, diamine component, and acid anhydride component) may contain other polymerization components (e.g., other acid anhydride components, other diamine components) in addition to the aromatic acid anhydride component and aromatic diamine component, as long as the effects of the present invention are not impaired. Examples of other diamine components (non-aromatic diamine components) include diaminoadamantanes (e.g., 1,3-diaminoadamantane, 3,3'-diamino-1,1'-diaminoadamantane, 3,3'-diaminomethyl-1,1'-diadamantane, etc.), diaminoalkanes (e.g., hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, 3-methylheptamethylenediamine, 4,4'-dimethylheptamethylenediamine, 2,11-diaminododecane, 2,2-dimethylpropane, etc.), Examples of suitable amines include propylenediamine, 3-methoxyhexaethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, 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 alone or in combination of two or more.

[0060] In addition, when the polymerization components contain other polymerization components (other diamine components, etc.), the ratio of the other polymerization components to the total polymerization components may be a small ratio, for example, 20 mol% or less (e.g., 15 mol% or less, 10 mol% or less, 5 mol% or less, 3 mol% or less, 1 mol% or less).

[0061] The polyimide film may contain other components in addition to polyimide (resin component). For example, the polyimide film may contain inorganic particles from the viewpoint of handleability (smoothness). The other components may be one or more.

[0062] When inorganic particles are contained, the inorganic particles are usually dispersed in the polyimide film. Examples of inorganic particles include oxides {e.g., SiO2 (silica), TiO2 (titanium (IV) oxide), etc.}, inorganic acid salts {e.g., phosphate (hydrogen) salts such as CaHPO4 (calcium hydrogen phosphate), CaPO4 (calcium phosphate), Ca2P2O7 (calcium diphosphate), etc., and carbonates such as CaCO3 (calcium carbonate)}. The inorganic particles may be used alone or in combination of two or more kinds.

[0063] The inorganic particles to be dispersed may have an average particle size of, for example, 0.1 to 3.5 μm (eg, 0.2 to 3 μm), preferably 0.3 to 2.5 μm. The method for measuring the average particle size of the inorganic particles is not particularly limited, and any known method may be used.

[0064] The particle size distribution of inorganic particles (inorganic particles to be dispersed) should be narrow, i.e., the proportion of inorganic particles of similar size to the total inorganic particles should be high. 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% by volume or more (e.g., 80 to 100% by volume) of the total inorganic particles.

[0065] When inorganic particles are contained, the proportion of inorganic particles in the polyimide film may be, for example, 0.01 mass % or more (e.g., 0.02 mass % or more), preferably 0.03 mass % or more (e.g., 0.04 mass % or more), and more preferably 0.05 mass % or more.

[0066] The upper limit of the proportion of inorganic particles in the polyimide film may be selected from a range of about 5% by mass or less (e.g., 3% by mass or less, 2% by mass or less, 1.5% by mass or less), and may be 1% by mass or less (e.g., 0.9% by mass or less), preferably 0.8% by mass or less (e.g., 0.7% by mass or less), and more preferably 0.6% by mass or less (e.g., 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).

[0067] The polyimide film may be in a laminated state, and in particular in a wound state, that is, in a roll form (roll). The width of the polyimide film (e.g., a roll-shaped polyimide film) is not particularly limited, and 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, or 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 (e.g., a roll-shaped polyimide film) may be, for example, 1 m or more (e.g., 5 m or more), 10 m or more (e.g., 20 m or more), preferably 30 m or more (e.g., 40 m or more), more preferably 50 m or more (e.g., 100 m or more), or may 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, etc.

[0068] The polyimide film may be surface-treated (for example, by electrical treatment such as corona treatment or plasma treatment, or by blasting). Such surface treatment may be performed on one or both sides. Depending on the surface treatment (plasma treatment, etc.) and its extent, it may cause a decrease in adhesion (for example, the value embodied in the aforementioned T2 or T2 / T1) when exposed to conditions such as high temperatures. On the other hand, in the present invention, sufficient adhesion can be achieved without surface treatment. Therefore, the polyimide film may be plasma-treated, but it is also preferable to select one that is not plasma-treated or that is only slightly plasma-treated.

[0069] The method for producing the polyimide film is not particularly limited, but some representative methods will be described below. To obtain a polyimide film, first, polymerization components (components containing an aromatic diamine component and an aromatic acid anhydride component) are polymerized in an organic solvent to obtain a polyamic acid solution (hereinafter also referred to as a polyamic acid solution).

[0070] Specific examples of organic solvents used to form the polyamic acid solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N,N-dimethylformamide and N,N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol 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 solvents may be used alone or in combination with two or more of them. Furthermore, they may be used in combination with aromatic hydrocarbons such as xylene and toluene.

[0071] The polymerization method of the polyamic acid solution may be any known method, for example, (1) A method in which the entire amount of the diamine component (aromatic diamine component) is first placed in a solvent, and then the acid anhydride component (aromatic acid anhydride component) is added in an amount equivalent to the entire amount of the diamine component (aromatic diamine component) to polymerize it. (2) A method in which the entire amount of the acid anhydride component (aromatic acid anhydride component) is first placed in a solvent, and then the diamine component (aromatic diamine component) is added in an amount equivalent to the acid anhydride component (aromatic acid anhydride component) to polymerize the resulting mixture. (3) A method of polymerizing by adding one diamine component (aromatic diamine component) to a solvent, mixing one acid anhydride component (aromatic acid anhydride component) in a ratio of 95 to 105 mol % to the reactants for the time required for the reaction, adding the other aromatic diamine component, and then adding the other acid anhydride component (aromatic acid anhydride component) so that the total diamine component (aromatic diamine component) and the total acid anhydride component (aromatic acid anhydride component) are approximately equivalent in weight, (4) A method of polymerizing by adding one acid anhydride component (aromatic acid anhydride component) to a solvent, mixing one diamine component (aromatic diamine component) in a ratio of 95 to 105 mol % relative to the reactants for a time required for reaction, adding the other acid anhydride component (aromatic acid anhydride component), and then adding the other diamine component (aromatic diamine component) so that the total diamine components (aromatic diamine components) and the total acid anhydride components (aromatic acid anhydride components) are approximately equivalent in weight; (5) In a solvent, one diamine component (aromatic diamine component) and one acid anhydride component (aromatic acid anhydride component) are reacted in excess to prepare a polyamic acid solution (A), and in a different solvent, the other diamine component (aromatic diamine component) and one acid anhydride component (aromatic acid anhydride component) are reacted in excess to prepare a polyamic acid solution (B).The polyamic acid solutions (A) and (B) thus obtained are mixed to complete the polymerization. In this case, if the diamine component (aromatic diamine component) is in excess when preparing the polyamic acid solution (A), the acid anhydride component (aromatic acid anhydride component) is added in excess in the polyamic acid solution (B); if the acid anhydride component (aromatic acid anhydride component) is in excess in the polyamic acid solution (A), the diamine component (aromatic diamine component) is added in excess in the polyamic acid solution (B); the polyamic acid solutions (A) and (B) are mixed together, and the total diamine component (aromatic diamine component) and total acid anhydride component (aromatic acid anhydride component) used in the reaction are adjusted to be approximately equivalent in amount. The polymerization method is not limited to these, and other known methods may be used.

[0072] The acid anhydride component (aromatic acid anhydride component) and the diamine component (aromatic diamine component) that constitute the polyamic acid are polymerized in a ratio such that the number of moles of each is approximately equal, but one of them may be blended in excess of the other within a range of 10 mol %, preferably 5 mol %.

[0073] The polymerization reaction is preferably carried out in an organic solvent while stirring. The polymerization temperature is not particularly limited, but is usually carried out at an internal temperature of the reaction solution of 0 to 80°C. 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 several steps or the temperature may be adjusted as necessary. There is no particular restriction on the order of addition of the two reactants, 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. The polymerization reaction may also be controlled by adding a small amount of an 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.

[0074] The polyamic acid solution thus obtained may typically contain 5 to 40% by mass, preferably 10 to 30% by mass, of solids. Its viscosity, measured with a Brookfield viscometer, is not particularly limited, but is typically 10 to 2,000 Pa·s, and for stable liquid transfer, is preferably 100 to 1,000 Pa·s. The polyamic acid in the organic solvent solution may be partially imidized.

[0075] When obtaining a polyimide film containing inorganic particles, the inorganic particles may be contained in a polyamic acid solution. To obtain a polyamic acid solution containing inorganic particles, the inorganic particles may be added to a prepolymerized polyamic acid solution, or the polyamic acid solution may be polymerized in the presence of the inorganic particles.

[0076] It is preferable to use the inorganic particles as a slurry (inorganic particle slurry) dispersed in a solvent (for example, a polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone) because this prevents aggregation.

[0077] The method for producing the inorganic particle slurry is not particularly limited and may be a conventionally known method. Examples of methods for producing the inorganic particle slurry include a method of mixing inorganic particles and a solvent using a mixer. Mixers with high shear force, such as a high-speed disperser, homomixer, ball mill, coalesce mixer, or stirring disperser, are preferably used. Furthermore, wet pulverization may be performed to reduce the average particle size. For example, a bead mill, a sand mill, or the like may be used for the wet pulverization.

[0078] The inorganic particle slurry may be a commercially available product in which inorganic particles are dispersed in a solvent in advance. The inorganic particle slurry may also contain other organic solvents, compounding agents, etc., as necessary.

[0079] The concentration of inorganic particles in the inorganic particle slurry is not particularly limited, but is, for example, 1 to 80 mass %, preferably 1 to 60 mass %, and more preferably 1 to 40 mass %.

[0080] Furthermore, it is preferable to filter the inorganic particle slurry through a filter having a predetermined pore size (for example, a cut filter having a pore size of 15 μm or less, preferably a pore size of 13 μm or less, more preferably a pore size of 11 μm or less, even more preferably a pore size of 5 μm or less, and particularly preferably a pore size of 3 μm or less) from the viewpoints of suppressing aggregation of inorganic particles and removing inorganic particles of a predetermined particle size (for example, inorganic particles of 15 μm or more) in the polyimide film.

[0081] The material of the filter is not particularly limited, and examples thereof include polymer materials (eg, polyethylene, polypropylene, polytetrafluoroethylene, etc.) and metals (eg, stainless steel, etc.).

[0082] The amount of inorganic particles added may be appropriately selected according to the desired content in the polyimide film (for example, 0.03 to 0.8 parts by mass per 100 parts by mass of polyimide when the polyimide is formed).

[0083] Next, a method for producing a polyimide film will be described. The polyimide film can be produced (produced) through, for example, step (1) of subjecting a polyamic acid solution to a cyclization reaction to obtain a gel film (converting a polyamic acid or a polyamic acid solution into a gel film), and step (2) of drying (and removing the solvent) the obtained gel film and subjecting it to a heat treatment. The drying and heat treatment promote drying and imidization.

[0084] In step (1), the method for cyclizing the polyamic acid solution is not particularly limited, but specific examples include (i) a method in which the polyamic acid solution is cast into a film and thermally dehydrated and cyclized to obtain a gel film (thermal cyclization method), or (ii) a method in which a catalyst (cyclization catalyst) and a dehydrating agent (conversion agent) are mixed into the polyamic acid solution, and chemically dehydrated to produce a gel film, which is then heated to obtain a gel film (chemical cyclization method), and the latter method (chemical cyclization method) is particularly preferred.

[0085] Surprisingly, the chemical ring-closure method (and furthermore, the selection of the polymerization components as described above while selecting the chemical ring-closure method) appears to be an effective way to obtain the physical properties (characteristics) required for the polyimide film of the present invention. Furthermore, the chemical ring-closure method is suitable from the viewpoint of mass productivity.

[0086] The polyamic acid solution may contain a gelation retarder, etc. The gelation retarder is not particularly limited, and acetylacetone, etc., can be used.

[0087] Examples of the cyclization catalyst include amines, such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), and heterocyclic tertiary amines (isoquinoline, pyridine, β-picoline, etc.). These may be used alone or in combination of two or more. Of these, heterocyclic tertiary amines such as β-picoline are preferred.

[0088] 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 alone or in combination of two or more. Among these, acetic anhydride and / or benzoic anhydride are preferred, with acetic anhydride being particularly preferred.

[0089] The amounts of the cyclization catalyst and dehydrating agent used are not particularly limited, but may be, for example, about 1 mol or more (e.g., 1.5 to 10 mol) per mol of amide group (or carboxyl group) of the polyamic acid (or polyamic acid).

[0090] A gel film can usually be obtained by casting (applying) a polyamic acid solution (particularly a polyamic acid solution mixed with a cyclization catalyst and a conversion agent) onto a support, and then partially drying and curing (imidizing).

[0091] More specifically, the polyamic acid solution may be cast onto a support from a slitted nozzle to form a film, and then heated by receiving heat from the support or from a heat source such as hot air or an electric heater to cause a ring-closing reaction. Volatile components such as the liberated organic solvent are dried to form a gel film, which can then be peeled off from the support.

[0092] Here, the gel film needs to be self-supporting in order to be peeled off, but the gel film obtained by the chemical ring-closure method and the gel film obtained by the thermal ring-closure method usually differ greatly in this aspect. That is, the chemical ring-closure method allows gelation (conversion) using a catalyst, resulting in a self-supporting gel film (flexible or wet gel film) that contains a lot of solvent, while the thermal ring-closure method requires a significant amount of heat treatment to gel (to make it self-supporting), resulting in a relatively hard gel film (with little residual solvent).

[0093] The support is not particularly limited, but examples include a metal (e.g., stainless steel) rotating drum, 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 medium, or (ii) radiant heat from an electric heater or the like.

[0094] In step (2), the gel film is dried (solvent removed) and then heat-treated. Typically, step (2) may include a step of passing the gel film through a heating furnace (such as a tenter heating furnace) while holding both ends in the width direction of the gel film to dry it, and then heat-treating it.

[0095] Specifically, the gel film peeled from the support may be stretched in the conveying direction while controlling the running speed with a rotating roll, although this is not particularly limited. The thickness of the polyimide film may be adjusted by controlling the running speed.

[0096] The stretching in the machine direction may be carried out at a predetermined temperature (for example, a temperature of 140°C or lower). The stretching ratio (MDX) is usually 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).

[0097] The drying temperature may be, for example, 210°C or higher (eg, 213 to 500°C), preferably 215°C or higher (eg, 218 to 400°C), and more preferably 220°C or higher (eg, 220 to 300°C).

[0098] Drying may be performed while suppressing drying unevenness (variation) in the film width direction. For example, the drying temperature unevenness 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 preferably 18°C ​​or less (e.g., 3 to 18°C).

[0099] The drying temperature unevenness can be measured, for example, by taking multiple points at a predetermined interval (for example, 200 mm) along the width direction of the film and measuring the difference (width) between the maximum and minimum values ​​of the drying temperature.

[0100] The gel film (particularly the gel film stretched in the machine direction) is dried and then heat-treated. The heat-treatment temperature is not particularly limited and may be, for example, 200°C or higher (e.g., 250 to 600°C), preferably 300°C or higher, and more preferably 350°C or higher.

[0101] 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 further by combining it with other conditions).

[0102] After drying, the film may be stretched in the width direction. The stretching in the width direction may be carried out together with the heat treatment.

[0103] In stretching in the transverse direction, the stretch ratio (TDX) may be, 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).

[0104] The physical properties (characteristics) required for the polyimide film (and furthermore, the polyimide film of the present invention) may be efficiently adjusted by such stretching and its conditions (and furthermore, by combining it with other conditions).

[0105] In this way, a polyimide film is obtained, which may be further subjected to an annealing treatment.

[0106] The method of annealing is not particularly limited, and any known method may be used. The annealing temperature 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 may be performed by running the film under low tension through a furnace heated to the above temperature range. The tension of the film during running may be, for example, 10 to 50 N / m, and more preferably 20 to 30 N / m.

[0107] The polyimide film (surface) obtained as described above may be subjected to a plasma treatment. The plasma treatment may be performed on both sides or one side of the polyimide film. As mentioned above, in consideration of adhesion when exposed to conditions such as high temperatures, it may be preferable not to subject the polyimide film to plasma treatment, or to subject it to a small degree of plasma treatment.

[0108] The method of plasma treatment is not particularly limited, and any known method may be used. The processing gas for the plasma processing is not particularly limited, but examples thereof include inert gases (e.g., He, Ar, Kr, Xe, Ne, Rn, N, etc.), O, H2O, air, CO2, etc. The processing gas may be used alone or in combination of two or more.

[0109] The processing pressure of the plasma processing is not particularly limited, but may be, for example, 0.1 Pa to 1330 kPa. The treatment intensity (E value) of the plasma treatment is not particularly limited, but is, for example, 50 W·min / m 2 More than 75W min / m 2 It can be more than 2000W·min / m 2 Below, 1800W min / m 2 The following may also be used: The processing time of the plasma treatment is not particularly limited, but may be, for example, 1 second to 10 minutes.

[0110] The physical properties (characteristics) (e.g., glass transition temperature, coefficient of linear expansion, etc.) of the polyimide film to which the coupling agent is applied may correspond to the physical properties (characteristics) of the polyimide film of the present invention (hereinafter, sometimes simply referred to as "polyimide film 1"). That is, the physical properties (characteristics) (for example, glass transition temperature, linear expansion coefficient, etc.) of the polyimide film to which the coupling agent is applied may be the same as the physical properties (characteristics) of the polyimide film 1 described later.

[0111] (Method of Producing Polyimide Film of the Present Invention) The method for producing the polyimide film of the present invention (polyimide film 1) will be described below.

[0112] The method for producing the polyimide film 1 includes a step of applying a coupling agent-containing solution to one or both surfaces of a polyimide film, followed by drying. 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.

[0113] The coupling agent-containing solution may generally contain a coupling agent and a solvent, and may also contain other components as necessary {for example, a surface treatment agent other than the coupling agent {for example, a silane compound [for example, a mono- to tetraalkoxysilane such as tetramethoxysilane or tetraethoxysilane, preferably a mono- to tetra-C1-4 alkoxysilane], etc.}}.

[0114] The coupling agent-containing solution can be prepared, for example, by mixing the coupling agent and the solvent (and, if necessary, other components).

[0115] The solvent is not particularly limited and examples thereof include water, alcohols (e.g., methanol, ethanol, etc.), esters (e.g., organic acid esters such as ethyl lactate and ethyl acetate), etc. From the viewpoint of the reactivity of the coupling agent (e.g., the reactivity of the reactive functional group with the polyimide), etc., esters, alcohols, etc. may be preferred. One or more solvents may be used. It is preferable to use a solvent different from the solvent used to form the polyamic acid solution (for example, a solvent other than N,N-dimethylacetamide).

[0116] 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, the formation of layer (A) on the surface of the polyimide film, etc., and may 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).

[0117] When the solvent contains an organic acid ester (e.g., ethyl lactate), the ratio of the organic acid ester (e.g., ethyl lactate) to the entire solvent may be, from the viewpoint of the reactivity of the coupling agent (e.g., the reactivity of the reactive functional group with the polyimide), 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).

[0118] 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) relative to the entire solvent is not particularly limited, but may be, for example, about 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).

[0119] In the drying, the drying temperature may be, for example, about 100°C or higher (e.g., 110°C or higher, 120°C or higher), preferably about 130°C or higher (e.g., 140°C or higher), from the viewpoints of the formation of layer (A) on the surface of the polyimide film and the adhesion between the polyimide film of the present invention and the metal layer, and may be, for example, about 280°C or lower (e.g., 250°C or lower), 220°C or lower (e.g., 210°C or lower), preferably about 200°C or lower (e.g., 190°C or lower).

[0120] The drying time may vary depending on the drying temperature, etc., but 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 may be, 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), from the viewpoints of the formation of layer (A) on the surface of the polyimide film and the adhesion between the polyimide film of the present invention and the metal layer.

[0121] (Polyimide film of the present invention) The polyimide film of the present invention (polyimide film 1) usually has specific physical properties.

[0122] The polyimide film 1 often satisfies at least one of the following physical properties, and typically may at least satisfy adhesion (peel strength from a metal layer) [particularly adhesion and one or more physical properties other than adhesion]. The following physical properties can be efficiently satisfied by, for example, the polyimide composition (of the polyimide film to be coated with a coupling agent), the film thickness, the film manufacturing conditions, or a combination (selection and adjustment) of these. The polyimide film 1 tends to maintain the physical properties (characteristics) (for example, glass transition temperature, linear expansion coefficient, etc.) of the polyimide film to which the coupling agent is applied.

[0123] The polyimide film 1 can achieve sufficient adhesion to a metal layer. Examples of such polyimide film 1 include polyimide films in which, when a metal layer is directly laminated (on the polyimide film 1) (without an adhesive layer), the peel strength (adhesion, peel strength, 90° peel strength) (T1) between the metal layer and the polyimide film 1 exceeds 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.

[0124] The upper limit of T1 is not particularly limited, but 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, or the like.

[0125] Such adhesion can be maintained at a relatively high level even under conditions such as high temperatures (e.g., severe conditions). Examples of such polyimide films 1 include polyimide films in which, when T1 is the peel strength (adhesion, peel strength) between a metal layer and polyimide film 1 when the metal layer is directly laminated (on the polyimide film 1) (laminate without an adhesive layer) and T2 is the peel strength (adhesion, peel strength) between the metal layer and polyimide film 1 after heating at 150°C for 168 hours, T2 / T1 is 0.3 or more (e.g., 0.4 or more), preferably 0.5 or more (e.g., more than 0.5, 0.55 or more), more preferably 0.6 or more (e.g., 0.65 or more), particularly 0.7 or more (e.g., 0.72 or more), and particularly preferably 0.75 or more (e.g., more than 0.75, 0.78 or more, 0.8 or more).

[0126] The upper limit of T2 / T1 may be 1, or may be less than 1 (for example, 0.99 or less, 0 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).

[0127] The value of T2 may be, for example, more than 0.2 kN / m (for example, 0.25 kN / m or more), preferably 0.3 kN / m or more (for example, 0.35 kN / m or more), and more preferably 0.4 kN / m or more.

[0128] The upper limit of T2 is not particularly limited, but 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, 0.9 kN / m or less, 0.8 kN / m or less, etc.

[0129] In measuring T1 (and further T2), the metal layer is not particularly limited, and may be a specific metal layer {for example, a layer corresponding to the examples described later, i.e., an 8.5 μm thick copper layer [for example, a 25 nm thick nickel / chromium alloy (nickel / chromium=80 / 20) layer (for example, a layer formed by sputtering) on ​​which a 100 nm thick copper layer (for example, a layer formed by sputtering) is formed, and on which an 8.5 μm thick copper layer (for example, a layer formed by plating)]}.

[0130] The method for measuring T1 (and further T2) may be, for example, in accordance with Method A of the copper foil peel strength test method described in JIS C 6471 (for example, a pulling angle of 90° and a pulling speed of 50 mm / min). More specifically, T1 (and further T2) may be measured by the method described in the Examples below.

[0131] In the polyimide film 1, the linear expansion coefficient αMD in the MD direction (the direction perpendicular to the machine conveying direction, longitudinal direction, length direction, longitudinal direction, or width direction (TD direction)) may be selected from a range of about 50 ppm / K or less (e.g., 40 ppm / K or less, 35 ppm / K or less, 30 ppm / K or less, or 25 ppm / K or less). From the viewpoint of dimensional stability (e.g., dimensional stability when a metal layer such as copper is laminated), the linear expansion coefficient αMD may be, for example, 20 ppm / K or less (e.g., 18 ppm / K or less), preferably 16 ppm / K or less (e.g., 15 ppm / K or less), more preferably 14 ppm / K or less (e.g., 13 ppm / K or less), or may be 12 ppm / K or less (e.g., 11 ppm / K or less, 10 ppm / K or less).

[0132] The lower limit of αMD may be 0 ppm / K, or may be greater than 0 ppm / K [for example, from the viewpoint of dimensional stability (for example, dimensional stability when laminating a metal layer such as copper), 1 ppm / K or more (for example, 1.5 ppm / K or more), preferably 2 ppm / K or more (for example, 2.5 ppm / K or more), and more preferably 3 ppm / K or more (for example, 3.5 ppm / K or more)], or may be 4 ppm / K or more (for example, 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).

[0133] Specific examples of αMD include 0 to 30 ppm / K, and from the viewpoint of dimensional stability (e.g., dimensional stability when laminating a metal layer such as copper), αMD may be 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).

[0134] In the polyimide film 1, the linear expansion coefficient αTD in the TD direction (width direction, transverse direction, transverse direction, direction perpendicular to the machine direction (MD) direction) may be selected from a range of about 50 ppm / K or less (e.g., 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 (e.g., dimensional stability when laminating a metal layer such as copper), it may be, for example, about 20 ppm / K or less (e.g., 18 ppm / K or less), preferably 16 ppm / K or less (e.g., 15 ppm / K or less), more preferably 14 ppm / K or less (e.g., 13 ppm / K or less), or may be 12 ppm / K or less (e.g., 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.

[0135] The lower limit of αTD may be, for example, −10 ppm / K or more (e.g., −9 ppm / K or more, −8 ppm / K or more, −7 ppm / K or more, −6 ppm / K or more), −5 ppm / K or more (e.g., −4 ppm / K or more, −3 ppm / K or more, −2 ppm / K or more, −1 ppm / K or more), 0 ppm / K or more, or more than 0 ppm / K [e.g., 1 ppm / K or more (e.g., 1.5 ppm / K or more)], and preferably 2 ppm / K or more.

[0136] A specific αTD may be, for example, -10 to 30 ppm / K, and from the viewpoint of dimensional stability (for example, dimensional stability when laminating a metal layer such as copper), it may be preferably -10 to 20 ppm / K (for example, -8 to 18 ppm / K), and more preferably -5 to 17 ppm / K (for example, -5 to 15 ppm / K, -5 to 10 ppm / K, or -5 to 8 ppm / K).

[0137] In the polyimide film 1, the value of (|αMD|+|αTD|) / 2 may be selected from a range of about 50 ppm / K or less (e.g., 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 (e.g., dimensional stability when laminating a metal layer such as copper), it may be, for example, about 20 ppm / K or less (e.g., 18 ppm / K or less), preferably 16 ppm / K or less (e.g., 15 ppm / K or less), more preferably 14 ppm / K or less (e.g., 13 ppm / K or less), or may be 12 ppm / K or less (e.g., 11 ppm / K or less, 10 ppm / K or less), etc.

[0138] The lower limit of (|αMD|+|αTD|) / 2 may be 0 ppm / K, or may be greater than 0 ppm / K [for example, from the viewpoint of dimensional stability (for example, dimensional stability when laminating a metal layer such as copper), 1 ppm / K or more (for example, 1.5 ppm / K or more), preferably 2 ppm / K or more (for example, 2.5 ppm / K or more), and more preferably 3 ppm / K or more (for example, 3.5 ppm / K or more)], or may be 4 ppm / K or more (for example, 4.5 ppm / K or more, 5 ppm / K or more).

[0139] A specific example of (|αMD|+|αTD|) / 2 is 0 to 30 ppm / K, and from the viewpoint of dimensional stability (e.g., dimensional stability when laminating a metal layer such as copper), it may be 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, 4 to 15 ppm / K, 5 to 14 ppm / K), etc.

[0140] In the polyimide film 1, the absolute value of the difference between |αMD| and |αTD| (|αMD|-|αTD|) may be selected from a range of about 30 ppm / K or less (e.g., 25 ppm / K or less, 20 ppm / K or less). From the viewpoint of dimensional stability (e.g., dimensional stability when laminating a metal layer such as copper), it may be, for example, about 15 ppm / K or less (e.g., 12 ppm / K or less), preferably 10 ppm / K or less (e.g., 8 ppm / K or less), more preferably 7 ppm / K or less (e.g., 6 ppm / K or less), or may be 5 ppm / K or less (e.g., 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.

[0141] The absolute value (lower limit value) of the difference between |αMD| and |αTD| (|αMD|-|αTD|) may be 0 ppm / K or 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).

[0142] Incidentally, αMD and αTD are not particularly limited, but may be measured in a specific temperature range (for example, 50 to 200°C) or under specific conditions (for example, a temperature rise rate of 10°C / min). Specifically, they may be measured by the method described in the Examples below.

[0143] 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 about 400°C or less (e.g., 395°C or less) from the viewpoint of adhesion to the metal layer, etc., and may be preferably 390°C or less (e.g., 385°C or less), and more preferably 380°C or less (e.g., 375°C or less).

[0144] The Tg (lower limit of Tg) of the polyimide film 1 may be selected from a range of about 150°C or higher (e.g., 160°C or higher, 170°C or higher) from the viewpoint of heat resistance, dimensional stability, etc. (and further, a balance or compatibility with adhesion to a metal layer), and is, for example, 180°C or higher (e.g., 190°C or higher), preferably 200°C or higher (e.g., 210°C or higher), and more preferably 220°C or higher (e.g., 22 5°C or higher), or 230°C or higher (e.g., 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.

[0145] These ranges (upper and lower limits) may be combined appropriately to select a range (for example, 200 to 400°C, 230 to 390°C, etc.; the same applies to the ranges hereinafter).

[0146] Specific examples of Tg of the polyimide film 1 include 180 to 400°C, preferably 200 to 390°C, and more preferably 220 to 380°C.

[0147] The method for measuring Tg may be any known method, and is not particularly limited. For example, the tan δ method (that is, the peak intensity of tan δ is taken as the value of Tg) may be used.

[0148] In the polyimide film 1, the thickness ratio of the polyimide film (the polyimide film to be coated with a coupling agent) to the layer (A) can be selected depending on the application, etc., and may be selected, for example, from a range of about 30,000 / 1 to 10 / 1 (e.g., 20,000 / 1 to 30 / 1) such that the thickness ratio of the polyimide film to be coated with a coupling agent / the layer (A) is about 10,000 / 1 to 40 / 1 (e.g., 8,000 / 1 to 50 / 1), preferably about 6,000 / 1 to 60 / 1 (e.g., 5,000 / 1 to 50 / 1), and more preferably about 3,000 / 1 to 70 / 1 (e.g., 2,900 / 1 to 80 / 1, 2,800 / 1 to 100 / 1, 2,700 / 1 to 200 / 1).

[0149] The 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 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). Since polyimide film 1 has layer (A), it was expected that the breakdown voltage would be low due to decomposition of the hydrolysis condensate of the coupling agent, etc., but the fact that polyimide film 1 had a high breakdown voltage was an unexpected effect. The reason why polyimide film 1 has a high breakdown voltage is not clear, but it is thought that the presence of layer (A) in polyimide film 1 results in the formation of chemical bonds on the polyimide film surface, reducing the unevenness (roughness) of the polyimide film surface, increasing the number of contact points with the electrodes and preventing localized conduction, or that layer (A) prevents conduction due to moisture.

[0150] The breakdown voltage of the polyimide film 1 may be selected by appropriately combining these ranges (upper and lower limits) (for example, 450 to 600 kV / mm).

[0151] The method for measuring the breakdown voltage is not particularly limited, but may be, for example, a method conforming to the plate electrode method of JIS C 2151.

[0152] [Polyimide film applications, metal laminated films, etc.] The polyimide film of the present invention is suitable for laminating with metal (metal layer).

[0153] Such a polyimide film can be laminated with a metal (metal layer) directly without an adhesive layer, and is therefore suitable as a polyimide film for laminating a metal (metal layer) directly without an adhesive layer.

[0154] Furthermore, a metal (metal layer) can be efficiently laminated (formed) on the polyimide film by metallizing (plating, etc.), and therefore the polyimide film of the present invention is also suitable for metallizing.

[0155] Such a preferred polyimide film will be described below, including its mode of use.

[0156] As described above, the polyimide film can be formed into a laminated film by laminating a metal (metal layer).

[0157] Such a laminated film can be called a laminated film (metal-laminated polyimide film, metal-laminated film) composed of a polyimide film and a metal layer (metal) laminated on the polyimide film.

[0158] In the laminated film, the metal layer may be laminated (formed) on the polyimide film, usually without an adhesive layer (or directly).

[0159] In such a laminated film, the metal layer may be a metal foil or the like, or may be formed by metallizing, but is preferably formed by metallizing.

[0160] The metallizing (metallizing method) is not particularly limited, but a representative example is plating (plating method). Specific examples of metallizing include wet plating (e.g., electrolytic plating) and dry plating (e.g., vacuum deposition, sputtering, ion plating, etc.).

[0161] These methods may be used alone or in combination of two or more. An example of combining two or more methods is, for example, when a metal layer is composed of an underlayer and an overlayer as described below, forming the underlayer by a dry plating method (for example, forming a relatively thin layer) and forming the overlayer by a wet plating method.

[0162] The metal constituting the metal layer is not particularly limited, but examples thereof include metals such as copper, nickel, chromium, manganese, aluminum, iron, molybdenum, cobalt, tungsten, vanadium, titanium, and talc, alloys of these metals, oxides of these metals, and carbides of these metals.

[0163] The metal layer may be made of one or more metals.

[0164] The metal layer may be a single layer or multiple layers (for example, two or three layers).

[0165] For example, the metal layer may be composed of an underlayer (underlayer metal layer, base metal layer) and an overlayer (overlayer metal layer, wiring layer) laminated (formed) on the underlayer. The underlayer and overlayer (e.g., underlayer) may also be multilayered.

[0166] When the metal layer is multi-layered, the metals constituting each layer may be the same or different.

[0167] For example, in the case of a copper laminated film, the metal layer in the copper laminated film may be composed of only a copper layer, or the copper layer (overlying layer) may be formed via an underlying layer (underlying metal layer). In this case, the underlying layer may be one layer or two or more layers, and may be composed of at least one selected from copper and non-copper metals.

[0168] Specific examples of metal layers having a copper layer as an upper layer include an underlayer (e.g., a sputtering layer) made of at least one layer selected from a copper layer, a non-copper metal layer (e.g., a nickel / chromium layer), and a combination thereof, and a copper layer (e.g., a plated layer) laminated on this underlayer.

[0169] The metal layer may be formed on one side or both sides of the polyimide film. When a plasma-treated polyimide film is used, the metal layer may be formed on the plasma-treated side of the polyimide film.

[0170] The thickness of the metal layer (total thickness if multilayer, thickness of each metal layer if provided on both sides) can be selected appropriately depending on the application and the type of 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.

[0171] In particular, in wiring boards (printed wiring boards) and the like, the thickness of a metal layer [for example, a copper layer (including a metal layer having a copper layer as an upper 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).

[0172] When the metal layer includes an underlayer, the thickness of the underlayer is not particularly limited, and may be, for example, 1 to 500 nm (eg, 5 to 200 nm).

[0173] When the metal layer includes an underlayer, the proportion of the thickness of the underlayer to the total thickness of the metal layer may be selected, for example, from a range of approximately 30% or less, or may be 20% or less (e.g., 15% or less, 10% or less, 5% or less, 3% or less, 2% or less), etc.

[0174] 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 more preferably 20 μm or less (e.g., 15 μm or less, 12 μm or less, 10 μm or less).

[0175] According to the polyimide film of the present invention (the laminated film of the present invention), sufficient adhesive strength can be achieved even with a metal layer having such a relatively small (thin, low proportion) thickness.

[0176] In the laminated film, the thickness ratio of the polyimide film to the metal layer can be selected depending on the application, etc., and may be selected, for example, from a range of about polyimide film / metal layer (thickness ratio) = 1 / 0.001 to 1 / 100 (e.g., 1 / 0.01 to 1 / 50), or may be about 1 / 0.02 to 1 / 10 (e.g., 1 / 0.03 to 1 / 8), preferably 1 / 0.05 to 1 / 5 (e.g., 1 / 0.07 to 1 / 3), and more preferably 1 / 0.1 to 1 / 2 (e.g., 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.

[0177] Taking a copper laminated film (e.g., a copper laminated film suitable for printed wiring boards, etc.) as an example, a more specific example (concrete example) of the manufacturing method is to perform a surface treatment (e.g., nickel / chromium is sputtered to perform a surface treatment, followed by copper sputtering) under vacuum conditions on the surface of a polyimide film on which copper is to be formed to form a thin copper film, and then a copper layer is laminated by electroplating using a copper sulfate bath or the like.

[0178] The metal layer (copper plating layer, etc.) may be patterned by etching, etc. The etching method is not particularly limited, and any conventionally known method may be used.

[0179] In the laminated film, the metal layer and the polyimide film may be firmly adhered to each other.

[0180] Examples of such laminated films include those having a peel strength (adhesion strength, peel strength) value (T1) between the metal layer and the polyimide film of more 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.

[0181] The upper limit of T1 is not particularly limited, but 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, or the like.

[0182] Such adhesion can be maintained at a relatively high level even under conditions such as high temperatures (e.g., severe conditions). Examples of such laminate films include those in which, when the peel strength (adhesion, peel strength) between the metal layer and the polyimide film is T1 and the peel strength (adhesion, peel strength) between the metal layer and the polyimide film after heating at 150°C for 168 hours is T2, the ratio T2 / T1 is 0.3 or more (e.g., 0.4 or more), preferably 0.5 or more (e.g., more than 0.5, 0.55 or more), more preferably 0.6 or more (e.g., 0.65 or more), particularly 0.7 or more (e.g., 0.72 or more), and particularly preferably 0.75 or more (e.g., more than 0.75, 0.78 or more, 0.8 or more).

[0183] The upper limit of T2 / T1 may be 1 or 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).

[0184] The value of T2 may be, for example, more than 0.2 kN / m (for example, 0.25 kN / m or more), preferably 0.3 kN / m or more (for example, 0.35 kN / m or more), and more preferably 0.4 kN / m or more.

[0185] The upper limit of T2 is not particularly limited, but 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, 0.9 kN / m or less, 0.8 kN / m or less, etc.

[0186] The method for measuring T1 (and further T2) may be, for example, in accordance with Method A of the copper foil peel strength test method described in JIS C 6471 (for example, a pulling angle of 90° and a pulling speed of 50 mm / min). More specifically, T1 (and further T2) may be measured by the method described in the Examples below.

[0187] The laminated film can be used for a variety of purposes, for example, in circuit boards such as COF (Chip on Film) and flexible printed circuit boards (FPC) (particularly boards using fine-pitch wiring circuits). [Example]

[0188] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way, and many modifications can be made by those skilled in the art within the technical spirit of the present invention.

[0189] In the examples, the following compounds are abbreviated as follows: Paraphenylenediamine: PPD 4,4'-Diaminodiphenyl ether: 4,4'-ODA Pyromellitic dianhydride: PMDA 3,3',4,4'-Biphenyltetracarboxylic dianhydride: BPDA N,N-dimethylacetamide: DMAc

[0190] Each characteristic was evaluated by the following method.

[0191] Coefficient of thermal expansion (CTE) Measurements were performed using a TMA-50 (trade name, manufactured by Shimadzu Corporation) at a temperature range of 50 to 200°C at a heating rate of 10°C / min. The thermal expansion coefficient α was defined as α = (|αMD| + |αTD|) / 2, where αMD is the linear expansion coefficient in the machine direction (MD) of the film and αTD is the linear expansion coefficient in the width direction (TD).

[0192] Glass transition temperature (Tg) Measurements were performed using a DMS6100 (trade name: manufactured by Hitachi High-Tech Science) in a temperature range of 25 to 420°C, with a nitrogen flow rate of 50 mL / min, 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'), obtained by the measurement, shows a maximum was defined as the glass transition temperature (Tg).

[0193] 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 copper foil peel strength test method described in JIS C 6471, measured at a pulling angle of 90° and a pulling speed of 50 mm / min. The adhesion strength measured immediately after the copper-laminated polyimide film was prepared was defined as normal adhesion strength (T1), and the adhesion strength measured after heating at 150°C for 168 hours was defined as heat-resistant adhesion strength (T2).

[0194] Thickness of polyimide film (to be coated with coupling agent) Using a Mitutoyo Lightmatic (Series 318) thickness meter, 15 locations were randomly selected from the entire surface of the film, and the thickness was measured at these 15 locations, and the average was calculated to be the film thickness.

[0195] Layer (1) thickness Using an ULVAC-PHI X-ray photoelectron spectrometer, the Si intensity was measured in the depth direction from the film surface, and the point at which the slope of the relationship between Si intensity and depth (linear graph) changed was taken as the displacement point, and the depth from the film surface to the displacement point was taken as the thickness of layer (1).

[0196] Layer (2) thickness Using a secondary ion mass spectrometer manufactured by ULVAC-PHI, the Si intensity was measured in the depth direction from the film surface, and the depth from the displacement point to where the Si intensity became 0 was taken as the thickness of layer (2).

[0197] Evaluation of inorganic particles A sample dispersed in a polar solvent was measured using a laser diffraction / scattering particle size distribution analyzer LA-910 manufactured by Horiba, Ltd., and the average particle size was read as the volume average diameter from the results of analyzing the laser diffraction and scattered light intensity patterns.

[0198] -Measurement of breakdown voltage Measurements were taken in accordance with the plate electrode method of JIS C 2151, with an input voltage of 100V±10% 50 / 60Hz, an output voltage of DC 0 to +50KV / 5Ma, and a voltage rise time that was variable from 40 to 800 seconds. Before the measurement, the film test piece was dried at 200°C for 30 minutes before the measurement. The dimensions of the film test piece were 200 mm x 200 mm, and the measurement atmosphere was 25°C x 60% RH.

[0199] (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 and stirred until completely dissolved. 50.2 g of PMDA was then added and stirred for 1 hour. 71.3 g of 4,4'-ODA was then added, and after confirming complete dissolution, 52.4 g of BPDA and 39.1 g of PMDA were added and stirred for 3 hours to obtain a 3000 poise polyamic acid solution (20% solids by weight). To this solution, 0.3 μm average particle size silica DMAc slurry was added at 0.3% by weight per polyamic acid resin weight and thoroughly stirred to disperse.

[0200] (Preparation of coating liquid) A coating liquid (a solution containing a silane coupling agent) was prepared as follows. [Coating liquid 1] Coating liquid 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 liquid 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 liquid 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.).

[0201] [Example 1] (Preparation of polyimide film) The polyamic acid solution obtained in Synthesis Example 1 was cooled to −5° C., and then 21 parts by mass of DMAc, 16 parts by mass of acetic anhydride, and 14 parts by mass of 3-methylpyridine were mixed with 100 parts by mass of the solid content of polyamic acid to obtain a mixed solution. This mixture was poured onto a rotating drum at 85°C using a T-shaped slit die for 30 seconds, and the resulting self-supporting film was stretched 1.23 times in the running direction while heated at 100°C for 5 minutes. Next, both ends in the width direction were held and stretched 1.4 times in the width direction while heated at 270°C for 2 minutes, and then heated at 380°C for 90 seconds to obtain a polyimide film 500 mm wide, 25 μm thick, and 500 m long. Coating Liquid 1 was applied to one side of the polyimide film and dried at 130°C for 60 seconds to obtain Polyimide Film 1. In Polyimide Film 1, the thickness of Layer (1) was 20 nm, and the thickness of Layer (2) was 180 nm.

[0202] (Preparation of copper-laminated polyimide film) One side of polyimide film 1 was subjected to plasma treatment, followed by forming a 25 nm thick nickel / chromium alloy (nickel / chromium = 80 / 20) layer by sputtering. Next, a 100 nm thick copper layer was formed on this nickel / chromium alloy layer, also by sputtering. Next, the copper layer was electrolytically plated to a thickness of 8.5 μm. Finally, copper etching was performed to pattern the wiring width to 1 mm, thereby obtaining copper-laminated polyimide film 1. The adhesion of this copper-laminated polyimide film 1 was evaluated, and the results are shown in Table 1.

[0203] [Example 2] Polyimide film 2 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating liquid in Example 1 was changed to 200° C. In addition, copper-laminated polyimide film 2 was obtained using this polyimide film 2 in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 2 was evaluated, and the results are shown in Table 1.

[0204] [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 liquid in Example 1 was changed to 90 seconds. Furthermore, this polyimide film 3 was used to obtain a copper-laminated polyimide film 3 in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 3 was evaluated, and the results are shown in Table 1.

[0205] [Example 4] Polyimide film 4 was obtained in the same manner as in Example 3, except that Coating Liquid 2 was used instead of Coating Liquid 1. Furthermore, using this polyimide film 4, copper-laminated polyimide film 4 was obtained in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 4 was evaluated, and the results are shown in Table 1.

[0206] [Example 5] Polyimide film 5 was obtained in the same manner as in Example 3, except that Coating Liquid 3 was used instead of Coating Liquid 1. Furthermore, using this polyimide film 5, copper-laminated polyimide film 5 was obtained in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 5 was evaluated, and the results are shown in Table 1.

[0207] [Comparative Example 1] A polyimide film 6 was obtained in the same manner as in Example 1, except that the coating liquid of Example 1 was not applied. Furthermore, using this polyimide film 6, a copper-laminated polyimide film 6 was obtained in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 6 was evaluated, and the results are shown in Table 1.

[0208] Comparative Example 2 The polyamic acid solution obtained in Synthesis Example 1 was cooled to −5° C., and then 21 parts by mass of DMAc, 16 parts by mass of acetic anhydride, and 14 parts by mass of 3-methylpyridine were mixed with 100 parts by mass of the solid content of polyamic acid to obtain a mixed solution. This mixture was passed through a T-slit die onto a rotating drum at 85°C for 30 seconds, after which Coating Solution 3 was applied to one side of the resulting self-supporting film and dried at 120°C for 150 seconds. The film was then stretched 1.23 times in the running direction while heated at 100°C for 5 minutes. The film was then gripped at both widthwise ends and stretched 1.4 times in the widthwise direction while heated at 270°C for 2 minutes, after which it was heated at 380°C for 90 seconds to obtain Polyimide Film 7, 500 mm wide, 25 μm thick, and 500 m long. In addition, for the polyimide film 7, the Si intensity was measured in the depth direction from the film surface using a secondary ion mass spectrometer manufactured by ULVAC-PHI, in the same manner as in the thickness measurement method for the layer (2) described above, and the depth at which the Si intensity became 0 was measured and found to be 390 nm. Using polyimide film 7, copper-laminated polyimide film 7 was obtained in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 7 was evaluated, and the results are shown in Table 1.

[0209] In Table 1, αMD, αTD, α, Tg and breakdown voltage are values ​​for polyimide films 1 to 7.

[0210] [Table 1]

[0211] As shown in Table 1, the polyimide films of Examples 1 to 5 were able to maintain adhesion to the metal layer when exposed to high temperature conditions, compared to Comparative Examples 1 and 2. Moreover, the polyimide films of Examples 1 to 5 had higher breakdown voltages than those of Comparative Examples 1 and 2.

[0212] [Example 6] Polyimide film 8 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating liquid in Example 1 was changed to 170° C. In addition, copper-laminated polyimide film 8 was obtained using this polyimide film 8 in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 8 was evaluated. Table 2 shows the results.

[0213] [Example 7] Polyimide film 9 was obtained in the same manner as in Example 1, except that the drying temperature after application of the coating liquid in Example 1 was changed to 250° C. In addition, copper-laminated polyimide film 9 was obtained using this polyimide film 9 in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 9 was evaluated, and the results are shown in Table 2.

[0214] [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 liquid in Example 1 was changed to 280° C. In addition, a copper-laminated polyimide film 10 was obtained using this polyimide film 10 in the same manner as in Example 1. The adhesion of this copper-laminated polyimide film 10 was evaluated, and the results are shown in Table 2.

[0215] [Table 2] [Industrial Applicability]

[0216] The polyimide film of the present invention is useful for laminating metals and the like.

Claims

1. A polyimide film for metal lamination, having a layer (A) containing a hydrolysis condensate of a coupling agent on one or both sides.

2. A polyimide film for metal lamination, in which T1 is the peel strength between a copper layer and a polyimide film when the copper layer is directly laminated thereon, and T2 is the peel strength between the copper 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.

3. 2. The polyimide film according to claim 1, wherein the coupling agent has an amino group.

4. 4. The polyimide film according to claim 1, wherein the coupling agent comprises a silane coupling agent.

5. 4. The polyimide film according to claim 1, wherein the coupling agent comprises an amino-silane coupling agent.

6. 4. The polyimide film according to claim 1, wherein the layer (A) has a thickness of 100 to 400 nm.

7. 4. The polyimide film according to claim 1, wherein the layer (A) comprises a layer (1) of a hydrolysis condensate of a coupling agent.

8. 4. The polyimide film according to claim 1, wherein the layer (A) comprises a layer (2) containing a hydrolysis condensate of a coupling agent and a component derived from a polyimide.

9. 9. The polyimide film according to claim 8, wherein the thickness of the layer (2) is 300 nm or less.

10. 4. The polyimide film according to claim 1, wherein the coupling agent comprises 3-aminopropyltrimethoxysilane.

11. 3. The polyimide film according to claim 1, wherein the value of (|αMD| + |αTD|) / 2 is 15 ppm / K or less, where αMD is the linear expansion coefficient of the film in the machine direction and αTD is the linear expansion coefficient of the film in the width direction.

12. 3. The polyimide film according to claim 1, wherein αTD is −5 to +10 ppm / K.

13. 3. The polyimide film according to claim 1, wherein the polymerization components are 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 dianhydride.

14. 3. The polyimide film according to claim 1, further comprising inorganic particles.

15. 3. The polyimide film according to claim 1, which is in a roll form.

16. 3. The polyimide film according to claim 1, which contains inorganic particles in an amount of 0.01 to 5% by mass and is in the form of a roll having a length of 5 m or more.

17. 3. The polyimide film according to claim 1, which is used for metallizing.

18. 3. The polyimide film according to claim 1, for directly laminating a copper layer having a thickness of 20 μm or less.

19. 3. A laminated film comprising a polyimide film and a metal layer laminated directly on the polyimide film, wherein the polyimide film is the polyimide film according to claim 1 or 2.

20. 20. The laminated film according to claim 19, wherein the metal layer is a copper layer having a thickness of 20 μm or less.

21. 20. The laminated film according to claim 19, wherein the peel strength T1 between the metal layer and the polyimide film is 0.5 kN / m or more.

22. The laminated film according to claim 19, wherein 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.

23. A method for producing a polyimide film for metal lamination, comprising the steps of applying a solution containing a coupling agent to one or both surfaces of a polyimide film and then drying the solution.

24. The method according to claim 23, wherein the coupling agent-containing solution contains 0.1 to 5% by mass of the coupling agent.

25. The method according to claim 23 or 24, wherein the drying is carried out at a drying temperature of 130 to 200°C for a drying time of 40 to 100 seconds.

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