Polyimide film

Abstract

Provided is a polyimide film that can be used in metal lamination or the like. The polyimide film has a layer (A) containing a hydrolysis-condensation product of a coupling agent on one or both surfaces thereof.

Description

Technical Field

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

[0002] Due to its excellent heat resistance, chemical resistance, and electrical properties, polyimide film is widely used in electrical insulation materials for wires, base films for chip-on-film (COF), flexible printed circuit boards (FPC), carrier films for tape automated bonding (TAB) of ICs, and tapes for fixing lead frames of ICs.

[0003] As electronic devices become smaller, lighter, more functional, and multifunctional, and with higher-density packaging, the printed circuit boards used in these electronic devices are rapidly becoming higher-density due to the narrowing of conductor widths and spacing between conductors, multi-layering, flexibility, and thinner substrates.

[0004] Conventionally, there is known a substrate for a flexible printed circuit 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 (Patent Document 1).

[0005] On the other hand, when the polyimide film is bonded to the conductor layer via the adhesive layer, sufficient adhesiveness (close adhesion) may not be obtained between the polyimide film and the metal layer.

[0006] Among them, it is known that when manufacturing a polyimide film, a solution containing a heat-resistant surface treatment agent is applied to the surface of a cured film (self-supporting film) of polyamic acid, and the cured film is heat-treated to perform imidization, thereby obtaining a polyimide film with improved adhesion (Patent Document 2).

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent No. 2680816

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 62-267330 Summary of the Invention

[0011] (1) Technical issues to be resolved

[0012] An object of the present invention is to provide a polyimide film suitable for metal lamination (for lamination of metal layers) and the like.

[0013] (2) Technical solution

[0014] As described above, it is known that a polyimide film is produced by applying a surface treatment agent to the surface of a self-supporting film of polyamic acid and then heat-treating the film.

[0015] However, the inventors of the present application have found that although the adhesion between the polyimide film obtained in the above manner and the metal layer is improved immediately after the metal layer is laminated, the adhesion may be easily degraded when the metal layer laminated film is exposed to high temperature.

[0016] Therefore, the inventors of the present application studied polyimide films for metal lamination from a perspective completely different from the above-mentioned conventional polyimide films.

[0017] The inventors of the present application did not study coating a surface treatment agent on a self-supporting film of polyamic acid, but unexpectedly studied coating a surface treatment agent on an imidized polyimide film.

[0018] However, the case of coating a surface treatment agent on an imidized polyimide film is different from the case of coating it on a self-supporting film of polyamic acid. It is not known whether this is because polyimide hardly reacts with the surface treatment agent (i.e., because almost no chemical bond is formed between polyimide and the surface treatment agent), and therefore it is difficult to form a layer containing a hydrolysis condensate of the surface treatment agent on the polyimide film.

[0019] Furthermore, depending on the type of surface treatment agent, it may be difficult to efficiently form such a layer, and it is extremely difficult to form a layer containing a hydrolysis-condensation product of the surface treatment agent on an imidized polyimide film.

[0020] In this regard, the inventors of the present application have conducted further in-depth studies and have found that by treating a specific surface treatment agent (particularly a coupling agent such as a silane coupling agent) under specific conditions [for example, the coupling agent concentration in a solution containing the coupling agent, the drying conditions after coating the coupling agent (for example, the drying temperature, the drying time, etc.)], a polyimide film having a layer containing a hydrolysis condensate of the surface treatment agent can be effectively obtained.

[0021] Furthermore, the inventors of the present application have discovered that this polyimide film is suitable for laminating metal layers, and can achieve sufficient adhesion even without providing an adhesive layer (in particular, even a metal layer of relatively thin thickness can be laminated with sufficient adhesion). The metal layer-laminated polyimide film formed by laminating a metal layer on the film can suppress the decrease in the above-mentioned adhesion even when exposed to high temperature conditions.

[0022] Furthermore, the inventors of the present application discovered that, compared to the case of using a polyimide film obtained by coating a surface treatment agent on a self-supporting film of polyamic acid, when the film is made into a metal-layer-laminated polyimide film laminated with a metal layer, the above-mentioned decrease in adhesion when exposed to high temperature conditions can be suppressed. Further research was carried out, thereby completing the present invention.

[0023] That is, the present invention relates to the following inventions and the like.

[0024] [1] A polyimide film (particularly a polyimide film for metal lamination) having a layer (A) containing a hydrolysis condensate of a coupling agent (e.g., a silane coupling agent) (or formed using a hydrolysis condensate) on one or both sides.

[0025] [2] A polyimide film (particularly a polyimide film for metal lamination), wherein, when the peel strength (for example, 90° peel strength) between the copper layer and the polyimide film when a copper layer (for example, a copper layer with a thickness of 8.5 μm, a copper layer with a thickness of 8.5 μm formed via a metal layer (copper layer) formed by sputtering) is directly laminated is set as T1, and the peel strength (for example, 90° peel strength) between the copper layer and the polyimide film after heating at 150°C for 168 hours is set as T2, T1 is 0.4 kN / m or more, and T2 / T1 is 0.7 or more.

[0026] Furthermore, such a polyimide film can be produced, for example, by applying a solution containing a coupling agent onto (one or both sides of) a (imidized) polyimide film and drying (hydrolysis and condensation), as described later. Specifically, such a polyimide film can be obtained by applying a solution containing a coupling agent onto (one or both sides of) a (imidized) polyimide film and drying (hydrolysis and condensation).

[0027] [3] The polyimide film according to [1], wherein the coupling agent has an amino group.

[0028] [4] The polyimide film according to [1] or [3], wherein the coupling agent includes a silane coupling agent.

[0029] [5] The polyimide film according to any one of [1] and [3] to [4], wherein the coupling agent includes an amino-based silane coupling agent.

[0030] [6] The polyimide film according to any one of [1] and [3] to [5], wherein the thickness of the layer (A) is 100 to 400 nm.

[0031] [7] The polyimide film according to any one of [1] and [3] to [6], wherein the layer (A) (on the surface side) comprises a layer (or film) (1) of a hydrolysis condensate of a coupling agent.

[0032] [8] The polyimide film according to any one of [1] and [3] to [7], wherein the layer (A) includes a layer (2), and the layer (2) includes a hydrolysis condensate of a coupling agent and a component derived from polyimide.

[0033] [9] The polyimide film according to [8], wherein the thickness of the layer (2) is 300 nm or less.

[0034]

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

[0035]

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

[10] , wherein when the linear expansion coefficient in the mechanical transport direction (MD) of the film is set to αMD and the linear expansion coefficient in the width direction (TD) is set to αTD, the value of (|αMD|+|αTD|) / 2 is less than 15 ppm / K.

[0036]

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

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

[0037]

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

[12] , wherein (the polyimide constituting the polyimide film) comprises an aromatic diamine component and an aromatic anhydride component as polymerization components, wherein the aromatic diamine component comprises at least one selected from p-phenylenediamine and 4,4'-diaminodiphenyl ether, and the aromatic anhydride component comprises at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

[0038]

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

[13] , wherein the polyimide film contains inorganic particles.

[0039]

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

[14] , wherein the polyimide film is in a roll form.

[0040]

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

[15] , wherein the polyimide film contains inorganic particles at a ratio of 0.01 to 5% by mass, and the polyimide film is in a roll shape with a length of 5 m or more.

[0041]

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

[16] , wherein the polyimide film is used for metallization (for electroplating, etc.).

[0042]

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

[17] , wherein the polyimide film is used to directly laminate a metal layer (for example, directly laminate a copper layer with a thickness of 20 μm or less) (or without an adhesive layer).

[0043]

[19] A laminated film comprising 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 described in any one of [1] to

[18] .

[0044]

[20] The laminated film according to

[19] , wherein the metal layer is a copper layer having a thickness of 20 μm or less.

[0045]

[21] 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.

[0046]

[22] A laminate film according to any one of

[19] to

[21] , wherein, when the peel strength (e.g., 90° peel strength) between the metal layer and the polyimide film is set to T1, and the peel strength (e.g., 90° peel strength) between the metal layer and the polyimide film after heating at 150°C for 168 hours is set to T2, T1 is greater than 0.4 kN / m, and T2 / T1 is greater than 0.7.

[0047]

[23] A method for producing a polyimide film (particularly a polyimide film for metal lamination, the polyimide film described in any one of [1] to

[18] ), which comprises (or includes) a step of applying a solution containing a coupling agent (e.g., a silane coupling agent) on one or both sides of the polyimide film and then drying the solution.

[0048]

[24] The production method according to

[23] , wherein the solution containing a coupling agent (e.g., a silane coupling agent) contains 0.1 to 5% by mass of the coupling agent (e.g., a silane coupling agent).

[0049]

[25] The production method according to

[23] or

[24] , wherein the drying is performed at a drying temperature of 130 to 200° C. and a drying time of 40 to 100 seconds.

[0050] (3) Beneficial effects

[0051] According to the present invention, a polyimide film can be provided. This polyimide film is suitable for use in metal lamination (for metal layer lamination, for metal layer formation) and the like.

[0052] For example, in one embodiment of a polyimide film, a metal layer (e.g., a copper layer) can be laminated (formed) with sufficient adhesion. Since this adhesion can be ensured even without providing an adhesive layer (even if the metal layer is directly formed), the metal layer can also be suitably formed by metallization [or metallization method or metallization treatment, such as electroplating (wet or dry electroplating method, such as vacuum evaporation method, sputtering method, ion plating method)].

[0053] Therefore, according to such a polyimide film, sufficient adhesion can be achieved even with a relatively thin metal layer (for example, a thickness of 30 μm or less, 20 μm or less, or 10 μm or less).

[0054] In another embodiment of the polyimide film of the present invention, the above-mentioned sufficient adhesion can be effectively maintained even when exposed to high temperature conditions.

[0055] In another embodiment of the polyimide film of the present invention, it can be used as a base film (substrate film) and even has effective functions {for example, heat resistance, dimensional stability (for example, dimensional stability when forming a metal layer, dimensional stability after the metal layer is formed (for example, during processing)), etc.}, and can simultaneously achieve the above-mentioned sufficient adhesion to the metal layer.

[0056] In another embodiment of the polyimide film of the present invention, a high breakdown voltage can be achieved.

[0057] Therefore, high insulation properties can be achieved by this polyimide film. DETAILED DESCRIPTION

[0058] [Polyimide film]

[0059] The polyimide film of the present invention may have a layer (A) (hereinafter, sometimes simply referred to as "layer (A)") containing a hydrolysis-condensation product of a coupling agent (or formed of a hydrolysis-condensation product) on the surface.

[0060] The layer (A) may be a layer containing an element corresponding to a coupling agent [for example, silicon (corresponding to a silane coupling agent) etc.].

[0061] The layer (A) may be formed on one surface (or one side) of the polyimide film, or may be formed on both surfaces (or both sides).

[0062] Such a polyimide film can be formed, for example, by applying a solution containing a coupling agent onto (one or both sides of) a (imidized) polyimide film and drying (hydrolysis and condensation).

[0063] (Layer(A))

[0064] The coupling agent may be, for example, a coupling agent having a hydrolyzable (condensable) group (eg, an alkoxy group, a halogen atom, etc.) and a reactive functional group (eg, an amino group, an epoxy group, a mercapto group, a (meth)acryloyl group, a vinyl group, etc.).

[0065] Examples of the coupling agent include silane coupling agents, titanium coupling agents, and aluminum coupling agents, and a silane coupling agent is preferred.

[0066] The coupling agent may be used alone or in combination of two or more.

[0067] Examples of the silane coupling agent include silane coupling agents having a silyl group bonded to a hydrolyzable (condensable) group (for example, an alkoxy group, a halogen atom, etc.).

[0068] In the silane coupling agent, the number of silicon atoms may be 1 or more, and may be 2 or more (for example, an oligomer-type or polymer-type silane coupling agent).

[0069] The specific silane coupling agent is not particularly limited, and examples thereof include amino-based silane coupling agents (silane coupling agents containing an amino group), epoxy-based silane coupling agents (silane coupling agents containing an epoxy group), mercapto-based silane coupling agents (silane coupling agents containing a mercapto group), (meth)acryloyloxy-based silane coupling agents (silane coupling agents containing a (meth)acryloyloxy group), vinyl-based silane coupling agents (silane coupling agents containing a vinyl group), and the like. Preferably, an amino-based silane coupling agent is used.

[0070] The silane coupling agents can be used alone or in combination of two or more.

[0071] Examples of amino-based silane coupling agents include alkoxysilanes having an amino group [e.g., aminoalkylalkoxysilanes (e.g., aminoalkylmono-trialkoxysilanes such as 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane, preferably aminoC1-4alkylmono-triC1-4alkoxysilane), (aminoalkylamino)alkylalkoxysilanes (e.g., 3-(2-aminoethylamino)propyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, etc., preferably aminoC1-4alkylmono-triC1-4alkoxysilane), (aminoalkylamino)alkylmono- to tri-C1-4alkoxysilanes, such as methyldimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, and the like; (aminoalkylamino)alkylmono- to tri-C1-4alkoxysilanes, preferably (aminoC1-4amino)C1-4alkylmono- to tri-C1-4alkoxysilanes); phenylaminoalkylalkoxysilanes (for example, phenylaminoalkylmono- to trialkoxysilanes such as N-phenyl-3-aminopropyltrimethoxysilane, preferably phenylaminoC1-4alkylmono- to tri-C1-4alkoxysilanes); and the like.

[0072] Examples of epoxy-based silane coupling agents include alkoxysilanes having an epoxy group [e.g., glycidoxyalkylalkoxysilanes (e.g., glycidoxyalkylmono- to tri-alkoxysilanes such as 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane, preferably glycidoxy C1-4 alkylmono- to tri-C1-4 alkoxysilanes), epoxycycloalkylalkoxysilanes (e.g., epoxycycloalkylmono- to tri-C1-4 alkoxysilanes such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, preferably epoxy C3-10 cycloalkylmono- to tri-C1-4 alkoxysilanes)] and the like.

[0073] Examples of the mercapto-based silane coupling agent include alkoxysilanes having a mercapto group [e.g., mercaptoalkylalkoxysilanes (e.g., mercaptoalkylmono- to trialkoxysilanes such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane, preferably mercaptoC1-4alkylmono- to tri-C1-4alkoxysilanes)].

[0074] Examples of the (meth)acryloyloxy-based silane coupling agent include alkoxysilanes having a (meth)acryloyl group [e.g., (meth)acryloyloxyalkylmono- to trialkoxysilanes such as 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, and 3-(meth)acryloyloxypropylmethyldiethoxysilane, preferably (meth)acryloyloxy C2-4 alkylmono- to tri-C1-4 alkoxysilane].

[0075] Examples of the vinyl silane coupling agent include vinyl group-containing silanes {e.g., halogenated silanes having a vinyl group (e.g., vinyl mono- to trihalogenated silanes such as vinyltrichlorosilane), vinyl group-containing alkoxysilanes [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 tris(methoxyethoxy)silane, vinyl tris(β-methoxyethoxy)silane, vinyl mono- to tris(C1-4 alkoxy C1-4 alkoxy)silanes), styryl group-containing silanes (e.g., styryl mono- to trialkoxysilanes such as p-styryltrimethoxysilane, preferably styryl mono- to tri-C1-4 alkoxysilanes)]} and the like.

[0076] Examples of the titanium coupling agent include isostearyl titanates (e.g., mono- to triisostearoyl titanates such as isopropyl triisostearoyl titanate, isopropyl dimethacryloyl isostearyl titanate, and isopropyl isostearyl dialcryloyl titanate), amino group-containing titanates (e.g., isopropyl tris(N-aminoethyl-aminoethyl) titanate), isopropyl tridecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate oxy) titanate, tetraisopropyl bis(dioctyl phosphite oxy) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl)phosphite oxy titanate, bis(dioctyl pyrophosphate oxy) oxyacetate titanate, bis(dioctyl pyrophosphate oxy)ethylene titanate, isopropyl trioctanoyl titanate, and isopropyl tricumylphenyl titanate.

[0077] Examples of the aluminum coupling agent include alkyl acetoacetate aluminum diisopropylate and the like.

[0078] 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 is preferably a coupling agent having an amino group (eg, an amino-based silane coupling agent).

[0079] Although not yet clear, it is believed that when a coupling agent having an amino group is used, the reaction between the polyimide film to which the coupling agent is applied and the coupling agent is suppressed to a certain extent, resulting in amino groups remaining 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 believed that the surface of the polyimide film of the present invention contains amino groups.

[0080] In addition, although it is not yet clear, it is believed that if a metal layer is stacked on the polyimide film of the present invention, a coordination bond is formed between the amino group and the metal atom (for example, copper atom, etc.), so the metal layer tends to become stable, and thus even when exposed to high temperature conditions, it is easy to obtain close adhesion between the metal layer and the polyimide film of the present invention.

[0081] Furthermore, layer (A) may contain a surface treatment agent other than the coupling agent {for example, a hydrolysis condensate of a silane compound [for example, mono-tetraalkoxysilane such as tetramethoxysilane and tetraethoxysilane, preferably mono-tetra-C1-4alkoxysilane], etc.}.

[0082] The layer (A) may have a layer (or film) (1) of a hydrolysis condensate of a coupling agent.

[0083] The layer (1) can be formed on the surface side of the layer (A).

[0084] The layer (1) may be formed substantially only of the hydrolysis condensate of the coupling agent and may not contain polyimide (or a component derived from polyimide).

[0085] When the polyimide film of the present invention has layer (A) on both surfaces (or both sides), layer (1) may be formed on both surfaces (or both sides) or on one surface (or one side) of the polyimide film.

[0086] The layer (A) may include a layer (2) containing a hydrolysis condensate of a coupling agent and a component derived from polyimide.

[0087] The layer (2) can be formed on the polyimide film side of the layer (A).

[0088] When the layer (A) includes the layer (1) and the layer (2), the layers can be formed in the order of the layer (2) and the layer (1) from the polyimide film (surface) side.

[0089] When the polyimide film of the present invention has layer (A) on both surfaces (or both sides), layer (2) may be formed on both surfaces (or both sides) or on one surface (or one side) of the polyimide film.

[0090] The thickness of layer (A) is not particularly limited. From the perspective of the adhesion between the polyimide film of the present invention and the metal layer, it can be, for example, about 50 nm or more (for example, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more), and preferably about 100 nm or more (for example, 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).

[0091] The thickness (upper limit) of layer (A) is not particularly limited, and may be, for example, about 500 nm or less (for example, 480 nm or less, 450 nm or less, 430 nm or less), and may preferably be about 400 nm or less (for example, 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).

[0092] The thickness of layer (A) can be measured by a known method without particular limitation. For example, the thickness of layer (1) or layer (2) can be measured by the method for measuring the thickness of layer (1) or layer (2) described in the Examples below.

[0093] The thickness of layer (1) is not particularly limited. From the perspective of the adhesion between the polyimide film of the present invention and the metal layer, it can be, for example, about 5 nm or more (for example, 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more), and preferably about 10 nm or more (for example, 11 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, 15 nm or more).

[0094] The thickness (upper limit) of layer (1) is not particularly limited, and for example, it can be about 150 nm or less (for example, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less), and preferably about 100 nm or less (for example, 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).

[0095] The thickness of the layer (1) can be measured by a known method without particular limitation. For example, the thickness can be measured by the method described in the examples below.

[0096] The thickness of layer (2) is not particularly limited, and for example, it can be approximately 50 nm or more (for example, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more), and preferably approximately 100 nm or more (for example, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more).

[0097] The thickness (upper limit) of layer (2) is not particularly limited, and can be, for example, about 350 nm or less (for example, 340 nm or less, 330 nm or less, 320 nm or less, 310 nm or less), preferably about 300 nm or less (for example, 290 nm or less, 280 nm or less, 270 nm or less, 260 nm or less), and further preferably about 250 nm or less (for example, 240 nm or less, 230 nm or less, 220 nm or less, 210 nm or less, 200 nm or less).

[0098] The thickness of the layer (2) can be measured by a known method without particular limitation. For example, the thickness can be measured by the method described in the examples described later.

[0099] (Polyimide film (coupling agent coating target))

[0100] Hereinafter, a polyimide film having a coupling agent applied to its surface (ie, a polyimide film to which the coupling agent is applied) will be described.

[0101] The thickness of the polyimide film can be appropriately selected according to the purpose, for example, from the perspective of being suitable for use as a substrate (base film) of a laminated film (playing the role of a substrate of a laminated film), for example, it can be about 1 μm or more (for example, 2 μm or more), preferably about 3 μm or more (for example, 4 μm or more), further preferably about 5 μm or more (for example, 6 μm or more), and can be about 7 μm or more (for example, 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).

[0102] The thickness (upper limit) of this polyimide film is not particularly limited, and may be, for example, about 300 μm or less (for example, 250 μm or less), preferably about 200 μm or less (for example, 150 μm or less), further preferably about 100 μm or less (for example, 80 μm or less), and may be 70 μm or less (for example, 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).

[0103] 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.

[0104] The polyimide film may be a laminate of a plurality of polyimide films, or may generally be a single polyimide film.

[0105] The polyimide film may be an unstretched film or a stretched film (uniaxially or biaxially stretched film). For such a stretched film, the stretching conditions (eg, stretching ratio in the TD direction and / or MD direction, etc.) may be the conditions described below.

[0106] In the present invention, sufficient adhesion and the like can be easily and effectively achieved even with a stretched film.

[0107] Composition, manufacturing method, etc.

[0108] The polyimide film (or the polyimide or polyamic acid constituting the polyimide film) generally contains an aromatic diamine component and an aromatic acid anhydride component (as polymerization components) in its raw materials.

[0109] Examples of the aromatic diamine component include p-phenylenediamine, 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, m-phenylenediamine, diaminodiphenylpropane (e.g., 4,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane), diaminodiphenylpropane, and the like. diaminodiphenylmethane (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)ethylphosphine oxide, bis-(4-aminophenyl)phenylphosphine oxide, 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'-dimethoxybiphenyl Aniline, 2,4-bis(p-β-amino-tert-butylphenyl) ether, bis(p-β-amino-tert-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 aromatic diamines can be used alone or in combination of two or more.

[0110] From the perspective of easily and effectively achieving adhesion to the metal layer, heat resistance, dimensional stability, etc., the aromatic diamine component preferably contains at least one selected from p-phenylenediamine and 4,4'-diaminodiphenyl ether, and more preferably contains p-phenylenediamine and 4,4'-diaminodiphenyl ether.

[0111] When the aromatic diamine component contains p-phenylenediamine and 4,4'-diaminodiphenyl ether, the molar ratio of p-phenylenediamine 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).

[0112] Examples of the aromatic acid anhydride component (aromatic tetracarboxylic acid component) 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-naphthalene dicarboxylic 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). Tetracarboxylic dianhydride, 2,7-dichloro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-tetrachloro-1,4,5,8-naphthalenetetracarboxylic dianhydride), 1,8,9,10-phenanthrenetetracarboxylic 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, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 3,4,3',4'-benzophenonetetracarboxylic dianhydride, and preferably pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride. These aromatic acid anhydrides can be used alone or in combination of two or more.

[0113] In combination with the aromatic diamine component described above, the aromatic anhydride component preferably includes at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, and more preferably includes pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, from the perspective of easily and effectively achieving adhesion to the metal layer, heat resistance, dimensional stability, etc.

[0114] When the aromatic acid anhydride component contains at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, the proportion of the 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) can be selected within the range of 30 mol% or more (e.g., about 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 further 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%).

[0115] When the aromatic acid anhydride component includes pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride, the molar ratio of pyromellitic dianhydride to 3,3',4,4'-biphenyltetracarboxylic dianhydride can be, for example, about 95 / 5 to 40 / 60 (e.g., 90 / 10 to 45 / 55), and preferably about 85 / 15 to 50 / 50 (e.g., 80 / 20 to 55 / 45).

[0116] The raw material components (polymer component, diamine component and acid anhydride component) of the polyimide film may contain other polymer components (for example, other acid anhydride components, other diamine components) in addition to the above-mentioned aromatic acid anhydride component and aromatic diamine component, within a range not inhibiting the effects of the present invention.

[0117] 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'-diamantane, etc.), diaminoalkanes (e.g., hexamethylenediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, 3-methylheptanediamine, 4,4'-dimethylheptanediamine, 2,11-diaminododecane, 2,2-dimethyl Propylene diamine, 3-methoxyhexamethylene diamine, 2,5-dimethylhexamethylene diamine, 2,5-dimethylheptanediamine, 5-methylnonanediamine, 1,4-diaminocyclohexane, 1,12-diaminooctadecane, etc.), 1,2-bis(3-aminopropoxy)ethane, 2,5-diamino-1,3,4-oxadiazole, 2,2-bis(4-aminophenyl)hexafluoropropane, N-(3-aminophenyl)-4-aminobenzamide, 4-aminophenyl-3-aminobenzoate, etc. These other diamines can be used alone or in combination of two or more.

[0118] In addition, when the polymerization components contain other polymerization components (other diamine components, etc.), the proportion of other polymerization components relative to the total polymerization components can be a small proportion, for example, it can be 20 mol% or less (for example, 15 mol% or less, 10 mol% or less, 5 mol% or less, 3 mol% or less, 1 mol% or less).

[0119] The polyimide film may contain other components besides the polyimide (resin component). For example, from the perspective of operability (slipperiness), the polyimide film may contain inorganic particles. The other components may be one or more.

[0120] When inorganic particles are contained, the inorganic particles are generally dispersed in the polyimide film.

[0121] Examples of inorganic particles include oxides {e.g., SiO2 (silicon dioxide), TiO2 (titanium (IV) dioxide), etc.}, inorganic acid salts {e.g., phosphate (hydrogen) salts such as CaHPO4 (calcium hydrogen phosphate), CaPO4 (calcium phosphate), Ca2P2O7 (dicalcium phosphate), carbonates such as CaCO3 (calcium carbonate), etc.}, and the like.

[0122] The inorganic particles may be used alone or in combination of two or more.

[0123] The average particle size of the inorganic particles to be dispersed may be, for example, 0.1 to 3.5 μm (eg, 0.2 to 3 μm), and preferably 0.3 to 2.5 μm.

[0124] In addition, the method for measuring the average particle size of the inorganic particles is not particularly limited, and a known method can be used.

[0125] The particle size distribution of the inorganic particles (inorganic particles to be dispersed) is preferably narrow, that is, the higher the proportion of inorganic particles of similar size among all inorganic particles, the better. Specifically, it is preferred that inorganic particles of a specific particle size (e.g., 0.5-2.5 μm, 1-3.5 μm, etc.) account for 80% or more (e.g., 80-100% by volume) of all inorganic particles.

[0126] 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 further preferably 0.05 mass % or more.

[0127] In the polyimide film, the upper limit of the proportion of inorganic particles can be selected in the range of about 5 mass % or less (for example, 3 mass % or less, 2 mass % or less, 1.5 mass % or less), can be 1 mass % or less (for example, 0.9 mass % or less), can be preferably 0.8 mass % or less (for example, 0.7 mass % or less), can be further preferably 0.6 mass % or less (for example, 0.55 mass % or less, 0.5 mass % or less, 0.45 mass % or less, 0.4 mass % or less, 0.3 mass % or less), etc.

[0128] The polyimide film may be in a laminated state, and particularly in a wound state, that is, in a roll form.

[0129] The width of the polyimide film (for example, a rolled polyimide film) is not particularly limited, and can be, for example, 30 mm or more, 45 mm or more, 50 mm or more, 75 mm or more, 100 mm or more, 150 mm or more, 200 mm or more, 300 mm or more, 500 mm or more, etc., and can be less than 3000 mm, less than 2000 mm, less than 1000 mm, etc.

[0130] The polyimide film can have a relatively large size. The length of such a polyimide film (e.g., a rolled polyimide film) is, 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), and can 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.

[0131] The polyimide film may be subjected to surface treatment (for example, electrical treatment such as corona treatment, plasma treatment, or blasting treatment). This surface treatment may be performed on one side or both sides.

[0132] Furthermore, surface treatment (plasma treatment, etc.) or the degree of the surface treatment may be a factor that causes a decrease in adhesion (for example, the aforementioned T2 or the value expressed as T2 / T1) when exposed to high temperature conditions.

[0133] On the other hand, in the present invention, sufficient adhesion can be achieved even without surface treatment.

[0134] Therefore, the polyimide film may be subjected to plasma treatment, or a polyimide film which has not been subjected to plasma treatment or has been subjected to plasma treatment but to a lesser degree may be appropriately selected.

[0135] The method for producing the polyimide film is not particularly limited, and the following describes methods for producing the polyimide film including a representative method.

[0136] When obtaining a polyimide film, first, polymerization components (components including 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 polyamide acid solution).

[0137] As the specific example of the organic solvent used in forming the polyamic acid solution, for example, can list out the sulfoxide solvents such as dimethyl sulfoxide, diethyl sulfoxide, N, N-dimethylformamide, N, the formamide solvents such as N, N-dimethylacetamide, N, the acetamide solvents such as N-methyl-2-pyrrolidone, the pyrrolidone solvents such as N-vinyl-2-pyrrolidone, phenol, o-cresol, m-cresol or p-cresol, xylenol, halogenated phenol, catechol, the phenol solvents such as hexamethylphosphoramide, gamma-butyrolactone etc. aprotic polar solvents etc. These organic solvents can be used alone or in combination of two or more. Further, can also be used in combination with aromatic hydrocarbons such as xylene, toluene.

[0138] The polymerization method of the polyamic acid solution can be carried out by any known method, for example, the following methods can be mentioned:

[0139] (1) A method of first adding the total amount of the diamine component (aromatic diamine component) to a solvent, and then adding the acid anhydride component so that the total amount of the acid anhydride component (aromatic acid anhydride component) and the diamine component (aromatic diamine component) becomes equivalent, thereby carrying out polymerization;

[0140] (2) A method of first adding the total amount of the acid anhydride component (aromatic acid anhydride component) to a solvent, and then adding the diamine component (aromatic diamine component) so that the amount of the diamine component (aromatic diamine component) and the acid anhydride component (aromatic acid anhydride component) is equivalent, thereby performing polymerization;

[0141] (3) A method of adding one diamine component (aromatic diamine component) to a solvent, mixing the mixture for a desired reaction time at a ratio of 95 to 105 mol % of the acid anhydride component (aromatic anhydride component) to the reaction components, adding the other aromatic diamine component, and then adding the other acid anhydride component (aromatic anhydride component) so that the total amount of the diamine component (aromatic diamine component) and the total amount of the acid anhydride component (aromatic anhydride component) are substantially equivalent, thereby carrying out polymerization;

[0142] (4) A method in which one acid anhydride component (aromatic acid anhydride component) is added to a solvent, the mixture is mixed for a time required for the reaction at a ratio of 95 to 105 mol % of the diamine component (aromatic acid anhydride component) to the reaction components, and then the other acid anhydride component (aromatic acid anhydride component) is added. The other diamine component (aromatic acid anhydride component) is then added so that the total amount of the diamine component (aromatic diamine component) is substantially equivalent to the total amount of the acid anhydride component (aromatic acid anhydride component), thereby carrying out polymerization.

[0143] (5) A method of preparing a polyamic acid solution (A) by reacting a diamine component (aromatic diamine component) and an acid anhydride component (aromatic anhydride component) in a solvent so that either one of the diamine component (aromatic diamine component) and the acid anhydride component (aromatic anhydride component) is in excess, and preparing a polyamic acid solution (B) by reacting the other diamine component (aromatic diamine component) and the acid anhydride component (aromatic anhydride component) in another solvent so that either one of the diamine component (aromatic diamine component) and the acid anhydride component (aromatic anhydride component) is in excess. The polyamic acid solutions (A) and (B) thus obtained are mixed to complete polymerization. At this time, when the diamine component (aromatic diamine component) is excessive when preparing the polyamic acid solution (A), the acid anhydride component (aromatic anhydride component) is made excessive in the polyamic acid solution (B). Furthermore, when the acid anhydride component (aromatic anhydride component) is excessive in the polyamic acid solution (A), the diamine component (aromatic diamine component) is made excessive in the polyamic acid solution (B), and the polyamic acid solutions (A) and (B) are mixed so that all the diamine components (aromatic diamine components) and all the acid anhydride components (aromatic anhydride components) used in the above reaction are substantially equivalent.

[0144] In addition, the polymerization method is not limited to these methods, and other well-known methods can also be used.

[0145] The anhydride component (aromatic anhydride component) and the diamine component (aromatic diamine component) constituting the polyamic acid are polymerized in a ratio such that the molar numbers of the two components are approximately equal, but one of them may be blended in excess within a range of 10 mol%, preferably 5 mol%, relative to the other.

[0146] The polymerization reaction is preferably carried out in an organic solvent while stirring. The polymerization temperature is not particularly limited, and it is usually carried out at an internal temperature of the reaction solution of 0 to 80°C. The polymerization time is not particularly limited, and it is preferably carried out continuously for 10 minutes to 30 hours. The polymerization reaction can be divided into polymerization reactions, or the temperature can be increased or decreased as needed. There is no particular restriction on the order of adding the two reactants, but it is preferred to add the aromatic anhydride to the solution of the aromatic diamine component. Vacuum degassing during the polymerization reaction is an effective method for preparing an organic solvent solution of high-quality polyamic acid. In addition, the polymerization reaction can be controlled by adding a small amount of end-capping agent to the aromatic diamines before the polymerization reaction. The end-capping agent is not particularly limited, and known end-capping agents can be used.

[0147] The polyamic acid solution obtained in the above manner can generally contain 5 to 40% by mass of solids, preferably 10 to 30% by mass of solids. Furthermore, its viscosity is not particularly limited; however, the viscosity, as measured using a Brookfield viscometer, is generally 10 to 2000 Pa·s. For stable liquid delivery, the viscosity is preferably 100 to 1000 Pa·s. Furthermore, the polyamic acid in the organic solvent solution may be partially imidized.

[0148] When obtaining a polyimide film containing inorganic particles, the polyamic acid solution may contain inorganic particles. When obtaining a polyamic acid solution containing inorganic particles, inorganic particles may be added to a polymerized polyamic acid solution in advance, or the polyamic acid solution may be polymerized in the presence of inorganic particles.

[0149] It is preferred to use the inorganic particles in the form of a slurry (inorganic particle slurry) dispersed in a solvent (eg, a polar solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, or N-methylpyrrolidone) because aggregation can be prevented.

[0150] The method for producing the inorganic particle slurry is not particularly limited and can be in accordance with existing known methods. As the method for producing the inorganic particle slurry, for example, a method of mixing the inorganic particles with a solvent using a mixer can be cited. As the mixer, a mixer with high shearing force such as a high-speed homogenizer, a homomixer, a ball mill, a Cowles mixer, or a stirring homogenizer is preferably used. In addition, a wet crushing process can also be performed to refine the average particle size. For example, a ball mill, a sand mill, etc. can be used when performing a wet crushing process.

[0151] As the inorganic particle slurry, a commercially available product prepared by pre-dispersing inorganic particles in a solvent can be used. In addition, the inorganic particle slurry may contain other organic solvents, additives, and the like as needed.

[0152] The concentration of the inorganic particles in the inorganic particle slurry is not particularly limited, and is, for example, 1 to 80 mass %, preferably 1 to 60 mass %, and more preferably 1 to 40 mass %.

[0153] In addition, by using a filter with a specified pore size (for example, a cut filter with 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, further preferably a pore size of 5 μm or less, and particularly preferably a pore size of 3 μm or less) on the inorganic particle slurry (filter treatment), the aggregation of the inorganic particles can be suppressed, which is preferred from the perspective of being able to remove inorganic particles of a specified particle size (for example, inorganic particles of 15 μm or more) in the polyimide film.

[0154] 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.).

[0155] The amount of the 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 the polyimide when forming the polyimide).

[0156] Next, the method for producing a polyimide film will be described. The polyimide film can be produced (manufactured) by, for example, the following steps: step (1) of subjecting a polyamic acid solution to a cyclization reaction to obtain a gel film (converting the polyamic acid or polyamic acid solution into a gel film); and step (2) of drying (and removing the solvent) the obtained gel film and performing a heat treatment. Alternatively, drying and imidization can be performed by drying and heat treatment.

[0157] In step (1), the method for subjecting the polyamic acid solution to a cyclization reaction is not particularly limited. Specifically, examples include (i) a method in which the polyamic acid solution is cast into a film and subjected to thermal dehydration and cyclization 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 with the polyamic acid solution to subject it to chemical decyclization to obtain a gel film, and the gel film is obtained by heating (chemical cyclization method). The latter method (chemical cyclization method) is particularly preferred.

[0158] The chemical ring closure method (further, selecting the aforementioned polymer components and the chemical ring closure method) surprisingly makes it easy and efficient to obtain the required physical properties (characteristics) of the polyimide film of the present invention. Furthermore, the chemical ring closure method is also suitable from the perspective of mass production.

[0159] The polyamic acid solution may further contain a gelation retarder, etc. The gelation retarder is not particularly limited, and acetylacetone, etc. can be used.

[0160] Examples of cyclization catalysts include amines, such as aliphatic tertiary amines (trimethylamine, triethylenediamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), and heterocyclic tertiary amines (for example, isoquinoline, pyridine, β-picoline, etc.). These cyclization catalysts may be used alone or in combination of two or more. Among these cyclization catalysts, heterocyclic tertiary amines such as β-picoline are preferred.

[0161] Examples of the dehydrating agent include acid anhydrides, such as aliphatic carboxylic anhydrides (e.g., acetic anhydride, propionic anhydride, and butyric anhydride), and aromatic carboxylic anhydrides (e.g., benzoic anhydride). These dehydrating agents may be used alone or in combination of two or more. Among these dehydrating agents, acetic anhydride and / or benzoic anhydride are preferred, with acetic anhydride being particularly preferred.

[0162] The amount of the cyclization catalyst and the dehydrating agent used is not particularly limited, and can be, for example, about 1 mol or more (eg, 1.5 to 10 mol) per mol of the amide group (or carboxyl group) of the polyamic acid (or polyamic acid).

[0163] The gel film can generally be obtained by casting (coating) a polyamic acid solution (particularly a polyamic acid solution mixed with a cyclization catalyst and a conversion agent) on a support, and partially drying and curing (imidization) the solution.

[0164] More specifically, it can be obtained by casting a polyamic acid solution onto a support from a metal nozzle with a slit to form a film, heating it by heat from the support or from a heat source such as hot air or an electric heater to cause a ring-closing reaction, and drying volatile components such as free organic solvents to form a gel film, which is then peeled off from the support.

[0165] In order to be peeled, the gel film must be self-supporting. Generally, the morphology of gel films obtained by chemical ring closure methods differs significantly from that of gel films obtained by thermal ring closure methods. Specifically, the chemical ring closure method allows for gelation (conversion) using a catalyst, resulting in a self-supporting gel film (soft or moist gel film) containing a large amount of solvent. However, the thermal ring closure method requires extensive heat treatment for gelation (making it self-supporting), resulting in a harder gel film (one with less residual solvent).

[0166] The support is not particularly limited, and examples thereof include metal (e.g., stainless steel) rollers, endless belts, 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.

[0167] The temperature of the support can be controlled by (i) a liquid or gaseous heat medium, (ii) radiant heat from an electric heater, or the like.

[0168] In step (2), the gel film is dried (desolventized) and then heat-treated. Typically, step (2) may include: holding both ends of the gel film in the width direction and passing it through a heating furnace (such as a tenter heating furnace) to dry it, and then heat-treating it.

[0169] Specifically, the gel film to be peeled from the support is not particularly limited, but is usually stretched in the conveying direction while being controlled by rotating rollers. Furthermore, the thickness of the polyimide film can be adjusted by the running speed.

[0170] Stretching in the conveying direction can be performed at a predetermined temperature (e.g., 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 (e.g., 1.15 to 1.4 times).

[0171] During drying, the drying temperature may be, for example, 210° C. or higher (e.g., 213 to 500° C.), preferably 215° C. or higher (e.g., 218 to 400° C.), and more preferably 220° C. or higher (e.g., 220 to 300° C.).

[0172] Furthermore, drying can be performed while suppressing drying unevenness (deviation) in the film width direction. For example, the drying temperature unevenness in the film width direction can be less than 25°C (e.g., 0 to 24°C), preferably 22°C or less (e.g., 1 to 21°C), more preferably 20°C or less (e.g., 2 to 19°C), and particularly 18°C ​​or less (e.g., 3 to 18°C).

[0173] Drying temperature unevenness can be measured, for example, by selecting a plurality of points at predetermined intervals (eg, 200 mm) along the film width direction and defining the difference (difference) between the maximum and minimum drying temperatures as the drying temperature unevenness.

[0174] The gel film (especially the gel film stretched in the conveying direction) is heat-treated after drying. The heat treatment temperature is not particularly limited, but may be 200°C or higher (e.g., 250-600°C), preferably 300°C or higher, and more preferably 350°C or higher.

[0175] Furthermore, as described above, the L value can be effectively adjusted by adjusting and setting the heat treatment temperature (for example, setting the maximum heating temperature) (and combining with other conditions).

[0176] Furthermore, after drying, the film may be further stretched in the width direction. Stretching in the width direction may be performed simultaneously with the heat treatment.

[0177] The stretching ratio (TDX) in the width direction stretching is, for example, 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times (for example, 1.15 to 1.4 times).

[0178] In addition, the physical properties (characteristics) required for the polyimide film (and the polyimide film of the present invention) may be effectively adjusted by the above-mentioned stretching or its conditions (and a combination with other conditions).

[0179] A polyimide film can be obtained in the above manner and can be further subjected to an annealing treatment.

[0180] The method of annealing treatment is not particularly limited, and a known method can be used.

[0181] The annealing temperature is not particularly limited, and may be, for example, 200-500°C, preferably 200-370°C, and more preferably 210-350°C. Specifically, the annealing treatment can be performed by moving the film under low tension in a furnace heated within the aforementioned temperature range. The film tension during movement may be, for example, 10-50 N / m, and more preferably 20-30 N / m.

[0182] The polyimide film obtained in the above manner may be subjected to a plasma treatment (on its surface). The plasma treatment may be performed on both sides of the polyimide film or on one side.

[0183] Furthermore, as described above, in consideration of adhesion when exposed to high temperature conditions, it may be preferable not to perform plasma treatment on the polyimide film, or to perform plasma treatment but to reduce the degree of plasma treatment.

[0184] The method of plasma treatment is not particularly limited, and a known method can be used.

[0185] The processing gas for plasma treatment is not particularly limited, and examples thereof include inert gases (e.g., He, Ar, Kr, Xe, Ne, Rn, N2, etc.), O2, H2O, air, CO2, etc. The processing gas may be used alone or in combination of two or more.

[0186] The treatment pressure of the plasma treatment is not particularly limited, and may be, for example, 0.1 Pa to 1330 kPa.

[0187] The treatment intensity (E value) of the plasma treatment is not particularly limited, and can be, for example, 50 W·min / m 2 Above, 75W・min / m 2 Above, 2000W・min / m 2 Below, 1800W・min / m 2 The following etc.

[0188] The treatment time of the plasma treatment is not particularly limited, and can be, for example, 1 second to 10 minutes.

[0189] The physical properties (e.g., glass transition temperature, linear expansion coefficient, etc.) of the polyimide film to which the coupling agent is applied can correspond to the physical properties (e.g., characteristics) of the polyimide film of the present invention (hereinafter, sometimes simply referred to as "polyimide film 1").

[0190] That is, the physical properties (characteristics) of the polyimide film to which the coupling agent is applied (for example, glass transition temperature, linear expansion coefficient, etc.) may be the same as the physical properties (characteristics) of the polyimide film 1 described later.

[0191] (Method for producing polyimide film of the present invention)

[0192] Hereinafter, the method for producing the polyimide film (polyimide film 1) of the present invention will be described.

[0193] The method for producing the polyimide film 1 includes the steps of applying a solution containing a coupling agent on one or both surfaces of a polyimide film and then drying the solution.

[0194] As the polyimide film to which the solution containing the coupling agent is applied, a polyimide film other than a gel film of polyamic acid can be generally used.

[0195] The solution containing the coupling agent can generally contain the coupling agent and a solvent, and can also contain other components {for example, a surface treatment agent other than the coupling agent {for example, a silane compound [for example, mono-tetraalkoxysilane such as tetramethoxysilane and tetraethoxysilane, preferably mono-tetra-C1-4 alkoxysilane], etc.}} as needed.

[0196] The solution containing the coupling agent can be prepared by, for example, mixing the coupling agent and a solvent (and other components as needed).

[0197] 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 perspective of the reactivity of the coupling agent (e.g., the reactivity of the reactive functional group with the polyimide), esters and alcohols are preferred. One or more solvents may be used.

[0198] In addition, as the solvent, 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).

[0199] From the perspectives of the reactivity of the coupling agent, the formation of the layer (A) on the surface of the polyimide film, etc., the content of the coupling agent in the solution containing the coupling agent may be, for example, about 0.05% by mass or more (for example, 0.1% by mass or more), preferably about 0.5% by mass or more (for example, 1% by mass or more), for example, about 10% by mass or less (for example, 7% by mass or less), and preferably about 5% by mass or less (for example, 3% by mass or less).

[0200] When the solvent contains an organic acid ester (e.g., ethyl lactate), from the perspective of the reactivity of the coupling agent (e.g., the reactivity of the reactive functional group with the polyimide), the proportion of the organic acid ester (e.g., ethyl lactate) relative to the total solvent may be, for example, about 30 parts by mass or more (e.g., 40 parts by mass or more), preferably about 50 parts by mass or more (e.g., 60 parts by mass or more, 70 parts by mass or more), and more preferably about 80 parts by mass or more (e.g., 90 parts by mass or more).

[0201] When the solvent contains an organic acid ester (e.g., ethyl lactate), the ratio (upper limit) of the organic acid ester (e.g., ethyl lactate) to the entire solvent is not particularly limited, and for example, it can be approximately 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).

[0202] During drying, from the perspective of the formation of layer (A) on the surface of the polyimide film, the adhesion between the polyimide film of the present invention and the metal layer, etc., the drying temperature can be, for example, above 100°C (for example, above 110°C, above 120°C), preferably above 130°C (for example, above 140°C), for example, below 280°C (for example, below 250°C), below 220°C (for example, below 210°C), and preferably below 200°C (for example, below 190°C).

[0203] When drying is performed, the drying time also depends on the drying temperature, etc., but from the perspective of the formation of layer (A) on the surface of the polyimide film, the close adhesion between the polyimide film of the present invention and the metal layer, etc., the drying time can be, for example, more than 20 seconds (for example, more than 30 seconds), preferably more than 40 seconds (for example, more than 50 seconds, more than 60 seconds), for example, it can be less than 150 seconds (for example, less than 140 seconds, less than 130 seconds), and preferably less than 120 seconds (for example, less than 110 seconds, less than 100 seconds).

[0204] (Polyimide film of the present invention)

[0205] The polyimide film (polyimide film 1) of the present invention generally has specific physical properties and the like.

[0206] The polyimide film 1 often satisfies at least one of the following physical properties. Typically, it satisfies at least adhesion (peel strength with the metal layer) [particularly adhesion and one or more physical properties other than adhesion]. The following physical properties can be effectively satisfied by, for example, the composition of the polyimide (of the polyimide film to be coated with the coupling agent), the film thickness, the film manufacturing conditions, and a combination (selection and adjustment) of these parameters.

[0207] Furthermore, the polyimide film 1 easily maintains the physical properties (characteristics) of the polyimide film to which the coupling agent is applied (for example, glass transition temperature, linear expansion coefficient, etc.).

[0208] The polyimide film 1 can achieve sufficient adhesion with the metal layer. Examples of such polyimide films 1 include polyimide films having a peel strength (adhesion, peel strength, 90° peel strength) value (T1) of greater than 0.3 kN / m (e.g., 0.35 kN / m or greater), preferably 0.4 kN / m or greater (e.g., 0.45 kN / m or greater), and more preferably 0.5 kN / m or greater, when a metal layer is directly laminated (laminated without an adhesive layer) (on the polyimide film 1).

[0209] The upper limit of T1 is not particularly limited, and 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, or 1 kN / m or less.

[0210] The above-mentioned adhesion can be maintained at a high level even under conditions such as high temperature (for example, severe conditions). As the above-mentioned polyimide film 1, for example, the following polyimide film can be cited: when the peel strength (adhesion, peel strength) between the metal layer and the polyimide film 1 when the metal layer is directly laminated (laminated without an adhesive layer) (on the polyimide film 1) is T1, and the peel strength (adhesion, peel strength) between the metal layer and the polyimide film 1 after heating at 150°C for 168 hours is T2, T2 / T1 is 0.3 or more (for example, 0.4 or more), preferably 0.5 or more (for example, greater than 0.5, 0.55 or more), more preferably 0.6 or more (for example, 0.65 or more), particularly 0.7 or more (for example, 0.72 or more), particularly preferably 0.75 or more (for example, greater than 0.75, 0.78 or more, 0.8 or more), etc.

[0211] In addition, the upper limit value of T2 / T1 can 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, or 0.9 or less).

[0212] Furthermore, the value of T2 may be, for example, greater 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 further preferably 0.4 kN / m or more.

[0213] The upper limit of T2 is not particularly limited, and 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.

[0214] In addition, in the measurement of T1 (and T2), the metal layer is not particularly limited and can be a specific metal layer {for example, a metal layer corresponding to the embodiment described later, that is, a copper layer with a thickness of 8.5 μm [for example, a copper layer with a thickness of 8.5 μm (for example, a layer formed by electroplating) formed by laminating a 25 nm thick nickel / chromium alloy (nickel / chromium = 80 / 20) layer (for example, a layer formed by sputtering) and a 100 nm thick copper layer (for example, a layer formed by sputtering) formed on the layer]}.

[0215] T1 (and T2) can be measured, for example, according to Method A (for example, a tensile angle of 90° and a tensile speed of 50 mm / min) in the test method for peel strength of copper foil described in JIS C 6471.

[0216] More specifically, T1 (and T2) can be measured by the method of Examples described later.

[0217] In the polyimide film 1, the linear expansion coefficient αMD in the MD direction (mechanical transport direction, longitudinal direction, length direction, long side direction, direction perpendicular to the width direction (TD direction)) can be selected within the range of about 50 ppm / K or less (for example, 40 ppm / K or less, 35 ppm / K or less, 30 ppm / K or less, 25 ppm / K or less). From the perspective of dimensional stability (for example, dimensional stability when a metal layer such as copper is stacked), for example, it can be about 20 ppm / K or less (for example, 18 ppm / K or less), preferably about 16 ppm / K or less (for example, 15 ppm / K or less), further preferably about 14 ppm / K or less (for example, 13 ppm / K or less), or about 12 ppm / K or less (for example, 11 ppm / K or less, 10 ppm / K or less), etc.

[0218] The lower limit of αMD can be 0 ppm / K or greater than 0 ppm / K [for example, from the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), it is 1 ppm / K or greater (for example, 1.5 ppm / K or greater), preferably 2 ppm / K or greater (for example, 2.5 ppm / K or greater), and further preferably 3 ppm / K or greater (for example, 3.5 ppm / K or greater)], and can also be 4 ppm / K or greater (for example, 4.5 ppm / K or greater, 5 ppm / K or greater, 5.5 ppm / K or greater, 6 ppm / K or greater, 6.5 ppm / K or greater, 7 ppm / K or greater).

[0219] As a specific αMD, it can be, for example, 0~30ppm / K. From the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), it can be preferably 1~20ppm / K (for example, 2~18ppm / K), and can be further preferably 3~17ppm / K (for example, 4~16ppm / K, 5~15ppm / K, 6~14ppm / K, 6~12ppm / K, 6~10ppm / K), etc.

[0220] In the polyimide film 1, the linear expansion coefficient αTD in the TD direction (width direction, transverse direction, right-angle direction, direction perpendicular to the longitudinal direction (MD)) can be selected within a range of about 50 ppm / K or less (for example, 40 ppm / K or less, 35 ppm / K or less, 30 ppm / K or less, 25 ppm / K or less). From the perspective of dimensional stability (for example, dimensional stability when a metal layer such as copper is stacked), for example, it can be about 20 ppm / K or less (for example, 18 ppm / K or less), preferably about 16 ppm / K or less (for example, 15 ppm / K or less), further preferably about 14 ppm / K or less (for example, 13 ppm / K or less), and can be 12 ppm / K or less (for example, 11 ppm / K or less, 10 ppm / K or less, 9 ppm / K or less, 8 ppm / K or less, 7 ppm / K or less, 6 ppm / K or less, 5 ppm / K or less).

[0221] The lower limit value of αTD can be, for example, greater than -10 ppm / K (for example, greater than -9 ppm / K, greater than -8 ppm / K, greater than -7 ppm / K, greater than -6 ppm / K), greater than -5 ppm / K (for example, greater than -4 ppm / K, greater than -3 ppm / K, greater than -2 ppm / K, greater than -1 ppm / K), greater than 0 ppm / K [for example, greater than 1 ppm / K (for example, greater than 1.5 ppm / K)], and can preferably be greater than 2 ppm / K.

[0222] From the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), the specific αTD can be, for example, -10~30ppm / K, preferably -10~20ppm / K (for example, -8~18ppm / K), and further preferably -5~17ppm / K (for example, -5~15ppm / K, -5~10ppm / K, -5~8ppm / K), etc.

[0223] In the polyimide film 1, the value of (|αMD|+|αTD|) / 2 can be selected within the range of about 50 ppm / K or less (for example, 40 ppm / K or less, 35 ppm / K or less, 30 ppm / K or less, 25 ppm / K or less). From the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), for example, it can be about 20 ppm / K or less (for example, 18 ppm / K or less), preferably about 16 ppm / K or less (for example, 15 ppm / K or less), further preferably about 14 ppm / K or less (for example, 13 ppm / K or less), and can be about 12 ppm / K or less (for example, 11 ppm / K or less, 10 ppm / K or less).

[0224] (|αMD|+|αTD|) / 2 (the lower limit value) can be 0 ppm / K, can be greater than 0 ppm / K [for example, from the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), it is 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 further preferably 3 ppm / K or more (for example, 3.5 ppm / K or more)], and can be 4 ppm / K or more (for example, 4.5 ppm / K or more, 5 ppm / K or more).

[0225] From the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), the specific (|αMD|+|αTD|) / 2 can be, for example, 0~30ppm / K, preferably 1~20ppm / K (for example, 2~18ppm / K), and further preferably 3~17ppm / K (for example, 4~16ppm / K, 4~15ppm / K, 5~14ppm / K), etc.

[0226] In the polyimide film 1, the absolute value of the difference between |αMD| and |αTD| (|αMD|-|αTD|) can be selected within the range of about 30 ppm / K or less (for example, 25 ppm / K or less, 20 ppm / K or less). From the perspective of dimensional stability (for example, dimensional stability when stacking metal layers such as copper), it can be, for example, about 15 ppm / K or less (for example, 12 ppm / K or less), preferably about 10 ppm / K or less (for example, 8 ppm / K or less), further preferably about 7 ppm / K or less (for example, 6 ppm / K or less), or about 5 ppm / K or less (for example, 4.5 ppm / K or less, 4 ppm / K or less, 3.5 ppm / K or less, 3 ppm / K or less, 2.5 ppm / K or less, 2 ppm / K or less, 1.5 ppm / K or less, 1 ppm / K or less), etc.

[0227] The absolute value (lower limit) of the difference between |αMD| and |αTD| (|αMD| - |αTD|) can be 0 ppm / K or greater than 0 ppm / K (for example, greater than 0.1 ppm / K, greater than 0.2 ppm / K, greater than 0.3 ppm / K, greater than 0.4 ppm / K, or greater than 0.5 ppm / K).

[0228] αMD and αTD are not particularly limited and can be values ​​measured within a specific temperature range (e.g., 50-200°C) and can be measured under specific conditions (e.g., a heating rate of 10°C / min). Specifically, they can be measured using the method described in the Examples below.

[0229] From the perspective of adhesion to the metal layer, the glass transition temperature (Tg) of the polyimide film 1 (or the polyimide constituting the polyimide film, the same below) can be selected within the range of about 400°C or less (for example, 395°C or less), preferably 390°C or less (for example, 385°C or less), and further preferably 380°C or less (for example, 375°C or less).

[0230] From the perspectives of heat resistance, dimensional stability, etc. (and the balance and consideration of adhesion with the metal layer), the Tg (lower limit of Tg) of the polyimide film 1 can be selected within the range of about 150°C or above (for example, 160°C or above, 170°C or above), for example, it can be 180°C or above (for example, 190°C or above), preferably 200°C or above (for example, 210°C or above), and further preferably 220°C or above (for example, 225°C or above). The temperature may be above 230°C (for example, above 235°C, above 240°C, above 245°C, above 250°C, above 255°C, above 260°C, above 265°C, above 270°C, above 275°C, above 280°C, above 285°C, above 290°C, above 295°C, above 300°C, above 305°C, above 310°C, above 315°C, above 320°C, above 325°C, above 330°C), etc.

[0231] Furthermore, these ranges (upper limit and lower limit) may be appropriately combined to select a range (for example, 200 to 400° C., 230 to 390° C., etc., and the same applies to the description of ranges hereinafter).

[0232] Specific examples of the Tg of the polyimide film 1 include 180 to 400° C., preferably 200 to 390° C., and more preferably 220 to 380° C.

[0233] The method for measuring Tg may be a known method without particular limitation, and for example, the tan δ method (ie, the peak intensity of tan δ is defined as the value of Tg) may be used.

[0234] In the polyimide film 1, the thickness ratio of the polyimide film (polyimide film to be coated with the coupling agent) to the layer (A) can be selected according to the application, etc. For example, it can be selected within the range of about 30000 / 1 to 10 / 1 (for example, 20000 / 1 to 30 / 1), can be about 10000 / 1 to 40 / 1 (for example, 8000 / 1 to 50 / 1), can be preferably about 6000 / 1 to 60 / 1 (for example, 5000 / 1 to 50 / 1), and can further preferably be about 3000 / 1 to 70 / 1 (for example, 2900 / 1 to 80 / 1, 2800 / 1 to 100 / 1, 2700 / 1 to 200 / 1).

[0235] The breakdown voltage of the polyimide film 1 can be, for example, approximately 445 kV / mm or more (e.g., 448 kV / mm or more), preferably approximately 450 kV / mm or more (e.g., 453 kV / mm or more), and more preferably approximately 455 kV / mm or more (e.g., 458 kV / mm or more, 460 kV / mm or more).

[0236] The upper limit of the breakdown voltage of the polyimide film 1 is not particularly limited, and may be, for example, approximately 700 kV / mm or less (e.g., 650 kV / mm or less), preferably approximately 630 kV / mm or less (e.g., 600 kV / mm or less, 580 kV / mm or less, 550 kV / mm or less).

[0237] Since the polyimide film 1 includes the layer (A), it is expected that the breakdown voltage will be lowered due to decomposition of the hydrolysis condensate of the coupling agent, etc. However, the fact that the polyimide film 1 has a high breakdown voltage is an unexpected effect.

[0238] Although the reason why the polyimide film 1 has a high breakdown voltage has not been determined, it is predicted that this is because by providing the polyimide film 1 with layer (A), chemical bonds are formed on the surface of the polyimide film, reducing the unevenness (roughness) of the surface of the polyimide film, thereby increasing the number of contacts with the electrode and hindering local conduction, or because layer (A) prevents moisture-based conduction.

[0239] The breakdown voltage of the polyimide film 1 can be selected by appropriately combining these ranges (upper limit and lower limit) to fall within a range (eg, 450 to 600 kV / mm).

[0240] The method for measuring the breakdown voltage is not particularly limited, and the breakdown voltage can be measured, for example, by a flat plate electrode method according to JIS C 2151.

[0241] [Applications of polyimide films, metal laminate films, etc.]

[0242] The polyimide film of the present invention is suitable for metal (metal layer) lamination.

[0243] Such a polyimide film can be laminated with a metal (metal layer) without an adhesive layer (directly). Therefore, it is suitable as a polyimide film for laminating a metal (metal layer) without an adhesive layer (directly).

[0244] Furthermore, the polyimide film can be efficiently laminated (formed) with metal (metal layer) by metallization (electroplating, etc.). Therefore, the polyimide film of the present invention is also suitable for metallization.

[0245] Hereinafter, embodiments including the use of such a suitable polyimide film will be described.

[0246] As described above, the polyimide film can be made into a laminated film in which a metal (metal layer) is laminated.

[0247] Such a laminated film can be 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.

[0248] In the laminated film, the metal layer may generally be laminated (formed) on the polyimide film without an adhesive layer (or directly).

[0249] In such a laminated film, the metal layer may be a metal foil or the like, or may be a metal layer formed by metallization, and is preferably a metal layer formed by metallization.

[0250] Metallization (metallization method) is not particularly limited, and electroplating (electroplating method) can be typically cited. Specific examples of metallization include wet plating (e.g., electrolytic plating) and dry plating (e.g., vacuum evaporation, sputtering, ion plating, etc.).

[0251] These methods may be combined alone or in combination of two or more. As an example of combining two or more methods, for example, when a metal layer is formed by a base layer and an upper layer as described later, the base layer may be formed (e.g., formed thinly) by dry plating and the upper layer may be formed by wet plating.

[0252] The metal constituting the metal layer is not particularly limited, and 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.

[0253] The metal constituting the metal layer may be one kind or two or more kinds.

[0254] The metal layer can be a single layer or multiple layers (for example, 2 to 3 layers).

[0255] For example, the metal layer can be composed of a substrate layer (substrate metal layer, base metal layer) and an upper layer (upper metal layer, circuit layer) stacked (formed) on the substrate layer. In addition, the substrate layer or the upper layer (e.g., substrate layer) can also be multi-layered.

[0256] In addition, when the metal layer is a multi-layer structure, the metals constituting the respective layers may be the same or different.

[0257] Taking a copper laminate film as an example, the metal layer in the copper laminate film may be composed solely of a copper layer, or a copper layer (upper layer) may be formed via an underlayer (underlayer metal layer). In this case, the underlayer may be one layer or two or more layers, and may be composed of at least one selected from copper and non-copper metals.

[0258] When listing specific examples of metal layers having a copper layer as an upper layer, there can be listed an underlayer (e.g., a sputtered layer) which is at least one layer selected from a copper layer, a non-copper metal layer (e.g., a nickel / chromium layer), and a combination of the two, and a copper layer (e.g., an electroplated layer) stacked on the underlayer.

[0259] The metal layer may be formed on one side or both sides of the polyimide film. In addition, when a polyimide film subjected to plasma treatment is used, the metal layer may be formed on the plasma-treated side of the polyimide film.

[0260] The thickness of the metal layer (the total thickness in the case of multiple layers, the thickness of each metal layer in the case of being provided on both sides) can be appropriately selected according to the application or the scheme of the metal layer, and can be greater than 1 nm (for example, 2 nm to 100 μm), greater than 3 nm (for example, 5 nm to 50 μm), etc.

[0261] In particular, in circuit boards (printed circuit boards), the thickness of the metal layer [for example, a copper layer (including a metal layer having a copper layer as an upper layer)] can 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 further preferably 5 μm or more (for example, 5 to 30 μm, 5 to 20 μm, 5 to 15 μm), etc.

[0262] 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).

[0263] In the case where the metal layer includes a substrate layer, the ratio of the thickness of the substrate layer to the overall thickness of the metal layer can be selected within a range of approximately 30%, for example, and can be less than 20% (for example, less than 15%, less than 10%, less than 5%, less than 3%, less than 2%), etc.

[0264] In particular, the thickness of the metal layer can be relatively small (thin), for example, it can be less than 50 μm (for example, less than 40 μm), preferably less than 30 μm (for example, less than 25 μm), and further preferably less than 20 μm (for example, less than 15 μm, less than 12 μm, less than 10 μm).

[0265] According to the polyimide film of the present invention (as the laminated film of the present invention), sufficient adhesion can be achieved even with such a small (thin, low ratio) thickness of the metal layer.

[0266] In the laminated film, the thickness ratio of the polyimide film to the metal layer can be selected according to the purpose, etc., for example, it can be selected within the range of polyimide film / metal layer (thickness ratio) = 1 / 0.001~1 / 100 (for example, 1 / 0.01~1 / 50), can be about 1 / 0.02~1 / 10 (for example, 1 / 0.03~1 / 8), preferably about 1 / 0.05~1 / 5 (for example, 1 / 0.07~1 / 3), and further preferably about 1 / 0.1~1 / 2 (for example, 1 / 0.15~1 / 1, 1 / 0.2~1 / 0.8).

[0267] According to the polyimide film of the present invention (as the laminated film of the present invention), even at such a thickness ratio, the polyimide film can fully exhibit its function as a base film.

[0268] If a copper laminate film (for example, a copper laminate film suitable for a printed circuit board, etc.) is taken as an example, a more specific example of a manufacturing method (specific example) is given, and the following method can be listed: a method of performing substrate treatment on the surface of the polyimide film on which copper is to be formed under vacuum conditions (for example, performing substrate treatment on nickel / chromium by sputtering, and then sputtering copper), and after forming a thin copper film, laminating the copper layer by electrolytic plating using a copper sulfate bath, etc.

[0269] In addition, the metal layer (copper plating layer, etc.) can be patterned by etching, etc. The etching method is not particularly limited, and a conventionally known method can be used.

[0270] In the laminated film, the metal layer and the polyimide film can be firmly adhered to each other.

[0271] Examples of such a laminated film include laminated films having a peel strength (adhesion, peel strength) between the metal layer and the polyimide film (T1) greater than 0.3 kN / m (for example, 0.35 kN / m or more), preferably laminated films having a peel strength (adhesion, peel strength) of 0.4 kN / m or more (for example, 0.45 kN / m or more), and further preferably laminated films having a peel strength (adhesion) of 0.5 kN / m or more.

[0272] The upper limit of T1 is not particularly limited, and 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, or 1 kN / m or less.

[0273] This adhesion can be maintained at a high level even when subjected to conditions such as high temperatures (e.g., harsh conditions). Examples of such laminated films include the following: 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, T2 / T1 is 0.3 or more (e.g., 0.4 or more), preferably 0.5 or more (e.g., greater than 0.5, 0.55 or more), further 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., greater than 0.75, 0.78 or more, 0.8 or more).

[0274] In addition, the upper limit value of T2 / T1 can 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, or 0.9 or less).

[0275] The value of T2 is, for example, greater 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 further preferably 0.4 kN / m or more.

[0276] The upper limit of T2 is not particularly limited, and 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.

[0277] T1 (and T2) can be measured, for example, according to Method A (for example, a tensile angle of 90° and a tensile speed of 50 mm / min) in the test method for peel strength of copper foil described in JIS C 6471.

[0278] More specifically, T1 (and T2) can be measured by the method of Examples described later.

[0279] The laminated film can be used for various applications, for example, it can be used for circuit boards (particularly boards using fine pitch circuits) such as COF (Chip on Film) and flexible printed circuits (FPC).

[0280] Example

[0281] Next, the present invention will be further described in detail with reference to examples. However, the present invention is not limited to these examples, and a person skilled in the art with ordinary knowledge in the art can make various modifications within the technical concept of the present invention.

[0282] In the examples, the following compounds are referred to by the following abbreviations.

[0283] p-phenylenediamine: PPD

[0284] 4,4'-Diaminodiphenyl ether: 4,4'-ODA

[0285] Pyromellitic dianhydride: PMDA

[0286] 3,3',4,4'-Biphenyltetracarboxylic dianhydride: BPDA

[0287] N,N-dimethylacetamide: DMAc

[0288] The various properties were evaluated by the following methods.

[0289] ・Coefficient of thermal expansion (CTE)

[0290] Measurements were performed using a TMA-50 (manufactured by Shimadzu Corporation) within a temperature range of 50°C to 200°C at a heating rate of 10°C / minute. The coefficient of thermal expansion α was defined as α = (|αMD| + |αTD|) / 2, using the linear expansion coefficient αMD in the machine direction (MD) and the linear expansion coefficient αTD in the width direction (TD) of the film.

[0291] ・Glass transition temperature (Tg)

[0292] Measurements were performed using a DMS6100 (manufactured by Hitachi High-Tech Science Corporation) within the measurement temperature range of 25°C to 420°C, with nitrogen flowing at 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'), the ratio of the loss modulus (E") to the storage modulus (E'), reached a maximum was defined as the glass transition temperature (Tg).

[0293] ・Adhesion strength between copper and polyimide laminated film (90° peel strength)

[0294] The adhesion between the copper and polyimide laminated film was evaluated according to Method A in the test method for peel strength of copper foil described in JIS C 6471, with measurement performed at a tensile angle of 90° and a tensile speed of 50 mm / min.

[0295] The adhesion measured immediately after the copper-laminated polyimide film was formed was defined as normal adhesion (T1), and the adhesion measured after heating at 150°C for 168 hours was defined as heat-resistant adhesion (T2).

[0296] ・Thickness of the polyimide film (to which the coupling agent is applied)

[0297] Using a Litematic (Serise 318) thickness gauge manufactured by Mitutoyo Corporation, 15 locations were randomly selected from the entire surface of the film, and the thickness of the 15 locations was measured. The average thickness was calculated as the film thickness.

[0298] ・Thickness of layer (1)

[0299] An X-ray photoelectron spectrometer manufactured by ULVAC-PHI, INCORPORATED. was used to measure the Si intensity from the film surface in the depth direction. The point where the slope of the relationship between Si intensity and depth (line 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).

[0300] ・Thickness of layer (2)

[0301] The Si intensity was measured from the film surface in the depth direction using a secondary ion mass spectrometer manufactured by ULVAC-PHI, INCORPORATED. The depth from the displacement point to when the Si intensity became 0 was defined as the thickness of layer (2).

[0302] ・Evaluation of inorganic particles

[0303] The sample dispersed in an organic solvent was measured using a laser diffraction / scattering particle size distribution analyzer LA-910 manufactured by HORIBA, LTD. The average particle size was read as the volume average diameter based on the results of analyzing the laser diffraction and scattered light intensity patterns.

[0304] ・Determination of breakdown voltage

[0305] The measurement was conducted according to the plate electrode method of JIS C 2151 under the conditions of input voltage of 100V±10% 50 / 60Hz, output voltage of DC 0~+50kV / 5Ma, and voltage rise time of 40~800 seconds (variable).

[0306] In addition, the film test piece before the test was dried at 200° C. for 30 minutes and then measured.

[0307] The size of the film test piece was 200 mm × 200 mm, and the measurement atmosphere was 25° C. × 60% RH.

[0308] (Preparation of polyamic acid solution)

[0309] [Synthesis example 1]

[0310] In a separatory bottle with a capacity of 2000mL, 25.7g of PPD was placed, 960g of DMAc was added thereto, and the mixture was stirred until completely dissolved. Next, 50.2g of PMDA was added and stirred for 1 hour. Then, 71.3g of 4,4'-ODA was added, and after confirming that the mixture was completely dissolved, 52.4g of BPDA and 39.1g of PMDA were added and stirred for 3 hours to obtain a polyamic acid solution (solid content was 20% by mass) of 3000 poise. 0.3% by mass of silicon dioxide DMAc slurry with an average particle size of 0.3 μm was added per unit weight of polyamic acid resin and the mixture was fully stirred and dispersed.

[0311] (Preparation of coating solution)

[0312] The coating liquid (a solution containing a silane coupling agent) was prepared in the following manner.

[0313] [Coating liquid 1]

[0314] 90 parts by mass of ethyl lactate (Musashino Chemical Laboratory, Ltd.), 10 parts by mass of ethanol, and 1 part by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.) were mixed to prepare a coating liquid 1.

[0315] [Coating liquid 2]

[0316] 90 parts by mass of ethyl lactate (Musashino Chemical Laboratory, Ltd.), 10 parts by mass of ethanol, and 2 parts by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.) were mixed to prepare a coating liquid 2.

[0317] [Coating liquid 3]

[0318] 90 parts by mass of ethyl lactate (Musashino Chemical Laboratory, Ltd.), 10 parts by mass of ethanol, and 3 parts by mass of 3-aminopropyltrimethoxysilane (Tokyo Chemical Industry Co., Ltd.) were mixed to prepare a coating liquid 3.

[0319] [Example 1]

[0320] (Manufacturing of Polyimide Film)

[0321] 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-picoline were mixed with 100 parts by mass of the solid content of the polyamic acid to obtain a mixed solution.

[0322] The mixture was cast onto a drum at 85°C using a T-die for 30 seconds. The resulting self-supporting film was then stretched 1.23 times in the machine direction while being heated at 100°C for 5 minutes. Subsequently, the film was held at both ends in the width direction and stretched 1.4 times in the width direction while being heated at 270°C for 2 minutes. The film was then heated at 380°C for 90 seconds to produce a polyimide film with a width of 500 mm, a thickness of 25 μm, and a length of 500 m.

[0323] Coating liquid 1 was applied to one surface of the polyimide film and dried at 130°C for 60 seconds to obtain polyimide film 1. In this polyimide film 1, the thickness of layer (1) was 20 nm and the thickness of layer (2) was 180 nm.

[0324] (Manufacturing of Copper-Laminated Polyimide Film)

[0325] A single surface of the polyimide film 1 was plasma treated, followed by sputtering to form a 25 nm thick nickel / chromium alloy (nickel / chromium = 80 / 20) layer. A 100 nm thick copper layer was then formed on the nickel / chromium alloy layer, also by sputtering. The copper layer was then electrolytically plated to a thickness of 8.5 μm. Finally, copper etching was performed to pattern the lines to a width of 1 mm, yielding a copper-laminated polyimide film 1.

[0326] The adhesion of the copper-laminated polyimide film 1 was evaluated. The results are shown in Table 1.

[0327] [Example 2]

[0328] A polyimide film 2 was obtained in the same manner as in Example 1 except that the drying temperature after application of the coating liquid was 200° C. A copper-laminated polyimide film 2 was obtained in the same manner as in Example 1 using this polyimide film 2 .

[0329] The adhesion of the copper-laminated polyimide film 2 was evaluated. The results are shown in Table 1.

[0330] [Example 3]

[0331] 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 was set to 90 seconds. A copper-laminated polyimide film 3 was obtained in the same manner as in Example 1 using this polyimide film 3 .

[0332] The adhesion of the copper-laminated polyimide film 3 was evaluated. The results are shown in Table 1.

[0333] [Example 4]

[0334] A polyimide film 4 was obtained in the same manner as in Example 3 except that the coating liquid 2 was used instead of the coating liquid 1. Furthermore, a copper-laminated polyimide film 4 was obtained in the same manner as in Example 1 using this polyimide film 4 .

[0335] The adhesion of the copper-laminated polyimide film 4 was evaluated. The results are shown in Table 1.

[0336] [Example 5]

[0337] A polyimide film 5 was obtained in the same manner as in Example 3 except that the coating liquid 3 was used instead of the coating liquid 1. Furthermore, a copper-laminated polyimide film 5 was obtained in the same manner as in Example 1 using the polyimide film 5 .

[0338] The adhesion of the copper-laminated polyimide film 5 was evaluated. The results are shown in Table 1.

[0339] [Comparative Example 1]

[0340] 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, a copper-laminated polyimide film 6 was obtained in the same manner as in Example 1 using this polyimide film 6 .

[0341] The adhesion of the copper-laminated polyimide film 6 was evaluated. The results are shown in Table 1.

[0342] [Comparative Example 2]

[0343] 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 the polyamic acid to obtain a mixed solution.

[0344] Using a T-die, the mixture was poured onto a drum at 85°C for 30 seconds. Coating Solution 3 was then 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 machine direction while heating at 100°C for 5 minutes. The film was then held at both ends in the width direction and stretched 1.4 times in the width direction while heating at 270°C for 2 minutes. The film was then heated at 380°C for 90 seconds, yielding a polyimide film 7 with a width of 500 mm, a thickness of 25 μm, and a length of 500 m.

[0345] 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, INCORPORATED. in the same manner as the thickness measurement method of the above-mentioned layer (2), and the depth at which the Si intensity became 0 was measured, and the result was 390 nm.

[0346] Using the polyimide film 7 , the same procedure as in Example 1 was followed to obtain a copper-laminated polyimide film 7 .

[0347] The adhesion of the copper-laminated polyimide film 7 was evaluated. The results are shown in Table 1.

[0348] In Table 1, αMD, αTD, α, Tg, and breakdown voltage are the values ​​of polyimide films 1 to 7.

[0349] [Table 1]

[0350]

[0351] As shown in Table 1, compared with Comparative Examples 1 and 2, the polyimide films of Examples 1 to 5 can maintain adhesion to the metal layer when exposed to high temperature conditions.

[0352] Furthermore, compared to Comparative Examples 1 and 2, the polyimide films of Examples 1 to 5 had higher breakdown voltages.

[0353] [Example 6]

[0354] A polyimide film 8 was obtained by the same method as in Example 1 except that the drying temperature after application of the coating liquid was 170° C. A copper-laminated polyimide film 8 was obtained by the same procedure as in Example 1 using this polyimide film 8 .

[0355] The adhesion of the copper-laminated polyimide film 8 was evaluated. The results are shown in Table 2.

[0356] [Example 7]

[0357] A polyimide film 9 was obtained by the same method as in Example 1 except that the drying temperature after application of the coating liquid was 250° C. A copper-laminated polyimide film 9 was obtained by the same procedure as in Example 1 using this polyimide film 9 .

[0358] The adhesion of the copper-laminated polyimide film 9 was evaluated. The results are shown in Table 2.

[0359] [Example 8]

[0360] A polyimide film 10 was obtained by the same method as in Example 1 except that the drying temperature after application of the coating liquid was 280° C. A copper-laminated polyimide film 10 was obtained by the same procedure as in Example 1 using this polyimide film 10 .

[0361] The adhesion of the copper-laminated polyimide film 10 was evaluated. The results are shown in Table 2.

[0362] [Table 2]

[0363]

[0364] Industrial Applicability

[0365] The polyimide film of the present invention can be used for metal lamination and the like.

Claims

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

2. A polyimide film for metal lamination, wherein: When the peel strength between the copper layer and the polyimide film when the copper layer is directly laminated is T1 and the peel strength between the copper layer and the polyimide film after heating at 150° C. for 168 hours is T2, T1 is 0.4 kN / m or more and T2 / T1 is 0.7 or more.

3. The polyimide film according to claim 1, wherein The coupling agent has an amino group. The polyimide film according to claim 1 or 3, wherein The coupling agent includes a silane coupling agent. The polyimide film according to claim 1 or 3, wherein The coupling agent includes an amino-based silane coupling agent. The polyimide film according to claim 1 or 3, wherein The thickness of layer (A) is 100 to 400 nm.

7. The polyimide film according to claim 1 or 3, wherein The layer (A) comprises a layer (1) of a hydrolysis condensate of a coupling agent.

8. The polyimide film according to claim 1 or 3, wherein The layer (A) includes the layer (2), and the layer (2) includes a hydrolysis condensate of a coupling agent and a component derived from polyimide.

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

10. The polyimide film according to claim 1 or 3, wherein The coupling agent comprises 3-aminopropyltrimethoxysilane. The polyimide film according to claim 1 or 2, wherein When the linear expansion coefficient in the machine conveying direction of the film is αMD and the linear expansion coefficient in the width direction is αTD, the value of (|αMD|+|αTD|) / 2 is 15 ppm / K or less.

12. The polyimide film according to claim 1 or 2, wherein αTD is -5~+10ppm / K.

13. The polyimide film according to claim 1 or 2, wherein The polyimide film uses aromatic diamine components and aromatic anhydride components as polymerization components, the aromatic diamine component includes at least one selected from p-phenylenediamine and 4,4'-diaminodiphenyl ether, and the aromatic anhydride component includes at least one selected from pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride.

14. The polyimide film according to claim 1 or 2, wherein The polyimide film contains inorganic particles.

15. The polyimide film according to claim 1 or 2, wherein The polyimide film is in a roll shape.

16. The polyimide film according to claim 1 or 2, wherein The polyimide film contains inorganic particles at a ratio of 0.01 to 5% by mass, and the polyimide film is in a roll shape with a length of 5 m or more.

17. The polyimide film according to claim 1 or 2, wherein The polyimide film is used for metallization.

18. The polyimide film according to claim 1 or 2, wherein The polyimide film is used for directly laminating a copper layer having a thickness of 20 μm or less.

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

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. 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 When the peel strength between the metal layer and the polyimide film is T1 and the peel strength between the metal layer and the polyimide film after heating at 150° C. for 168 hours is T2, T1 is 0.4 kN / m or more, and T2 / T1 is 0.7 or more.

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

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

25. The manufacturing method according to claim 23 or 24, wherein: Drying is performed at a drying temperature of 130 to 200°C and a drying time of 40 to 100 seconds.

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