JP5711989B2 - Method for producing polyimide multilayer film - Google Patents

Description

  The present invention relates to a method for producing a polyimide multilayer film having a plurality of resin layers containing a polyimide resin, a polyimide multilayer film obtained by the production method, and a flexible metal-clad laminate obtained from the film.

  A flexible printed wiring board (hereinafter also referred to as FPC) generally uses a thin insulating film having flexibility as a substrate (base film), and a metal foil is heated and pressure-bonded to the surface of the substrate via various adhesive materials. Thus, a circuit pattern is formed on the metal-clad laminate bonded together, and a cover layer is applied to the surface. In a flexible printed wiring board (three-layer FPC) composed of three layers of an insulating film, an adhesive layer, and a metal foil, a polyimide film or the like has been widely used as an insulating film. This is because polyimide has excellent heat resistance and electrical characteristics. Moreover, as the adhesive layer, a thermosetting adhesive such as epoxy resin or acrylic resin is generally used.

  Conventionally, a thermosetting resin such as an epoxy resin or an acrylic resin used as an adhesive layer is excellent in low-temperature workability because it can be bonded at a relatively low temperature. At present, other properties typified by heat resistance are insufficient.

  In order to solve the above problem, a two-layer FPC using a polyimide material for the adhesive layer has been proposed. In addition, although it can be said that the FPC obtained by the method using a polyimide material for the adhesive layer is strictly three layers, the two polyimide layers are regarded as a single body to form a two-layer FPC. This two-layer FPC is superior in heat resistance, electrical characteristics, and dimensional stability compared to a three-layer FPC using an epoxy resin or an acrylic resin as an adhesive layer, and has attracted attention as a material that can meet the required characteristics in the future. ing.

  The two-layer FPC is manufactured using a flexible metal-clad laminate having a structure in which a metal foil is laminated on a substrate. Examples of the method for producing the flexible metal-clad laminate include a casting method, a metalizing method, and a laminating method. The casting method is a method in which an organic solvent solution of polyamic acid, which is polyimide or a precursor thereof, is cast and applied onto a metal foil and then imidized. The metalizing method is a method in which a metal layer is provided directly in the form of a polyimide film by sputtering or plating. The laminating method is a method of bonding a polyimide film and a metal foil through a thermoplastic polyimide layer. Among these, the laminating method is superior in that the thickness range of the metal foil that can be handled is wider than that of the casting method, and the cost required for the apparatus is lower than that of the metalizing method. In the flexible metal-clad laminate produced by the above laminating method, as a substrate, a layer containing a thermoplastic polyimide (thermoplastic polyimide layer) on at least one surface of a layer containing a non-thermoplastic polyimide (non-thermoplastic polyimide layer) An adhesive film provided with is widely used. In this adhesive film, the non-thermoplastic polyimide layer becomes an insulating film, and the thermoplastic polyimide layer becomes an adhesive layer. In other words, this adhesive film can be referred to as a polyimide film having a multilayer structure (polyimide multilayer film). Typical methods for producing the polyimide multilayer film include a coating method, a heat laminating method, a casting film forming method, and the like. The coating method is a method in which a solution of a resin composition containing a thermoplastic polyimide and a precursor thereof is applied to one side or both sides of a polyimide film to be a non-thermoplastic polyimide layer and dried. The thermal laminating method is a method in which a polyimide film to be a thermoplastic polyimide layer is heated and bonded to one side or both sides of a polyimide film to be a non-thermoplastic polyimide layer. Examples of the casting film forming method include a sequential method (sequential coating method) and a coextrusion method (coextrusion casting film forming method). The sequential method is a method in which a solution containing non-thermoplastic polyimide or its precursor and a solution containing thermoplastic polyimide or its precursor are sequentially coated on a support. The coextrusion method is a method in which both a non-thermoplastic polyimide varnish and a thermoplastic polyimide varnish are simultaneously extruded on a support using a coextrusion die. Especially, since it is easy to control the heat shrinkage rate of a polyimide-type multilayer film to a desired range, a coextrusion method is used preferably (for example, refer patent documents 1-4).

JP-A-11-99554 Japanese Patent Laid-Open No. 7-214637 Japanese Patent Laid-Open No. 10-138318 JP 2010-1111719 A

  In the coextrusion method, a plurality of solutions extruded from a coextrusion die are continuously extruded onto a smooth support, and a part of the solvent is volatilized to obtain a self-supporting multilayer gel film. The multilayer gel film is peeled off from the body, and finally imidization proceeds by high-temperature heat treatment. When the multilayer gel film is peeled off from the support, a part of the surface layer of the multilayer gel film or a part of the part having a different thickness at the end of the multilayer gel film may remain on the support. An object of the present invention is to provide a technique for controlling the adhesion strength between a multilayer gel film and a support and stably producing a multilayer polyimide film having few defects such as film residue.

  As a result of intensive studies in view of the above problems, the present inventor has controlled the adhesion strength between the multilayer gel film formed on the support and the support, thereby reducing the number of defects such as film residue and the like. Has been found to be stably produced, and the present invention has been completed.

That is, the present invention is a method for producing a polyimide-based multilayer film having a plurality of resin layers containing polyimide,
(1) A multilayer in which a plurality of types of resin solutions containing polyimide or a precursor thereof are used, and a multilayer liquid film is formed on a support by laminating a liquid film composed of each resin solution using a multilayer coextrusion die. A liquid film forming step;
(2) A gel film forming step in which the obtained multilayer liquid film is a self-supporting multilayer gel film, and the outermost layer in contact with the support among the plurality of liquid films constituting the polyimide multilayer film. The liquid film contains an imidization catalyst, does not contain a chemical dehydrating agent, and the adhesion strength between the multilayer gel film formed on the support and the support is 0.2 kg / 20 cm to 2.4 kg. It is related with the manufacturing method of the polyimide-type multilayer film characterized by being / 20cm.

  A structure in which a layer containing a thermoplastic polyimide resin is provided on the surface of the polyimide multilayer film on the side in contact with the support is preferable.

  The multilayer coextrusion die is a three-layer coextrusion die, and it is preferable to add a solution containing a chemical dehydrating agent and an imidization catalyst to the central layer.

  Of the plurality of liquid films constituting the polyimide-based multilayer film, it is preferable that the outermost liquid film not in contact with the support does not contain an imidization catalyst and / or a chemical dehydrating agent.

  The present invention relates to a polyimide multilayer film obtained by the method for producing a polyimide multilayer film.

  The present invention relates to a flexible metal-clad laminate obtained by bonding a metal foil to the polyimide multilayer film.

  The present invention has been made in view of the above-described problems, does not cause peeling between layers of a multilayer film, maintains good peelability of the film from the support, and has few film residue defects. The present invention relates to a method for producing a polyimide-based multilayer film.

  Embodiments of the present invention will be described below.

  The method for producing a polyimide-based multilayer film according to the present invention is a method for producing a polyimide-based multilayer film having a structure in which a plurality of polyimide-containing resin layers are directly laminated, and contains polyimide or a precursor thereof. A multi-layer liquid film forming step of forming a multi-layer liquid film in which a plurality of types of resin solutions are used, and a multi-layer coextrusion die is used to laminate a liquid film made of each resin solution on the support, and the obtained multi-layer liquid A gel film forming step in which the film is a self-supporting multilayer gel film, and an imidation catalyst is provided on the outermost liquid film in contact with the support among the plurality of liquid films constituting the polyimide-based multilayer film. Is contained, no chemical dehydrating agent is contained, and the adhesion strength between the multilayer gel film formed on the support and the support is 0.2 kg / 20 cm to 2.4 kg / 20. It is characterized in that it is m. The adhesion strength is further preferably 0.2 kg / 20 cm to 2.1 kg / 20 cm from the viewpoint of reducing defects such as film residue. The adhesion strength is further preferably 0.2 kg / 20 cm to 1.6 kg / 20 cm from the viewpoint of reducing defects such as film residue.

  The non-thermoplastic polyimide in the present invention generally means a polyimide that does not soften or show adhesiveness even when heated. In the present invention, a film obtained by forming a non-thermoplastic film alone, heated at 450 ° C. for 1 minute, not wrinkled or stretched, retaining its shape, or DSC (differential) Scanning calorimetry) means a polyimide having substantially no glass transition temperature.

  The thermoplastic polyimide generally means a polyimide having a glass transition temperature by DSC (differential scanning calorimetry). The thermoplastic polyimide in the present invention refers to one having a glass transition temperature of 150 ° C to 350 ° C.

  The aromatic dianhydride used for the non-thermoplastic polyimide is not particularly limited, but pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, Bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane Anhydride, (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride , P-phenylenebis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and derivatives thereof, Can be preferably used alone or in a mixture.

  Among them, it is selected from the group consisting of pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride. Preferably, it is at least one acid dianhydride, and in terms of solvent solubility during production, pyromellitic dianhydride and 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride are further included. preferable.

  The aromatic diamine used in the non-thermoplastic polyimide is not particularly limited, but 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, p-phenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3′-diamino Diphenyl ether, 3,4'-diaminodiphenyl ether, 1,5 -Diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4 ' -Diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, 2,2-bis [4- (4-aminophenoxy) phenyl ] Propane and derivatives thereof are mentioned, and a mixture of these alone or in an arbitrary ratio can be preferably used.

  Of these, p-phenylenediamine and 4,4′-diaminodiphenyl ether are preferably used in terms of controlling the linear expansion coefficient and strength.

  In addition, it is preferable that non-thermoplastic polyimide contains a thermoplastic block component at the point which can improve the adhesiveness of non-thermoplastic polyimide and thermoplastic polyimide. As the diamine constituting the non-thermoplastic polyimide, 2,2-bis [4- (4-aminophenoxy) phenyl] propane is preferably used in terms of forming a thermoplastic block.

  The aromatic acid dianhydride used for the thermoplastic polyimide is not particularly limited, but pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4 , 4′-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′ , 4,4′-benzophenonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride Thing, bi (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and derivatives thereof, A mixture that is used alone or mixed at an arbitrary ratio can be preferably used.

  Among them, it is selected from the group consisting of pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride. At least one kind of acid dianhydride is preferable, and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used in terms of increasing the peel strength of the copper foil of the flexible metal-clad laminate. Preferably, pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dihydrate are used in order to improve solder heat resistance while increasing the copper foil peeling strength of the flexible metal-clad laminate. It is preferable to use an anhydride in combination.

  The aromatic diamine used for the thermoplastic polyimide is not particularly limited, but 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, p-phenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether 3,4'-diaminodiphenyl ether, 1,5- Diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'- Diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, 2,2-bis [4- (4-aminophenoxy) phenyl] Examples thereof include propane and derivatives thereof, and a mixture of these singly or in an arbitrary ratio can be preferably used.

  Among these, 2,2-bis [4- (4-aminophenoxy) phenyl] propane constituting thermoplastic polyimide is preferable in terms of improving the peel strength of the metal foil of the metal foil-clad laminate.

  The polyimide-based multilayer film according to the present invention may have any number of layers, and the polyimide-based multilayer film used for the copper-clad laminate is usually a thermoplastic polyimide so that the copper foil can be laminated. Further, in order to suppress the heat shrinkage rate, the layers other than the outermost layer of the polyimide-based multilayer film are usually non-thermoplastic polyimides, but the center layer described below is non-thermoplastic polyimide and the outermost layers on both sides thereof. It is not necessarily limited to the structure which arranged thermoplastic polyimide as. Also, from the viewpoint of equipment, cost, and productivity, the total number of polyimide multilayer films is usually kept to a minimum. As a result, a three-layer structure with non-thermoplastic polyimide on both sides of non-thermoplastic polyimide The polyimide film is preferable in that a double-sided metal-clad laminate can be produced and the flexible printed wiring board can be reduced in weight, size and density.

  As a manufacturing method of a three-layer polyimide film, a three-layer polyimide film is manufactured by simultaneously casting a three-layer polyamic acid on a support by three-layer coextrusion. At that time, it is preferable to contain an imidization catalyst in the polyamic acid solution in direct contact with the support in order to control the adhesion strength. By including an imidization catalyst, imidation of the polyamic acid that is in direct contact with the support is promoted, and due to the difference in solvent solubility between the polyamic acid and the polyimide, the solvent oozes out and partially adheres to the support. The three-layer gel film can be easily peeled off. Further, the amount of the chemical dehydrating agent and the imidization catalyst added to the central layer is usually determined by various characteristics, and is not determined in consideration of the adhesion between the support and the gel film. Therefore, it is difficult to predict the adhesion between the support and the gel film, but the adhesion strength between the support and the gel film can be easily controlled by mixing the imidization catalyst with the polyamic acid that is in direct contact with the support. . For this reason, it is useful to include an imidization catalyst in the polyamic acid solution that is in direct contact with the support. When a chemical dehydrating agent is contained in addition to the imidization catalyst, imidization proceeds chemically without increasing the temperature, resulting in thickening, making it difficult to cast onto a support. Although it is possible to form a film only when a chemical dehydrating agent is contained immediately before casting, it is not preferable from the viewpoint of equipment and cost. When no chemical dehydrating agent is contained, there is no thickening as described above, and it is not necessary to care for the elapsed time after mixing, which is preferable from the viewpoint of productivity.

  In the method for producing a three-layer polyimide film of the present invention, a polyamic acid solution is simultaneously supplied to a three-layer die by three-layer coextrusion, and is cast onto a support as a three-layer thin film from the discharge port of the die. There is a method of producing a three-layer polyimide film by heating on a support and then peeling the three-layer gel film from the support and heating at a high temperature of 200 ° C. or higher.

  In the present invention, the central layer is preferably a non-thermoplastic polyimide layer. Hereinafter, an example in which the central layer is a non-thermoplastic polyimide layer will be described.

  The polyamic acid solution of the non-thermoplastic polyimide layer that is the central layer preferably contains a chemical dehydrating agent and an imidization catalyst, but the content of the chemical dehydrating agent includes the chemical dehydrating agent and the imidization catalyst. 0.5-4.5 mol is preferable with respect to 1 mol of amic acid units in the polyamic acid contained in the caking solution, and 1.0-4.0 mol is more preferable. The content of the imidization catalyst is preferably 0.05 to 2.0 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the solution containing the chemical dehydrating agent and the imidization catalyst. 1.0 mol, further 0.1 to 0.8 mol is particularly preferable.

  The content of the imidization catalyst in the polyamic acid solution in direct contact with the support is 0.05 to 4.0 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the solution containing the imidization catalyst. Preferably, it is 0.05 to 2.0 mol, more preferably 0.1 to 1.8 mol.

  With regard to the imidization time, it suffices to take a sufficient time for the imidization and drying to be substantially completed, and it is not limited uniquely. In general, a chemical curing method using a chemical dehydrating agent is used. In the case of employing a heat curing method that does not use a chemical dehydrating agent, the time is appropriately set in the range of 60 to 1800 seconds.

  The tension applied during imidization is preferably in the range of 1 kg / m to 15 kg / m, and particularly preferably in the range of 5 kg / m to 10 kg / m. If the tension is smaller than the above range, sagging or meandering may occur during film conveyance, which may cause problems such as wrinkling during winding or inability to uniformly wind. On the other hand, when it is larger than the above range, the metal-clad laminate produced using the substrate for metal-clad laminate may deteriorate in dimensional characteristics because it is heated at a high temperature with a strong tension applied.

  The thickness of the three-layer polyimide film is preferably 7.5 μm or more and 125 μm or less. The thickness of the thermoplastic polyimide layer on at least one side of the non-thermoplastic polyimide layer in the three-layer polyimide film is preferably 1.7 μm or more. If it is less than 1.7 μm, the adhesiveness with the copper foil may deteriorate depending on the roughness of the surface of the metal foil.

  Below, the manufacturing method of the three-layer polyimide film by three-layer coextrusion is described.

  Describing a commonly used method, the solution extruded from a three-layer die is continuously extruded onto a smooth support, and then at least one of the three-layer thin film solvent on the support. A three-layer gel film having self-supporting property is obtained by volatilizing a part. The three-layer polyamic acid on the support is preferably heated at a maximum temperature of 100 to 200 ° C.

Further, the three-layer gel film is peeled off from the support, and finally, the three-layer gel film is sufficiently heat-treated at a high temperature (250 to 600 ° C.) to substantially remove the solvent and imide. A three-layer polyimide film can be obtained by allowing the conversion to complete. The three-layer gel film peeled off from the support is in the intermediate stage of curing from polyamic acid to polyimide and has self-supporting properties.
(AB) × 100 / B (1)
In formula (1), A and B represent the following.
A: Weight of the three-layer film B: The volatile content calculated from the weight after heating the three-layer film at 450 ° C. for 20 minutes is in the range of 5 to 200% by weight, preferably 10 to 100% by weight, more preferably It is in the range of 30 to 80% by weight. It is preferable to use a three-layer gel film in this range, which is preferable in that defects such as film breakage, film color unevenness due to uneven drying, and characteristic variations can be suppressed in the baking process. Further, for the purpose of improving the melt fluidity of the thermoplastic polyimide layer, the imidization rate may be intentionally lowered and / or the solvent may be left.
The support according to the present invention casts a three-layer liquid film extruded from a three-layer die, and heat-drys the three-layer liquid film on the support to give self-supporting properties. . The shape of the support is not particularly limited, but in consideration of the productivity of the adhesive film, it is preferably a drum shape or a belt shape. The material of the support is not particularly limited, and examples thereof include metal, plastic, glass, porcelain, etc., preferably metal, and more preferably SUS material having excellent corrosion resistance. Further, metal plating such as Cr, Ni, Sn may be performed.

  Although various types of structures can be used as the three-layer die, for example, a T-die for manufacturing a multi-layer film can be used. In addition, any conventionally known structure can be suitably used, and feed block T dies and multi-manifold T dies are exemplified as particularly suitable ones.

As the preferred solvent for synthesizing the polyamic acid in the present invention, any solvent can be used as long as it dissolves the polyamic acid, but amide solvents, that is, N, N-dimethylformamide, N, N-dimethylacetamide N-methyl-2-pyrrolidone and the like can be exemplified. Of these, N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.
In the present invention, any monomer addition method may be used for the polymerization of the non-thermoplastic polyamic acid. As typical polymerization methods, the following methods may be mentioned. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent, and this is reacted with a substantially equimolar aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, a method of polymerizing with an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps,
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize,
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar,
5) A method of polymerizing by reacting a mixture of substantially equimolar aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent,
And so on. These methods may be used singly or in combination.

Especially, it is preferable that the polyamic acid of a non-thermoplastic polyimide layer is obtained by the following process (a)-(c).
(A) Aromatic dianhydride and an excess molar amount of aromatic diamine are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. (B) Subsequently, (C) Furthermore, aromatic dianhydride is added and polymerized so that the aromatic dianhydride and aromatic diamine are substantially equimolar in all steps, and polyamic acid is added. Obtain a solution.

  Among the above methods, the prepolymer obtained in (a) is preferably a thermoplastic block component. Next, a method for determining whether the prepolymer is a thermoplastic block component will be described.

(Judgment method of thermoplastic block component)
Correct the acid dianhydride and diamine used in the preparation of the prepolymer to equimolar amounts (if there are multiple types of acid dianhydrides used, the ratio is fixed, and the diamine used is multiple types) The ratio was fixed.) The obtained polyamic acid solution was cast on an aluminum foil using a comma coater, heated at 130 ° C. for 100 seconds, and then a self-supporting gel film was formed from the aluminum foil. Peel off and fix to metal frame. Thereafter, when the film was softened or melted when heat-treated at 300 ° C. for 20 seconds and 450 ° C. for 1 minute, it was determined as a thermoplastic block component when the appearance was deformed.

The acid dianhydride and diamine that can serve as the thermoplastic block component are not particularly limited. Examples of the acid dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, It is preferable to use 4′-benzophenone tetracarboxylic dianhydride as an essential component, and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride is essential in terms of balancing viscoelasticity and heat resistance. More preferably, it is used as a component. As the diamine, it is preferable to use 2,2-bis [4- (4-aminophenoxy) phenyl] propane as an essential component. The method for producing a thermoplastic polyamic acid of a thermoplastic polyimide according to the present invention comprises (a) A step of reacting acid dianhydride or diamine with an excess molar amount of diamine or acid dianhydride in an organic polarity to obtain a prepolymer having amino groups or acid anhydrides at both ends; Subsequently, it is preferable to polymerize by adding acid dianhydride or diamine so that the ratio of acid dianhydride and diamine in all steps becomes a determined ratio. In (b), there are a method of adding acid dianhydride or diamine, a method of adding powder, a method of adding an acid solution in which acid dianhydride is dissolved in an organic polar solvent in advance, and the reaction is uniform. In view of easy progress, a method of adding an acid solution is preferable.

  The solid component concentration during the polymerization is preferably 10 to 30% by weight. The solid component concentration can be determined by the polymerization rate and the polymerization viscosity. The polymerization viscosity can be set according to the case where the polyamic acid solution of thermoplastic polyimide is applied to the support film, or when it is coextruded with non-thermoplastic polyimide. The polymerization viscosity is preferably 100 poise or less at a component concentration of 14% by weight. In the case of coextrusion, for example, the polymerization viscosity is preferably 100 poise to 1200 poise at a solid component concentration of 14% by weight, and 150 poise to 800 poise is preferable because the film thickness of the resulting three-layer polyimide film can be made uniform. The aromatic acid dianhydride and the aromatic diamine described above can be used by changing the order in consideration of the characteristics and productivity of the three-layer polyimide film.

  In addition, a filler can be added for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, and corona resistance. The filler is not particularly limited, and preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

  The particle size of the filler is not particularly limited because it is determined by the film characteristics to be modified and the type of filler to be added, but generally the average particle size is 0.05 to 20 μm, preferably 0.1. It is 10-10 micrometers, More preferably, it is 0.1-7 micrometers, Most preferably, it is 0.1-5 micrometers. If the particle size is below this range, the modification effect is less likely to appear. If the particle size is above this range, the surface properties may be greatly impaired or the mechanical properties may be greatly deteriorated. Further, the number of added parts of the filler is not particularly limited because it is determined by the film properties to be modified, the filler particle diameter, and the like. Generally, the addition amount of the filler is 0.01 to 50 parts by weight, preferably 0.01 to 20 parts by weight, and more preferably 0.02 to 10 parts by weight with respect to 100 parts by weight of the polyimide. If the amount of filler added is less than this range, the effect of modification by the filler hardly appears, and if it exceeds this range, the mechanical properties of the film may be greatly impaired.

Addition of the filler is, for example,
(1) A method of adding to a polymerization reaction solution before or during polymerization (2) A method of kneading fillers using three rolls after the completion of polymerization (3) A dispersion containing fillers is prepared, and this is added to polyamide Method of mixing with acid organic solvent solution (4) Any method such as a method of dispersing by bead mill or the like may be used, but a method of mixing a dispersion containing filler with a polyamic acid solution, particularly a method of mixing just before film formation It is preferable because the contamination by the filler in the production line is minimized.

  When preparing a dispersion containing a filler, it is preferable to use the same solvent as the polymerization solvent for the polyamic acid. Moreover, in order to disperse | distribute a filler favorably and stabilize a dispersion state, a dispersing agent, a thickener, etc. can also be used in the range which does not affect a film physical property.

When added for improving the slidability of the film, the particle size is 0.1 to 10 μm, preferably 0.1 to 5 μm. If the particle diameter is below this range, the effect of improving the slidability is hardly exhibited, and if it exceeds this range, it tends to be difficult to produce a high-definition wiring pattern. Further, in this case, the dispersion state of the filler is also important, and it is preferable that the aggregate of fillers of 20 μm or more is 50 pieces / m ² or less, preferably 40 pieces / m ² or less. If there are more filler aggregates of 20 μm or more than this range, it may cause repellency when the adhesive is applied, or decrease the adhesion area when creating a high-definition wiring pattern, and the insulation reliability of the flexible printed circuit board itself Tend to drop.

  Polyimide is obtained by a dehydration conversion reaction from a polyimide precursor, that is, a polyamic acid. As a method for performing the conversion reaction, there are two methods of a thermal curing method using only heat and a chemical curing method using a chemical dehydrating agent. Is the most widely known. However, since it is excellent in productivity, it is more preferable to employ a chemical curing method. In the thermal curing method and the chemical curing method, it is preferable to use an imidization catalyst in terms of allowing the imidization reaction to proceed quickly.

  The chemical dehydrating agent is a dehydrating ring-closing agent for polyamic acid, and the main components thereof are aliphatic acid anhydride, aromatic acid anhydride, N, N'-dialkylcarbodiimide, lower aliphatic halide, halogenated lower fat. An aromatic acid anhydride, an aryl sulfonic acid dihalide, a thionyl halide, or a mixture of two or more thereof can be preferably used. Of these, aliphatic acid anhydrides and aromatic acid anhydrides work particularly well. The imidation catalyst is a component having an effect of promoting the dehydration ring closure action on the polyamic acid. For example, an aliphatic tertiary amine, an aromatic tertiary amine, or a heterocyclic tertiary amine can be used. Of these, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, or β-picoline are preferred. Furthermore, introduction of an organic polar solvent into a solution composed of a chemical dehydrating agent and an imidization catalyst can be appropriately selected.

  The means for controlling the adhesion strength between the multilayer gel film and the support in the present invention is not particularly limited, and there are an approach from the support side and an approach from the multilayer gel film side. The adhesion strength changes due to the influence of the material of the support, surface processing, surface treatment, etc., but the approach from the gel film side is preferable in order to respond in a timely manner according to the adhesion strength during film formation. In the present invention, the adhesion strength was controlled by including an imidization catalyst in the outermost liquid film in contact with the support. The kind of imidation catalyst is not specifically limited, For example, an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine can be used. Of these, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, lutidine, pyridine, and β-picoline are preferred. By including the imidization catalyst, the adhesion strength between the multilayer gel film and the support can be reduced. However, when the content is excessive, the multilayer gel film floats from the support and stable film formation cannot be continued. Controlling the adhesion strength between the multilayer gel film and the support within an appropriate range leads to providing a technique for stably producing a multilayer polyimide film having few defects such as film residue. The adhesion strength between the multilayer gel film and the support is 0.2 kg / 20 cm to 2.4 kg / 20 cm. The adhesion strength is further preferably 0.2 kg / 20 cm to 2.1 kg / 20 cm from the viewpoint of reducing defects such as film residue. The adhesion strength is further preferably 0.2 kg / 20 cm to 1.6 kg / 20 cm from the viewpoint of reducing defects such as film residue.

  The production method of the flexible metal-clad laminate according to the present invention is described as follows, but is not limited thereto.

  The method for producing a flexible metal-clad laminate according to the present invention preferably includes a step of bonding a metal foil to the three-layer polyimide film. The copper foil used in the flexible metal laminate may have a thickness of 1 to 25 μm, and either a rolled copper foil or an electrolytic copper foil may be used.

  As a method for laminating the three-layer polyimide film and the metal foil, for example, a hot roll laminating apparatus having a pair of metal rolls or a continuous process using a double belt press (DBP) can be used. Among these, it is preferable to use a hot roll laminating apparatus having a pair of metal rolls because the apparatus configuration is simple and advantageous in terms of maintenance cost.

  The “heat roll laminating apparatus having a pair of metal rolls” herein may be an apparatus having a metal roll for heating and pressurizing a material, and the specific apparatus configuration is particularly limited. It is not a thing.

  The process of bonding the three-layer polyimide film and the metal foil by thermal lamination is hereinafter referred to as “thermal lamination process”.

  The specific configuration of the means for carrying out the thermal laminating (hereinafter also referred to as “thermal laminating means”) is not particularly limited, but in order to improve the appearance of the resulting laminate, the pressure surface It is preferable to arrange a protective material between the metal foil and the metal foil.

  Examples of the protective material include materials that can withstand the heating temperature in the heat laminating process, for example, heat-resistant plastics such as non-thermoplastic polyimide films, metal foils such as copper foil, aluminum foil, and SUS foil. Among these, a non-thermoplastic polyimide film or a film made of a thermoplastic polyimide having a glass transition temperature (Tg) higher by 50 ° C. or more than the laminating temperature is preferably used from the viewpoint of excellent balance of heat resistance, reusability and the like. When using thermoplastic polyimide, adhesion of the thermoplastic polyimide to the roll can be prevented by selecting one that satisfies the above conditions.

  In addition, if the thickness of the protective material is thin, the role of buffering and protection at the time of lamination will not be sufficiently fulfilled, so the thickness of the non-thermoplastic polyimide film is preferably 75 μm or more.

  Further, the protective material does not necessarily have to be a single layer, and may have a three-layer structure of two or more layers having different characteristics.

  Further, when the laminate temperature is high, if the protective material is used as it is for the laminate, the appearance and dimensional stability of the resulting flexible metal-clad laminate may not be sufficient due to rapid thermal expansion. Therefore, it is preferable to preheat the protective material before lamination. As described above, when the protective material is preheated and then laminated, since the thermal expansion of the protective material is finished, the appearance and dimensional characteristics of the flexible metal-clad laminate are suppressed.

  Examples of the preheating means include a method of bringing a protective material into contact with a heating roll. The contact time is preferably 1 second or longer, and more preferably 3 seconds or longer. When the contact time is shorter than the above, since the lamination is performed without the thermal expansion of the protective material, the thermal expansion of the protective material occurs during the lamination, and the appearance and dimensional characteristics of the resulting flexible metal-clad laminate are deteriorated. There are things to do. The distance at which the protective material is held on the heating roll is not particularly limited, and may be appropriately adjusted from the diameter of the heating roll and the contact time.

  The heating method of the material to be laminated in the heat laminating means is not particularly limited, and a conventionally known method capable of heating at a predetermined temperature, such as a heat circulation method, a hot air heating method, an induction heating method, etc., is adopted. A heating means can be used. Similarly, the method for pressurizing the material to be laminated in the thermal laminating means is not particularly limited, and is a conventionally known method capable of applying a predetermined pressure such as a hydraulic method, a pneumatic method, a gap pressure method, or the like. A pressurizing means adopting the method can be used.

  The heating temperature in the thermal laminating step, that is, the laminating temperature, is preferably a glass transition temperature (Tg) of the three-layer polyimide film + 50 ° C. or more, and more preferably Tg + 100 ° C. or more of the three-layer polyimide film. If it is Tg + 50 degreeC or more temperature, a three-layer polyimide film and metal foil can be heat-laminated favorably. Moreover, if it is Tg + 100 degreeC or more, the lamination speed | rate can be raised and the productivity can be improved more.

  In particular, the polyimide film used as the core of the three-layer polyimide film of the present invention is designed to effectively relax thermal stress when laminated at Tg + 100 ° C. or higher. A flexible metal-clad laminate excellent in productivity can be obtained with good productivity.

  The contact time with the heating roll is preferably 0.1 seconds or more, more preferably 0.2 seconds or more, and particularly preferably 0.5 seconds or more. When the contact time is shorter than the above range, the relaxation effect may not be sufficiently generated. The upper limit of the contact time is preferably 5 seconds or less. Even if the contact is made for longer than 5 seconds, the relaxation effect is not increased, and it is not preferable because a decrease in the laminating speed and restrictions on the line handling occur.

  Moreover, even if it is brought into contact with a heating roll after lamination and subjected to slow cooling, the difference between the flexible metal-clad laminate and room temperature is still large, and the residual strain may not be alleviated. Therefore, it is preferable that the flexible metal-clad laminate after being brought into contact with the heating roll and gradually cooled is subjected to the post-heating step with the protective material still disposed. The tension at this time is preferably in the range of 1 to 10 N / cm. Moreover, it is preferable to make the atmospheric temperature of post-heating into the range of (temperature -200 degreeC)-(lamination temperature +100 degreeC).

  The “atmosphere temperature” here refers to the outer surface temperature of the protective material in close contact with both surfaces of the flexible metal-clad laminate. The actual temperature of the flexible metal-clad laminate varies somewhat depending on the thickness of the protective material, but if the temperature of the surface of the protective material is within the above range, the effect of post-heating can be exhibited. The outer surface temperature of the protective material can be measured using a thermocouple or a thermometer.

  The laminating speed in the thermal laminating step is preferably 0.5 m / min or more, and more preferably 1.0 m / min or more. If it is 0.5 m / min or more, sufficient thermal lamination is possible, and if it is 1.0 m / min or more, productivity can be further improved.

  The higher the pressure in the thermal laminating process, that is, the laminating pressure, there is an advantage that the laminating temperature can be lowered and the laminating speed can be increased. However, in general, when the laminating pressure is too high, the dimensions of the obtained laminate are obtained. Changes tend to get worse. On the other hand, when the lamination pressure is too low, the adhesive strength of the metal foil of the resulting laminate is reduced. Therefore, the laminating pressure is preferably in the range of 49 to 490 N / cm (5 to 50 kgf / cm), and more preferably in the range of 98 to 294 N / cm (10 to 30 kgf / cm). Within this range, the three conditions of laminating temperature, laminating speed, and laminating pressure can be improved, and productivity can be further improved.

  The adhesive film tension in the laminating step is preferably in the range of 0.01 to 4 N / cm, more preferably in the range of 0.02 to 2.5 N / cm, and 0.05 to 1. A range of 5 N / cm is particularly preferable. When the tension is below the above range, sagging or meandering occurs during conveyance of the laminate, and it is not uniformly fed to the heating roll, so that it may be difficult to obtain a flexible metal-clad laminate having a good appearance. On the other hand, if it exceeds the above range, the influence of tension becomes so strong that it cannot be relaxed by controlling the Tg and storage modulus of the adhesive layer, and the dimensional stability may be inferior.

  In order to obtain the flexible metal-clad laminate according to the present invention, it is preferable to use a thermal laminating apparatus that continuously press-bonds the material to be laminated while heating. Further, in this thermal laminating apparatus, a laminated material feeding means for feeding the laminated material may be provided before the thermal laminating means, or a laminated material winding for winding the laminated material is taken after the thermal laminating means. Means may be provided. By providing these means, the productivity of the thermal laminating apparatus can be further improved.

  The specific configuration of the laminated material feeding means and the laminated material winding means is not particularly limited. For example, a known roll shape capable of winding an adhesive film, a metal foil, or a laminated sheet to be obtained. A winder etc. can be mentioned.

  Furthermore, it is more preferable to provide a protective material winding means and a protective material feeding means for winding and feeding the protective material. If these protective material take-up means and protective material feeding means are provided, the protective material can be reused by winding the protective material once used in the thermal laminating step and installing it again on the pay-out side. .

  Further, when winding up the protective material, end position detecting means and winding position correcting means may be provided in order to align both ends of the protective material. As a result, the end portions of the protective material can be aligned and wound with high accuracy, so that the efficiency of reuse can be increased. The specific configurations of the protective material winding means, the protective material feeding means, the end position detecting means, and the winding position correcting means are not particularly limited, and various conventionally known devices can be used.

  The peel strength between the three-layer polyimide film and the metal foil of the flexible metal-clad laminate is preferably 10 N / cm or more.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In addition, the evaluation method of the peeling strength of the three-layer polyimide film and metal foil in a synthesis example, an Example, and a comparative example is as follows.

(Method for producing metal-clad laminate)
18 μm rolled copper foil (BHY-22B-T; made by Nikko Metal) on both sides of the three-layer polyimide film, and protective materials (Apical 125 NPI; made by Kaneka) on both sides, using a hot roll laminator, Lamination temperature was 380 ° C., laminating pressure was 294 N / cm (30 kgf / cm), and laminating speed was 1.0 m / min.

(Stripping strength of metal foil)
A sample was prepared according to “6.5 Peel strength” of JIS C6471, and a 3 mm wide metal foil part was peeled off at a peeling angle of 90 degrees and 200 mm / min, and the load was measured. The side of the thermoplastic polyimide layer that is in direct contact with the support was the B side, and the opposite side was the A side.

The abbreviations of monomers and solvents used in the synthesis examples are shown below.
DMF: N, N-dimethylformamide BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane ODA: 4,4′-diaminodiphenyl ether PDA: p-phenylenediamine BPDA: 3, 3 ′, 4 , 4'-biphenyltetracarboxylic dianhydride BTDA: 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride PMDA: pyromellitic dianhydride Below, a synthesis example of a polyamic acid solution is shown. .

(Synthesis Example 1; Synthesis of thermoplastic polyimide precursor)
After dissolving 43.9 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) in 219 kg of N, N-dimethylformamide (DMF) cooled to 10 ° C., 3,3 ′ 3.1 kg of 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was gradually added and dissolved by stirring for 1 hour under a nitrogen atmosphere. Here, 19.8 kg of pyromellitic dianhydride (PMDA) was added and dissolved by stirring for 1 hour in a nitrogen atmosphere. A separately prepared DMF solution of PMDA (PMDA: DMF = 0.9 kg: 10 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 1200 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution which is a precursor of thermoplastic polyimide having a solid content concentration of 17% by weight and a rotational viscosity at 23 ° C. of 1300 poise.

(Synthesis Example 2: Synthesis of thermoplastic polyimide precursor)
After 40.9 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) was dissolved in 227 kg of N, N-dimethylformamide (DMF) cooled to 10 ° C., 20.5 kg of '4,4'-biphenyltetracarboxylic dianhydride (BPDA) was gradually added and dissolved by stirring for 1 hour under a nitrogen atmosphere. To this was added 5.4 kg of pyromellitic dianhydride (PMDA), and the mixture was stirred and dissolved in a nitrogen atmosphere for 1 hour. A separately prepared DMF solution of PMDA (PMDA: DMF = 0.9 kg: 10 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 1200 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution which is a precursor of thermoplastic polyimide having a solid content concentration of 17% by weight and a rotational viscosity at 23 ° C. of 1300 poise.

(Synthesis Example 3: Synthesis of precursor of non-thermoplastic polyimide)
239 kg of N, N-dimethylformamide (DMF) cooled to 10 ° C., 6.9 kg of 4,4′-oxydianiline (ODA), 6.2 kg of p-phenylenediamine (PDA), 2,2-bis [4 After dissolving 9.4 kg of-(4-aminophenoxy) phenyl] propane (BAPP), 10.4 kg of pyromellitic dianhydride (PMDA) was added and dissolved by stirring for 1 hour in a nitrogen atmosphere. . To this, 20.3 kg of benzophenone tetracarboxylic dianhydride (BTDA) was added and dissolved by stirring for 1 hour under a nitrogen atmosphere. A separately prepared DMF solution of PMDA (PMDA: DMF = 0.9 kg: 7.0 kg) was gradually added to the reaction solution, and the addition was stopped when the viscosity reached about 3000 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution which is a precursor of a non-thermoplastic polyimide having a solid content concentration of 18% by weight and a rotational viscosity at 23 ° C. of 3200 poise.

Example 1
Using a multi-manifold type three-layer die having a lip width of 200 mm, the polyamic acid solution obtained in Synthesis Example 1 / the polyamic acid solution obtained in Synthetic Example 3 / the polyamic acid solution obtained in Synthetic Example 1 in the order of 3 It was extruded and cast into a SUS endless belt having a layer structure. In addition, immediately before the polyamic acid obtained in Synthesis Example 3 enters the three-layer die, 2.3 mol of acetic anhydride and 0.25 mol of isoquinoline were added to 1 mol of the polyamic acid unit and mixed with a mixer. . Further, immediately before the polyamic acid obtained in Synthesis Example 1 on the side in contact with the support (endless belt) enters the three-layer die, 1.4 mol of 3,5-diethylpyridine is added to 1 mol of the polyamic acid unit. Added and mixed with a mixer. After casting, this three-layer film is heated stepwise in the range of 50 ° C. to 130 ° C. for 100 seconds, and then the self-supporting three-layer gel film is peeled off by spring measurement, and the support and gel film are separated. The adhesion strength was measured. At the same time, the contact surface between the support surface and the peeled gel film support was observed. The results are summarized in Table 1. In addition, the surface layer of the observed gel film had a partly peeled mark, and the support surface was scattered with scattered gel film residue. This situation is referred to as having peeled debris because there is debris that has been peeled off. The peeled gel film was fixed to a pin sheet, dried and imidized stepwise in the range of 250 ° C. to 400 ° C., and the thickness of each layer of the obtained multilayer polyimide film was measured to be 3.2 μm / 12. It was 0.5 μm / 3.2 μm.

(Example 2)
The same procedure as in Example 1 was performed except that the polyamic acid of Synthesis Example 2 was used instead of the polyamic acid of Synthesis Example 1. The results are summarized in Table 1.

(Example 3)
The same procedure as in Example 1 was performed except that 1.8 mol of 3,5-lutidine was added to 1 mol of the polyamic acid unit immediately before the polyamic acid in contact with the support entered the three-layer die. The results are summarized in Table 1.

Example 4
The same procedure as in Example 1 was conducted except that 3.6 mol of 3,5-lutidine was added to 1 mol of the polyamic acid unit immediately before the polyamic acid contacting the support entered the three-layer die. The results are summarized in Table 1.

(Example 5)
The same procedure as in Example 2 was performed, except that 1.8 mol of 3,5-lutidine was added to 1 mol of the polyamic acid unit immediately before the polyamic acid in contact with the support entered the three-layer die. The results are summarized in Table 1.

(Example 6)
The same procedure as in Example 2 was performed except that 3.6 mol of 3,5-lutidine was added to 1 mol of the polyamic acid unit immediately before the polyamic acid in contact with the support entered the three-layer die. The results are summarized in Table 1.

(Example 7)
The imidation catalyst to be added to the polyamic acid in contact with the support was added and stirred immediately after the polymerization, and was the same as in Example 3 except that 10 hours or more had passed before the polyamic acid entered the three-layer die. Carried out. The results are summarized in Table 1.

(Example 8)
The imidation catalyst added to the polyamic acid in contact with the support was added and stirred immediately after polymerization, and was the same as in Example 5 except that 10 hours or more had passed before the polyamic acid entered the three-layer die. Carried out. The results are summarized in Table 1.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that no imidization catalyst was added to the polyamic acid in contact with the support. The results are summarized in Table 1.

(Comparative Example 2)
The same procedure as in Example 1 was performed except that the molar ratio of the imidization catalyst added immediately before the polyamic acid contacting the support enters the three-layer die to 2.8 mol of polyamic acid units was 2.8. The results are summarized in Table 1. In Comparative Example 2, since the adhesion strength between the support and the multilayer gel film was very weak, the multilayer gel film was peeled off from the support, and stable long operation was difficult. This situation is referred to as having a gel film floating from the support.

(Comparative Example 3)
The same procedure as in Example 2 was performed except that the imidization catalyst was not added to the polyamic acid in contact with the support. The results are summarized in Table 1.

(Comparative Example 4)
The same procedure as in Example 2 was performed except that the molar ratio of the imidization catalyst added immediately before the polyamic acid contacting the support enters the three-layer die to 1 mol of the polyamic acid unit was 2.8. The results are summarized in Table 1. As in Comparative Example 2, the gel film floated from the support.

(Comparative Example 5)
The imidation catalyst added to the polyamic acid in contact with the support was added immediately after polymerization, and at the same time, 2 mol of acetic anhydride was added to 1 mol of polyamic acid and stirred, and the same procedure as in Example 7 was performed. . Ten hours later, the polyamic acid was solidified and could not be cast on the support.

Claims (6)

A method for producing a polyimide-based multilayer film having a plurality of resin layers containing a polyimide resin,
(1) Using a plurality of types of resin solutions containing a polyimide resin or a precursor thereof, a multilayer liquid film is formed by laminating a liquid film composed of each resin solution on a support using a multilayer coextrusion die. A multilayer liquid film forming step;
(2) A gel film forming step in which the obtained multilayer liquid film is a self-supporting multilayer gel film, and the outermost layer in contact with the support among the plurality of liquid films constituting the polyimide multilayer film. The liquid film contains an imidization catalyst, does not contain a chemical dehydrating agent, and the adhesion strength between the multilayer gel film formed on the support and the support is 0.2 kg / 20 cm to 2.4 kg. / Ri 20cm der,
The adhesion strength is determined by using a multi-manifold type three-layer die having a lip width of 200 mm, extruding and casting each resin solution on a SUS endless belt, and then subjecting the resulting three-layer film to a range of 50 ° C to 130 ° C. A method for producing a polyimide-based multilayer film, characterized by being measured by stepwise heating for 100 seconds and then peeling off a self-supporting three-layer gel film through spring measurement .   The method for producing a polyimide-based multilayer film according to claim 1, wherein the polyimide-based multilayer film has a structure in which a layer containing a thermoplastic polyimide resin is disposed on a surface in contact with the support of the polyimide-based multilayer film.   The said multilayer coextrusion die is a three layer coextrusion die, The solution containing a chemical dehydrating agent and an imidation catalyst is added to a center layer, The manufacture of the polyimide-type multilayer film of Claim 1 or 2 characterized by the above-mentioned. Method.   The imidation catalyst and / or the chemical dehydrating agent are not included in the outermost liquid film that does not contact the support among the plurality of liquid films constituting the polyimide multilayer film. A method for producing a polyimide-based multilayer film according to claim 1.   The polyimide multilayer film obtained by the manufacturing method of the polyimide multilayer film of any one of Claims 1-4.   A flexible metal-clad laminate obtained by bonding a metal foil to the polyimide-based multilayer film according to claim 5.