JP2006218767A - Method for producing multilayer polyimide film and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the dispersion of film thickness in the width direction of each layer when a multilayer polyimide film is produced. <P>SOLUTION: In the production of the multilayer film having at least two kinds of polyimide layers, when a coextrusion-casting application method and a chemical curing method are adopted, when a polyimide varnish (a solution containing a polyimide resin precursor or the polyimide resin) is extruded on a support, the distance from the tip part (lip part) of an extrusion die to the surface of the support is set to exceed 2 mm and not to exceed 25 mm. When a multilayer liquid film is formed on the support, the occurrence of a neck-in phenomenon is suppressed to reduce the dispersion of film thickness of each layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a plurality of polyimide-containing layers, and relates to a method for producing a polyimide-based multilayer film that can be suitably used for the production of flexible printed wiring boards and the like, and in particular, the multilayer film includes: The present invention relates to a method for producing a polyimide-based multilayer film that can be suitably used in the case of an adhesive film in which a thermoplastic polyimide layer is formed on at least one side of a heat-resistant polyimide layer exhibiting high heat resistance and its use.

  In recent years, the demand for various printed circuit boards has increased with the reduction in weight, size and density of electronic products. Among these printed boards, the demand for flexible wiring boards is growing. The flexible wiring board is also referred to as a flexible printed wiring board (FPC). The flexible wiring board has a structure in which a circuit made of a metal layer is formed on an insulating film.

  The above-mentioned flexible wiring board is generally formed of various insulating materials, a flexible insulating film is used as a substrate, and a metal foil is bonded to the surface of the substrate by heating and pressure bonding via various adhesive materials. Manufactured by. A polyimide film or the like is preferably used as the insulating film, and an epoxy or acrylic thermosetting adhesive is generally used as the adhesive material. A flexible wiring board using such a thermosetting adhesive has a three-layer structure of substrate / adhesive material / metal foil, and is hereinafter referred to as “three-layer FPC” for convenience of explanation.

  The thermosetting adhesive used for the three-layer FPC has an advantage that it can be bonded at a relatively low temperature, but has relatively low heat resistance and poor electrical characteristics. Therefore, in the future, it is assumed that requirements for various characteristics such as heat resistance, flexibility, and electrical reliability will become stricter for flexible wiring boards. However, in a three-layer FPC using a thermosetting adhesive, It is considered difficult to sufficiently meet such demands.

  On the other hand, a flexible wiring board in which a metal layer is directly provided on an insulating film and a flexible wiring board using a thermoplastic polyimide as an adhesive layer have been proposed. Since these flexible wiring boards are in a state in which a metal layer is directly formed on an insulating substrate, they are hereinafter referred to as “two-layer FPC” for convenience of explanation. This two-layer FPC has characteristics superior to those of a three-layer FPC because a polyimide resin having excellent heat resistance, flexibility, electrical reliability, and the like is used as an adhesive or no adhesive is used. Therefore, it is industrially useful because it can sufficiently meet the demands for the various characteristics described above, and demand is expected to grow in the future.

  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. Casting is a method in which an organic solvent solution of polyimide or its precursor polyamic acid (referred to as “polyimide varnish” for convenience) is cast and applied onto a metal foil, followed by heat drying and / or imidization. It is. The metalizing method is a method in which a metal layer is directly provided on a polyimide film by sputtering, vapor deposition, and / or metal 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 the casting method, and the cost required for the apparatus is lower than that of the metalizing method. As an apparatus for performing the laminating method, a hot roll laminating apparatus or a double belt press apparatus for continuously laminating a roll-shaped material is used. Among these, the hot roll laminating method can be used more preferably from the viewpoint of productivity.

  In the flexible metal-clad laminate produced by the above laminating method, as a substrate, a layer of a resin composition containing thermoplastic polyimide on at least one surface of a polyimide film (heat-resistant polyimide layer) mainly composed of heat-resistant polyimide An adhesive film provided with a (thermoplastic polyimide layer) is widely used. In this adhesive film, the heat-resistant 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 or a precursor thereof is applied to one or both sides of a polyimide film to be a heat-resistant polyimide layer and dried. The thermal laminating method is a method in which a polyimide film containing thermoplastic polyimide as a main component is heated and bonded to one side or both sides of a polyimide film to be a heat resistant polyimide layer.

  Examples of the casting film forming method include a sequential method (sequential coating method) and a coextrusion method (coextrusion-casting coating method). The sequential method includes a solution of a resin composition containing a heat-resistant polyimide or a precursor thereof (referred to as “heat-resistant polyimide varnish” for convenience) and a solution of a resin composition containing a thermoplastic polyimide or a precursor thereof ( For the sake of convenience, this is referred to as “thermoplastic polyimide varnish”) on the support. The coextrusion-casting coating method is a method in which both a heat-resistant polyimide varnish and a thermoplastic polyimide varnish are simultaneously extruded onto a support using a coextrusion die (for example, Patent Documents 1 and 2). reference).

Among the above production methods, the coextrusion-casting coating method can form a multi-layered liquid film (multi-layer liquid film) at a time, for example, requires fewer steps, and requires fewer steps. Therefore, since there are few defect factors such as contamination, there is an advantage that productivity and product yield are higher than other methods. Therefore, it can be said that it is generally the most excellent manufacturing method.
No. 2946416 (Registered July 2, 1999 (1999), publication number: JP-A-11-99554, publication date: April 13, 1999 (1999)) Japanese Patent Laid-Open No. 7-214636 (published August 15, 1995)

  By the way, in the conventional coextrusion-casting coating method, production conditions and the like have been studied on the premise of a so-called thermal curing method in which imidization is substantially performed only by heating. Here, when a film is produced using a polyamic acid which is a precursor of polyimide, it is common to imidize after forming a gel film having self-indicating properties by volatilizing and removing the solvent by heating. However, the thermal curing method has a problem in that productivity is low because the process of forming a gel film and the process of imidization take a very long time. Such low productivity leads to an increase in total cost.

  Accordingly, as a result of studies to solve the above-mentioned productivity problems, the present inventors have found that it is effective to employ a method using a chemical dehydrating agent and a catalyst, that is, a so-called chemical curing method, in imidation. However, it has been revealed by the present inventors that there is still room for improvement in the quality of the resulting multilayer film.

  Specifically, the use of a chemical cure method can solve the problem of reduced productivity, but significant fluctuations in the film thickness in the width direction tend to occur in each layer, and the fluctuations increase. It was uniquely found by the present inventors.

  This invention is made | formed in view of said subject, The objective is providing the technique which can reduce the dispersion | variation in the film thickness in the width direction of each layer, when manufacturing a polyimide-type multilayer film. It is in.

  As a result of intensive investigations in view of the above problems, the present inventors have remarkably reduced the viscosity of a polyimide varnish containing a chemical dehydrating agent and a catalyst when a chemical curing method is employed in the coextrusion-casting coating method. The inventors have found that the phenomenon that the length in the width direction of the liquid film formed when the polyimide-based varnish is extruded becomes small (so-called neck-in phenomenon) occurs. Therefore, by suppressing the occurrence of the neck-in phenomenon, the present inventors have succeeded in suppressing or avoiding the variation in the film thickness of each layer, and completed the present invention.

  That is, the method for producing a polyimide-based multilayer film according to the present invention is a method for producing a multilayer film having at least two kinds of polyimide layers in order to solve the above-described problems, and is a polyimide resin precursor or a polyimide resin. A multilayer liquid film forming step of forming a multilayer liquid film in which a plurality of layers are laminated by extruding and casting at least two kinds of solutions containing at least two types of extrusion onto a support simultaneously from an extrusion means. The distance from the tip portion of the means to the support surface is set to be more than 2 mm and not more than 25 mm.

  In the manufacturing method, a coextrusion multilayer die is preferably used as the extrusion means. Moreover, it is particularly preferable that a chemical dehydrating agent and a catalyst are added to at least one of the above solutions.

  The chemical dehydrating agent is added to the solution so that the chemical dehydrating agent is in the range of 0.5 to 4.0 moles per mole of the amic acid unit in the polyamic acid contained in the solution to be added. However, it is more preferably in the range of 1.0 to 3.0 mol. In addition, the catalyst is added to the solution so that the catalyst is in the range of 0.05 to 2.0 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the solution to be added. Is preferable, and it is more preferably in the range of 0.05 to 1.0 mol.

  In the above production method, for example, as the polyimide-based multilayer film, an adhesive film formed by laminating an adhesive layer containing a thermoplastic polyimide on at least one side of a base layer containing a heat-resistant polyimide can be exemplified. The base layer is formed using a solution containing a heat-resistant polyimide precursor, and the adhesive layer is formed using a thermoplastic polyimide precursor and / or a solution containing a thermoplastic polyimide. It is done.

  The present invention also includes a polyimide multilayer film manufactured using the above manufacturing method, and a flexible printed wiring board using the polyimide multilayer film as an insulating layer.

  In the present invention, when extruding a polyimide resin precursor or a solution containing a polyimide resin, that is, a polyimide varnish, onto the support, the distance between the extrusion means and the support surface is defined. Thereby, it becomes possible to suppress the occurrence of the neck-in phenomenon in the liquid film formed on the support. Therefore, it is possible to further reduce the variation in the film thickness in the width direction of each layer and to effectively prevent the occurrence of a significant film thickness variation.

  In addition, since the chemical curing method is adopted for the coextrusion-casting coating method, the time for imidization can be shortened, the adhesive strength between the respective layers is lowered, the peeling between the layers in the manufacturing process, The difficulty in peeling off the gel film from the support can be suppressed or avoided. As a result, not only can the quality of the polyimide-based multilayer film be prevented from being deteriorated, but also there is an effect that a high-quality polyimide-based multilayer film can be provided with higher productivity and lower cost.

  An embodiment of the present invention will be described as follows, but the present invention is not limited to this.

  The present invention is a method for producing a polyimide-based multilayer film having at least two or more kinds of polyimide layers. When a polyimide-based multilayer film having a plurality of polyimide layers is produced by a coextrusion-casting method, an imidization method is used. As a chemical curing method. Here, at least two or more kinds of solutions selected from a solution containing a polyimide precursor and / or a solution containing polyimide (for convenience of description, these are collectively referred to as a polyimide varnish) are co-extruded multilayer die, etc. And a step of forming a multilayer liquid film of two or more layers by casting from the extrusion means to the support, and in this step, the distance between the tip portion of the extrusion means and the support surface is defined. This suppresses the neck-in phenomenon and reduces the variation in the film thickness of each layer.

  Hereinafter, a method for producing a polyimide-based multilayer film according to the present invention, a preferred method for synthesizing a polyamic acid which is a precursor of the polyimide in the production method, and a specific example of the present invention will be described in order.

(I) Manufacturing method of multilayer film As described above, the manufacturing method of the polyimide-based multilayer film according to the present invention is a method that employs a chemical curing method in the coextrusion-casting coating method. If it is classified as a general process, a step of preparing a plurality of types of polyimide varnish (varnish preparation step), a step of adding a chemical dehydrating agent and a catalyst to at least one of the prepared types of polyimide varnish (curing agent) Addition step), a step of simultaneously casting a plurality of types of polyimide varnishes on a support to form a multilayer liquid film (multilayer liquid film formation step), and a multilayer gel having self-supporting properties. It can be divided into a process of converting to a film (gel film forming process) and a process of imidizing a multilayer gel film (imidation process). Hereinafter, each step will be specifically described.

<Varnish preparation process>
The varnish preparation step may be a step for preparing a solution containing a polyimide precursor (polyamide acid) and / or a solution containing a polyimide (polyimide varnish), and its specific method is particularly limited. is not. The solvent to be used is not particularly limited as long as it is an organic solvent that can dissolve polyamic acid (or polyamic acid) or polyimide. Further, the method for dissolving or dispersing polyamic acid or polyimide in the solvent is not particularly limited, and a known method can be suitably used. Note that the dissolution in the present specification includes not only “dissolution” of the resin in the solvent but also “dispersion”.

  In particular, when preparing a polyamic acid solution as a polyimide-based varnish, the solution of the polyamic acid synthesis solvent obtained by synthesizing the monomer component into the polyamic acid in the synthesis solvent as described later is used as the polyimide varnish. It can be used as a system varnish. Various conditions such as the solid content concentration (resin component concentration) and viscosity of the polyimide varnish used in the present invention are not particularly limited. It can be set as appropriate depending on the type of film.

  Moreover, when implementing the manufacturing method concerning this invention, it is not necessary to prepare a polyimide-type varnish every time, You may use the polyimide-type varnish previously prepared and stored. Therefore, in the manufacturing method according to the present invention, the varnish preparation step is not essential.

<Curing agent addition process>
The curing agent addition step is a step of adding a chemical additive and a catalyst as a curing agent (chemical curing agent) to the polyimide varnish. That is, in the manufacturing method according to the present invention, since the chemical curing method is employed, it is necessary to add the curing agent to at least one of the plural types of polyimide varnish used.

  Generally, in the production of polyimide, it can be obtained by a reaction (imidation reaction) in which polyamic acid which is a precursor of polyimide is dehydrated and converted. As the method for performing the imidization reaction, two methods are most widely known: a thermal curing method performed only by heat and a chemical curing method using the above-described curing agent (particularly a chemical dehydrating agent). Among these, since the chemical curing method is excellent in productivity, in the present invention, the chemical curing method is adopted for imidization of at least one polyimide layer.

  The chemical dehydrating agent used as the curing agent is a main component of the curing agent and may be any dehydrating ring-closing agent for the amide group of the polyamic acid. Specifically, for example, an aliphatic acid anhydride, an aromatic acid anhydride, and the like. Products, N, N′-dialkylcarbodiimides, lower aliphatic halides, halogenated lower aliphatic acid anhydrides, arylsulfonic acid dihalides, and thionyl halides, but are not limited to these compounds. It is not something. These compounds may be used singly or as a mixture in which two or more kinds are appropriately combined. Among these, in particular, an aliphatic acid anhydride such as acetic acid and / or an aromatic acid anhydride can be more preferably used.

  The catalyst used as the curing agent may be any component that has an effect of promoting the dehydration ring-closing action of the chemical dehydrating agent on the amide group. Specifically, for example, an aliphatic tertiary amine, an aromatic tertiary amine, Although heterocyclic tertiary amine etc. can be mentioned, it is not specifically limited to these compounds. Among these compounds, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, or β-picoline can be more preferably used.

  The method of adding the curing agent to the polyimide varnish is not particularly limited, but in order to achieve efficient addition and dispersion, the curing agent may be prepared in a solution and then added to the polyimide varnish. preferable. Although the solvent used at this time is not specifically limited, The solvent used for the polyimide-type varnish can be used conveniently.

  The amount of the curing agent to be added is not particularly limited. However, if the amount is too large or too small, an undesirable problem may occur in the production process. Specifically, the chemical dehydrating agent is added in an amount within the range of 0.5 to 4.0 moles with respect to 1 mole of the amic acid unit in the polyamic acid contained in the polyimide varnish to be added. It is preferable that the amount be in the range of 1.0 to 3.0 mol, and it is particularly preferable that the amount is in the range of 1.2 to 2.5 mol. Moreover, it is preferable that the addition amount of a catalyst is the quantity which exists in the range of 0.05-2.0 mol with respect to 1 mol of amic acid units in the polyamic acid contained in the polyimide-type varnish used for addition. The amount is preferably in the range of 1.05 to 1.0 mol, and more preferably in the range of 0.3 to 0.8 mol.

  When the addition amount of the chemical dehydrating agent and the catalyst, that is, the content in the polyimide varnish exceeds the upper limit, a layer to which these curing agents are added when the multilayer liquid film formed by extrusion from the extrusion means is dried. There is a possibility that the solvent oozes out and accumulates between adjacent layers. In this case, the adhesive strength between the respective layers may be lowered, or problems may be caused such that the layers are separated in the obtained polyimide-based multilayer film. On the other hand, if the lower limit is less than the above lower limit, it may be difficult to peel the multilayer gel film from the support after the multilayer liquid film is dried on a smooth support to form a multilayer gel film.

<Multilayer liquid film formation process>
The multilayer liquid film forming step is a step for forming a multilayer liquid film in which a plurality of layers are laminated by extruding at least two or more kinds of polyimide varnishes onto a support simultaneously by extrusion means, and forming a multilayer liquid film. In the invention, the distance from the tip portion of the extrusion means to the support surface is set to be more than 2 mm and 25 mm or less. That is, in the present invention, it is essential to form a multilayer liquid film by a coextrusion-casting method, and at this time, the distance from the tip portion of the extrusion means to the surface of the support is set within a predetermined range. Is essential.

  The extrusion means (extrusion member) is not particularly limited as long as it can extrude the polyimide-based varnish onto a support and apply it by casting. Specifically, various extrusion dies are preferably used. More preferably, for example, a coextrusion multilayer die such as a T die used for producing a known multilayer film can be suitably used. The coextrusion multilayer die can extrude a plurality of polyimide varnishes with a single extrusion die, so that it is easy to efficiently form a multilayer liquid film with high quality. The specific structure of the coextrusion multilayer die is not particularly limited, and any conventionally known structure can be suitably used. The multilayer structure of the polyimide-based multilayer film to be manufactured and the specific manufacture What is necessary is just to select and use an appropriate thing according to conditions etc. A feed block T die and a multi-manifold T die can be cited as particularly suitable for use in the present invention.

  In general, an extrusion die applies a supplied solution to an object to be applied, so that a tip has a pair of flat plate portions called lip portions, and the solution is pushed out between the lip portions. Become. In the present invention, when an extrusion die is used as the extrusion means, the distance from the tip of the lip portion to the support surface may be set to be at least 2 mm and 25 mm or less, and more preferably within the range of 3 to 20 mm. You only have to set it.

  When the distance from the tip of the extrusion means to the support surface (referred to as the extrusion distance for convenience) exceeds the above range, the neck-in phenomenon, that is, the width of the multilayer liquid film formed when the polyimide varnish is extruded The phenomenon that the length in the direction becomes small becomes remarkable, and in the obtained polyimide-based multilayer film, the variation in film thickness in the width direction of each layer may increase. On the other hand, when the extrusion distance is less than the above range, the vicinity of the tip of the extrusion means is heated under the influence of heat from the support, so that the polyamide contained in the polyimide varnish passing through the extrusion means An acid may cause an imidization reaction. This imidization reaction is preferable because it adversely affects the fluidity of the polyimide varnish in the vicinity of the tip of the extrusion means, and as a result, the variation in the film thickness is further increased and the defect point of the multilayer gel film is induced. Absent.

  The support has a smooth surface so that a polyimide liquid varnish extruded from the extrusion means can be cast on the surface to form a multilayer liquid film, and the multilayer liquid film is heated to self-support. If it can be made into the multilayer gel film which has property, it will not specifically limit. Specifically, for example, it preferably has a drum shape or a belt shape. If it is such a shape, a multilayer liquid film (and multilayer gel film) can be formed continuously.

  The material of the support is not particularly limited and may include metals, plastics, glass, porcelain, etc., but it is preferable that the multilayer gel film is easily peeled off. Specifically, a metal is preferable, and more specifically, a stainless material (SUS material) excellent in corrosion resistance is preferable. Further, the surface of the metal may be plated with a metal such as Cr, Ni, or Sn.

<Gel film formation process>
A gel film formation process is a process of drying the multilayer liquid film formed on the support body, and forming the multilayer gel film which has self-supporting property. Specifically, it is only necessary to volatilize (evaporate) at least a part of the solvent of the formed multilayer liquid film.

  The method for volatilizing the solvent in the multilayer liquid film, that is, the method for converting the multilayer liquid film into the multilayer gel film is not particularly limited, but the method by heating and / or blowing is the simplest. When the heating method is employed, since the solvent is rapidly volatilized when the heating temperature is too high, a smile defect is formed in the polyimide multilayer film from which the trace of the volatilization is finally obtained. Therefore, the heating temperature is preferably less than the boiling point of the solvent used + 50 ° C.

<Imidization process>
An imidation process is a process made into a polyimide-type multilayer film by imidating the said multilayer gel film. In this step, the multilayer gel film is peeled off from the support and imidized by heating at a high temperature. By this heating, the solvent is substantially removed, and imidization proceeds by dehydration ring closure of the amide group.

  The heating temperature in this step is not particularly limited, and may be a temperature that can sufficiently realize imidization. Specifically, it is preferably in the range of 250 to 600 ° C, and preferably 300 to 550 ° C. Within the range is more preferable. Within this temperature range, imidization can be achieved efficiently and reliably, and the solvent can also be removed reliably. In addition, as shown in the Example mentioned later, it is preferable that heating temperature rises in steps. Thereby, imidation and removal of a solvent can be performed more efficiently.

  The heating time in this step is not particularly limited as long as the imidization and drying can be substantially completed. Generally, the heating time is appropriately set within a range of about 1 to 600 seconds. can do.

  Here, it is preferable to apply tension to the multilayer gel film during imidization. Thereby, the fall of the quality of the polyimide-type multilayer film obtained and the fall of manufacturing efficiency can be suppressed. The method for applying the tension is not particularly limited, and examples thereof include a method of fixing the end portion with a tenter clip, as shown in Examples described later. The tension applied to the multilayer gel film is preferably in the range of 9.8 to 147 N / m (1 to 15 kg / m), and in the range of 49 to 98 N / m (5 to 10 kg / m). It is particularly preferred. When the tension is lower than the above range, sagging or meandering occurs during film conveyance, which may cause problems such as wrinkling during winding or even winding. On the other hand, when it exceeds the above range, the dimensional characteristics of the obtained polyimide-based multilayer film may be deteriorated because it is heated at a high temperature under a strong tension.

  As will be described later, the present invention can be suitably used for the production of an adhesive film in which the adhesive layer (surface layer or outer layer) is a thermoplastic polyimide layer and the base layer (inner layer) is a heat-resistant polyimide layer. In particular, for the purpose of improving the melt fluidity of the thermoplastic polyimide layer as the adhesive layer, it is possible to intentionally lower the imidization rate and / or leave the solvent in the adhesive layer.

  Further, the production method according to the present invention does not need to include all of the varnish preparation step, the multilayer liquid film formation step, the curing agent addition step, the gel film formation step, and the imidization step, and each step is appropriately omitted. And other steps can be added.

(II) Synthesis of Polyamic Acid The production method according to the present invention can be suitably used for production of any polyimide multilayer film. Here, the polyimide-based multilayer film has a plurality of polyimide layers containing polyimide, and refers to a multilayer film including at least two different layers as a polyimide layer.

  In the present invention, examples of the polyimide-based multilayer film that can be specifically used include a polyimide-based adhesive film. This adhesive film has at least a layer containing a heat resistant polyimide (heat resistant polyimide layer) as a base layer (inner layer) and a layer containing a thermoplastic polyimide (thermoplastic polyimide layer) as a surface layer (outer layer). Have. As a more specific structure, the structure by which the thermoplastic polyimide layer was laminated | stacked on the at least one surface (preferably both surfaces) of a heat resistant polyimide layer can be mentioned, for example. Such an adhesive film can be suitably used as, for example, an insulating layer of a flexible wiring board.

  In the following description, the adhesive film comprising the heat-resistant polyimide layer and the thermoplastic polyimide layer is taken as an example, and the details of the synthesis of the polyamic acid that is the precursor of the polyimide and the preparation of the polyamic acid solution as the polyimide varnish are detailed. Explained.

<Synthesis method of polyamic acid>
The synthesis method (polymerization method) of the polyamic acid is not limited to a specific kind of polyimide such as the above-mentioned heat-resistant polyimide or thermoplastic polyimide, and any known method and a combination thereof can be used. . The method of synthesizing the polyamic acid has a great feature in the order of addition of the monomer components. By controlling the order of addition of the monomer components, various physical properties of the resulting polyimide can be controlled. Therefore, also in the present invention, a known monomer component addition method can be appropriately employed depending on the physical properties required for the polyimide layer to be obtained.

Specific examples of the method for synthesizing the polyamic acid, that is, the method for adding the monomer component, include the following methods. Examples of the monomer component include a diamine component composed of at least one diamine compound and an acid dianhydride component composed of at least one acid dianhydride. An aromatic tetracarboxylic dianhydride can be suitably used as the group diamine as the acid dianhydride component.
1) A diamine component is dissolved in an organic solvent, and a substantially equimolar amount of acid dianhydride is added and reacted with this to polymerize.
2) The acid dianhydride component and a diamine component that is in a small molar amount relative to this are reacted in an organic solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, the diamine component is added and polymerized so that the acid dianhydride and the diamine component are substantially equimolar in all steps.
3) The acid dianhydride component and the diamine component in an excess molar amount with respect to this are reacted in an organic solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after additionally adding the diamine component, the acid dianhydride component is added and polymerized so that the acid dianhydride component and the diamine component are substantially equimolar in all steps.
4) After the acid dianhydride component is dissolved in an organic solvent, the diamine component is added and polymerized so as to be substantially equimolar.
5) Polymerization is carried out by reacting a substantially equimolar mixture of an acid dianhydride component and a diamine component in an organic solvent.

  Each of the above synthesis methods may be used alone or in combination. In the present invention, the polyamic acid obtained using any of these synthesis methods may be used, and the specific polymerization method is not particularly limited.

  The polyamic acid solution obtained by the above synthesis method has a concentration usually in the range of 5 to 35% by weight, preferably in the range of 10 to 30% by weight. If the concentration is within this range, an appropriate molecular weight and solution viscosity can be obtained. The polyamic acid solution thus obtained can be used as it is as a polyimide varnish in the present invention.

  As the solvent for synthesis used in the synthesis of the polyamic acid, any solvent may be used as long as it dissolves the polyamic acid to be polymerized, and specifically, an organic polar solvent is preferably used. More specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like, and amide solvents such as N, N-dimethylformamide and N, N-dimethylacetamide are used. It can be particularly preferably used. The polyamic acid solution obtained by using such a solvent can be used as it is for the polyimide varnish.

<Heat resistant polyimide>
When the polyimide-based multilayer film produced in the present invention is an adhesive film, the heat-resistant polyimide layer (or high-heat-resistant polyimide layer) that is suitably used as the base layer (inner layer) is a non-thermoplastic polyimide as a resin component. The molecular structure and the layer thickness are not particularly limited as long as they are contained by weight% or more.

  The non-thermoplastic polyimide suitably used as the heat-resistant polyimide layer is produced by using polyamic acid as a precursor, but the specific production method is not particularly limited. It is produced by dissolving the dianhydride component and the diamine component in an organic solvent so as to be substantially equimolar amounts, and stirring under controlled conditions until the polymerization of these monomer components is completed. The In addition, the polyamic acid solution (polyimide varnish) used for formation of a heat resistant polyimide layer is called a heat resistant polyamic acid solution (heat resistant polyimide varnish) for convenience.

  Moreover, in this invention, when using the diamine component which has the rigid structure mentioned later (it calls a rigid diamine component for convenience), the synthesis method which obtains a prepolymer with the said diamine component can also be used suitably. If a prepolymer is obtained from a rigid diamine component, a polyimide layer having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained. When obtaining a prepolymer, the molar ratio of the rigid diamine component and the acid dianhydride component is preferably in the range of 100: 70 to 100: 99 or 70: 100 to 99: 100, and 100: 75 to 100: It is more preferably within the range of 90 or 75: 100 to 90: 100.

  When the molar ratio of the rigid diamine component and the acid dianhydride component is below the above range, it may be difficult to obtain the effect of improving the elastic modulus and the hygroscopic expansion coefficient in the resulting polyimide layer. On the other hand, when the molar ratio of the monomer components exceeds the above range, adverse effects such as the linear expansion coefficient in the resulting polyimide layer becoming too small and the tensile elongation becoming too small may occur.

  Although it does not specifically limit as a monomer component used in order to synthesize | combine the said heat resistant polyimide layer, As an acid dianhydride component, specifically, for example, 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, 4,4'-oxyphthalic 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- Carboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxy) Phenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylene bis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid mono Ester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and analogs of these compounds. These compounds may be used singly or as a mixture in which a plurality of types are combined in an arbitrary ratio.

  Among the above compounds, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4, It is more preferable to use at least one selected from 4′-biphenyltetracarboxylic dianhydride.

  Among these, from 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride When at least one selected from the above is used, these compounds may be 60 mol% or less, preferably 55 mol% or less, and preferably 50 mol% or less with respect to all the acid dianhydride components. It is more preferable. When at least one of these compounds is used, if the amount used exceeds the above range, the glass transition temperature (Tg) of the polyimide layer obtained becomes too low, or the storage elastic modulus during heating becomes too low to form a film. This is not preferable because it may be difficult.

  Moreover, when using a pyromellitic dianhydride, the preferable usage-amount should just exist in the range of 40-100 mol% with respect to all the acid dianhydride components, In the range of 45-100 mol%. It is preferable that it is within a range of 50 to 100 mol%. If pyromellitic dianhydride is used in this range, it becomes easy to keep the Tg and the storage modulus at the time of heat in a range suitable for use or film formation in the obtained polyimide layer.

  Examples of the diamine component used to synthesize the heat-resistant polyimide include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, and 3,3′-dimethylbenzidine. 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl Sulfone, 4,4′-oxydianiline, 3,3′-oxydianiline, 3,4′-oxydianiline, 1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane, 4,4 ′ -Diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphineoxy 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diamino Benzene, bis {4- (4-aminophenoxy) phenyl} sulfone, bis {4- (4-aminophenoxy) phenyl} propane, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diamino Mention may be made of benzophenone, 4,4'-diaminobenzophenone and analogs of these compounds. These compounds may be used singly or as a mixture in which a plurality of types are combined in an arbitrary ratio.

  As described above, a rigid diamine component and a diamine having a flexible structure (referred to as a flexible diamine component for convenience) can be used in combination as the diamine component. In this case, the use ratio of the rigid diamine component and the flexible diamine component may be a molar ratio in the range of 80:20 to 20:80, and preferably in the range of 70:30 to 30:70. , 60:40 to 30:70 is more preferable. If the use ratio of the rigid diamine component exceeds the above range, the tensile elongation of the resulting polyimide layer tends to be small, and if it falls below this range, the Tg becomes too low or the storage modulus during heat becomes too low. As a result, there are cases in which the film formation is difficult.

  The compound that can be used as the rigid diamine component in the present invention is the following general formula (1)

(In the formula, R ² represents the following group (2)

R ³ in the group (2) may be the same or different, and may be the same or different, —H, —CH ₃ , —OH, —CF. ₃ , —SO ₄ , —COOH, —CO—NH ₂ , —Cl, —Br, —F, and any one group selected from the group consisting of —CH ₃ O. )
The compound represented by these is pointed out.

  The compound that can be used as the flexible diamine component is a diamine compound having a flexible structure such as an ether group, a sulfone group, a ketone group, and a sulfide group, and preferably represented by the following general formula (3) It is.

(In the formula, R ⁴ represents the following group (4)

And R ⁵ in the group (4) may be the same or different, and —H, —CH ₃ , —OH, —CF _3. , —SO ₄ , —COOH, —CO—NH ₂ , —Cl, —Br, —F, and —CH ₃ O. )
<Thermoplastic polyimide>
When the polyimide-based multilayer film produced in the present invention is an adhesive film, the thermoplastic polyimide layer suitably used as the surface layer (outer layer) is a layer that exhibits a significant adhesive force by a laminating method. Various conditions such as the content of thermoplastic polyimide contained in the layer, the molecular structure, and the thickness are not particularly limited. However, in order to develop a significant adhesive force, it is preferable that substantially 50% by weight or more of thermoplastic polyimide is contained. As with the heat-resistant polyimide layer, the polyamic acid solution (polyimide varnish) used for forming the thermoplastic polyimide layer is referred to as a thermoplastic polyamic acid solution (thermoplastic polyimide varnish) for convenience.

  As the thermoplastic polyimide (in a broad sense) contained in the thermoplastic polyimide layer, thermoplastic polyimide (in a narrow sense), thermoplastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide, and the like can be suitably used. Among these, thermoplastic polyesterimide is particularly preferably used from the viewpoint of low moisture absorption characteristics. In addition, the said thermoplastic polyimide (broad sense) can be obtained by the conversion reaction from the precursor polyamic acid similarly to the said heat-resistant polyimide layer. Similarly, any known method can be used.

  The above-mentioned thermoplastic polyimide (in a broad sense) can be adjusted in various properties by combining various monomer components to be used. Generally, when the use ratio of the rigid diamine component is increased, the Tg is increased or the product is stored during heating. It is not preferable because the elastic modulus is increased and the adhesiveness and workability are reduced. The ratio of the rigid diamine component in the total diamine component is preferably 40 mol% or less, more preferably 30 mol% or less, and further preferably 20 mol% or less. Preferable specific examples of the thermoplastic polyimide include those obtained by polymerizing an acid dianhydride component containing biphenyltetracarboxylic dianhydrides and a diamine component having an aminophenoxy group.

  In addition, considering that it can be laminated with existing equipment and does not impair the heat resistance of the obtained polyimide-based multilayer film, the thermoplastic polyimide (in a broad sense) has a glass transition temperature (Tg) of 150 to 300 ° C. It is preferable to have within the range. In addition, Tg can be calculated | required from the value of the inflexion point of the storage elastic modulus measured with the dynamic viscoelasticity measuring apparatus (DMA).

  Thus, in the present invention, an acid dianhydride component and a diamine component are appropriately selected within the above range so that the physical properties required for a polyimide-based multilayer film (for example, an adhesive film) to be produced can be realized. What is necessary is just to determine and use the kind and compounding ratio.

<Filler>
In the manufacturing method concerning this invention, you may add suitably components other than a polyimide and a solvent with respect to the polyimide-type varnish obtained as mentioned above. Other components to be added are not particularly limited, and may be appropriately selected and used within a preferable range according to physical properties required for the obtained polyimide layer or polyimide multilayer film.

  Specific examples of the component include a filler. The filler can be added for the purpose of improving various properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Specific examples of the filler include, but are not limited to, inorganic compounds such as silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica. Moreover, you may add the filler of an organic compound as needed.

  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 in the range of 0.05 to 100 μm. It is sufficient that it is within a range of 0.1 to 75 μm, more preferably within a range of 0.1 to 50 μm, and further preferably within a range of 0.1 to 25 μm. If the particle diameter is below the above range, the modification effect is difficult to appear, and if it exceeds this range, the surface properties may be greatly impaired, or the mechanical properties may be greatly deteriorated.

  Also, the amount of filler added is not particularly limited, and is determined by the film characteristics to be modified, the filler particle diameter, and the like. Generally, the amount of filler added is preferably in the range of 0.01 to 100 parts by weight, more preferably in the range of 0.01 to 90 parts by weight with respect to 100 parts by weight of polyimide. More preferably, it is in the range of 0.02 to 80 parts by weight. If the amount of filler added is less than the above range, the effect of modification by the filler hardly appears, and if it exceeds the above range, the mechanical properties of the film may be greatly impaired.

  Furthermore, the method for adding the filler is not particularly limited. For example, (1) a method of adding to the polymerization reaction solution before or during the polymerization, (2) after the polymerization is completed, the filler is mixed using a three roll or the like. Any method may be used such as a method of tempering, (3) a dispersion containing a filler, and a method of mixing this with a polyamic acid solution (polyimide varnish). Among them, the method (3) is preferably used. be able to. When the method (3) is selected, it is particularly preferable to mix immediately before film formation on a support. This minimizes contamination of the production line by the filler.

  When preparing a dispersion containing the filler, it is preferable to use the same solvent as the solvent for the polyimide varnish or 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 as needed.

In addition to the filler, other resin components other than polyimide may be added for the purpose of improving various properties required for the polyimide layer.
(III) Use of the Present Invention The use (use) of the present invention is not particularly limited, but can be suitably used in the electronics field such as a flexible printed wiring board (FPC). Furthermore, it can be used for a heat-resistant adhesive tape whose surface is coated with an adhesive, an insulating tape for covering electric wires, and the like. That is, the present invention can include an FPC insulating substrate, a heat-resistant adhesive tape, an insulating tape, and a laminate including the layer made of the polyimide film, which are used in the production thereof. .

  The laminate according to the present invention is not particularly limited as long as it has a multilayer structure including the polyimide multilayer film. For example, a flexible metal-clad laminate in which metal layers are laminated by a laminating method can be given. Although the material of the metal layer to be laminated is not particularly limited, for example, when used for FPC, a copper layer to be a pattern wiring can be exemplified. Of course, it is needless to say that the layered product according to the present invention may include layers other than those described above.

  Moreover, the said flexible wiring board manufactured using the said polyimide-type multilayer film as a base film or using the said flexible metal-clad laminated board is also contained in this invention. Since the flexible wiring board has excellent adhesion between the metal layer, that is, the pattern wiring and the insulating layer, it has excellent quality. In addition, the manufacturing method of the said flexible wiring board is not specifically limited, The various methods which can be employ | adopted if it is a publicly known thing and those skilled in the art can be used.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. In addition, the thickness measurement of each layer in the multilayer film in the following examples and comparative examples was evaluated as follows.

[Measurement of thickness of each layer of multilayer film]
The film thickness of each layer was measured at intervals of 2.5 cm in the width direction by infrared spectroscopy. As a measuring device, a product name: FT / IR-4000 manufactured by JASCO Corporation was used, and measurement was performed under the conditions of 32 times of integration, reflection and an incident angle of 13 °. The case where the variation was within ± 15% with respect to the average thickness of each layer was evaluated as ◯, and the case where the variation was exceeded was evaluated as x.

[Synthesis Example 1; Synthesis of heat-resistant polyamic acid solution]
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 (p-PDA), 2,2-bis After 9.4 kg of [4- (4-aminophenoxy) phenyl] propane (BAPP) was dissolved, 10.4 kg of pyromellitic dianhydride (PMDA) was added and dissolved by stirring for 1 hour. To this, 20.3 kg of benzophenonetetracarboxylic dianhydride (BTDA) was added and dissolved by stirring for 1 hour to obtain a reaction solution.

  Stirring while adding the DMF solution of PMDA (PMDA: DMF = 0.9kg: 7.0kg), prepared separately, to the above reaction solution slowly, stop adding and stirring when the viscosity reaches about 3500 poise. It was. Then, a heat resistant polyamic acid solution (heat resistant polyimide varnish) was obtained by stirring for 1 hour. The resulting heat-resistant polyamic acid solution had a solid content concentration of 18% by weight and a rotational viscosity at 23 ° C. of 3500 poise.

[Synthesis Example 2: Synthesis of thermoplastic polyamic acid solution]
A 300 L reactor was charged with 78 kg of DMF and 11.56 kg of BAPP, and gradually added 7.87 kg of 3,3′4,4′-biphenyltetracarboxylic dianhydride (BPDA) while stirring under a nitrogen atmosphere. did. Subsequently, 0.38 kg of ethylenebis (trimellitic acid monoester acid anhydride) (TMEG) was added and stirred for 30 minutes in an ice bath to obtain a reaction solution.

  A separately prepared TMEG DMF solution (TMEG: DMF = 0.2 kg: 4 kg) was stirred while gradually added to the reaction solution, and the addition and stirring were stopped when the viscosity reached 3300 poise. Thereby, a thermoplastic polyamic acid solution (thermoplastic polyimide varnish) was obtained.

[Example 1]
To the heat-resistant polyamic acid solution obtained in Synthesis Example 1, acetic anhydride was added as a chemical dehydrating agent and isoquinoline was added as a catalyst. Acetic anhydride is added in an amount of 2.0 mol per 1 mol of the amic acid unit in the polyamic acid contained in the heat-resistant polyamic acid solution, and isoquinoline is contained in the heat-resistant polyamic acid solution. The addition amount was 0.5 mol with respect to 1 mol of the amic acid unit in the polyamic acid.

  A multi-manifold type three-layer coextrusion multilayer die having a lip width of 650 mm was used as the extrusion means, and an endless belt made of SUS was used as the support. The distance between the three-layer coextrusion multilayer die and the endless belt surface was set to 15 mm.

  With respect to the three-layer coextrusion multilayer die, the thermoplastic polyamic acid solution obtained in Synthesis Example 2 is supplied so as to be an outer layer, and the heat-resistant polyamic acid solution is supplied as an inner layer. Polyimide varnish) is continuously extruded onto an endless belt and cast to form a liquid film of a thermoplastic polyamic acid solution / a liquid film of a heat-resistant polyamic acid solution / a liquid film of a thermoplastic polyamic acid solution. A multilayer liquid film having a three-layer structure was formed. This multilayer liquid film was converted into a self-supporting multilayer gel film by heating at 130 ° C. for 100 seconds.

  The obtained multilayer gel film was peeled off from the endless belt, both ends were fixed to a tenter clip, and dried and imidized under the conditions of 300 ° C. × 16 seconds, 400 ° C. × 29 seconds, 450 ° C. × 17 seconds. Thereby, the multilayer film of the 3 layer structure which consists of a thermoplastic polyimide layer / heat-resistant polyimide layer / thermoplastic polyimide layer was obtained.

  From the obtained multilayer film, both ends fixed with a tenter clip were trimmed and removed, a sample having a center of 500 mm width was cut out, the thickness of each layer was measured in the sample, and the variation in film thickness was evaluated. The results are shown in Table 1. The thermoplastic polyimide layer that is one outer layer (the outer layer that is not in contact with the stainless steel belt) of the multilayer film is the first layer, the heat-resistant polyimide layer that is the inner layer is the second layer, and the thermoplastic that is the other outer layer. The polyimide layer was the third layer. Moreover, the variation in film thickness is shown as a percentage of the average film thickness.

[Example 2]
Except that the distance between the three-layer coextrusion multilayer die and the endless belt surface was set to 23 mm, a multilayer film was produced in the same manner as in Example 1, the sample was cut out, the thickness of each layer was measured, and the film thickness variation Evaluated. The results are shown in Table 1.

Example 3
A multilayer film was produced in the same manner as in Example 1 except that the distance between the three-layer coextrusion multilayer die and the endless belt surface was set to 5 mm, the sample was cut out, the thickness of each layer was measured, and the film thickness variation Evaluated. The results are shown in Table 1.

[Comparative Example 1]
A multilayer film was produced in the same manner as in Example 1 except that the distance between the three-layer coextrusion multilayer die and the endless belt surface was set to 30 mm, the sample was cut out, the thickness of each layer was measured, and the film thickness variation Evaluated. The results are shown in Table 1.

[Comparative Example 2]
An attempt was made to produce a multilayer film in the same manner as in Example 1 except that the distance between the three-layer coextrusion multilayer die and the endless belt surface was set to 2 mm. However, many defect points have occurred in the multilayer gel film, and as a result, a multilayer film having a good appearance could not be obtained.

  As is apparent from the results in Table 1, the production method according to the present invention can substantially prevent the occurrence of the neck-in phenomenon, so that it is possible to produce a multilayer film with small variations in the film thickness of each layer. On the other hand, if the distance between the extrusion means and the support deviates from the interval defined in the present invention, not only the variation in the film thickness of each layer is likely to increase, but it is also difficult to obtain a film having a good appearance. It turned out that it may become.

  Note that the present invention is not limited to the configurations described above, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples respectively. Embodiments and examples obtained by appropriately combining them are also included in the technical scope of the present invention.

As described above, in the present invention, when the chemical curing method is employed in the coextrusion-casting coating method, the distance between the extrusion means and the support is defined within a specific range. As a result, the neck-in phenomenon that is likely to occur due to the adoption of the chemical curing method can be effectively suppressed, so that it is possible to manufacture a high-quality multilayer film at low cost and with little variation in film thickness. Therefore, the present invention can be used not only in the field of manufacturing a polyimide-based multilayer film, but also in various electronic components such as FPC, TAB, high-density recording medium using the same, and its field of use. It can be widely applied to fields related to the manufacture of

Claims (12)

A method for producing a multilayer film having at least two polyimide layers,
Forming a multilayer liquid film in which a plurality of layers are laminated by extruding at least two or more types of polyimide resin precursors or polyimide resin solutions onto the support simultaneously from the extrusion means. Process,
A method for producing a polyimide-based multilayer film, characterized in that the distance from the tip portion of the extrusion means to the support surface is set to be more than 2 mm and 25 mm or less.   The method for producing a polyimide-based multilayer film according to claim 1, wherein a co-extrusion multilayer die is used as the extrusion means.   The method for producing a polyimide-based multilayer film according to claim 1 or 2, wherein a chemical dehydrating agent and a catalyst are added to at least one of the solutions.   The chemical dehydrating agent is added to the solution so that the chemical dehydrating agent is in the range of 0.5 to 4.0 moles per mole of the amic acid unit in the polyamic acid contained in the solution to be added. The method for producing a polyimide-based multilayer film according to claim 3.   The amount of the chemical dehydrating agent added is in the range of 1.0 to 3.0 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the solution to be added. Item 5. A method for producing a polyimide-based multilayer film according to Item 4.   The catalyst is added to the solution so as to be in the range of 0.05 to 2.0 mol with respect to 1 mol of amic acid unit in the polyamic acid contained in the solution to be added. The method for producing a polyimide-based multilayer film according to claim 3.   7. The addition amount of the catalyst is in the range of 0.05 to 1.0 mol with respect to 1 mol of amic acid unit in the polyamic acid contained in the solution to be added. The manufacturing method of the polyimide-type multilayer film of description.   6. The adhesive film according to claim 1, wherein the polyimide multilayer film is an adhesive film formed by laminating an adhesive layer containing a thermoplastic polyimide on at least one surface of a base layer containing a heat resistant polyimide. The manufacturing method of the polyimide-type multilayer film as described in a term.   A solution containing a heat-resistant polyimide precursor is used for forming the base layer, and a solution containing a thermoplastic polyimide precursor and / or a thermoplastic polyimide is used for forming the adhesive layer. The manufacturing method of the polyimide-type multilayer film of Claim 8 characterized by the above-mentioned.   The polyimide multilayer film manufactured using the manufacturing method of the polyimide multilayer film of any one of Claim 1 thru | or 9.   A flexible metal-clad laminate comprising the polyimide-based multilayer film according to claim 10 as an insulating layer and a metal layer directly laminated on the insulating layer. A flexible printed wiring board comprising the polyimide multilayer film according to claim 10 as an insulating layer.