JP4555706B2 - Method for producing polyimide multilayer film, and polyimide multilayer film obtained thereby - Google Patents

Description

  The present invention relates to a method for producing a polyimide-based multilayer film having a structure in which a resin layer containing polyimide is directly laminated, and a polyimide-based multilayer film obtained by this production method, and particularly contains a heat-resistant polyimide. Polyimide-based multilayer that can be suitably used for the production of an adhesive film including a structure in which a resin layer containing a thermoplastic polyimide is laminated on at least one surface of the resin layer, and the adhesiveness of each resin layer is good The present invention relates to a film production method and a polyimide-based multilayer film obtained thereby.

  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 the three-layer FPC because a polyimide resin having excellent heat resistance, flexibility, electrical reliability, and the like is used as a main component of the substrate (base material). 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. The casting method 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 on a metal foil, and then imidized. The metalizing method is a method in which a metal layer is directly provided on 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 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 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 film forming 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 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 (see, for example, Patent Documents 1 to 3).

  In the manufacturing method of the said polyimide-type multilayer film, generally it passes through the process of imidating after making a polyimide-type varnish into a gel film. In this gel film, a liquid film made of a polyimide varnish is made into a gel state having a self-indicating property by a treatment such as heat drying or partial imidization.

  For example, in the coating method, first, a liquid film of a heat-resistant polyimide varnish is formed on a support, and then a gel film that is not completely imidized is obtained. A thermoplastic polyimide varnish is applied to at least one surface of the gel film, and then dried and heated. Thereby, the polyimide-type multilayer film in which the thermoplastic polyimide layer was formed in the surface of the heat resistant polyimide layer used as a center layer is obtained.

  In the case of producing a single-layer polyimide film, a method of adding a dehydrating agent and a catalyst to a polyimide varnish (chemical imide method or chemical cure method, for example, see Patent Document 4) is generally used. It is also well known that by adopting this chemical imide method, it is possible to alleviate that the drying treatment of the gel film takes a long time or that the peelability of the film from the support deteriorates.

  In the casting film forming method, first, a liquid film made of a heat-resistant polyimide varnish or a thermoplastic polyimide varnish is formed on a support such as a metal belt or a metal roll. And these liquid films are made into the gel film which has the self-supporting property by heat-drying. This gel film has a multi-layer structure by either sequential method or coextrusion method. Thereafter, the gel film having a multilayer structure (multilayer gel film) is peeled off from the support and further imidized by heat treatment at a high temperature. Thereby, a polyimide-type multilayer film can be obtained.

  Among the manufacturing methods described above, the coextrusion method can form a multi-layered liquid film (multi-layer liquid film) at a time and requires fewer steps. This has the advantage of high productivity and product yield. In addition, it is known that in the coating method, it is difficult to firmly adhere between the polyimide layers in the obtained polyimide-based multilayer film, and it is often impossible to obtain an adhesive film having sufficient adhesive strength. Yes. Therefore, when manufacturing a polyimide-type multilayer film, it is preferable to employ a casting film forming method, particularly a coextrusion method (coextrusion casting film forming method).

By the way, in the above coextrusion method, a multilayer liquid film is formed at once using a multilayer coextrusion die. For example, when a multilayer film is produced from a thermoplastic resin in a heated and melted state, a multilayer coextrusion die is used. In addition, a technique for inserting an inner deckle into a specific flow path is known (see, for example, Patent Documents 5 to 6). In this way, by inserting the inner deckle into a part of the flow paths in the multilayer coextrusion die, it becomes possible to narrow only the width of the desired layer in the multilayer film to be formed.
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) JP 10-138318 A (published on May 26, 1998) Japanese Patent Laid-Open No. 5-78503 (published March 30, 1993) Japanese Patent Laid-Open No. 11-5244 (published on January 12, 1999) JP 2004-142339 A (published on May 20, 2004)

  However, in the above conventional technique, the following problems occur in continuously producing a polyimide-based multilayer film, and thus it may be difficult to efficiently and reliably proceed with continuous production.

  First, as a first problem, a polyimide-based multilayer film includes a thermoplastic polyimide layer serving as an adhesive layer, and tends to occur when a multilayer gel film is fired using a tenter furnace. The problem that a thermoplastic polyimide layer adheres to the tenter pin (fixing means) which fixes a gel film is mentioned.

  Specifically, in general, in the production of a polyimide film regardless of a single layer or a multilayer structure, the gel film is baked in the following process. That is, after forming a self-supporting gel film on the support, the gel film is peeled off from the support. Then, the gel film is fixed by inserting needle-like fixing means called tenter pins at both ends. The immobilized gel film is supported in a spread state, and in this state, the gel film is carried into a firing furnace (tenter furnace) and fired. Since the baking of the gel film is completed and the polyimide film is obtained by being completely imidized, the polyimide film is pulled out from the tenter pin and collected.

  However, since the thermoplastic polyimide layer functioning as an adhesive layer is easily plasticized by the heat of the firing furnace, it is easily fixed to the tenter pin after firing. As a result, in a multilayer film including a thermoplastic polyimide layer, a depinning failure that is difficult to remove from the tenter pin after firing is likely to occur. The occurrence of this unpinning failure greatly reduces the efficiency of continuous production because the operation of the production apparatus must be stopped when the polyimide multilayer film is produced continuously. This problem cannot be solved by any of the above techniques.

  Next, as a second problem, when a multilayer gel film is obtained by drying a multilayer liquid film in a sequential method or a coextrusion method, a liquid film composed of a heat-resistant polyimide varnish or a thermoplastic polyimide varnish is used as the multilayer liquid film. When the liquid film to be contained is contained, there is a problem that the time until gelation, that is, the time for drying treatment becomes long. When the liquid film is dried for a long time in this manner, the multilayer gel film after drying is firmly attached to the support, and thus the peelability from the support is greatly reduced.

  Here, if the said chemical imide method is employ | adopted, since a dehydrating agent and a catalyst are added to a polyimide-type varnish, progress of a gelatinization reaction can be speeded up. Therefore, the second problem can be solved by adopting the chemical imide method.

  However, as a third problem, the present inventors have found a new problem that when the chemical imide method is applied in the production of a polyimide-based multilayer film, depending on the situation, the interlayer of the multilayer gel film is easily peeled off. It was issued. This is because the gelation reaction progresses quickly in a system to which a dehydrating agent or a catalyst is added, so that water, which is a reaction product, and various substances such as a solvent, a dehydrating agent, and a catalyst contained in a liquid film are mixed with each other. Accumulate between film layers. As a result, although depending on the type and production conditions of the polyimide-based multilayer film, in the multilayer gel film, the adhesion between the layers is lowered, and each layer may be peeled off.

  In particular, when a method of casting a liquid film on a support is used, a phenomenon called neck-in tends to occur due to the influence of surface tension and tensile stress on the liquid film being cast. As shown in FIG. 9, the neck-in is a phenomenon in which the thickness of both end portions 138 of the liquid film 130 pushed out from the die 150 increases (see the left sectional view (hatched portion) in the drawing). The liquid film 130 to be formed is formed on the support 110 with a width contracted to a width that can be originally formed by the die 150. The varnish that has shrunk in the width direction is not evenly distributed over the entire width direction of the liquid film 130 but is localized at both ends 138 as shown in FIG. In the liquid film 130 to be formed, the thickness of both end portions 138 becomes extremely thick.

  Therefore, when a multilayer liquid film is formed using the casting film forming method, as shown in FIG. 10, the obtained multilayer liquid film 30 has a shape in which both end portions 38 are thick in the cross section in the width direction. At this stage, the three liquid films 31 to 33 forming the multilayer liquid film 30 are in close contact with each other. However, when the multilayer liquid film 30 in which both end portions 38 are thickened is gelled, various substances such as water, a solvent, a dehydrating agent, and a catalyst of the reaction product are obtained particularly at both end thickened portions 38. Is difficult to diffuse or evaporate. As a result, as shown in the lower part of FIG. 10, in the resulting multilayer gel film 40, delamination 39 occurs between the three gel layers 41 to 43 starting from the ends. This delamination problem cannot be solved by any of the above techniques.

  Of the techniques for inserting the inner deckle into the specific flow path of the multilayer coextrusion die, the technique disclosed in Patent Document 5 mainly aims to alleviate the neck-in. However, since this technique is primarily a molten thermoplastic resin, there is no need to consider delamination between layers. In fact, with this technology, the thickness of the end is adjusted by relaxation of the neck-in, and as a result, the yield can be improved in the production of the multilayer film of thermoplastic resin. Even if it is applied to a film, it is not a technology that can essentially solve the problem of delamination due to the adoption of the chemical imide method.

  Similarly, Patent Document 4 is also a technology for thermoplastic resin, and its effect is to avoid mixing different kinds of raw materials into the terminal ear (end) by inserting the inner deckle, It is to improve the recyclability of. Therefore, no effective avoidance of neck-in is disclosed in the first place. Thus, even if the technique using the inner deckle is applied to the production of the polyimide-based multilayer film, the above first to third problems are solved if the film end portion where the neck-in occurs is not made a single layer film. I can't do it.

  The present invention has been made in view of the above problems, and its purpose is to prevent a depinning failure in a fired film when producing a polyimide-based multilayer film by a casting film forming method, and a chemical imide method. Even when the peelability of the multilayer film from the support is improved, the peelability of the multilayer gel film from the support is improved and the peeling of the multilayer gel film between layers is effective. It is to provide a technique to avoid the problem.

  As a result of intensive studies in view of the above problems, the present inventors have pursued the cause and action of any of the above first to third problems, thereby changing the structure of the end of the multilayer liquid film. The inventors have found that it can be effectively eliminated, and have 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 polyimide-based multilayer film having a structure in which a plurality of polyimide-containing resin layers are directly laminated in order to solve the above problems. A multilayer liquid film forming step of forming a multilayer liquid film in which a liquid film made of each resin solution is laminated on a support using a plurality of types of resin solutions containing polyimide or a precursor thereof, and And a gel film forming step in which the multilayer liquid film is formed into a self-supporting multilayer gel film, and in the multilayer liquid film forming step, the width is relatively wider than other liquid films. A multilayer liquid film is formed so as to include a single liquid film and to have a single-layer structure in which both end portions are composed of only the wide liquid film.

  In the said manufacturing method, it is preferable that the width | variety of the edge part which consists only of the said wide liquid film exists in the range of 5-100 mm.

  In the multilayer liquid film forming step, it is preferable to simultaneously form a multilayer liquid film using a multilayer coextrusion die. For example, the multi-layer coextrusion die may include a plurality of flow paths for forming a liquid film, and one flow path is wider than the other flow paths. An example of the multilayer coextrusion die is one in which a channel wider than other channels is formed by inserting an inner deckle into the channel for forming a liquid film.

  In the above production method, at least one of the plurality of liquid films constituting the multilayer liquid film may contain a dehydrating agent and a catalyst in order to improve the peelability from the support. Although it is preferable, it does not need to be contained.

  In the manufacturing method, in the multilayer liquid film forming step, a plurality of liquid films can be sequentially formed and stacked.

  Furthermore, in the manufacturing method, the plurality of resin layers include a heat-resistant polyimide layer containing a heat-resistant polyimide and a thermoplastic polyimide layer containing a thermoplastic polyimide, and the multilayer liquid film formation In the step, it is preferable to form a multilayer liquid film so that the liquid film to be the heat resistant polyimide layer is a wide liquid film. At this time, in the multilayer liquid film forming step, it is more preferable to form the multilayer liquid film so that the liquid film to be the thermoplastic polyimide layer is in contact with at least one surface of the liquid film to be the heat resistant polyimide layer. . With such a multilayer film structure, an adhesive film having a heat-resistant polyimide film as a substrate can be produced.

  Furthermore, the manufacturing method includes a baking step of baking the multilayer gel film. In the baking step, the multilayer gel film is fixed with tenter pins at both ends of the multilayer gel film. It is possible to fire the film. Of course, the specific firing process is not limited to this.

  The present invention also includes a polyimide multilayer film produced by the method for producing a polyimide multilayer film. The polyimide-based multilayer film preferably includes a structure in which a heat-resistant layer containing a heat-resistant polyimide and an adhesive layer containing a thermoplastic polyimide are laminated on at least one surface of the heat-resistant layer.

  In the present invention, as described above, when the multilayer liquid film is formed by the casting film forming method, both ends of the obtained multilayer liquid film are limited to the wide liquid film. That is, the end portion of the multilayer liquid film has a single layer structure. Thereby, when the chemical imide method is adopted as the imidization method, in the multilayer gel film, promotion of delamination due to the occurrence of neck-in can be prevented. Therefore, it is possible to improve the peelability of the multilayer gel film from the support by avoiding prolonged processing time for forming the multilayer gel film, and also in the resulting multilayer gel film It can be effectively avoided or suppressed.

  Furthermore, since the end portion of the multilayer liquid film has a single layer structure, the end portion of the obtained multilayer gel film also has a single layer structure. Therefore, it is possible to select a resin layer that does not cause the occurrence of pinning failure when fixing the end portion during the firing step, and therefore it is possible to effectively avoid or suppress the occurrence of pinning failure. .

  As a result, the gel film forming process can be shortened, and the occurrence of unpinning failure in the firing process can be effectively prevented, so that the production efficiency can be further increased when continuously producing a polyimide-based multilayer film. Not only can it be improved, but also the adhesion between the layers can be improved, so that the quality of the resulting polyimide-based multilayer film can be improved.

  An embodiment of the present invention will be described below with reference to FIGS. 1 to 10, but the present invention is not limited to this. The present invention can be carried out in a mode in which various improvements, modifications and variations are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

(I) Production method of polyimide multilayer film The present invention is a technique for producing a multilayer film (polyimide multilayer film) of two or more layers comprising at least two or more types of polyimide compounds (polyimide-containing resin composition). is there.

  Specifically, in the present invention, when a multilayer liquid film is formed on the support, the width of any one liquid film among the liquid films of the plurality of layers constituting the multilayer liquid film is changed. By making it wider than this layer, only the end of the multilayer liquid film has a single layer structure. As a preferred embodiment, a form in which a multilayer liquid film is formed using a multilayer coextrusion die can be mentioned, and at this time, an inner deckle is inserted into a specific flow path of the multilayer coextrusion die. Thereby, since the width | variety of each liquid film formed simultaneously can be changed, the multilayer liquid film which became a single layer structure only in the edge part can be obtained in substantially one step.

  In the method for producing a polyimide-based multilayer film according to the present invention (sometimes simply abbreviated as a multilayer film for convenience of explanation), if the production method is classified into steps, the step of preparing the polyimide-based varnish (varnish) Preparation step), a step of adding a dehydrating agent and a catalyst to the polyimide varnish (curing agent addition step), a step of forming a multilayer liquid film on a support using the polyimide varnish (multilayer liquid film formation step), The obtained multilayer liquid film is dried to obtain a multilayer gel film (gel film forming step), and the obtained multilayer gel film is baked to complete imidization (baking step). Hereinafter, the production method will be specifically described based on the above-mentioned division of each process.

<Varnish preparation process>
The varnish preparation step is a step of preparing a polyimide varnish that is a solution of a polyimide compound. Here, the polyimide-based compound refers to a polyimide or its precursor polyamic acid (polyamic acid), and further a resin composition containing at least one of these, and a solution obtained by dissolving this in an organic solvent. This is called a polyimide varnish.

  In general, it is known that polyimide has low solubility in various organic solvents and it is difficult to prepare a solution. On the other hand, polyamic acid can be dissolved in a relatively wide variety of organic solvents. Therefore, when the polyimide compound used has sufficient solubility in any organic solvent, a polyimide varnish may be prepared using the organic solvent. When it does not have sufficient solubility, the polyimide varnish may be prepared by dissolving the polyamic acid which is a precursor of the corresponding polyimide compound in an arbitrary organic solvent. In the present invention, when the polyimide or polyamic acid is made into a solution, other components may be added. Therefore, the “polyimide compound” in the present invention includes polyimide, polyamic acid, and a resin composition containing at least one of these.

  The organic solvent used in the polyimide varnish is not particularly limited as long as it is an organic solvent capable of dissolving the polyimide compound. Specifically, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide are used. A formamide solvent such as N, N-dimethylformamide and N, N-diethylformamide; an acetamide solvent such as N, N-dimethylacetamide and N, N-diethylacetamide; N-methyl-2-pyrrolidone and N-vinyl Pyrrolidone solvents such as 2-pyrrolidone; phenol solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol; ether solvents such as tetrahydrofuran, dioxane, dioxolane; methanol, ethanol , Butanol It can be mentioned organic polar solvent, such as; the alcoholic solvent; cellosolve solvents such as butyl cellosolve; hexamethylphosphoramide, solvents such as γ- butyrolactone. These organic solvents may be used alone or in combination of two or more. Furthermore, aromatic hydrocarbons such as xylene and toluene can also be used.

  Among the above organic solvents, formamide solvents such as N, N-dimethylformamide (DMF) and N, N-diethylformamide (DMAc) can be particularly preferably used. In addition, since the water content in the organic solvent promotes the decomposition of the polyamic acid, it is preferable to remove water from the organic solvent as much as possible.

  The polyimide used in the present invention or the polyamic acid that is a precursor thereof is not particularly limited as long as it is a compound having a polyimide skeleton or a polyamic acid skeleton, and a conventionally known one can be used. Specifically, for example, a precursor (polyamic acid) obtained by dissolving and polymerizing an acid dianhydride component and a diamine component in a polymerization solvent, and dehydrating the polyamic acid chemically or thermally. And polyimide obtained by imidization.

  As the polymerization solvent, the above-described organic solvent for preparing a varnish can be suitably used. For example, if an organic solvent such as DMF or DMAc is used as a polymerization solvent, the resulting organic solvent solution of polyamic acid (polyamic acid solution) can be used almost directly as a polyimide varnish.

  The acid dianhydride component and the diamine component are not particularly limited, and known compounds can be used. Typically, a combination of pyromellitic anhydride and diaminophenyl ether may be mentioned, but other acid dianhydrides and diamines may be used in combination or in combination as required. These compounds may be copolymerized.

  The details of the polyimide, polyamic acid and the monomer raw materials (acid dianhydride component and diamine component) that are preferably used in the present invention are more specifically described in (II) Polyamic acid synthesis described later. explain.

<Curing agent addition process>
The said hardening | curing agent addition process is a process of adding a chemical dehydrating agent (dehydrating agent) and a catalyst with respect to at least 1 sort (s) of the polyimide-type varnish prepared at the said varnish preparation process. These dehydrating agents and catalysts are collectively referred to as curing agents. That is, in the present invention, it is preferable that at least one polyimide layer is imidized by a chemical imide method, and the multilayer liquid film formed in the subsequent multilayer liquid film forming step includes a plurality of liquid films. Of these, it is preferable that at least one layer contains a curing agent.

  The dehydrating agent used in the present invention is not particularly limited as long as it is a dehydrating ring-closing agent for polyamic acid. Specifically, for example, as a main component, an aliphatic acid anhydride, an aromatic acid anhydride, etc. Compounds, N, N′-dialkylcarbodiimides, lower aliphatic halides, halogenated lower aliphatic acid anhydrides, arylsulfonic acid dihalides, thionyl halides, and the like. These compounds may be used alone or in combination of two or more. Among these, aliphatic acid anhydrides and / or aromatic acid anhydrides can be particularly preferably used.

  Although the usage-amount of the said dehydrating agent is not specifically limited, In the polyimide-type varnish used as addition object, it exists in the range of 0.5-5 mol per mol of amic acid unit contained in the polyamic acid contained. The range of 0.7 to 4 mol is more preferable, and the range of 1.5 to 2.5 mol is particularly preferable.

  The catalyst used in the present invention is not particularly limited as long as it is a component having an effect of accelerating the dehydration ring-closing action of the dehydrating agent on the polyamic acid. Specifically, for example, an aliphatic tertiary amine is used. , Aromatic tertiary amines, heterocyclic tertiary amines, and the like. Among these, for example, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, diethylpyridine, and β-picoline are particularly preferably used.

  The amount of the catalyst used is preferably in the range of 0.05 to 3 moles per mole of amic acid unit contained in the polyamic acid contained in the polyimide varnish to be added, and 0.2 to 2 moles. The range is more preferable, and the range of 0.5 to 1 mol is particularly preferable.

  If the amount of the dehydrating agent and the catalyst used is less than the above range, the effect of improving the peelability from the support becomes insufficient, imidization becomes insufficient, the material breaks during firing, or the mechanical strength decreases. Sometimes. Moreover, when these amounts exceed the above range, the progress of imidization becomes too fast, and it may be difficult to cast a polyimide varnish into a film, or it is difficult to prevent delamination in a multilayer structure. It may become.

  In the present invention, it is preferable to add the dehydrating agent and the catalyst (curing agent) to one or more of a plurality of types of polyimide varnishes, but the addition of the curing agent itself is not essential (for example, examples described later) 5). Therefore, the curing agent addition step is not an essential step in the present invention. That is, it is not necessary to add a curing agent to all the liquid films constituting the multilayer liquid film, and it is not necessary to add a curing agent to any liquid film.

  The standard for adding the curing agent to the liquid film is not particularly limited, but the presence or absence of addition, the addition amount, etc. may be set in accordance with the reaction rate of imidization of the polyimide varnish used for each liquid film. For example, it is possible to add a curing agent only to a polyimide varnish that forms the thickest liquid film and not to add a curing agent to a polyimide varnish that forms a thin liquid film. As described above, it is preferable to mix the curing agent only in an arbitrary one-layer liquid film selected from the multilayer liquid films because the configuration of the manufacturing apparatus can be prevented from becoming complicated.

  Moreover, when adding a hardening | curing agent only to one layer, a more efficient imidation may be attained by selecting appropriately the liquid film added from the state of a multilayer structure. For example, when the multilayer liquid film has a three-layer structure, the curing agent may be added only to the liquid film serving as the central layer. When a curing agent is added to the central layer, the curing agent (dehydrating agent and catalyst) exudes from the central layer and diffuses to the upper and lower layers sandwiching the central layer. Therefore, not only can the configuration of the manufacturing apparatus be complicated, but also the imidization reaction can be promoted by addition to a single layer, which is even more preferable.

  Here, if the said hardening | curing agent is added to a polyimide-type varnish, while being able to accelerate | stimulate the gelling reaction at the time of making the said polyimide-type varnish into a liquid film and drying, by acceleration | stimulation of a gelation reaction, out of the system, Water, organic solvent, etc. generated by the curing agent and reaction are discharged.

  Specifically, the gel film is a gel film in which the liquid film has self-supporting property by heating and / or drying a polyimide varnish. In this gel film, at least an organic solvent remains, and in particular, when the resin content in the varnish is polyamic acid, a part of the polyamic acid is imidized. Further, when a curing agent is added, a part of the curing agent itself remains, or a part of the water generated by the reaction remains. Such organic solvent, water, curing agent, and the like are collectively referred to as residual components. These remaining components ooze out from the inside of the liquid film or gel film as the gelation proceeds. This is because gelation proceeds rapidly in a system to which a curing agent is added.

  The residual component discharged in this manner accumulates in the gap between the gel film and the support, whereby the gel film is easily peeled off from the support. Therefore, although depending on the type of polyimide, generally, if a curing agent is added, gelation and imidization are promoted, and the peelability of the gel film can be improved. As a result, the productivity of the multilayer film can be increased.

  The method for adding the curing agent to the polyimide varnish is not particularly limited as long as the curing agent can be sufficiently dispersed or dissolved in the polyimide varnish. Generally, the curing agent is dispersed or dissolved in the same organic solvent as that used for the polyimide varnish in advance to prepare a curing agent solution, which is added to the polyimide varnish and mixed. Methods can be mentioned (see examples).

  In this method, since the viscosity of the polyimide varnish is high, there is an advantage that the curing agent is easily dispersed or dissolved rather than adding the curing agent to the polyimide varnish as it is. Furthermore, since the curing agent can be handled substantially as a liquid, as described later, there is an advantage that the curing agent can be easily supplied in the multilayer film manufacturing apparatus according to the present invention.

<Multilayer liquid film formation process>
The multilayer liquid film forming step is a step of forming a multilayer liquid film formed by laminating a plurality of types of polyimide varnishes on a support and laminating liquid films composed of varnishes (resin solutions). It is. Here, in the present invention, the multilayer liquid film forming step includes a single layer of a wide liquid film that is relatively wider than the other liquid films, and both end portions are simply formed of the wide liquid film. A multilayer liquid film is formed so as to have a layer structure. In the present invention, the width direction of the multilayer liquid film refers to a direction perpendicular to the film forming direction of the liquid film that is continuously cast.

  The wide liquid film only needs to be relatively wider than other liquid films, and other specific configurations, formation conditions, and the like are not particularly limited. Since the multilayer liquid film is formed on the support, the wide liquid film included in the multilayer liquid film has a width that can be formed on the support and has a wider width than other liquid films. I just need it.

  The width of the other liquid film is not particularly limited, but it is necessary that both end portions of the multilayer liquid film have a single-layer structure by the wide liquid film, and the region of the single-layer structure is Since it is desirable to have a width that can be fixed with a tenter pin in the subsequent firing step, the width of the end portion consisting only of the wide liquid film may be in the range of 5 to 100 mm, and in the range of 10 to 50 mm. It is preferable to be within. When the width of the end portion is narrower than the lower limit, the end portion of the multilayer liquid film cannot function effectively as a single layer structure. On the other hand, when the above upper limit is exceeded, the width of the other liquid film becomes too narrow, or it is necessary to use a very wide support as the support, which may cause a reduction in production efficiency.

  The formation method of the multilayer liquid film including the wide liquid film is not particularly limited, and each liquid film may be sequentially formed by a casting method and laminated, or each liquid film may be formed simultaneously. Also good. Especially, in this invention, it is preferable to form a multilayer liquid film by the coextrusion method which extrudes and casts multiple types of polyimide-type varnish simultaneously on a support body.

  In the coextrusion method (coextrusion casting film forming method), a plurality of types of polyimide varnishes are simultaneously discharged and cast on a support to form a multilayer liquid film substantially in one step. In addition, since the liquid films are in direct contact with each other, there is also an advantage that the interlayer of the finally obtained polyimide-based multilayer film is firmly adhered. Therefore, not only can the increase in the number of steps be avoided, but also the time for forming the multilayer liquid film can be shortened compared with the method of sequential lamination (sequential method, sequential coating method). Accumulation of residual components between layers can also be avoided. In particular, in the present invention, when the coextrusion method is employed, it is preferable to simultaneously form a multilayer liquid film using a multilayer coextrusion die. The specific configuration of the multilayer coextrusion die will be described later.

  The support is smooth so as to form a multilayer liquid film and is not dissolved by the polyimide varnish, and is preferably limited as long as it is excellent also in the peelability of the gel film. It is not a thing. Specifically, for example, a metal belt, a metal roller, a resin belt, a resin film, a resin roller, or the like can be used.

  Among these, it is preferable that the said support body is a rotary body from the point of manufacturing efficiency. If it is a rotary body, a liquid film can be formed continuously by rotating the same support, and the next gel film forming step (drying and gelation of the liquid film) can be carried out. Specific examples of the support as the rotating body include a belt-like support that is rotatably stretched by a plurality of rotating shafts, and a drum (roller) -like support that is rotatable by a single rotating shaft. be able to. For example, in FIGS. 4 to 6 and FIG. 8, an endless belt stretched by two shaft rollers is used as the support 10.

  The material of the support is not particularly limited as long as it does not affect the formation of the liquid film, but the present invention includes a process of drying the multilayer liquid film at a high temperature. Can be suitably used. Further, it is preferable that the surface of the metal support is sufficiently polished. By such polishing, the gel film produced after drying can be easily peeled off from the support. Furthermore, in order to improve the peelability of the gel film, it is more preferable to subject the surface of the metal support to surface treatment such as plating, fluororesin coating, or fluororesin-containing plating.

  Further, among the curing agents used in the present invention, in particular, dehydrating agents are generally highly corrosive, and therefore, metals such as stainless steel and hastelloy steel are preferably used as the support material. By using such a metal material, it can endure both a dehydrating agent and high-temperature heating. Furthermore, the support used in the present invention is preferably heatable. As described above, after the multilayer liquid film is formed, it is required to heat and dry the liquid film as quickly as possible. By such rapid heating and drying, it is possible to effectively suppress or avoid the accumulation of residual components discharged with the progress of the gelation reaction between the layers of each liquid film (gel film). The adhesion between the layers can be improved.

<Specific configuration of multilayer liquid film>
A specific configuration of the multilayer liquid film formed in the multilayer liquid film forming step will be described. As will be described later, since the present invention can be suitably used for the production of a polyimide-based adhesive film, in the following description, an example of producing a multilayer film having a three-layer structure, which is a representative example of a polyimide-based adhesive film, is used. Will be described.

  A multilayer film having a three-layer structure used as an adhesive film has a structure in which an adhesive layer containing a thermoplastic polyimide is laminated on at least one surface, preferably both surfaces, of a heat-resistant layer containing a heat-resistant polyimide. Therefore, in this case, the multilayer liquid film is configured such that the liquid film serving as the adhesive layer is in contact with at least one surface of the liquid film serving as the heat-resistant layer. For convenience of explanation, a liquid film that serves as a heat-resistant layer is referred to as a heat-resistant liquid film, and a liquid film that serves as an adhesive layer is referred to as an adhesive liquid film. In the case of a three-layer structure, the liquid film in which one surface is in contact with the heat-resistant liquid film and the other surface is in contact with the surface of the support is the lower liquid film, and only one surface is in contact with the heat-resistant liquid film. The surface uses the exposed liquid film as the upper liquid film.

  Specific examples of such a multilayer liquid film include the configurations shown in FIGS. The multilayer liquid film 30 shown in FIG. 1 has a three-layer structure, and a lower adhesive liquid film 31 is formed on the support 10, and a heat-resistant liquid film 32, which is a central layer, is laminated thereon. An upper adhesive liquid film 33 is formed thereon. Similarly, the multilayer liquid film 30 shown in FIG. 2 has a two-layer structure. A heat-resistant liquid film 32 is formed on the support 10 and an upper adhesive liquid film 33 is formed thereon. Similarly, the multilayer liquid film 30 shown in FIG. 3 also has a two-layer structure. A lower adhesive liquid film 31 is formed on the support 10, and a heat resistant liquid film 32 is formed thereon. Therefore, the multilayer liquid film shown in FIG. 2 has a configuration in which the lower adhesive liquid film is removed from the multilayer liquid film shown in FIG. 1, and the multilayer liquid film shown in FIG. 3 is the multilayer liquid film shown in FIG. The upper adhesive liquid film is removed from the structure.

  As described above, when the liquid film is formed on the support by the casting film forming method, neck-in occurs at both ends, so that the thickness at both ends of the liquid film increases. In this case, as shown in FIGS. 9 and 10, the end portion 38 (the end portion 138 in FIG. 9) of the multilayer liquid film 30 (the liquid film 130 in FIG. 9) has a thick structure. Here, the multilayer liquid film 30 can be converted into the multilayer gel film 40 by heating and drying, but in the thick part of the end portion 38, diffusion and evaporation of afterimage components such as a solvent are hindered. As a result, as shown in the lower part of FIG. 10, as the gelation of the multilayer liquid film proceeds, the accumulation of the remaining components causes the lower gel layer 41 and the middle gel layer 42, and the middle gel layer 42 and the upper gel. Separation 39 occurs between the layers 43.

  Therefore, in the present invention, in order to effectively avoid or suppress such delamination phenomenon between layers, in the multilayer liquid film forming step, only the width of one liquid film arbitrarily selected from the multilayer liquid film 30 is used. Is widened (wide liquid film), and the structure of the end where neck-in occurs is a single layer structure. Specifically, as shown in FIGS. 1 to 3, the heat-resistant liquid film 32 is a wide liquid film. By forming such a wide liquid film, even if the multilayer liquid film 30 is converted into the multilayer gel film 40, delamination between layers can be substantially prevented as shown in the lower part of FIGS. it can.

  Moreover, when baking the multilayer gel film 40, although an edge part is fixed by fixing means, such as a tenter pin, as shown in the bottom of FIGS. 1-3, in this invention, in a multilayer gel film, a downward liquid film The lower gel layer 41 converted from 31 and the upper gel layer 33 converted from the upper liquid film 33 do not reach the end, and the end is a single-layer structure of only the central gel layer 43 converted from the heat-resistant liquid film 32. It has become. Therefore, since the tenter pin 17 is stabbed only in the central gel layer 43, a depinning failure can be effectively avoided or suppressed as described later.

  In the present invention, it is very preferable that the adjacent liquid films in the multilayer liquid film are formed of different types of polyimide varnishes. If the same kind of polyimide varnish is used, the adjacent liquid films may be converted into one liquid film. Moreover, what is necessary is just to select the arbitrary liquid films contained in a multilayer liquid film suitably as the liquid film made into a wide liquid film in this invention. However, as described above, when the plurality of liquid films include the heat-resistant layer and the adhesive layer, the liquid film that becomes the heat-resistant layer is preferably a wide liquid film. As a result, it is possible to substantially prevent the occurrence of unpinning failure after firing as described above.

<Configuration of various dies>
The specific configuration of the die used in the present invention is not particularly limited, and various known configurations can be suitably used.

  As the multilayer coextrusion die, for example, as shown in FIG. 4, a three-layer coextrusion die having a configuration in which one central layer channel 52a and two outer layer channels 52b are formed inside the die body 51. 50. A means for supplying a polyimide varnish for the central layer is connected to the central layer flow path 52a, and a polyimide varnish for the central layer (for example, a heat-resistant polyimide varnish) is circulated. . Further, a means for supplying an upper layer polyimide varnish (for example, a thermoplastic polyimide varnish) is connected to the left side of the outer layer flow path 52b in the drawing. It comes to circulate. Similarly, a means for supplying a polyimide varnish for the lower layer is connected to the right side of the flow path 52b for the outer layer, and a polyimide varnish for the lower layer (for example, a thermoplastic polyimide varnish). Has come to circulate.

  The three-layer coextrusion die 50 is configured such that the three flow paths merge in the die body 51 and are connected to one discharge port 54. Therefore, the three kinds of supplied polyimide varnishes merge in the die body 51 and are discharged from the discharge port 53 as a liquid film having a three-layer structure. As a result, a multilayer liquid film 30 having a three-layer structure in which outer layers (upper liquid film and lower liquid film) are laminated on both surfaces of the central liquid film can be directly formed on the support (endless belt) 10.

  Next, as the slide die, for example, as shown in FIG. 5, an upper layer flow path 62b, a central layer flow path 62a, and a lower layer flow path 62c are arranged in this order in the die body 61. A slide die 60 having a configuration can be given. In this configuration, the upper layer discharge port 63b corresponding to the upper layer flow channel 62b, the center layer discharge port 63a corresponding to the center layer flow channel 62a, and the lower layer discharge port 63c corresponding to the lower layer flow channel 62c are arranged in this order. The portions of the die body 61 provided with the discharge ports are inclined surfaces 64 inclined downward from the upper layer discharge ports 63b toward the lower layer discharge ports 63c. In addition, a lip portion 65 protruding outward from the die body 61 is formed at a position on the outer side when viewed from the lower layer discharge port 63c so that the liquid film can be satisfactorily cast on the support 10 (endless belt). Has been.

  In the slide die 60, as in the three-layer coextrusion die, means for supplying polyimide varnish to the upper layer flow path 62b, the central layer flow path 62a, and the lower layer flow path 62c are connected. Has been. Therefore, the polyimide varnish supplied from these is discharged from each discharge port. Here, the lower layer polyimide varnish discharged from the lower layer discharge port 63 c below the inclined surface 64 flows directly onto the inclined surface 64 and flows down from the lip portion 65 onto the lower support.

  A central layer discharge port 63a is formed above the inclined surface 64 when viewed from the lower layer discharge port 63c. Therefore, the central layer polyimide varnish discharged from the central layer discharge port 63a is placed on the inclined surface 64 in a state of being laminated on the lower layer polyimide varnish continuously discharged from the lower layer discharge port 63c. It flows out and flows down from the lip portion 65 onto the lower support.

  Further, an upper layer discharge port 63b is formed above the inclined surface 64 when viewed from the center layer discharge port 63a. Therefore, the upper layer polyimide varnish discharged from the upper layer discharge port 63b is laminated on the center layer polyimide varnish continuously discharged from the center layer discharge port 63a. Since the central layer polyimide varnish is laminated on the lower polyimide varnish as described above, it flows out on the inclined surface 34 in a state where a liquid film having a three-layer structure of the upper layer, the central layer and the lower layer is formed. , It flows down from the lip 35 onto the lower support. As a result, a multilayer liquid film 30 having a three-layer structure is formed on the support 10 (endless belt).

  Next, as a single layer die (single layer extrusion die), as shown in FIG. 6, corresponding to the upper layer, the central layer, and the lower layer polyimide varnish, each having a configuration in which single layer dies are arranged in parallel. Can do. In this configuration, an upper-layer single-layer die 71b, a central-layer single-layer die 71a, and a lower-layer single-layer die 71c are arranged in this order from the downstream side in the traveling direction (arrow in the figure) of the endless belt (support). ing. Each single-layer die has the same structure, and a polyimide varnish flow path 72b, 72a or 72c is formed inside the main body, and a discharge port 73b, 73a or 73c is formed at the tip of the die. ing.

  Since the lower layer single layer die 71c is provided on the most upstream side when viewed from the traveling direction, the lower layer polyimide varnish discharged from the die is cast onto the endless belt 10 to form a liquid film (below A liquid film 31) is formed. A single layer die 71a for the central layer is provided immediately downstream of this, so that the central layer polyimide varnish discharged from this die is cast on the lower liquid film 31 and the central liquid film 32 is formed. Form. In this state, a liquid film having a two-layer structure of the central liquid film 32 and the lower liquid film 31 is formed on the support.

  Furthermore, since the upper layer single layer die 71b is provided on the most downstream side, the upper layer polyimide varnish discharged from this die is cast on the central liquid film 32 to form the upper liquid film 33. To do. As a result, a multilayer liquid film 30 having a three-layer structure is formed.

  In addition to the above structures, a liquid film having a multilayer structure can be formed on the support by using a method such as spraying, knife-edge coating, or gravure coating.

  In particular, in the present invention, it is preferable that a plurality of types of polyimide varnishes can be simultaneously discharged onto a support, and among these, it is more preferable to use a multilayer coextrusion die. The method of forming a plurality of liquid films simultaneously (coextrusion method) has a higher adhesiveness to each other than the method of sequentially laminating liquid films (sequential method). Especially, a multilayer coextrusion die is used. The co-extrusion method is preferable because the adhesion between the liquid films can be further improved. There are two types of the coextrusion die, a multi-manifold type and a feed block type, and it is more preferable to use a multi-manifold type co-extrusion die. By this. The uniformity of the thickness of each layer to be formed can be further increased.

  By the way, in the present invention, a specific method for forming a wide liquid film by widening only the width of one liquid film arbitrarily selected from a multilayer liquid film is not particularly limited. In the present invention, it is preferable to use a multi-layer coextrusion die as described above. However, when a multi-layer liquid film including the wide liquid film is formed using the multi-layer coextrusion die, before the integration inside the die. In each channel (in the case of FIG. 4, in the center layer channel 52 a and the two outer layer channels 52 b), a channel for forming a wide liquid film is widened, and other channels, that is, widths What is necessary is just to narrow the flow path for forming the liquid film which wants to narrow. By differentiating the widths of these flow paths, the multilayer liquid film discharged from the discharge port after joining can be configured to include a wide liquid film.

  In the multilayer coextrusion die, the method for varying the width of the flow path before joining is not particularly limited, and a die having flow paths with different widths may be manufactured and used from the beginning. From the standpoint of performance, it is possible to suitably use a resin solution in which the flow rate of the resin solution is adjusted by inserting an inner deckle into a flow path for forming a liquid film other than the wide liquid film. If the inner deckle is used, the width of the flow path can be arbitrarily adjusted.

  Specifically, for example, as shown in FIG. 7 (a), the inner deckle 54a may be inserted into the manifold 55 and the land 56, or as shown in FIG. 7 (b), the pre-land 57 may be used. The inner deckle 54b may be inserted into the inner deckle 54b.

  These inner deckles are usually inserted at both ends of a flow path for forming a liquid film whose width is desired to be narrowed. However, the present invention is not limited to this method, and a liquid film whose width is desired to be narrowed is formed. A long inner deckle may be inserted into this flow path, and a short inner deckle may be inserted into the flow path for forming a wide liquid film. If the inner deckle is used in this manner, the width of the entire multilayer liquid film can be set to an arbitrary length, and an arbitrarily selected one-layer liquid film can be a wide liquid film.

<Gel film formation process>
The gel film forming step is a step of obtaining a multilayer gel film having self-supporting property from the multilayer liquid film formed in the multilayer liquid film forming step. Usually, a multilayer liquid film is converted into a gel film by drying and gelling. In particular, in the present invention, as described above, a dehydrating agent and a catalyst (curing agent) are added in advance to at least one of the plurality of types of polyimide varnishes used in the multilayer liquid film forming step (that is, chemical imide). Method is employed). Therefore, the conversion time to the gel film can be shortened, and the peelability from the support can be improved.

  Specifically, when the chemical imide method is adopted, the added curing agent not only promotes gelation and imidization, but also accumulates residual components in the gap between the support and the multilayer gel film, so that the multilayer gel The film peelability is improved.

  Here, as a result of intensive studies by the present inventors, the residual component is not accumulated between the multilayer gel film and the support, but accumulated between each layer (individual gel film) constituting the multilayer gel film. It has been uniquely found that the adhesion between the respective layers decreases, peeling between the layers occurs, and the multilayer structure is destroyed. That is, when a multilayer liquid film is formed using a polyimide-based varnish to which a curing agent is added, and this is dried to obtain a multilayer gel film, there also arises a problem that the layers are easily separated. In particular, it has been clarified that the delamination between the layers is likely to occur at the end of the multilayer liquid film whose thickness is increased by neck-in. This is because the diffusion and evaporation of the remaining components are hindered.

  Therefore, in the present invention, as described in the multilayer liquid film forming step, the end of the multilayer liquid film to be formed into a gel film has a single layer structure. The delamination between the layers is particularly likely to occur at the end, but if the end is a single-layer structure as described above, delamination at the end will not occur. It becomes possible to suppress. In other words, in the present invention, the single layer structure at the end of the multilayer liquid film not only improves the peelability of the multilayer gel film from the support but also effectively avoids the occurrence of delamination of the multilayer gel film. Or it can be suppressed.

  The gelation method and conditions in this step are not particularly limited, and can be converted into a gel film by partially evaporating an organic solvent from a multilayer liquid film or imidizing part of a polyamic acid. As long as the conditions are appropriate. Usually, a drying method by heating or the like can be employed. The drying method in this case is not particularly limited as long as it is a method capable of proceeding with gelation, but a method capable of effectively evaporating the remaining components at the initial stage is more preferable. Specifically, a drying method by heating can be suitably used. The specific heating method is not particularly limited, and a conventionally known heating method can be suitably used. The heating temperature is preferably 60 ° C. or higher and 200 ° C. or lower, and 80 ° C. or higher and 150 ° C. or lower. It is more preferable that

  By setting the heating temperature at the time of gelation (drying temperature of the multilayer liquid film) within the range of 60 to 200 ° C., not only can the gelation of the liquid film proceed efficiently, but also the remaining components in the initial stage of drying. Can be effectively evaporated. As a result, delamination between layers can be more effectively suppressed. On the other hand, if the temperature is below the above temperature range, the remaining components may not be effectively evaporated. Moreover, when it exceeds the said temperature range, it will become easy to adhere a multilayer gel film on a support body, and it exists in the tendency for the peelability of a multilayer gel film to fall.

  Moreover, although it does not specifically limit about drying time, It is preferable to exist in the range of 1 to 600 seconds irrespective of a heating method. When the heating time is within the above range, the multilayer gel film can be produced efficiently and reliably. On the other hand, when the drying time is out of the above range, it may be hardly dried or excessively dried.

<Baking process>
The firing step is a step of firing the multilayer gel film obtained in the gel film forming step to complete imidization. As a result, the remaining components in the multilayer gel film are completely evaporated, and when the polyamic acid is contained, the imidization reaction is completed. As a result, a polyimide multilayer film in which a plurality of polyimide layers are laminated can be obtained.

  The heating method used in the baking step is not particularly limited as long as it is a method capable of effectively heating the multilayer gel film peeled off from the support to be fired into the multilayer film. Specifically, for example, A method of spraying hot air of 100 ° C. or higher from the upper surface or lower surface of the film or from both surfaces to heat the film, a method of irradiating the film with far infrared rays, or the like can be suitably used.

  The firing temperature in the firing step is not particularly limited as long as imidization can be completed and the remaining components can be sufficiently evaporated, but is preferably 200 ° C. or more and 600 ° C. or less, It is preferable to gradually increase the temperature. If the firing temperature is too high, unevenness of temperature is likely to occur in the firing of the multilayer film and flatness tends to be lost. If it is too low, sufficient firing treatment may not be performed. The firing time is not particularly limited, and the firing can be performed within a conventionally known range as long as imidization can be completed.

  Here, as the baking means (baking apparatus or baking section) used in the present invention, a conventionally known one can be suitably used, and is not particularly limited. For example, both ends of the gel film are clipped or tenter pins. It is preferable to use a type in which the gel film is transported into a heating and firing furnace. Conventionally, when a multilayer film including a thermoplastic polyimide layer is baked, a depinning failure tends to occur because the thermoplastic polyimide layer is plasticized by baking.

  Here, the present inventors have found that the defect of depinning from the tenter pin is due to the fact that, among the multilayer films stuck in the tenter pin, a layer containing a component that is easily plasticized by heat, such as thermoplastic polyimide, adheres to the tenter pin. I found out. Therefore, as a result of further intensive studies, the present inventors have found that it is very effective to suppress the depinning failure to have a single-layer structure at the end.

  That is, in the present invention, since both ends of the multilayer gel film have a single-layer structure, if the single-layer part is not a layer containing a component that is easily plasticized by heat, such as a heat-resistant polyimide layer, Depinning failure can be effectively avoided or prevented. Therefore, in the present invention, even in the case of including a layer that is easily plasticized by firing, such as a thermoplastic polyimide layer, in the firing step, the single-layer structure portions that are both ends of the multilayer gel film are formed with tenter pins. The multilayer gel film can be baked in a fixed state. Even when an immobilizing means other than a tenter pin is used, the effect of plasticization can be effectively avoided or suppressed.

  In addition, this single-layer structure at the end can avoid problems in the gel film forming step performed before the firing step. Therefore, in the manufacturing method of the multilayer film, making the end portion of the multilayer liquid film into a single layer structure exhibits different actions in different manufacturing processes, and can solve different problems.

  In addition, the manufacturing method concerning this invention does not need to include all the said varnish preparation processes, a hardening | curing agent addition process, a multilayer liquid film formation process, a gel film formation process, and a baking process. For example, as described above, each step can be omitted or other steps can be added as appropriate, such as omitting the curing agent addition step.

<Preferred example of manufacturing apparatus>
The specific structure of the production apparatus used in the method for producing a polyimide-based multilayer film according to the present invention is not particularly limited, and a known apparatus or member is appropriately selected according to the production scale or purpose. Can be used. For example, in Examples 1 to 5 described later, in Examples 1 to 5, since a polyimide-based multilayer film is manufactured at a small laboratory level, a syringe or an aluminum foil is used. Utilizes industrial production level manufacturing equipment.

  Specifically, as an industrial production level manufacturing apparatus, for example, as shown in FIG. 8, tanks for varnish 11, 12, 13, tank for curing agent 14, support (endless belt) 10, continuous type The structure provided with the drying furnace 15, the continuous baking furnace 16, the multilayer film winding part 18, and the multilayer coextrusion die 50 can be mentioned. This manufacturing apparatus is an apparatus for manufacturing the above-described adhesive film, that is, a multilayer film having a structure in which a thermoplastic polyimide layer is formed on both surfaces of a heat-resistant polyimide layer.

  The varnish tanks 11, 12, and 13 are solution supply means for supplying a polyimide varnish. Among these, at least one solution supply means, in the case of the example shown in FIG. A polyimide varnish containing an agent and a catalyst (curing agent) can be supplied.

  Of the three varnish tanks, the varnish tank 11 is a central layer tank 11 for storing a polyimide-based varnish for forming a heat-resistant polyimide layer, and the varnish tanks 12 and 13 are thermoplastic. An upper layer tank 12 and a lower layer tank 13 store polyimide varnish for forming a polyimide layer. These tanks for varnish are all connected to the multilayer coextrusion die 50 through the pipe 20. The center layer tank 11 has a liquid mixer (not shown) interposed in the middle of the pipe 20 and is connected to the curing agent tank 14 by the pipe 20.

  Specific configurations of the varnish tanks 11 to 13 and the curing agent tank 14 are not particularly limited, and conventionally known tanks can be suitably used. The same applies to the pipe 20, and conventionally known pipes can be suitably used. The size, material, and the like of these tanks and pipes are appropriately set depending on the production scale, the type of multilayer film to be produced, detailed production conditions, and the like, and are not particularly limited. The configuration other than the tank and piping is basically the same.

  The curing agent tank 14 and the liquid mixer (not shown) add a curing agent solution (dehydrating agent and catalyst) to the polyimide varnish for the center layer, and are therefore referred to as curing agent supply means. it can. The specific configuration of the curing agent supply means is not limited to these combinations. Further, the specific configuration of the liquid mixer is not particularly limited, and various known configurations can be suitably used.

  In the varnish tanks 11 to 13, the curing agent tank 14, and the liquid mixer, the curing agent addition step in the manufacturing method according to the present invention is performed, and after these steps are performed, the multilayer liquid film formation step is performed. The The manufacturing apparatus shown in FIG. 8 includes a multilayer coextrusion die 50 as means for forming a multilayer liquid film. Since the specific configuration of the multilayer coextrusion die 50 has been described above, it will be omitted. Moreover, since it can be said that this site | part is a film forming means (film forming part), you may use another die | dye as needed, and may be equipped with structures other than die | dye. Further, in the configuration shown in FIG. 8, an endless belt is used as the support 10, but since the details of the support 10 have been described above, the description thereof is omitted.

  The multilayer liquid film formed on the support is heated by a heating means and dried to gel (gel film forming step). Thereby, a multilayer gel film having self-supporting property is obtained. The drying means used for drying the multilayer liquid film is not particularly limited, but generally, since drying by heating is efficient, a conventionally known heating / drying apparatus can be suitably used. . In particular, in the present invention, a continuous drying furnace 15 that heats the multilayer liquid film 30 in a state where the multilayer liquid film 30 on the endless belt (support) 10 is carried in can be preferably used. Since an endless belt is used as the support 10 and continuous drying is possible, as described above, if the endless belt 10 itself is a heatable support, further rapid heating is possible. -It is preferable because drying is possible.

  In the present embodiment, as shown in FIG. 8, a multilayer liquid film 30 is formed by a multilayer coextrusion die 50 above one end (the end on the right side in the figure) of the endless belt 10, and the endless belt 10. As a result of this rotation, the multilayer liquid film 30 is moved (conveyed) to the lower side of the right end via the other end (left end in the figure). Therefore, the configuration shown in FIG. 8 includes a continuous drying furnace 15 provided as a heating means so as to cover most of the endless belt 17 on the left side in the drawing. With such a continuous drying furnace 15, the multilayer liquid film 30 on the endless belt 10 can be dried from the upper side to the lower side of the right end of the endless belt 10, and the apparatus configuration Can also be made compact. In addition, conditions, such as heating temperature in the said continuous-type drying furnace 15, are as having described in the gel film formation process, The concrete description is abbreviate | omitted.

  As shown in FIG. 8, in the continuous drying furnace 15, the multilayer liquid film 30 becomes the multilayer gel film 40 by the above-described drying treatment, so that the multilayer gel film 40 is discharged from the continuous drying furnace 15 and the multilayer gel film 40 is discharged. The film 40 is peeled off from the endless belt 10 and baked. The firing means used here is not particularly limited as long as it is fired to imidize the gel film, but the multilayer gel film 40 on the support 10 is carried in, and the multilayer gel is loaded. The continuous firing furnace 16 for firing the film 40 is preferable.

  After peeling off the multilayer gel film 40, the remaining components remaining in the multilayer gel film 40 (an organic solvent, a reaction solution generated by a gelling reaction, a dehydrating agent, a catalyst, etc.) are further heated and baked to a high temperature. In addition to complete evaporation, in particular, when the liquid film is formed of a polyimide-based varnish containing polyamic acid, imidation of the polyamic acid, which is only partially made by gelation, is terminated. Thereby, a polyimide-type multilayer film can be manufactured.

  The specific configuration of the continuous firing furnace 16 is not particularly limited as long as it is a heating furnace capable of effectively heating the multilayer gel film 40 to be fired into a polyimide-based multilayer film. Specifically, For example, a hot-air furnace in which hot air is sprayed on the entire film and heated, or a far-infrared furnace equipped with a far-infrared generator that irradiates the film with far-infrared rays can be suitably used.

  Moreover, it is preferable to use the method of raising temperature gradually at the time of baking. Therefore, as the continuous firing furnace 16, it is more preferable to use a staged heating furnace connecting a plurality of heating furnaces. As each heating furnace used at this time, only a hot air furnace or only a far infrared furnace may be used, or a hot air furnace and a far infrared furnace may be mixed. Moreover, it is preferable that a heat insulating means for partitioning each heating furnace is provided between the heating furnaces so as not to transmit heat from the heating furnace at the preceding stage in the traveling direction to the heating furnace at the next stage. The heat insulating means is not particularly limited, and a known configuration can be used.

  Various conditions such as the heating temperature (firing temperature) in the continuous firing furnace 16 are not particularly limited and are the same as described in the firing step, and thus detailed description thereof is omitted. Similarly, when the multilayer gel film 40 is heated and fired in the continuous firing furnace 16, the method for transporting the multilayer gel film 40 in the continuous firing furnace 16 is not particularly limited, and has a conventionally known configuration. However, as described above, in the present invention, the occurrence of unpinning failure can be effectively avoided even if the transport method using the tenter pin 17 is employed.

  The manufacturing apparatus shown in FIG. 8 is provided with a multilayer film winding unit 18 for winding a polyimide multilayer film that has been baked in a continuous baking furnace 16 and completely imidized. The specific configuration is not particularly limited, and a conventionally known configuration can be appropriately employed. In addition, the manufacturing apparatus concerning this invention is not limited to the said structure, The structure of those other than these may be provided suitably, and a one part structure may not be provided as needed.

(II) Synthesis of Polyamic Acid The multilayer film according to the present invention is preferably constituted by laminating at least two kinds of polyimide-based films. And as above-mentioned, it is preferable that one film is a heat resistant polyimide layer. Thereby, the polyimide-type multilayer film concerning this invention will have heat resistance at least. The other film is preferably a thermoplastic polyimide layer as described above. Thereby, as for the polyimide-type multilayer film concerning this invention, a thermoplastic polyimide layer will play the role of an adhesive agent under high temperature. Such a multilayer film makes it easy to attach an insulating film (heat-resistant polyimide layer) to a metal foil such as a copper foil by a thermocompression bonding method. Therefore, a high-performance polyimide film for a printed circuit board is produced. It becomes possible to do.

<Heat resistant polyimide layer>
Here, if the heat-resistant polyimide layer is made of a resin composition containing 90% by weight or more of non-thermoplastic polyimide, its specific composition, polyimide molecular structure used, layer thickness, etc. It is not limited. As described above, the non-thermoplastic polyimide used for the heat-resistant polyimide layer is produced using polyamic acid as a precursor.

  Any known method can be used as a method for producing this polyamic acid (synthesis method, polymerization method), and is not particularly limited. Usually, an acid dianhydride component composed of one or more acid dianhydrides and a diamine component composed of one or more diamines are dispersed or dissolved in a synthesis solvent so as to be substantially equimolar amounts. A method of stirring until the polymerization of each monomer component is completed under controlled temperature conditions can be suitably used. In addition, aromatic tetracarboxylic dianhydride etc. are used suitably as an acid dianhydride component, and aromatic diamine etc. are used suitably as a diamine component.

  The obtained polyamic acid is in a state of being dispersed or dissolved in a synthesis solvent, that is, in an organic solvent solution (polyamic acid solution), and the solid content concentration is usually within a range of 5 to 35% by weight, preferably 10 to 30% by weight. %. If the solid content concentration is within this range, a polyamic acid having an appropriate molecular weight is synthesized, and the polyamic acid solution also has a preferable solution viscosity for work.

  In addition, you may add an inorganic or organic filler to the said heat resistant polyimide layer and the polyimide-type varnish for forming this as needed.

<Polyamide acid polymerization method>
As the polymerization method of the polyamic acid, any conventionally known method and a combination thereof can be used. A characteristic of the polyamic acid polymerization method is the order of addition of the monomer components. Therefore, various physical properties of the obtained polyimide can be controlled by controlling the order of addition of the monomer components. Therefore, in the present invention, any monomer component addition method may be used for the polymerization of the polyamic acid. Examples of typical polymerization methods include the following methods. These methods may be used singly or in combination. In the present invention, a polyamic acid obtained using any of the following polymerization methods may be used.

(1) An aromatic diamine is dissolved in an organic polar solvent, and substantially equimolar aromatic tetracarboxylic dianhydride is added and reacted with this to polymerize.
(2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, the aromatic diamine is further added and polymerized so that the aromatic tetracarboxylic dianhydride and the aromatic diamine are substantially equimolar in all steps.
(3) An aromatic tetracarboxylic dianhydride is reacted with an excess molar amount of an aromatic diamine in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding aromatic diamine here, aromatic tetracarboxylic dianhydride is added so that aromatic tetracarboxylic dianhydride and aromatic diamine compound are substantially equimolar in all steps. Add and polymerize.
(4) After the aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent, an aromatic diamine compound is added and polymerized so as to be substantially equimolar.

  In particular, in the present invention, in order to obtain a heat-resistant polyimide, a polymerization method for obtaining a prepolymer using a diamine having a rigid structure to be described later (referred to as a rigid diamine for convenience) may be used. By using this polymerization method, a polyimide film having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained.

  In the above polymerization method, the molar ratio of the rigid diamine and the acid dianhydride used when preparing the prepolymer is preferably in the range of 100: 70 to 100: 99 or 70: 100 to 99: 100, and more preferably 100: 75 to More preferably within the range of 100: 90 or 75: 100 to 90: 100. If the molar ratio is below the above range, it is difficult to obtain an effect of improving the elastic modulus and the hygroscopic expansion coefficient. If the molar ratio is above the above range, the linear expansion coefficient becomes too small, or the tensile elongation is deteriorated. Sometimes.

<Acid dianhydride component used in the production of non-thermoplastic polyimide>
In the present invention, in producing the non-thermoplastic polyimide contained in the heat-resistant polyimide layer, the acid dianhydride component used for the synthesis of the polyamic acid as a precursor is not particularly limited, 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- Dicarboxyl Enyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (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), or the like. These compounds may be used singly or in combination of two or more at any ratio.

  Among the acid dianhydrides, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4 At least one compound selected from the group of 4,4′-biphenyltetracarboxylic dianhydride can be particularly preferably used.

  Of the four particularly preferred acid dianhydrides, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3,3 ′, 4,4 The amount used in the case of using at least one selected from '-biphenyltetracarboxylic dianhydride is preferably 60 mol% or less, more preferably 55 mol% or less, based on the total acid dianhydride. More preferably, it is more preferably 50 mol% or less. When using at least one of these three types of tetracarboxylic dianhydrides, if the amount used exceeds the above range, the glass transition temperature (Tg) of the resulting heat-resistant polyimide layer becomes too low, or the polyamic acid solution This is not preferable because the storage elastic modulus at the time of heating becomes too low and film formation itself may become difficult.

  The amount of pyromellitic dianhydride used as the tetracarboxylic dianhydride is preferably in the range of 40 to 100 mol%, more preferably in the range of 45 to 100 mol%, and 50 to 100 mol. % Is more preferable. If pyromellitic dianhydride is used within this range, the Tg of the resulting heat-resistant polyimide layer and the storage modulus of the polyamic acid solution when heated can be easily maintained within a range suitable for use or film formation.

<Diamine component used for production of non-thermoplastic polyimide>
In the present invention, in producing the non-thermoplastic polyimide contained in the heat-resistant polyimide layer is not particularly limited as a diamine component used for the synthesis of the polyamic acid as a precursor, specifically, For example, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'- Dimethoxybenzidine, 2,2′-dimethoxybenzidine, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-oxydianiline, 3,3 '-Oxydianiline, 3,4'-oxydianiline, 1,5-diaminonaphthalene, 4,4'-diamino Phenyldiethylsilane, 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, 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- Examples thereof include bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone, 4,4′-diaminobenzophenone, and the like. These compounds may be used singly or in combination of two or more at any ratio.

  As the diamine component, a rigid diamine having a rigid structure and a diamine having a flexible structure can be used in combination. The preferable use ratio in that case should just be in the range of 80 / 20-20 / 80 by molar ratio, It is more preferable to exist in the range of 70 / 30-30 / 70, 60 / 40-30 / 70 More preferably, it is in the range. When the use ratio of rigid diamine exceeds the above range, the tensile elongation of the resulting heat-resistant polyimide layer tends to be small. Moreover, if the ratio of the rigid diamine used is below the above range, the Tg of the resulting heat-resistant polyimide layer becomes too low, or the storage elastic modulus of the polyamic acid solution when heated becomes too low, making film formation difficult. It may be accompanied by harmful effects such as

  The rigid diamine in the present invention is a group selected from the group consisting of divalent aromatic groups represented by the following general formula (1).

In addition, R < ² > in General formula (1) is represented by General formula group (2).

R ³ in the general formula group (2) is the same or different and is H—, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —COOH, —CO—NH ₂ , Cl—, Br—, F -, and CH ₃ is any one group selected from the group consisting of O-.

  On the other hand, the diamine having a flexible structure has a flexible structure such as an ether group, a sulfone group, a ketone group, or a sulfide group, and is preferably represented by the following general formula (3).

Incidentally, R ⁴ in the general formula (3) in the general formula group (4)

In which R ⁵ is the same or different and is H—, CH ₃ —, —OH, —CF ₃ , —SO ₄ , —COOH, or a group selected from the group consisting of divalent organic groups , —CO—NH ₂ , Cl—, Br—, F—, and CH ₃ O—.

  In the present invention, the polyimide varnish for forming the heat-resistant polyimide layer is the above acid dianhydride component so that the finally obtained heat-resistant polyimide layer (polyimide film) is a film having desired characteristics. And the kind of diamine component and the compounding ratio can be appropriately determined and used.

  Here, as a preferable polymerization solvent for synthesizing the polyamic acid, any solvent can be used as long as it dissolves the polyamic acid. However, amide solvents, that is, N, N-dimethylformamide, N, N-dimethyl are used. Examples thereof include acetamide and N-methyl-2-pyrrolidone, and N, N-dimethylformamide, N, N-dimethylacetamide and the like can be particularly preferably used. These polymerization solvents can be used as they are as solvents for polyimide varnish.

<Thermoplastic polyimide layer>
The thermoplastic polyimide layer concerning this invention should just be formed from the resin composition containing a thermoplastic polyimide. Here, the thermoplastic polyimide used (in a broad sense) includes thermoplastic polyimide (in a narrow sense), thermoplastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide, and the like, but is not particularly limited. . These resins may be used alone or in combination of two or more. Among the above resins, thermoplastic polyesterimide can be particularly preferably used because of its low hygroscopicity.

  When the thermoplastic polyimide layer is laminated on the heat-resistant polyimide layer as an adhesive layer to become an adhesive film, it is sufficient that it can exhibit a significant adhesive force especially when laminating laminates by the laminating method. The conditions such as the content of the thermoplastic polyimide (broadly defined), the molecular structure, and the thickness of the thermoplastic polyimide layer are not particularly limited. However, it is preferable that substantially 50% by weight or more of thermoplastic polyimide (in a broad sense) is contained in order to develop a significant adhesive force.

  The said thermoplastic polyimide (broad sense) can also be obtained by the conversion reaction from the polyamic acid which is the precursor similarly to the said non-thermoplastic polyimide. As the method for producing the polyamic acid, any known synthesis method can be used as in the case of the non-thermoplastic polyimide precursor.

  Moreover, it is preferable that the thermoplastic polyimide (broad sense) used for this invention has the Tg in the range of 150-300 degreeC. 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). When Tg is within the above range, lamination can be performed with an existing apparatus, and the heat resistance of the obtained adhesive film (multilayer film) is not impaired.

  The polyamic acid that is a precursor of the thermoplastic polyimide (in a broad sense) used in the present invention is not particularly limited, and any conventionally known polyamic acid can be used. Regarding the production of this polyamic acid solution, the monomer raw materials and production conditions described for the non-thermoplastic polyimide can be used in exactly the same manner.

  The thermoplastic polyimide (in a broad sense) can be adjusted in various characteristics by combining various monomer raw materials to be used. In general, when the use ratio of the rigid diamine increases, the Tg increases or the polyamic acid increases. In some cases, the storage elastic modulus of the solution when heated increases, resulting in poor adhesion and workability. The use ratio of the rigid diamine is preferably 40 mol% or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

  A preferred specific example of the thermoplastic polyimide (in a broad sense) is imidization of polyamic acid obtained by polymerizing an acid dianhydride component containing biphenyltetracarboxylic dianhydrides and a diamine component having an aminophenoxy group. However, it is not particularly limited.

  The thermoplastic polyimide layer may contain the above-described thermoplastic polyimide (in a broad sense) and may contain other components. For example, as in the case of the heat-resistant polyimide layer, an inorganic or organic filler may be added to the thermoplastic polyimide layer and the polyimide varnish for forming the thermoplastic polyimide layer, if necessary. Here, the thermoplastic polyimide layer only needs to be able to exert a significant adhesive force by a laminating method, such as the composition of each component used in the layer, the molecular structure of thermoplastic polyimide (in a broad sense), the thickness, etc. Various conditions are not particularly limited. However, in order for the thermoplastic polyimide layer to exhibit a significant adhesive force, it is preferable that the thermoplastic polyimide layer (substantially broad) is substantially 50% by weight or more.

(III) Utilization of the Present Invention The method for producing a multilayer film according to the present invention can be widely used for producing a polyimide-based multilayer film in which a plurality of polyimide layers are laminated. The specific type of the multilayer film is not particularly limited, as long as it has a structure in which a plurality of polyimide-containing resin layers are directly laminated and includes two or more types of polyimide layers. However, as a representative example of the multilayer film, a polyimide-based adhesive film can be exemplified.

  The polyimide-based adhesive film includes at least a structure in which a heat-resistant polyimide layer and a thermoplastic polyimide layer are directly laminated. The heat-resistant polyimide layer is made of a resin composition containing a heat-resistant polyimide, and is a polyimide layer that functions as an insulating layer (insulating film). Moreover, the said thermoplastic polyimide layer consists of a resin composition containing a thermoplastic polyimide, and is a polyimide layer which functions as an adhesive layer (adhesive film). Such an adhesive film can be suitably used as a substrate material such as a two-layer FPC.

  A more specific configuration of the polyimide-based adhesive film is not particularly limited, and it is sufficient that at least a heat-resistant polyimide layer is included in order to exhibit heat resistance. Therefore, for example, a thermoplastic polyimide layer may be laminated on both sides of the heat-resistant polyimide layer, only one side may be laminated, a polyimide layer other than these may be included, and heat resistance A plurality of laminated structures of a polyimide layer and a thermoplastic polyimide layer may be included. Further, the plurality of polyimide layers include a heat-resistant polyimide layer and a thermoplastic polyimide layer directly laminated thereon, and the thermoplastic polyimide layer may be positioned on at least one surface layer. .

  Thus, the present invention can be applied to the production of a multilayer film in which any kind of polyimide layer is combined. For example, when the polyimide-based multilayer film obtained in the present invention is used as a raw material for a two-layer FPC, a structure in which a thermoplastic polyimide layer is in close contact with one side or both sides of a heat-resistant polyimide layer may be used. In this case, it is formed from a polyimide varnish (thermoplastic polyimide varnish) to be a thermoplastic polyimide layer on at least one surface of a liquid film formed from a polyimide varnish (heat resistant polyimide varnish) to be a heat resistant polyimide layer. A production method in which a liquid film having a multilayer structure in contact with the liquid film is formed on a support, and this is heated and dried to obtain a gel film and then fired at a high temperature can be mentioned as a particularly preferable embodiment.

  In particular, from the practical aspect of FPC, the specific configuration of the adhesive film is most preferably a three-layer structure in which a thermoplastic polyimide layer is in close contact with both surfaces of a heat-resistant polyimide layer. Therefore, when manufacturing such an adhesive film (multilayer film) having a three-layer structure, a liquid film formed from a thermoplastic polyimide varnish is formed on both sides of a liquid film formed from a heat-resistant polyimide varnish. A most preferred embodiment is a production method in which a liquid film having a three-layer structure in contact is formed on a support, and this is heated and dried, followed by high-temperature firing.

  Here, the curing agent (dehydrating agent and catalyst) may be added to any polyimide varnish that forms any polyimide layer, but the curing agent need not necessarily be added to all polyimide varnishes. For example, when manufacturing the said adhesive film for two-layer FPC, it is preferable to add a hardening | curing agent only to a heat resistant polyimide-type varnish.

  Thermoplastic polyimide varnish generally has a low molecular weight, a high gelation reaction rate, and a fine microstructure. Therefore, when a curing agent is added to the thermoplastic polyimide varnish, only the polyimide varnish forms a gel film having a dense structure first, so that the central liquid film (becomes a heat-resistant polyimide layer) in the multilayer liquid film. A gel film having a dense structure is formed on the outer layer of the liquid film. As a result, the residual component discharged from the heat-resistant polyimide varnish loses the escape field and is accumulated between the layers, so that the delamination phenomenon between the layers is more likely to occur.

  In contrast, when a curing agent is added only to the heat-resistant polyimide varnish, the remaining components are discharged to the outside of the liquid film as the gelation reaction of the heat-resistant polyimide varnish proceeds. Among these remaining components, the curing agent (dehydrating agent and catalyst) penetrates into the adjacent liquid film, that is, the inside of the thermoplastic polyimide varnish, and gradually promotes the gelation reaction of the thermoplastic polyimide varnish. . As a result, the adhesion between the gel film generated from the heat-resistant polyimide varnish and the gel film generated from the thermoplastic polyimide varnish and the interlayer is improved, so that delamination between layers can be more effectively suppressed or avoided. .

  When the multilayer film concerning this invention is an adhesive film, it can use suitably for manufacture of the laminated body containing a polyimide layer. That is, the laminated body manufactured using the said adhesive film may be contained in this invention. The specific configuration of the laminate is not particularly limited, but as a typical configuration, an adhesive film is used as an insulating film (heat resistant film), and a metal layer is laminated on the surface of the adhesive film. A laminate having the following structure can be given. Although the manufacturing method of the said laminated body is not specifically limited, With respect to the adhesive film concerning this invention, the method of adhere | attaching metal foil to at least one surface by the lamination method, Preferably a hot roll lamination method is mentioned. Can do.

  Although it does not specifically limit as a metal layer laminated | stacked on the said adhesive film, When using the laminated body concerning this invention as a flexible metal-clad laminated board for an electronic device and an electrical equipment use, for example, copper Alternatively, a metal foil made of a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including 42 alloy), aluminum, an aluminum alloy, or the like can be given. Moreover, in general flexible metal-clad laminates, copper foils such as rolled copper foil and electrolytic copper foil are frequently used, but these copper foils can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil.

  Moreover, the flexible wiring board formed using the said adhesive film or the said laminated body may also be contained in this invention. Specifically, a flexible printed wiring board (FPC) can be mentioned. Although the specific manufacturing method of the said flexible printed wiring board is not specifically limited, Specifically, for example, a metal foil is laminated on an adhesive film, a pattern etching process is performed, and a desired pattern circuit is formed on the metal foil. The method of forming can be mentioned. Thus, the adhesive film as a multilayer film according to the present invention can be used as a high-performance polyimide film for printed circuit boards.

  The present invention will be described more specifically based on Examples and Comparative Examples, and FIGS. 4, 7 and 8. However, 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. The curing agents in the following examples and comparative examples were prepared as follows.

[Curing agent]
19.6 g of DMF as a solvent, 6.5 g of acetic anhydride as a dehydrating agent, and 3.9. A curing agent was prepared by dissolving at a rate of kg.

Synthesis Example 1 Preparation of Polyamic Acid Solution as Heat Resistant Polyimide Varnish
76.2 kg of DMF cooled to 10 ° C. and 3.7 kg of p-phenylenediamine (PDA) were added, and while stirring under a nitrogen atmosphere, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride ( 9.8 kg of BPDA) was gradually added and stirred for 30 minutes. To the solution, 41.4 g of 10% DMF dispersion of calcium hydrogenphosphate particles having a particle size distribution with a median average diameter of 2 μm and a particle size ratio of 7 μm or more is 0.05%, and sufficiently stirred. did.

  Next, a solution in which 300 g of BPDA was dissolved in 2 kg of DMF was separately prepared, and this was gradually added to the above reaction solution while paying attention to the viscosity and stirred. When the viscosity reached 3500 poise, the addition was stopped and a polyamic acid, which is a precursor of heat-resistant polyimide, was synthesized. The obtained polyamic acid solution had a solid content concentration of 15% by weight, and this was used as a heat-resistant polyimide varnish.

[Synthesis Example 2; Preparation of polyamic acid solution as thermoplastic polyimide varnish]
78 kg of DMF cooled to 10 ° C., 11.56 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) were added, and 7.87 kg of BPDA was gradually added while stirring under a nitrogen atmosphere. Added. Subsequently, 380 g of ethylene bis (trimellitic acid monoester acid anhydride) (TMEG) was added and stirred for 30 minutes.

  Next, a solution in which 300 g of TMEG was dissolved in 3 kg of DMF was separately prepared, and this was gradually added to the reaction solution while being careful of the viscosity and stirred. The addition was stopped when the viscosity reached 3000 poise, and a polyamic acid, which is a precursor of thermoplastic polyimide, was synthesized. The solid content concentration was adjusted to 14% by weight by adding 43.7 kg of DMF to the obtained polyamic acid solution, and this was used as a thermoplastic polyimide varnish.

[Example 1]
In this example, a three-layer coextrusion die 50 having the structure shown in FIG. 4 was used as the multilayer coextrusion die. The width of the flow path of the three-layer coextrusion die 50 is 120 mm, and inner deckles having a width of 10 mm (type shown in FIG. 7B) are inserted into both ends of the outer-layer flow paths 52b and 52c, respectively. did. Therefore, the width of the central layer flow path 52a remains 120 mm, and the widths of the outer layer flow paths 52a and 52c become 100 mm.

  30 g of the curing agent was added to and mixed with 100 g of a heat-resistant polyimide varnish cooled to 0 ° C. The obtained mixed liquid was defoamed with a centrifugal separator and then filled into a syringe, and this syringe was connected to the central layer flow path 52a of the three-layer coextrusion die 50 serving as the central layer of the multilayer liquid film. At the same time, syringes filled with only the thermoplastic polyimide varnish cooled to 0 ° C. were connected to the outer layer flow paths 52b and 52c of the three-layer coextrusion die 50 serving as the outer layer of the multilayer liquid film.

  Each syringe was operated, and a heat-resistant polyimide varnish (containing a curing agent) was injected into the three-layer coextrusion die at a rate of 1.0 kg / hr and a thermoplastic polyimide varnish at a rate of 0.16 kg / hr. As a result, a multilayer liquid film having a three-layer structure is extruded from the lip of the three-layer coextrusion die and cast on an aluminum foil (support) that moves at a speed of 1.0 m / min. A liquid film was formed on the aluminum foil.

  When the both end portions of the obtained multilayer liquid film are observed, the heat resistant polyimide type varnish is in a region extending about 5 mm from the edge of the both end portions due to the color difference between the heat resistant polyimide varnish and the thermoplastic polyimide varnish. It was confirmed that the varnish formed a single layer liquid film.

  The multilayer liquid film was placed in a drying furnace together with an aluminum foil and dried at 130 ° C. for 100 seconds to obtain a multilayer gel film. The obtained multilayer gel film was visually observed, but peeling was not observed. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Both ends of the peeled multilayer gel film, that is, a single layer structure, are fixed with a tenter pin and fired at temperatures of 300 ° C. × 30 seconds, 400 ° C. × 50 seconds, 450 ° C. × 10 seconds to complete imidization. It was. Thereby, a polyimide multilayer film having a three-layer structure in which a thermoplastic polyimide layer (adhesive layer) was laminated on both surfaces of a heat-resistant polyimide layer (insulating layer) was obtained. Although the multilayer film taken out from the baking furnace was pulled out from the tenter pin, it could be easily pulled out from the tenter pin, and no depinning failure occurred. Moreover, the adhesion between the layers in this multilayer film was good.

[Example 2]
In the present example, a three-layer coextrusion die 50 having the structure shown in FIG. The width of the flow path of the three-layer coextrusion die 50 is 120 mm, and an inner deckle (type shown in FIG. 7B) having a width of 20 mm is inserted into both ends of the outer-layer flow paths 52b and 52c. did. Therefore, the width of the central layer flow path 52a remains 120 mm, and the widths of the outer layer flow paths 52b and 52c become 80 mm.

  A multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1 except that the injection rate of the thermoplastic polyimide varnish was 0.11 kg / hr. When the both end portions of the obtained multilayer liquid film are observed, the heat-resistant polyimide type varnish is in a region extending about 10 mm from the edge of the both end portions due to the color difference between the heat-resistant polyimide varnish and the thermoplastic polyimide varnish. It was confirmed that the varnish formed a single layer liquid film.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. The obtained multilayer gel film was visually observed, but peeling was not observed. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. Although the multilayer film taken out from the baking furnace was pulled out from the tenter pin, it could be easily pulled out from the tenter pin, and no depinning failure occurred. Moreover, the adhesion between the layers in this multilayer film was good.

Example 3
In the present example, a three-layer coextrusion die 50 having the structure shown in FIG. The width of the flow path of the three-layer coextrusion die 50 is 120 mm, and inner deckles having a width of 30 mm (type shown in FIG. 7B) are inserted into both ends of the outer-layer flow paths 52b and 52c, respectively. did. Accordingly, the width of the central layer flow path 52a remains 120 mm, and the widths of the outer layer flow paths 52b and 52c become 60 mm.

  A multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1 except that the injection rate of the thermoplastic polyimide varnish was 0.09 kg / hr. When both ends of the obtained multilayer liquid film are observed, the heat-resistant polyimide-based varnish is in a region extending from the edge of the both ends to a width of about 15 mm due to the color difference between the heat-resistant polyimide-based varnish and the thermoplastic polyimide-based varnish. It was confirmed that the varnish formed a single layer liquid film.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. The obtained multilayer gel film was visually observed, but peeling was not observed. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. Although the multilayer film taken out from the baking furnace was pulled out from the tenter pin, it could be easily pulled out from the tenter pin, and no depinning failure occurred. Moreover, the adhesion between the layers in this multilayer film was good.

Example 4
In this embodiment, the same multi-layer coextrusion die as that of the third embodiment, that is, the three-layer coextrusion die 50 having the structure shown in FIG. What was inserted in was used. Therefore, the width of the central layer flow path 52a of the three-layer coextrusion die 50 remains 120 mm, and the width of the outer layer flow paths 52b and 52c is 60 mm.

  A curing agent is not added to the heat-resistant polyimide varnish, a curing agent having the above composition is added to the thermoplastic polyimide varnish, and the injection rate of the thermoplastic polyimide varnish is 0.2 kg / hr. Except for the above, a multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1. When both ends of the obtained multilayer liquid film are observed, the heat-resistant polyimide-based varnish is in a region extending from the edge of the both ends to a width of about 15 mm due to the color difference between the heat-resistant polyimide-based varnish and the thermoplastic polyimide-based varnish. It was confirmed that the varnish formed a single layer liquid film.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. The obtained multilayer gel film was visually observed, but peeling was not observed. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. Although the multilayer film taken out from the baking furnace was pulled out from the tenter pin, it could be easily pulled out from the tenter pin, and no depinning failure occurred. Moreover, the adhesion between the layers in this multilayer film was good.

Example 5
In this embodiment, the same multi-layer coextrusion die as that of the third embodiment, that is, the three-layer coextrusion die 50 having the structure shown in FIG. What was inserted in was used. Therefore, the width of the central layer flow path 52a of the three-layer coextrusion die 50 remains 120 mm, and the width of the outer layer flow paths 52b and 52c is 60 mm.

  Do not add a curing agent to the heat-resistant polyimide varnish or the thermoplastic polyimide varnish, and the injection rate of the heat-resistant polyimide varnish is 1.3 kg / hr, and the injection rate of the thermoplastic polyimide varnish is A multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1 except that the amount was 0.09 kg / hr. When both ends of the obtained multilayer liquid film are observed, the heat-resistant polyimide-based varnish is in a region extending from the edge of the both ends to a width of about 15 mm due to the color difference between the heat-resistant polyimide-based varnish and the thermoplastic polyimide-based varnish. It was confirmed that the varnish formed a single layer liquid film.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. The obtained multilayer gel film was visually observed, but peeling was not observed. Further, the obtained multilayer gel film was in close contact with the aluminum foil as compared to the multilayer gel films obtained in Examples 1 and 2. However, the multilayer gel film could be peeled off from the aluminum foil by pulling it from the aluminum foil.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. Although the multilayer film taken out from the baking furnace was pulled out from the tenter pin, it could be easily pulled out from the tenter pin, and no depinning failure occurred. Moreover, the adhesion between the layers in this multilayer film was good.

Example 6
In this example, as the multilayer coextrusion die, the three-layer coextrusion die 50 having the structure shown in FIG. 4 was used as in Example 1, and the manufacturing apparatus shown in FIG. 8 was used. The width of the flow path of the three-layer coextrusion die 50 is 650 mm, and an inner deckle (type shown in FIG. 7B) with a width of 100 mm is inserted into both ends of the outer-layer flow paths 52b and 52c. did. Therefore, the width of the central layer flow path 52a remains 650 mm, and the width of the outer layer flow paths 52b and 52c is 450 mm.

  A varnish tank 11 for storing a heat-resistant polyimide-based varnish cooled to 0 ° C. was connected to a central layer flow path 52a of a three-layer coextrusion die (multilayer coextrusion die) 50 and fed at a rate of 5 kg / hr. . At the same time, a curing agent having the above composition was added from the curing agent tank 14 at a rate of 1.5 kg / hr from the middle of the pipe 20 for feeding the heat-resistant polyimide varnish. At the same time, tanks 12 and 13 for varnish storing thermoplastic polyimide varnish cooled to 0 ° C. are connected to flow paths 52b and 52c for outer layer of three-layer coextrusion die 50, and liquid is fed at a rate of 0.7 kg / hr. did.

  Since the multilayer liquid film 30 having a three-layer structure is extruded from the lip of the three-layer coextrusion die 50, it is cast on a stainless endless belt (support 10) that moves at a speed of 1.0 m / min. The multilayer liquid film 30 was formed on the endless belt 10. When the end of the obtained multilayer liquid film 30 is observed, the liquid film of the heat-resistant polyimide varnish covers a width of about 50 mm from both ends due to the difference in color between the heat-resistant polyimide varnish and the thermoplastic polyimide varnish. Was confirmed to form a single layer structure.

  The multilayer liquid film 30 having a three-layer structure on the endless belt 10 was dried at 130 ° C. for 100 seconds by passing through the continuous drying furnace 15 together with the endless belt 10. No delamination was observed in the multilayer gel film 40 having a three-layer structure after drying. When the obtained multilayer gel film 40 was pulled from the endless belt 10, it could be easily peeled off. The part (both ends in the width direction) of the peeled multilayer gel film 40 was fixed with the tenter pin 17 and passed through the continuous firing furnace 16. The firing furnace was formed from three temperature ranges of 300 ° C., 400 ° C., and 450 ° C., and the multilayer gel film 40 was subjected to stepwise heating and firing.

  When the multilayer film taken out from the baking furnace was pulled out from the tenter pin 17, the multilayer film could be easily pulled out from the tenter pin 17, and this was collected. The obtained polyimide-based multilayer film was a film having a three-layer structure with good interlayer adhesion.

[Comparative Example 1]
In the present example, a three-layer coextrusion die 50 having the structure shown in FIG. The width of the flow path of the three-layer coextrusion die 50 was 120 mm, and no inner deckle was inserted into any of the flow paths 52a to 52c. Therefore, the width of all the channels remains 120 mm.

  A multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1 except that the injection rate of the thermoplastic polyimide varnish was 0.17 kg / hr. When the both end portions of the obtained multilayer liquid film were observed, it was confirmed that the entire multilayer liquid film had the same color, and a three-layer structure was formed at both end portions.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. When the obtained multilayer gel film was visually observed, delamination between layers was observed at the end of the multilayer gel film. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. When the multilayer film taken out from the baking furnace was pulled out from the tenter pin, the film adhered to the tenter pin and could not be pulled out easily. Furthermore, the obtained multilayer film became a multilayer film having a three-layer structure in which the interlaminar adhesion was disturbed at the end.

[Comparative Example 2]
In the present example, a three-layer coextrusion die 50 having the structure shown in FIG. The width of the flow path of the three-layer coextrusion die 50 was 120 mm, and no inner deckle was inserted into any of the flow paths 52a to 52c. Therefore, the width of all the channels remains 120 mm.

  Do not add a curing agent to the heat-resistant polyimide varnish or the thermoplastic polyimide varnish, and the injection rate of the heat-resistant polyimide varnish is 1.3 kg / hr, and the injection rate of the thermoplastic polyimide varnish is A multilayer liquid film having a three-layer structure was formed on an aluminum foil in the same manner as in Example 1 except that the amount was 0.17 kg / hr. Therefore, from the viewpoint of not adding a curing agent, a multilayer liquid film was formed in the same procedure as in Example 5 except for the injection speed of the thermoplastic polyimide varnish. When the both end portions of the obtained multilayer liquid film were observed, it was confirmed that the entire multilayer liquid film had the same color, and a three-layer structure was formed at both end portions.

  Further, the multilayer liquid film was converted into a multilayer gel film under the same conditions as in Example 1. The obtained multilayer gel film was visually observed, but peeling was not observed. Thereafter, the multilayer gel film was peeled off from the aluminum foil. Since it could be easily peeled off, the peelability was good.

  Furthermore, the multilayer gel film was baked on the same conditions as Example 1, and the polyimide multilayer film of the 3 layer structure by which the thermoplastic polyimide layer was laminated | stacked on both surfaces of the heat resistant polyimide layer was obtained. When the multilayer film taken out from the baking furnace was pulled out from the tenter pin, the film adhered to the tenter pin and could not be pulled out easily.

  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, according to the present invention, in the method for producing a polyimide-based multilayer film in which a multilayer liquid film is converted into a multilayer gel film and then imidized, both ends of the multilayer liquid film have a single-layer structure. At the same time, it is possible to substantially prevent delamination of the multilayer gel film and multilayer film, and to effectively avoid the depinning defect after firing, thereby obtaining a polyimide multilayer film having high interlayer adhesion. be able to. Therefore, the present invention can be used not only in the field of manufacturing polyimide films, but also in the manufacture of various electronic components such as FPC, TAB, high-density recording media using the film, and fields of use thereof. It can be applied to a wide range of fields.

An example of the configuration of each of the multilayer liquid film (upper figure) formed in the method for producing a polyimide-based multilayer film according to the present invention and the multilayer gel film (lower figure) obtained by converting the multilayer liquid film It is a typical sectional view showing (three-layer structure). Regarding each of the multilayer liquid film (upper figure) formed in the method for producing a polyimide-based multilayer film according to the present invention and the multilayer gel film (lower figure) obtained by converting the multilayer liquid film, It is typical sectional drawing which shows an example (two-layer structure). Each of the multilayer liquid film (upper figure) formed in the method for producing a polyimide-based multilayer film according to the present invention and the multilayer gel film (lower figure) obtained by converting the multilayer liquid film is further configured. It is typical sectional drawing which shows another example (two-layer structure). It is typical sectional drawing which shows an example of a structure of the multilayer coextrusion die | dye which can be used in the manufacturing method of the polyimide type multilayer film concerning this invention. It is a typical sectional view showing an example of composition of a slide die which can be used in a manufacturing method of a polyimide system multilayer film concerning the present invention. It is typical sectional drawing which shows an example of the structure which combined the several single layer die | dye which can be used in the manufacturing method of the polyimide-type multilayer film concerning this invention. (A) * (b) is a typical perspective view which shows an example of an inner deckle which can be used when forming the multilayer liquid film containing a wide liquid film using a multilayer coextrusion die in this invention. It is. It is a schematic diagram which shows an example of the manufacturing apparatus which can be used for the manufacturing method of the polyimide type multilayer film concerning this invention. It is a schematic diagram explaining the neck-in phenomenon which arises when forming a film using a die. It is typical sectional drawing which shows the state in case the neck in has arisen in the process which converts a multilayer liquid film (upper figure) into a multilayer gel film (lower figure).

Explanation of symbols

10 Support / Endless belt 17 Tenter pin (fixing means)
30 Multi-layer liquid film 31 Lower adhesive liquid film (liquid film to be a thermoplastic polyimide layer)
32 Heat-resistant liquid film (wide liquid film, liquid film that becomes heat-resistant polyimide layer)
33 Upper Adhesive Liquid Film (Liquid film that becomes a thermoplastic polyimide layer)
38 (both) end portions 39 peeling 40 multilayer gel film 41 lower gel layer 42 center gel layer 43 upper gel layer 50 multilayer coextrusion die 51 die body 52a center layer channel 52b outer layer channels 54a and 54b inner deckle 60 Slide die 71, 72, 73 Single layer die

Claims (10)

A method for producing a polyimide-based multilayer film having a structure in which a plurality of resin layers containing polyimide are directly laminated,
A multilayer liquid film forming step for forming a multilayer liquid film in which a liquid film made of each resin solution is laminated on a support using a plurality of types of resin solutions containing polyimide or a precursor thereof, and the obtained multilayer Including a gel film forming step in which the liquid film is a self-supporting multilayer gel film,
Further, the multilayer liquid film forming step includes a single layer of a wide liquid film that is relatively wider than other liquid films, and has a single-layer structure in which both end portions are formed only of the wide liquid film. In addition, a multilayer liquid film is formed ,
At least one of the plurality of liquid films constituting the multilayer liquid film contains a dehydrating agent and a catalyst,
The plurality of resin layers include a heat-resistant polyimide layer containing a heat-resistant polyimide and a thermoplastic polyimide layer containing a thermoplastic polyimide,
In the multilayer liquid film forming step, the multilayer liquid film is formed so that the liquid film serving as the heat-resistant polyimide layer is a wide liquid film .   2. The method for producing a polyimide-based multilayer film according to claim 1, wherein a width of an end portion composed of only the wide liquid film is in a range of 5 to 100 mm.   3. The method for producing a polyimide-based multilayer film according to claim 1, wherein in the multilayer liquid film forming step, a multilayer liquid film is simultaneously formed using a multilayer coextrusion die.   The multilayer coextrusion die has a plurality of channels for forming a liquid film, and one channel is wider than the other channels. A method for producing a polyimide-based multilayer film.   The multilayer coextrusion die is characterized in that a flow channel having a width wider than other flow channels is formed by inserting an inner deckle into the flow channel for forming a liquid film. The manufacturing method of the polyimide-type multilayer film of Claim 4.   The method for producing a polyimide-based multilayer film according to claim 1 or 2, wherein in the multilayer liquid film forming step, a plurality of liquid films are sequentially formed and laminated. The multilayer liquid film is formed in the multilayer liquid film forming step so that the liquid film to be a thermoplastic polyimide layer is in contact with at least one surface of the liquid film to be the heat resistant polyimide layer. The manufacturing method of the polyimide-type multilayer film of 1 characterized by the above-mentioned. Furthermore, it includes a firing step for firing the multilayer gel film,
The said baking process WHEREIN: The said multilayer gel film is baked in the state which fixed the part of the single layer structure which is the both ends of a multilayer gel film with the tenter pin, The one of Claim 1 thru | or 7 characterized by the above-mentioned. A method for producing a polyimide multilayer film. A polyimide multilayer film produced by the method for producing a polyimide multilayer film according to any one of claims 1 to 8 . The polyimide multilayer film according to claim 9 , comprising a structure in which a heat-resistant layer containing a heat-resistant polyimide and an adhesive layer containing a thermoplastic polyimide are laminated on at least one surface of the heat-resistant layer.

Images