JP4773726B2 - Multilayer extruded polyimide film and use thereof - Google Patents

Description

  The present invention relates to a multilayer extruded polyimide film produced by a multilayer extrusion method (coextrusion-casting coating method) and formed by laminating a plurality of polyimide layers, and a typical application technique thereof. The present invention relates to a multilayer extruded polyimide film that can be suitably used as an adhesive film that also serves as an insulating substrate in the production of a metal-clad laminate, and a metal-clad laminate and a flexible wiring board obtained by using the same.

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

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

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

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

  The two-layer FPC is manufactured using a flexible metal-clad laminate having a structure in which a metal foil is laminated on a substrate. Examples of the method for producing the flexible metal-clad laminate include a casting method, a metalizing method, and a laminating method. Casting is a method in which an organic solvent solution of polyimide or its precursor polyamic acid (referred to as “polyimide varnish” for convenience) is cast and applied onto a metal foil, followed by heat drying and / or imidization. It is. The metalizing method is a method in which a metal layer is directly provided on a polyimide film by sputtering, vapor deposition, and / or metal plating. The laminating method is a method of bonding a polyimide film and a metal foil through a thermoplastic polyimide layer.

  However, any of the above manufacturing methods is difficult to apply to the production of a two-layer FPC as it is in view of the need for further miniaturization of FPC wiring. Specifically, in the casting method, it is necessary to use a thinner metal foil in order to make the FPC wiring finer, but it is difficult to cast a polyimide varnish to such a metal foil.

  In the lamination method, in order to provide a thermoplastic polyimide layer on the surface of the polyimide film, it is necessary to coat the polyimide film with a polyimide-based varnish of thermoplastic polyimide. The possibility increases. In addition, it is possible to achieve higher wiring density by reducing the thickness of the metal foil to be laminated, but handling of the metal foil, for example, running stability of the metal foil during continuous production, laminating properties, etc. Is extremely difficult to apply.

  On the other hand, in the metalizing method, it is easy to control the thickness of the metal layer by electrolytic plating, so it is easy to cope with higher wiring density, but compared to the casting method and laminating method, the polyimide layer The adhesion between the metal layer and the metal layer is inferior. Therefore, recently, development of a polyimide film suitable for the metalizing method is expected.

  As such a polyimide film, specifically, a polyimide laminate (multilayer polyimide film) having a polyimide layer with high adhesion to a metal layer formed by vapor deposition or sputtering as an outermost layer has been proposed. . Such a multilayer polyimide film can improve the adhesion to the metal layer compared to a single-layer polyimide film, so it is easy to achieve improved adhesion, which is a problem of the metalizing method It becomes.

  Generally, as a method for producing a multilayer polyimide film, a coating method, a multilayer extrusion method (or a coextrusion-casting coating method) and the like can be mentioned. The coating method is a method of manufacturing a multilayer polyimide film by forming one polyimide layer first and then laminating the surface by coating another polyimide layer. The multilayer extrusion method is a method in which a plurality of polyimide varnishes for forming each layer are simultaneously extruded to form a multilayered liquid film (multilayer liquid film), and then a multilayer polyimide film is formed by heating, baking, etc. It is.

  As a technique for producing a multilayer polyimide film by a coating method, for example, a technique disclosed in Patent Document 1 can be mentioned. In this technology, an intermediate layer made of PMDA-based polyimide using pyromellitic dianhydride as a raw material is coated on at least one surface of a film base made of BPDA-based polyimide using biphenyltetracarboxylic dianhydride as a raw material. It is formed by. Since the intermediate layer is excellent in adhesion to the metal layer, if a metal vapor deposition layer and a metal plating layer are sequentially formed thereon, the excellent properties of the BPDA polyimide film base material are not impaired, and the metal vapor deposition layer is bonded. It is said that the strength can be increased.

  Examples of the technique for producing a multilayer polyimide film by the multilayer extrusion method include techniques disclosed in Patent Documents 2 to 5. In the technology employing these multilayer extrusion methods, thermal imidization is employed as a method for imidizing polyamic acid which is a polyimide precursor. In addition, the multilayer polyimide film obtained by a multilayer extrusion method is called a multilayer extrusion polyimide film for convenience.

  Specifically, Patent Document 2 discloses a multilayer extruded polyimide film in which an aromatic polyimide layer containing a flexible bond in a main chain is integrally laminated on at least one surface of a high heat resistant aromatic polyimide layer. A metal film is formed on the aromatic polyimide layer containing a flexible bond in the main chain by metal vapor deposition and / or metal plating.

  Patent Document 3 discloses a multilayer aromatic polyimide film in which a low-viscosity thermoplastic aromatic polyimide layer is integrally laminated on at least one surface of a highly heat-resistant aromatic polyimide film. In this technique, a method for producing a multilayer aromatic polyimide film using two or more layers of extrusion dies (in the same document (Method b)) is disclosed, but a production method by a coating method (in the same document ( (Method a), (Method c), and Method (d)) are also disclosed. In particular, in Method (a), polyamic acid (polyamide acid) is imidized by chemical imidization.

  Furthermore, Patent Document 4 discloses that a thermocompression-bonding aromatic polyimide layer is integrally formed on at least one surface of a high heat-resistant aromatic polyimide layer A having a prescribed linear expansion coefficient and tensile strength by a coextrusion-casting film forming method. A thermocompression-bonding multilayer extruded polyimide film obtained by laminating and having a total thickness of 10 to 160 μm and a prescribed ratio of each layer is disclosed. Similarly, U.S. Patent No. 6,057,049 includes a first polyamic acid layer derived from the reaction of an aromatic tetracarboxylic dianhydride and an aromatic diamine, and 4,4'-oxydiphthalic dianhydride and (diaminophenoxy). ) Coextrusion of at least one second polyamic acid derived from the reaction of benzene to form a self-supporting multilayer polyamic acid film, which is heat treated to completely convert the polyamic acid layer into a multilayer polyimide film Is disclosed.

  Among the above-mentioned multilayer polyimide film production methods, the coating method involves a multi-step production process, and therefore, there is a high possibility that minute foreign matter will be mixed in the film or near the surface of the film, resulting in a deterioration in the quality of the multilayer polyimide film. It becomes easy.

  Further, since the adhesion between the polyimide layers differs depending on the combination of the polyimide layer to be coated and the polyimide layer to be coated, it is difficult to control the adhesion at the interface of the polyimide layer. For example, the technique disclosed in Patent Document 1 employs a coating method, but has a problem that the adhesion between the film base made of BPDA-based polyimide and the intermediate layer made of PMDA-based polyimide is weakened. Yes.

  Alternatively, among the techniques disclosed in Patent Document 3, (a method), (c method), and (d method), which are manufacturing methods using a coating method, provide a gel film having self-indicating properties with thermoplasticity. The polyimide-type varnish used as an aromatic polyimide layer is applied. In this case, the solvent from a gel film elutes at the interface of the gel film used as a highly heat-resistant aromatic polyimide film and the polyimide-type varnish used as a thermoplastic aromatic polyimide layer at the time of subsequent drying. Therefore, in the laminated body after heat-drying, the adhesiveness of the interface of each polyimide layer becomes inadequate. Further, since the gel film contains an organic solvent, a difference in drying occurs between the surface in close contact with the support and the opposite surface (that is, the surface in contact with air). In this case, since the gel film is curled, when the polyimide varnish to be the thermoplastic aromatic polyimide layer is applied to both surfaces of the gel film, the accuracy of the applied thickness of the polyimide varnish decreases.

  Therefore, it is preferable to employ a multilayer extrusion method in the production of the multilayer polyimide film. However, in the case of producing a multilayer polyimide film by a multilayer extrusion method, studies have been made on the premise of a so-called thermal curing method (thermal imidization method) that is substantially imidized by heating (see Patent Documents 2 to 4). ).

  The thermal curing method has a problem in that productivity is lowered because the process of volatilization, removal, and imidization of the solvent takes a very long time after the multilayer liquid film is formed. Low productivity leads to an increase in the total cost of the multilayer polyimide film. Therefore, the conventional multilayer extrusion method has a problem that a multilayer polyimide film cannot always be provided at a cost required by the market.

In addition, when a polyimide film is continuously produced, a drying method in which the film edge is held and heated in a tenter furnace is preferably used. When a thermal curing method is selected using this drying method, a tenter is used. The film strength in the furnace is weakened, and a phenomenon such that the film is torn by the shrinkage force of the solvent from the film edge holding jig and the film is torn is not preferable.
JP-A-6-124978 (published on May 6, 1994) JP-A-8-276534 (published on October 22, 1996) JP-A-8-224843 (published September 3, 1996) JP 11-99554 A (published on April 13, 1999 (No. 2946416, registered on July 2, 1999)) Japanese Patent Laid-Open No. 7-214636 (August 15, 1995)

  Thus, when producing a multilayer extruded polyimide film, a chemical cure method (chemical imidization method) in which a polyimide-varnish is mixed with a chemical dehydrating agent and a catalyst is used as an imidization method. Is highly preferred.

  However, when the above chemical curing method is adopted, particularly when a metal-clad laminate is produced using the obtained multilayer polyimide film as an adhesive film, the metal layer obtained by the metalizing method and the multilayer polyimide film are bonded. There arises a problem that the property becomes low. Therefore, it has been difficult to obtain a multilayer polyimide film having sufficient adhesion even if a chemical curing method is simply combined with the manufacturing technology of the multilayer extruded polyimide film.

  The present invention has been made in view of the above problems, and its purpose is to dramatically improve the adhesion even when a chemical curing method is employed as an imidization method in a multilayer extruded polyimide film. It is to provide a technology that can be made high.

  As a result of intensive studies in view of the above-mentioned problems, the present inventors have controlled the linear expansion coefficient between the surface layer and the base layer in the multilayer extruded polyimide film, so that the metal layer formed by the metalizing method and the polyimide film The present inventors have found that it is possible to improve adhesiveness and have completed the present invention.

That is, in order to solve the above-mentioned problems, the multilayer extruded polyimide film according to the present invention simultaneously extrudes a plurality of types of organic solvent solutions containing polyimide or a precursor thereof onto a support to form a multilayered liquid film. A multilayer extruded polyimide film comprising a plurality of polyimide layers that are formed and imidized to form and laminated together,
The plurality of polyimide layers include a base layer serving as a base of the entire film and a surface layer exposed on the film surface, and at least one of the base layer and the surface layer includes the organic solvent. The solution is imidized by adding a chemical dehydrating agent and a catalyst,
When the linear expansion coefficients in the range of 100 to 200 ° C. in the polyimide as the base layer and the polyimide as the surface layer are K1 and K2, respectively, these linear expansion coefficients are expressed by the following relational expression K2 / K1> 1. 1
It is characterized by satisfying.

  In the multilayer extruded polyimide film, the thickness of the entire film is preferably in the range of 10 to 75 μm, the surface layer is made of at least thermoplastic polyimide, and the base layer is at least heat-resistant polyimide. It is preferable that it consists of.

Moreover, the manufacturing method of the multilayer extrusion polyimide film concerning this invention is equipped with the several polyimide layer laminated | stacked integrally, and the said several polyimide layer has the base layer and film which become the base of the whole film A method for producing a multilayer extruded polyimide film comprising a surface layer exposed on a surface, wherein a plurality of types of organic solvent solutions containing polyimide or a precursor thereof are simultaneously extruded onto a support to form a multilayer structure liquid A multilayer liquid film forming step for forming a film; and an imidization step for imidizing the multilayer liquid film. Further, at least one of the plurality of types of organic solvent solutions includes a chemical dehydrating agent and a catalyst. In the multilayer liquid film forming step, the polyimide as the base layer and the polyimide as the surface layer are added. The linear expansion coefficient in the range of 00 to 200 ° C., when the K1 and K2, respectively, these linear expansion coefficients have the following relationship K2 / K1> 1.1
The organic solvent solution forming each layer is selected so as to satisfy the above conditions.

  In the method for producing a multilayer extruded polyimide film, the chemical dehydrating agent is within a range of 0.5 to 5 mol with respect to 1 mol of amic acid unit in the polyamic acid contained in the organic solvent solution to be added. The catalyst is preferably added to the organic solvent solution so that the catalyst is added in an amount of 0.05 to 1 mol of the amide acid unit in the polyamic acid contained in the organic solvent solution to be added. It is preferably added to the organic solvent solution so as to be within a range of 3 mol. Moreover, the multilayer extrusion polyimide film obtained by the said manufacturing method is also contained in this invention.

  Furthermore, the present invention includes a flexible metal-clad laminate including the multilayer extruded polyimide film as an insulating layer and a metal layer directly laminated on the insulating layer by a metalizing method. In this flexible metal-clad laminate, the metal layer is preferably a copper layer. In addition, the present invention includes a flexible wiring board manufactured using the flexible metal-clad laminate.

  As described above, in the present invention, in the multilayer extruded polyimide film, the linear expansion coefficient of the polyimide layer serving as the base layer and the surface layer is set so that the surface layer side becomes larger. Thereby, even if a metal layer is directly laminated on the surface layer by a metalizing method, the adhesion between the metal layer and the polyimide film is improved. Therefore, when a flexible metal-clad laminate is manufactured using the multilayer extruded polyimide film, the adhesion between the metal layer and the insulating layer (polyimide film) can be dramatically improved. As a result, it is possible to obtain a high-quality multilayer extruded polyimide film, a flexible metal-clad laminate using the same, or a flexible wiring board.

  An embodiment of the present invention will be described as follows, 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) Multilayer extruded polyimide film according to the present invention The multilayer extruded polyimide film according to the present invention is produced by a multilayer extrusion method. Here, the multi-layer extrusion method (or coextrusion-casting method) is a method in which an organic solvent solution containing polyimide or a precursor thereof (referred to as a polyimide varnish for convenience of explanation) is used on a plurality of types. Are simultaneously extruded (coextrusion) and cast on the support to form a multilayered liquid film (multilayer liquid film). Therefore, the multilayer extruded polyimide film according to the present invention can be obtained by imidizing a multilayer liquid film, and has a configuration including a plurality of polyimide layers laminated together.

<Structure of multilayer extruded polyimide film>
Although the multilayer extrusion polyimide film concerning this invention will not be specifically limited if it has the structure provided with a some polyimide layer, What is necessary is just to provide at least a surface layer and a base layer. The surface layer is a polyimide layer exposed on the film surface, and the base layer is a polyimide layer that becomes the base (core) of the entire film. The base layer may be a layer in which a surface layer and other layers are directly laminated and not exposed to the film surface, but one surface may be exposed. For example, the multilayer extruded polyimide film may have a two-layer structure of a surface layer and a base layer. In this case, the surface layer is laminated on one side of the base layer, but what is on the other side? Are not laminated, and the surface of the base layer may be exposed. That is, as long as the base layer is a layer that becomes the core of the film in order to ensure the strength, rigidity, durability, and the like of the entire film, both surfaces may not be covered with the surface layer or the like.

  Although the other structure of the said multilayer extrusion polyimide film is not specifically limited, It is preferable that the thickness of the whole film exists in the range of 10-75 micrometers. If the thickness of the entire film is below the above range, it may not be possible to maintain sufficient rigidity and strength to be used as an insulating substrate for flexible metal-clad laminates and flexible wiring boards. As described later, even if the linear expansion coefficient is controlled as will be described later, there is a case where a thickness that can effectively function as a surface layer or a base layer cannot be obtained. On the other hand, if the thickness of the entire film exceeds the above range, flexibility may not be exhibited effectively.

Further, when the thickness of the base layer is T1 and the thickness of the surface layer is T2, these thicknesses are expressed by the following relational expression (i)
(1/2) × T1> T2 (i)
Is preferably satisfied. When the thickness relationship of the multilayer extruded polyimide film deviates from the above range, the linear expansion coefficient of the multilayer extruded polyimide film becomes too large. Therefore, for example, when the multilayer extruded polyimide film is used as a flexible printed wiring board (FPC), a mismatch occurs in the coefficient of linear expansion with the metal layer to be laminated, which causes warping of the FPC. There is a case.

<Polyimide used for each layer>
The surface layer of the multilayer extruded polyimide film according to the present invention is not particularly limited as long as it can exhibit adhesiveness. Specifically, for example, non-thermoplastic polyimide, thermoplastic polyimide (narrow sense), heat Plastic polyamideimide, thermoplastic polyetherimide, thermoplastic polyesterimide and the like can be suitably used. Among these, thermoplastic polyimide is particularly preferably used because it has good adhesion to the metal layer formed by the metalizing method and has low moisture absorption characteristics.

  As will be described later, the polyimide used in the present invention substantially comprises an equimolar amount of an acid dianhydride component composed of at least one acid dianhydride and a diamine component composed of at least one diamine compound. Can be obtained by polymerizing these monomer components.

  Here, in the multilayer extrusion polyimide film according to the present invention, in order to obtain a polyimide layer having physical properties suitable for an adhesive layer (surface layer), polymerization is performed using a diamine compound having at least a flexible structure as a diamine component. Is preferred. A diamine compound having a flexible structure is a compound having an ether group, a sulfone group, a ketone group, a sulfide group, or the like. The diamine compound having the flexible structure is preferably used so as to be 20 mol% or more in the total diamine component (all diamine compounds used for polymerization) during polymerization. When the use ratio of the diamine compound having a flexible structure is less than the above range, the adhesiveness of the surface layer to be obtained, particularly the adhesiveness with the metal layer tends to be lowered. In particular, the adhesion at the interface between the surface layer (adhesive layer) and the metal layer is remarkable after a long exposure in a high temperature environment and / or after a long exposure in a high temperature and high humidity environment. Since it falls, it is not preferable.

  On the other hand, the polyimide used as the base layer is not particularly limited because a preferable one can be appropriately selected depending on the combination with the surface layer or the adhesive layer and the specific structure of the multilayer structure. As will be described later, when the multilayer extruded polyimide film is used for manufacturing a flexible metal-clad laminate or a flexible wiring board, heat-resistant polyimide having high heat resistance is preferably used.

  In the multilayer extruded polyimide film according to the present invention, in order to obtain a polyimide layer having physical properties suitable for the base layer, a diamine compound having a rigid structure represented by at least paraphenylenediamine or substituted benzidine is used as the diamine component. It is preferable to perform polymerization. If a diamine compound having a rigid structure is used, a polyimide layer having a high elastic modulus and a small hygroscopic expansion coefficient tends to be easily obtained.

  The diamine component having the rigid structure is preferably used so as to be 20 mol% or more and 80 mol% or less in the total diamine component (all diamine compounds used for polymerization) at the time of polymerization. When the use ratio of the diamine compound having a rigid structure is less than the above range, it is difficult to obtain an appropriate effect of improving the elastic modulus and the hygroscopic expansion coefficient. On the other hand, when the use ratio exceeds the above range, the thermal expansion coefficient may become too small or the tensile elongation may become small.

  When obtaining a polyimide layer having physical properties suitable as the base layer, as described later, a polymerization method through a prepolymer is preferable, and in this case, the use ratio of the diamine component having a rigid structure and the acid dianhydride component is determined. It is preferable to specify. Furthermore, when the final polyamic acid is obtained instead of the prepolymer, the use ratio of the diamine component having a rigid structure and the diamine component having a flexible structure is within a range of 80/20 to 20/80 in molar ratio. It is preferable that it is within a range of 70/30 to 30/70.

  When the usage ratio of the diamine component having a rigid structure exceeds the above range, the tensile elongation of the resulting polyimide layer (base layer) tends to be small. In addition, when the use ratio of the diamine component having a rigid structure is less than the above range, the Tg of the polyamic acid becomes too low, the storage elastic modulus at the time of heating becomes too low, and the film formation becomes difficult. This is not preferable because it may cause harmful effects.

<Other components contained in the polyimide layer>
When the above multilayer extruded polyimide film is used for the production of flexible metal-clad laminates and flexible wiring boards, the surface layer (adhesive layer) is a polyimide layer that comes into direct contact with the metal layer, so the base layer is a polyimide that does not come into contact with the metal layer. It can be said that it is a layer. Further, the base layer may be only one layer, but may be a plurality of layers of two or more if necessary. Furthermore, layers other than the surface layer and the base layer may be included as necessary.

  The surface layer and the base layer (and other layers) may contain components other than polyimide. Although it does not specifically limit as components other than a polyimide, For example, a filler can be mentioned. By adding the filler, it is possible to modify various characteristics of the film such as slidability, thermal conductivity, conductivity, corona resistance, loop stiffness, etc. in the resulting multilayer extruded polyimide film.

  The specific type of the filler is not particularly limited, and may be appropriately selected and used based on the film properties to be modified. Preferred examples include silica, titanium oxide, alumina, and nitriding. Examples include inorganic compound particles such as silicon, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

  The particle diameter of the filler is not particularly limited because it is determined by the film characteristics to be modified and the kind of filler to be added, etc., but generally the average particle diameter is 0.05 to 10.0 μm. It may be within the range, preferably within the range of 0.1 to 7.5 μm, more preferably within the range of 0.1 to 5.0 μm, and even more preferably within the range of 0.1 to 2.5 μm. If the particle diameter is below this range, the effect of improving the film properties is less likely to appear, and if it exceeds this range, the surface properties may be greatly impaired or the mechanical properties may be greatly reduced.

  Also, the amount of filler added is not particularly limited because it is determined by the film properties to be modified, the particle size of the filler, and the like, but is generally 0.01-100 parts per 100 parts by weight of polyimide. It may be in the range of parts by weight, preferably in the range of 0.01 to 90 parts by weight, and more preferably in the range of 0.02 to 80 parts by weight. If the added amount of the filler is below this range, the effect of improving the film properties is hardly exhibited, and if it exceeds this range, the mechanical properties of the film may be greatly impaired.

Although the addition method of the said filler is not specifically limited, For example, the following method can be mentioned.
1) Filler is added to the reaction solution before or during polymerization of polyamic acid (polyamic acid) which is polyimide or its precursor 2) Using a kneader such as a three-roller for the polymerized polyimide Kneading the filler 3) Prepare a dispersion liquid (filler dispersion liquid) in which the filler is dispersed in the dispersion medium, and mix this with the organic solvent solution of the polyamic acid (polyamic acid solution). It is more preferable to mix the filler dispersion with the polyamic acid solution. This method not only facilitates uniform dispersion of the filler in the polyimide layer, but also causes the contamination of the multilayer extrusion polyimide film production line by mixing the filler dispersion liquid immediately before forming the liquid film. This is preferable because it can be minimized.

  When preparing the filler dispersion, it is preferable to select and use a solvent for the polyamic acid solution. By using the same solvent, various properties of the polyamic acid solution are not changed, and the formability of the liquid film is not impaired. Further, a dispersant, a thickener or the like may be added to the filler for the purpose of satisfactorily dispersing the filler and stabilizing the dispersion state. The amount of these additives to be used is not particularly limited as long as it does not affect the film properties of the polyamic acid solution, the gel film, or the finally obtained multilayer extruded polyimide film.

<Linear expansion coefficient of surface layer and base layer>
As described later, in the multilayer extruded polyimide film according to the present invention, at least one of the base layer and the surface layer is imidized by adding a chemical dehydrating agent and a catalyst to the organic solvent solution. That is, in the multilayer extruded polyimide film, at least one layer, preferably all layers are imidized by a chemical curing method (chemical imidization method). Thereby, it is possible to shorten the imidization time as compared with the thermal curing method (thermal imidization method), and it is possible to effectively avoid the occurrence of various problems associated with drying in a tenter furnace.

Furthermore, in the said multilayer extrusion polyimide film, the adhesiveness can be improved by controlling the linear expansion coefficient of a surface layer and a base layer. Specifically, when the linear expansion coefficient in the range of 100 to 200 ° C. in the polyimide as the base layer and the polyimide as the surface layer is K1 and K2, respectively, these linear expansion coefficients are expressed by the following relational expression ( ii)
K2 / K1> 1.1 (ii)
Meet.

That is, when the linear expansion coefficients in the range of 100 to 200 ° C. are compared, the linear expansion coefficient K2 of the surface layer is increased so as to exceed 1.1 times the linear expansion coefficient K1 of the base layer (linear expansion coefficient). By setting the ratio K2 / K1 to 1.1 or more, the adhesiveness of the multilayer extruded polyimide film can be improved (see Examples described later). Further, the linear expansion coefficient ratio K2 / K1 is preferably less than 20. That is, the linear expansion coefficients K1 and K2 are expressed by the following relational expression (iii)
1.1 <K2 / K1 <20 (iii)
Is more preferable. When the linear expansion coefficient ratio exceeds the above range, the difference in linear expansion coefficient tends to be too large, and curling may occur after film formation.

(II) Manufacturing method of multilayer extruded polyimide film according to the present invention The manufacturing method of the multilayer extruded polyimide film according to the present invention is not particularly limited as long as it is a manufacturing method employing a multilayer extrusion method and a chemical curing method. Specifically, for example, multiple types of polyimide-based varnish are simultaneously extruded onto a support to form a multilayer liquid film, an imidization process for imidizing the multilayer liquid film, And a curing agent addition step of adding a dehydrating agent and a catalyst to at least one polyimide varnish.

  Furthermore, the production method according to the present invention includes at least one of a varnish preparation step for preparing a polyimide varnish used for forming a multilayer liquid film and a gel film formation step for imidizing the multilayer liquid film to form a gel film. More preferably. Hereinafter, the manufacturing method according to the present invention will be described in detail by specifically describing each of the above steps.

<Varnish preparation process>
As described above, the polyimide varnish used in the present invention may be an organic solvent solution containing polyimide or a polyamic acid (polyamic acid) which is a precursor thereof, but an organic solvent solution containing polyamic acid, that is, It is highly preferred to use a polyamic acid solution.

  The method for preparing the polyamic acid solution is not particularly limited, but usually, the aromatic acid dianhydride component and the aromatic diamine component, which are monomer components, are dissolved in an organic solvent in a substantially equimolar amount. The obtained solution may be stirred under controlled temperature conditions until the polymerization of the monomer components is completed. The polyamic acid solution thus obtained can be usually obtained at a resin concentration (solid content concentration) in the range of 5 to 35% by weight, preferably in the range of 10 to 30% by weight. When the resin concentration is within this range, the molecular weight of the polyamic acid is easily set within a suitable range, and the solution viscosity is easily set within a suitable range.

  As the polyamic acid polymerization method (synthetic method), any conventionally known method and a combination thereof can be used. In particular, in the polyamic acid polymerization method, it is important to control the order of addition of each monomer component, and various physical properties and structure of the resulting polyimide can be controlled by appropriately changing the order of addition.

As typical polymerization methods, the following five methods can be mentioned. The acid dianhydride component and the diamine component used in these polymerization methods include at least one aromatic tetracarboxylic dianhydride and an aromatic diamine compound, respectively. In addition, dissolution in an organic polar solvent includes not only complete dissolution in the solvent but also a dispersed state.
1) A diamine component is dissolved in an organic polar solvent, and an acid dianhydride component substantially equimolar with the diamine component is added for polymerization.
2) An acid dianhydride component and a small molar amount of the diamine component are reacted with each other in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, the diamine component is added and polymerized so that finally all the acid dianhydride components and all the diamine components are substantially equimolar.
3) The acid dianhydride component is reacted with an excess molar amount of the diamine component in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding the diamine component to the reaction solution, the acid dianhydride component was added so that all the acid dianhydride components and all the diamine components were finally substantially equimolar. Polymerize.
4) After dissolving an acid dianhydride component in an organic polar solvent, a diamine component is added and polymerized so as to be substantially equimolar with the acid dianhydride component.
5) Polymerization is performed by reacting a substantially equimolar mixture of an acid dianhydride component and a diamine component in an organic polar solvent.

  The above polymerization methods may be used alone or in combination. For the polyimide layer in the present invention, polyamic acid obtained by any of the above polymerization methods may be used regardless of the surface layer or the base layer. In addition, thermoplastic polyimide can be suitably used as the surface layer, and heat-resistant polyimide can be suitably used as the base layer, but the polyamic acid polymerization method that is a precursor of each of these polyimides is not particularly limited. All methods, reaction conditions, and monomer raw materials of the cultivated land including each method can be used (for example, refer to Examples described later).

  The polymerization solvent used for the polymerization of the polyamic acid is not particularly limited as long as it is a solvent capable of dissolving or dispersing the polyamic acid, but an organic polar solvent is preferably used as described above. it can.

  Specifically, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, N-dimethylacetamide and N, N-diethylacetamide Acetamide solvents such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and the like; pyrrolidone solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol and the like Examples thereof include ether solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolv solvents such as butyl cellosolve; hexamethylphosphoramide and γ-butyrolactone. These solvents may be used alone or as a mixture of two or more. Furthermore, aromatic hydrocarbons such as xylene and toluene can also be used.

  Among the above solvents, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide can be particularly preferably used. It should be noted that moisture should be removed as much as possible in order to promote the decomposition of the polyamic acid.

  Moreover, the said solvent for superposition | polymerization can be used suitably as an organic solvent for varnish preparation. Therefore, if the polyamic acid is polymerized using the above-mentioned polymerization solvent, the resulting polyamic acid organic solvent solution (polyamic acid solution) can be used almost as it is as the polyimide varnish.

<Examples of specific monomer components>
The monomer component used for the polymerization of the polyamic acid is not particularly limited. For example, the monomer components that can be preferably used in the heat-resistant polyimide suitably used as the base layer are shown below.

  In the polymerization of the polyamic acid which is a precursor of the heat-resistant polyimide, as a compound that can be suitably used as the acid dianhydride component, specifically, for example, pyromellitic dianhydride, 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3 , 3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 2,2-bis (3,4 -Dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3 -Dicarbo Ciphenyl) 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-phenylene bis (trimellitic acid monoester anhydride), ethylene bis (trimellitic acid monoester) Acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride), and the like. These compounds may be used singly or as a mixture in combination at an arbitrary ratio.

  In particular, in order to obtain a heat-resistant polyimide layer, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 4,4′-oxyphthalic dianhydride, 3, Use of at least one acid dianhydride selected from the group consisting of 3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenebis (trimellitic acid monoester anhydride) preferable.

  Moreover, when using a pyromellitic dianhydride as an acid dianhydride component, it is preferable to use within the range of 40-100 mol% in all the acid dianhydrides. By using pyromellitic dianhydride within this range, it is possible to easily maintain the glass transition temperature (Tg) and the storage elastic modulus during heating in a range suitable for use or film formation. .

  Specific examples of compounds that can be suitably used as the diamine component in the polymerization of the polyamic acid that is a precursor of the heat-resistant polyimide include, for example, 4,4′-diaminodiphenylpropane and 4,4′-diaminodiphenylmethane. , Benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 4,4'-diaminodiphenyl Sulfide, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-oxydianiline, 3,3′-oxydianiline, 3,4′-oxydianiline, 1,5 -Diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiph Nilsilane, 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- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4 -Aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3- Bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3 ′ -Diaminobenzophenone, 4,4'-diaminobenzophenone, and the like. These compounds may be used singly or as a mixture in combination at an arbitrary ratio.

  As described above, in the case of obtaining a heat-resistant polyimide, a polymerization method through a prepolymer is preferable. In this case, it is preferable to define a use ratio of a diamine component having a rigid structure and an acid dianhydride component (see above < When the polyimide used in each layer> section) is used to obtain a final polyamic acid instead of a prepolymer, the ratio of the diamine component having a rigid structure and the diamine component having a flexible structure is a molar ratio. Is preferably in the range of 80/20 to 20/80, and more preferably in the range of 70/30 to 30/70. When the usage ratio of the diamine component having a rigid structure exceeds the above range, the tensile elongation of the resulting polyimide layer (base layer) tends to be small.

<Multilayer liquid film formation process>
In the multilayer liquid film forming step, the polyamic acid solution (polyimide varnish) prepared as described above is cast-coated on a support to form a multilayer liquid film, and in the gel film forming step, the multilayer liquid film is formed. A multi-layered gel film having self-indicating properties is obtained by heating or the like.

  In the multilayer liquid film forming step, a multilayer liquid film is formed using a multilayer extrusion method (coextrusion-casting coating method). For example, a polyamic acid solution serving as a base layer and a polyamic acid solution serving as a surface layer are simultaneously supplied to an extruder having two or more layers of extrusion dies, and at least two of these solutions are discharged from the discharge port of the die. Extruded as a thin film layer (multilayer liquid film).

  The die may be a multi-layer liquid film to be molded, that is, a die having a plurality of discharge ports corresponding to the laminated structure of the multi-layer polyimide film to be obtained, and its specific type and structure are particularly limited. Is not to be done. A T die widely used in the case of producing a film composed of a plurality of layers can be suitably used. As a more specific type, any conventionally known dice can be suitably used. In particular, a feed block T die or a multi-manifold T die can be more preferably used. For example, in an embodiment described later, a three-layer multi-manifold T die is used.

  The support may have a smooth surface (formation surface) so that the discharged polyamic acid solution (polyimide varnish) can be formed as a multilayer liquid film. The specific structure of the said support body is not specifically limited, For example, a metal belt, a metal roller, a resin belt, a resin film, a resin roller etc. can be mentioned. For example, in an embodiment described later, an endless belt made of stainless steel is used. In the present invention, a chemical dehydrating agent and a catalyst are added to at least one kind of polyamic acid solution. Among these, the chemical dehydrating agent is generally highly corrosive, so that the stability of the support is improved by using stainless steel. A multilayer liquid film can be formed more satisfactorily.

  The discharge condition of the polyamic acid solution (polyimide varnish) from the die to the support is not particularly limited, and a plurality of polyamic acid solutions extruded simultaneously from the die are continuously cast on a smooth support. It is only necessary that the multilayer liquid film can be formed. In the examples described later, for example, each of the polyamic acid solutions is extruded and cast on the endless belt that runs 20 mm below the T die.

  A plurality of polyamic acid solutions (polyimide varnish) used in the multilayer liquid film forming step are used. As described in the section <Linear expansion coefficient of surface layer and base layer> of (I) multilayer extruded polyimide film, When the linear expansion coefficient in the range of 100 to 200 ° C. in the polyimide as the base layer and the polyimide as the surface layer is K1 and K2, respectively, the linear expansion coefficient is K2 / K1> 1.1. In addition, a polyamic acid solution for forming each layer may be selected.

<Curing agent addition process>
In the curing agent addition step, a chemical dehydrating agent (dehydrating agent) and a catalyst are added to at least one of a plurality of types of polyamic acid solutions (polyimide varnish) used in the multilayer liquid film forming step. These chemical dehydrating agents and catalysts are collectively referred to as curing agents. That is, in the present invention, at least one polyimide layer is imidized by a chemical curing method.

  The chemical 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, aliphatic acid anhydrides, aromatic acid anhydrides, N , N′-dialkylcarbodiimide, 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. The amount of the chemical dehydrating agent to be added is not particularly limited, but in the polyamic acid solution (polyimide varnish) to be added, 0.5 mol with respect to 1 mol of the amic acid unit in the contained polyamic acid. Within the range of -5 mol is preferable, and within the range of 0.7-4 mol is more preferable.

  The catalyst used in the present invention is not particularly limited as long as it is a component having an effect of promoting the dehydration ring-closing action of the chemical dehydrating agent on the polyamic acid. Specifically, for example, for example, an aliphatic tertiary class Examples thereof include amines, aromatic tertiary amines, and heterocyclic tertiary amines. Among these catalysts, for example, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, diethylpyridine, and β-picoline are particularly preferably used. The addition amount of the catalyst is preferably in the range of 0.05 to 3 mol with respect to 1 mol of amic acid unit in the polyamic acid contained in the polyamic acid solution (polyimide varnish) to be added. More preferably within the range of 2 to 2 mol.

  When the addition amount of the dehydrating agent and the catalyst is less than the above range, imidization may be insufficient, and may break during firing or mechanical strength may decrease. Moreover, when these addition amounts exceed the said range, progress of imidation will become quick too much and it may become difficult to cast a polyimide-type varnish in a film form.

  As the imidization method of polyamic acid, the two most widely known methods are a thermal cure method (thermal imidization method) performed only by heating and a chemical cure method (chemical imidization method) using the above curing agent. It has been. In the present invention, at least one of the surface layer and the base layer may be imidized by a chemical cure method. Thereby, since the time efficiency of imidation can be improved compared with the use of a thermal curing method, productivity can be increased.

<Gel film formation process>
In the gel film forming step, the self-supporting property is obtained by gelling the solvent from the multilayer liquid film formed in the multilayer liquid film forming step by volatilization (volatilization / evaporation) or partial imidization. A multilayer gel film is obtained.

  The gelation method in this step is not particularly limited, but generally, a method by heating and / or blowing can be suitably used. The specific heating method and blowing method are not particularly limited, and conventionally known heating methods and blowing methods can be suitably used, and the heating conditions and blowing conditions are not particularly limited. Here, when the heating method is employed, at least the upper limit of the heating temperature is preferably less than the boiling point of the organic solvent contained in the polyamic acid solution (polyimide varnish) + 50 ° C. If the heating temperature is too high, the organic solvent is volatilized rapidly from the multilayer liquid film, so that the trace of the volatilization remains in the multilayer gel film. This trace becomes a factor of forming minute defects in the finally obtained multilayer extruded polyimide film, and may cause deterioration of the quality of the multilayer extruded polyimide film.

  The multilayer gel film is peeled off from the support and imidized. Here, in continuous production, an example can be given in which the multilayer gel film is continuously peeled off from the support and continuously conveyed to a heating furnace. It is preferable to convey to a heating furnace by a roll-to-roll under temperature conditions lower by 50 ° C. or more than the boiling point of the solvent. When the temperature at the time of transporting the multilayer gel film is close to the boiling point of the main remaining organic solvent, the multilayer gel film contracts due to evaporation of the remaining organic solvent. Thereby, in the multilayer extrusion polyimide film finally obtained, the thickness precision may fall, or mechanical characteristics (an elastic modulus, a linear expansion coefficient, etc.) may differ greatly in a film width direction.

<Imidization process>
In the imidization step, the multilayer gel film is baked to complete imidization. Thereby, the multilayer extrusion polyimide film in which the some polyimide layer was laminated | stacked can be obtained. The heating method used in the imidization step is not particularly limited as long as it can effectively heat the multilayer gel film to substantially remove the organic solvent and advance the imidization, Various conventionally known methods can be suitably used.

  The heating temperature in the imidization step is not particularly limited as long as the imidization can be completed and the organic solvent can be sufficiently evaporated, but it is preferably 250 ° C to 600 ° C, It is preferable to gradually increase the temperature. If the heating temperature is too high, drying of the multilayer extruded polyimide film tends to cause temperature unevenness and flatness tends to be lost, and if it is too low, sufficient drying and imidization may not be performed. The drying time is not particularly limited, and the drying can be performed within a conventionally known range as long as imidization can be completed.

  In order to improve the adhesiveness of the surface layer (adhesive layer), the gel layer serving as the surface layer is an imide so as to intentionally lower the imidization rate or intentionally leave an organic solvent. The control conditions may be controlled. Thereby, the melt fluidity of the polyimide of the surface layer can be improved.

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

(III) Use of the Present Invention The use (use) of the present invention is not particularly limited, but can be suitably used in the electronics field such as a flexible printed wiring board (FPC). Furthermore, it can be used for a heat-resistant adhesive tape whose surface is coated with an adhesive, an insulating tape for covering electric wires, and the like. That is, the present invention can include an FPC insulating substrate, a heat-resistant adhesive tape, an insulating tape, a laminate including the layer made of the polyimide film, and the like, and the like. .

  The laminate according to the present invention is not particularly limited as long as it has a multilayer structure including the multilayer extruded polyimide film. In particular, a flexible metal-clad laminate including a multilayer extruded polyimide film as an insulating layer and a metal layer directly laminated on the insulating layer by a metalizing method can be given. As a method for laminating the metal layer at this time, a metalizing method, that is, a method such as sputtering, vapor deposition, and / or metal plating can be particularly preferably used.

  Conventionally, adhesion between a metal layer formed by a metalizing method and a polyimide layer serving as an insulating layer has been insufficient. On the other hand, in the present invention, the ratio of the linear expansion coefficient between the surface layer and the base layer is defined, and at least one layer (preferably, all layers) is imidized by a chemical cure method. Therefore, even if a metal layer is formed on the surface of the multilayer extruded polyimide film formed by the multilayer extrusion method by the metalizing method, high adhesion can be exhibited.

  Although the material of the metal layer to be laminated is not particularly limited, for example, when used for FPC, a copper layer to be a pattern wiring can be exemplified. Of course, it is needless to say that the layered product according to the present invention may include layers other than those described above.

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

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention. The linear expansion coefficient of the single-layer polyimide film obtained from the polyamic acid solution obtained in the following synthesis example, and the adhesion strength of the copper layer in the two-layer copper-clad laminate obtained in the examples and comparative examples are Measured or evaluated by the following method.

[Linear expansion coefficient of polyimide film]
For the measurement, Rigaku Denki's thermophysical tester, trade name: TMA-8140 was used. About the polyimide film obtained from the polyamic acid solution (polyimide varnish) of Synthesis Example 1-3, the temperature was first raised from room temperature to 400 ° C. under the condition of 10 ° C./min, and then once cooled to room temperature. The temperature was raised under the same conditions, and the linear expansion coefficient in the temperature range of 100 to 200 ° C. was determined. Moreover, about the polyimide film obtained from the polyamic-acid solution of the synthesis example 4-6, it heated up from room temperature to 300 degreeC on the conditions of 10 degree-C / min, and calculated | required the linear expansion coefficient of the temperature range of 100-200 degreeC.

[Adhesion strength of copper layer of 2-layer copper-clad laminate]
The two-layer copper-clad laminate obtained in Examples or Comparative Examples was exposed to an environment of 121 ° C. and 100% RH for 96 hours to perform a pressure cooker test (PCT). Moreover, after PCT, the thermal load (thermal exposure) which is left to stand at 150 degreeC for 150 hours was performed. The adhesion strength between the polyimide layer and the copper layer (metal layer) as the surface layer in each of the two-layer copper-clad laminate after PCT and after the PCT and after the heat load is measured according to JIS. According to C-6481, measurement was performed under the conditions of a pattern width of 1 mm and a 90 ° peel.

(Synthesis example)
In the following Examples and Comparative Examples, the polyamic acid solution (polyimide varnish) synthesized by the following synthesis examples was used. In addition, in order to measure the linear expansion coefficient of the polyimide obtained from each polyamic acid solution, a single layer polyimide film was formed from each polyamic acid solution alone. In each of the following synthesis examples, the synthesis reaction was performed at a temperature in the range of 5 to 10 ° C. in a dry nitrogen atmosphere. In the following synthesis examples, the following abbreviations are used for some compounds.
DMF: N, N-dimethylformamide DMAc: N, N-dimethylacetamide PMDA: pyromellitic dianhydride BPDA: 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride BTDA: 3,3 ′ 4,4′-benzophenonetetracarboxylic dianhydride TMHQ: p-phenylenebis (trimellitic acid monoester acid anhydride)
ODA: diaminodiphenyl ether p-PDA: p-phenylenediamine BAPP: 2,2-bis [4- (4-aminophenoxy) phenyl] propane TMEG: 3,3 ′, 4,4′-ethylene glycol dibenzoate tetracarboxylic acid Dianhydride BAPS: Bis [4- (4-aminophenoxy) phenyl] sulfone [Synthesis Example 1]
In a 2000 ml separable flask, 71.8 g of ODA was charged, and 809 g of DMF was added thereto and dissolved. Next, 104.3 g of PMDA was added in powder form and stirred for 1 hour. Thereafter, a separately prepared DMF solution of p-PDA (12.9 g of p-PDA dissolved in 52 g of DMF) was gradually added and stirred for 1 hour to complete the reaction. A first polyamic acid solution (resin concentration 18%) having a component ratio (at the time of preparation) of PMDA / ODA / p-PDA = 100/75/25 was obtained.

  A separately prepared conversion agent solution (a solution obtained by adding 18.1 g of acetic anhydride and 6.6 g of β-picoline to 56.9 g of DMF and mixing) was added to 150 g of the first polyamic acid solution, and 0 ° C. The mixture was stirred and cooled while cooling. The obtained conversion agent-containing first polyamic acid solution was applied onto an aluminum foil (support) to form a single-layer liquid film. A comma coater was used for coating. This liquid film was heated together with the aluminum foil at 140 ° C. to obtain a gel film having self-indicating properties. Thereafter, the gel film was peeled off from the aluminum foil, the end portion was fixed to a frame with a pin, and heated at 250 ° C., 350 ° C., 450 ° C., and 550 ° C. for 0.5 minutes each. As a result, a polyimide film having a thickness of 25 μm was obtained. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film.

[Synthesis Example 2]
In a 1500 ml separable flask, 71.8 g of ODA was charged, and 683 g of DMF was added thereto and dissolved. Next, 78.2 g of PMDA was added in powder form and stirred for 2 hours to complete the reaction. Thereby, the second polyamic acid solution having a monomer component ratio (when charged) of PMDA / ODA = 100/100 (Resin concentration 18%) was obtained.

  Using the second polyamic acid solution, a polyimide film having a thickness of 25 μm was obtained in the same manner as in Synthesis Example 1. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film.

[Synthesis Example 3]
A 2000 ml separable flask was charged with 56.4 g of ODA and 30.5 g of p-PDA, and further added 1123 g of DMAc and dissolved by stirring. Next, 129.1 g of TMHQ was added in the form of powder, and the mixture was stirred for 2 hours to be reacted. Next, 55.4 g of PMDA was added in powder form, and the mixture was stirred and reacted until it was completely dissolved. Separately, a DMAc solution of PDMA (a solution in which 6.1 g of PMDA was dissolved in 100 g of DMAc) was added while paying attention to an increase in the reaction temperature and stirred for 2 hours to complete the reaction. This obtained the 3rd polyamic-acid solution (resin density | concentration of 18.5%) whose monomer component ratio (at the time of preparation) is PMDA / TMHQ / ODA / p-PDA = 50/50/50/50.

  A polyimide film having a thickness of 25 μm was obtained in the same manner as in Synthesis Example 1 using the third polyamic acid solution. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film.

[Synthesis Example 4]
A glass flask having a volume of 2000 ml was charged with 780 g of DMF and 115.6 g of BAPP, and 78.7 g of BPDA was gradually added while stirring. Subsequently, 3.8 g of TMEG was added and stirred for 30 minutes in an ice bath. To this reaction solution, a separately prepared TMEG DMF solution (a solution in which 2.0 g of TMEG was dissolved in 20 g of DMF) was gradually added and stirred while paying attention to the viscosity. When the viscosity reached 3000 poise, the addition and stirring were stopped to obtain a fourth polyamic acid solution.

  The fourth polyamic acid solution was applied onto a PET film (support) with a comma coater to form a single-layer liquid film. Thereafter, the liquid film was heated together with the PET film at 80 ° C. to obtain a self-indicating gel film. Thereafter, the gel film was peeled off from the PET film, and the end portion was fixed to a frame with a pin, and heated at 120 ° C., 150 ° C., 200 ° C., 250 ° C., and 300 ° C. for 2 minutes each. As a result, a polyimide film having a thickness of 25 μm was obtained. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film. Various properties of this polyimide film are shown in Table 1.

[Synthesis Example 5]
780 g of DMF and 103.9 g of BAPP were added to a glass flask having a capacity of 2000 ml, and 28.6 g of BTDA was gradually added while stirring. Subsequently, 65.4 g of TMEG was added and stirred for 30 minutes in an ice bath. To this reaction solution, a separately prepared TMEG DMF solution (2.1 g of TMEG dissolved in 20 g of DMF) was gradually added while stirring the viscosity, followed by stirring. When the viscosity reached 3000 poise, the addition and stirring were stopped to obtain a fifth polyamic acid solution.

  A polyimide film having a thickness of 25 μm was used in the same manner as in Synthesis Example 4 except that the fifth polyamic acid solution was used, and the gel film was heated at 120 ° C., 150 ° C., 200 ° C., and 250 ° C. for 2 minutes each. Got. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film. Various properties of this polyimide film are shown in Table 1.

[Synthesis Example 6]
780 g of DMF and 117.2 g of BAPS were added to a glass flask having a capacity of 2000 ml, and 71.7 g of BPDA was gradually added while stirring. Subsequently, 5.6 g of TMEG was added and stirred for 30 minutes in an ice bath. To this reaction solution, a separately prepared TMEG DMF solution (5.5 g of TMEG dissolved in 20 g of DMF) was gradually added while stirring the viscosity, followed by stirring. When the viscosity reached 3000 poise, the addition and stirring were stopped to obtain a sixth polyamic acid solution.

  A polyimide film having a thickness of 25 μm was obtained in the same manner as in Synthesis Example 1 using the sixth polyamic acid solution. Table 1 shows the linear expansion coefficient (unit: ppm / ° C.) of this polyimide film.

[Example 1]
[Production of multilayer extruded polyimide film]
The first polyamic acid solution was used to form a polyimide layer serving as a base layer. To this first polyamic acid solution, acetic anhydride was added as a chemical dehydrating agent, and isoquinoline was added as a catalyst. The amount of addition was such that 2 mol of acetic anhydride and 1 mol of isoquinoline per mol of the polyamic acid amic acid unit contained in the first polyamic acid solution.

  Moreover, in order to form the polyimide layer used as a surface layer, the said 2nd polyamic acid solution was used. To this second polyamic acid solution, acetic anhydride was added as a chemical dehydrating agent, and isoquinoline was added as a catalyst. The amount of addition was such that acetic anhydride was 2 mol and isoquinoline was 2 mol with respect to 1 mol of the polyamic acid amic acid unit contained in the second polyamic acid solution.

  Next, a multilayer liquid film was formed on a stainless steel endless belt (support) using each of the above polyamic acid solutions. This multilayer liquid film was extruded onto the endless belt using a three-layer multi-manifold T die so that the outer layer (surface layer) was the second polyamic acid solution and the inner layer (base layer) was the first polyamic acid solution. . The extrusion conditions were such that the respective polyamic acid solutions were extruded and cast onto the endless belt running 20 mm below the T die.

  The resulting multilayer liquid film having a three-layer structure was heated at 130 ° C. for 100 seconds to form a gel film, which was peeled off from the endless belt. This gel film was fixed to a tenter clip, and dried and imidized under conditions of 300 ° C. × 30 seconds, 400 ° C. × 50 seconds, 450 ° C. × 40 seconds, and 520 ° C. × 20 seconds to obtain a multilayer extruded polyimide film. . In the obtained multilayer extruded polyimide film, the thickness of the polyimide layer (formed from the second polyamic acid solution) serving as the surface layer is 4 μm, and the thickness of the polyimide layer (formed from the first polyamic acid solution) serving as the base layer is 17 μm. Met.

[Manufacture of two-layer copper-clad laminate]
Using a sputtering machine (made by Showa Vacuum, model: NSP-6) equipped with an ion gun manufactured by IONTECH (model: NPS-3000FS) on the surface layer of the multilayer extruded polyimide film having the above three-layer structure, surface treatment is performed. gave. Surface treatment conditions were an acceleration voltage of 900 V, a beam current of 20 mA, and an accelerator voltage of 120 V under a vacuum of 6 × 10 ⁻² Pa in an argon atmosphere.

  Next, a chromium layer was first formed as a base layer on the surface layer after the surface treatment using the sputtering machine. This chromium layer was formed to a thickness of 2.5 μm (250 mm) under the conditions of a vacuum degree of 0.7 Pa, an output of 400 W, and an oxygen / argon = 1/99 atmosphere. The first copper layer was laminated on the chromium layer using the sputtering machine. The first copper layer was laminated with a thickness of 20 μm (2000 mm) under the conditions of a degree of vacuum of 0.2 Pa and an output of 400 W.

A second copper layer was further formed on this first copper layer by sulfuric acid electrolytic copper plating. This second copper layer has a plating solution composition of CuSO ₄ .5H ₂ O: 80 g / l, H ₂ SO ₄ : 200 g / l, NaCl: 70 mg / l, and the additive Top Lucina 81-HL (trade name, (Okuno Pharmaceutical Co., Ltd.): 2.5 ml / l, and a cathode current density of 2 A / dm ² , and a thickness of 35 μm. Thus, a sputtered two-layer copper clad laminate was produced.

  About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

[Example 2]
As the polyimide varnish for forming the outer layer (surface layer), the second polyamic acid solution is used, and as the polyimide varnish for forming the inner layer (base layer), the third polyamic acid solution is used, A multilayer extruded polyimide film was obtained in the same manner as in Example 1, and a two-layer copper clad laminate was produced. About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

[Comparative Example 1]
As the polyimide varnish for forming the outer layer (surface layer), the third polyamic acid solution is used, and as the polyimide varnish for forming the inner layer (base layer), the first polyamic acid solution is used, A multilayer extruded polyimide film was obtained in the same manner as in Example 1, and a two-layer copper clad laminate was produced. About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

Example 3
While using a fourth polyamic acid solution as the polyimide varnish for forming the outer layer (surface layer), using a third polyamic acid solution as the polyimide varnish for forming the inner layer (base layer), drying and A multilayer extruded polyimide film was obtained in the same manner as in Example 1 except that the imidization conditions were 300 ° C. × 30 seconds, 400 ° C. × 50 seconds, and 450 ° C. × 40 seconds. Manufactured. About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

Example 4
As the polyimide varnish for forming the outer layer (surface layer), the fifth polyamic acid solution is used, and as the polyimide varnish for forming the inner layer (base layer), the first polyamic acid solution is used, A multilayer extruded polyimide film was obtained in the same manner as in Example 3, and a two-layer copper clad laminate was produced. About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

Example 5
As the polyimide varnish for forming the outer layer (surface layer), the sixth polyamic acid solution is used, and as the polyimide varnish for forming the inner layer (base layer), the first polyamic acid solution is used, A multilayer extruded polyimide film was obtained in the same manner as in Example 3, and a two-layer copper clad laminate was produced. About the obtained 2 layer copper clad laminated board, the adhesive strength after heat load was measured after normal state and PCT. The results are shown in Table 2 together with the linear expansion coefficient ratio of the base layer and the surface layer.

  As is apparent from the results in Table 2, the adhesiveness between the metal layer and the multilayer extruded polyimide film can be improved by controlling the linear expansion coefficient ratio between the surface layer and the base layer.

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

  As described above, in the present invention, when a multilayer extruded polyimide film is produced by the multilayer extrusion method, at least one polyimide layer is imide by a chemical curing method (a method in which a chemical dehydrating agent and a catalyst are added to imidize). And the linear expansion coefficient ratio of the base layer and the surface layer is controlled. Therefore, the adhesiveness between the metal method formed by the metalizing method and the multilayer extruded polyimide film can be improved. Therefore, the present invention can be used not only in the field of manufacturing a polyimide film but also in a wide range of fields related to the manufacture of various electronic components such as FPC using the film and its field of use. Is possible.

Claims (9)

A plurality of organic solvent solutions containing polyimide or a precursor thereof are simultaneously extruded onto a support to form a multi-layered liquid film, which is obtained by imidization, and a plurality of layers laminated together A multilayer extruded polyimide film comprising a polyimide layer,
The plurality of polyimide layers include a base layer serving as a base of the entire film and a surface layer exposed on the film surface, and at least one of the base layer and the surface layer includes the organic solvent. A chemical dehydrating agent and a catalyst are added to the solution and imidized by a chemical cure method.
When the linear expansion coefficients in the range of 100 to 200 ° C. in the polyimide as the base layer and the polyimide as the surface layer are K1 and K2, respectively, these linear expansion coefficients are expressed by the following relational expression K2 / K1> 1. 1
And K1 is 13 to 17 ppm / ° C, and K2 is 32 to 70 ppm / ° C.
The surface layer is made of at least thermoplastic polyimide, and the base layer is made of at least heat-resistant polyimide.   The multilayer extruded polyimide film according to claim 1, wherein the entire film has a thickness in the range of 10 to 75 µm. A multi-layer extruded polyimide comprising a plurality of polyimide layers laminated together, and the plurality of polyimide layers including a base layer as a base of the entire film and a surface layer exposed on the film surface A method for producing a film,
A multilayer liquid film forming step of simultaneously extruding a plurality of types of organic solvent solutions containing polyimide or a precursor thereof onto a support to form a liquid film having a multilayer structure; and an imidization step of imidizing the multilayer liquid film; As well as
Furthermore, at least one of the plurality of types of organic solvent solutions includes a curing agent addition step for adding a chemical dehydrating agent and a catalyst and imidizing by a chemical curing method,
In the multilayer liquid film forming step, when the linear expansion coefficients in the range of 100 to 200 ° C. in the polyimide as the base layer and the polyimide as the surface layer are K1 and K2, respectively, these linear expansion coefficients are as follows: Relational expression K2 / K1> 1.1
And the organic solvent solution forming each layer is selected so that K1 is 13 to 17 ppm / ° C. and K2 is 32 to 70 ppm / ° C.
The surface layer is made of at least a thermoplastic polyimide, and the base layer is made of at least a heat-resistant polyimide. The chemical dehydrating agent is added to the organic solvent solution so that the chemical dehydrating agent is in the range of 0.5 to 5 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the organic solvent solution to be added. It adds, The manufacturing method of the multilayer extrusion polyimide film of Claim 3 characterized by the above-mentioned. The catalyst is added to the organic solvent solution so as to be in the range of 0.05 to 3 mol with respect to 1 mol of the amic acid unit in the polyamic acid contained in the organic solvent solution to be added. The method for producing a multilayer extruded polyimide film according to claim 3 or 4 , wherein: The multilayer extrusion polyimide film obtained by the manufacturing method of the multilayer extrusion polyimide film of any one of Claim 3 thru | or 5 . Claim 1, 2 or are together provided with the insulating layer a multilayer extruded polyimide film according to 6, the flexible metal-clad laminate characterized in that it comprises a metal layer laminated directly by metallizing method on the insulating layer . The flexible metal-clad laminate according to claim 7 , wherein the metal layer is a copper layer. A flexible wiring board manufactured using the flexible metal-clad laminate according to claim 7 or 8 .