JPWO2007083526A1 - Polyimide film and use thereof - Google Patents

Abstract

Provided are a polyimide film having high flexibility and dimensional stability and good handling properties, and use thereof. A polyimide film formed by imidizing a polyamic acid obtained by polymerizing an acid dianhydride component and a diamine component, wherein the diamine component is at least 2,2-bis (4- (4-aminophenoxy) phenyl) A polyimide film comprising propane, having an elastic modulus of less than 4 GPa, and an average linear expansion coefficient at 100 to 200 ° C. of 15 to 30 ppm. By designing the thickness, elastic modulus, and linear expansion coefficient of the film, a flexible copper-clad laminate having high flexibility and dimensional stability can be obtained in high yield.

Description

  The present invention relates to a polyimide film and use thereof, and more particularly to a polyimide film that can be suitably used for a flexible printed circuit board that is required to have higher bending resistance and use thereof.

  In recent years, demand for various types of printed circuit boards has increased with the reduction in weight, size, and density of electronic products. Among these, flexible laminates (also referred to as “flexible printed circuit boards” (hereinafter also referred to as “FPC”)) are known. Demand) is growing particularly. The flexible laminate has a structure in which a circuit made of a metal foil is formed on an insulating film.

  The FPC is generally made of various insulating materials, and is manufactured by a method in which 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 through various adhesive materials. Is done. As the insulating film, for example, a polyimide film is preferably used.

  The FPC is required to improve its performance at the same time as its demand increases. Specifically, with high functionality and downsizing of mobile phones and the like in recent years, high flexibility and dimensional stability are required for FPC. In order to solve such a demand, various improvements have been made on the FPC.

  For example, in order to achieve high flexibility, attempts have been made to reduce the thickness of a polyimide film used for FPC, or to reduce the thickness of a copper layer. Specifically, the techniques disclosed in Patent Documents 1 to 4 can be listed.

  Patent Document 1 discloses a highly flexible FPC using a polyimide film on which a treatment layer of either a metal layer, a fluororesin layer, or a matte treatment surface is provided. As the polyimide film, a polyimide film having a thickness of 12.5 μm or less is used.

In Patent Document 2, as a flexible copper-clad laminate capable of producing an FPC having excellent flexibility and heat resistance, a copper layer having a thickness of 10 μm or less is directly formed on one or both sides of a polyimide film having a thickness of 10 μm or less. A flexible copper-clad laminate obtained in this way is disclosed. It is described that the polyimide film is made of a polyimide polymer having an initial tensile elastic modulus of 400 kg / mm ² or more.

  Patent Document 3 discloses a copper-clad polyimide obtained by adhering a polyimide film and a copper foil through an adhesive layer having a specific configuration as a copper-clad polyimide film for suppressing a decrease in flexibility in an FPC material. A film is disclosed. It is described that the polyimide film has a thickness of 12.5 to 125 μm.

  Furthermore, in Patent Document 4, as a copper-clad laminate for FPC having excellent heat resistance, folding resistance and flexibility, a conductive foil is laminated after a resin composition having a specific configuration is applied to a polyimide film. A copper-clad laminate for FPC obtained by the above is disclosed. As the polyimide film, a polyimide film having a thickness of 25 μm is used.

  In order to achieve high dimensional stability, attempts have been made to modify the polyimide composition or the polyimide polymerization method. Specifically, techniques disclosed in Patent Documents 5 to 9 can be listed.

  Patent Document 5 discloses a polyimide film for a flexible printed circuit board having a film thickness of 5 to 20 μm, a Young's modulus of 4 to 7 GPa, and a thermal expansion coefficient of 14 to 22 ppm / ° C. The said polyimide film is a polyimide film containing a specific aromatic diamine component and an aromatic tetracarboxylic acid compound component.

  Patent Document 6 discloses a polyimide film excellent in high elastic modulus, alkali etching property, flexibility, low humidity expansion coefficient, thermal dimensional stability and film forming property. Specifically, at least pyromellitic dianhydride, and 3,4′-oxydianiline and 4,4′-oxydianiline are used, and the 3,4′-oxydianiline is 5 mol based on diamine. It is a polyimide film manufactured from polyamic acid which is not less than 50% and less than 50% by mole. The Young's modulus of the polyimide film is 4.0 to 6.5 [GPa].

  Patent Document 7 discloses a polyimide copolymer having thermal dimensional stability and excellent mechanical properties. In the polyamic acid used for the production of the polyimide copolymer of Patent Document 7, 4,4′-diaminodiphenyl ether (hereinafter also referred to as “ODA”) and paraphenylenediamine (hereinafter also referred to as “p-PDA”) as the diamine component. ) Is used. In addition, in the production of the polyamic acid, first, one of the two diamines is reacted with pyromellitic dianhydride (hereinafter also referred to as “PMDA”) to obtain an acid anhydride-terminated amic acid prepolymer. Is synthesized. Thereafter, the polyamic acid is produced by reacting the other diamine with the acid anhydride-terminated amic acid prepolymer. It is disclosed that by using such a polyamic acid, a polyimide having excellent thermal dimensional stability and mechanical properties can be obtained.

  Patent Document 8 also discloses a polyimide copolymer having thermal dimensional stability and excellent mechanical properties. In the polyamic acid used for the production of this polyimide copolymer, ODA and p-PDA are used as diamines. In the production of the polyamic acid, first, a diamine component containing 80% by weight or more of one of the two kinds of diamines is reacted with an aromatic tetracarboxylic dianhydride component containing 70% by weight or more of PMDA. Thus, an acid anhydride-terminated amic acid prepolymer is synthesized. Next, a polyamic acid is synthesized by reacting this amic acid prepolymer with a diamine component containing 80% by weight or more of the other of the two diamines. It is disclosed that by using the polyamic acid thus obtained, a polyimide having excellent thermal dimensional stability and mechanical properties can be obtained.

  Patent Document 9 discloses a copolymerized polyimide and a copolymerized polyimide resin molded body having high elasticity, low thermal expansion comparable to metals, and low water absorption. It is described that the polyamic acid used for manufacture of the copolymerization polyimide of patent document 9 is manufactured as follows. Specifically, first, an aromatic diamine compound having a rigid structure and an aromatic tetracarboxylic acid compound are aromatic to an aromatic diamine compound having a rigid structure in an organic solvent non-reactive with the reaction components. The tetracarboxylic acid compound is mixed for a time required for the reaction at a ratio of 90 mol% or more and less than 100 mol%. Thereafter, an aromatic diamine compound having a flexible structure is added, and then an aromatic tetracarboxylic acid compound (A) is added. Further, an aromatic tetracarboxylic acid compound (B; A ≠ B) is added in an amount such that the wholly aromatic tetracarboxylic acid component and the wholly aromatic diamine component are approximately equimolar. Then, a copolymerized polyamic acid solution is obtained by mixing for a time required for the reaction. It is disclosed that the copolymerized polyimide of Patent Document 9 can be obtained by cyclizing and removing the copolymerized polyamic acid solution thus obtained.

Moreover, the polyimide film disclosed by patent document 10 can be mentioned as a polyimide film with a low elasticity modulus. Specifically, it has a low elastic modulus necessary for forming a circuit board that can be bent, specifically a tensile elastic modulus (room temperature) of 200 to 300 kgf / mm ² , and a linear expansion coefficient of 15. Polyimides that are ˜25 ppm / K (100-200 ° C.) are disclosed. The polyimide film comprises 1 equivalent mole of pyromellitic dianhydride, 50 to 70 mole% paraphenylenediamine, 5 to 25 mole% 4,4′-methylenedianiline, and 5 to 4,4′-oxydianiline 5 Obtained by thermally imidizing polyamic acid which is a random copolymer having a repeating structural unit obtained by reacting 0.9 to 1.1 equivalent mole of diamine consisting of 30 mol% in an organic solvent. Is disclosed.

Furthermore, Patent Document 11 discloses a low-modulus polyimide adhesive composition that does not contain halogen. Specifically, low modulus polyimide siloxane polymers, thermoset substantially non-halogenated epoxies (optionally including an epoxy catalyst), plasticizers, and flame retardants that do not contain insoluble halogens. A polyimide adhesive composition comprising a conductive filler and optionally an adhesion promoter. It is described that the polyimide adhesive composition can be used for a flexible circuit at a relatively low bonding temperature.
JP-A-8-153940 (published on June 11, 1996) Japanese Patent Laid-Open No. 8-156176 (published on June 18, 1996) Japanese Patent Laying-Open No. 2005-53940 (published March 3, 2005) Japanese Patent Laying-Open No. 2004-256678 (published on September 16, 2004) JP 2003-109989 A (published on April 11, 2003) JP 2003-176370 A (published June 24, 2003) JP-A-1-131242 (published on May 24, 1989; Patent No. 2744786 (registered on February 6, 1998)) JP-A-1-131241 (published on May 24, 1989; Patent No. 2847701 (registered on November 6, 1998)) Japanese Laid-Open Patent Publication No. 9-235373 (published on September 9, 1997) JP 2003-192788 A (released July 9, 2003) Japanese Patent Laying-Open No. 2005-194527 (published July 21, 2005)

  As described above, various developments have been made on polyimide films having high flexibility and / or high dimensional stability. However, these conventional polyimide films can be used for highly functional and miniaturized electronic devices. Not enough.

  Specifically, in Patent Documents 1 to 4, the thickness of the polyimide film or the metal layer is reduced in order to achieve high flexibility. However, if the film is made too thin, the stiffness becomes too low, handling is difficult, and the processing yield is decreasing. In addition, there is a problem that the degree of freedom in designing the substrate is reduced when the copper layer is thinned.

  Moreover, although the techniques of Patent Documents 5 to 9 have improved to some extent with respect to high dimensional stability, they have a high elastic modulus and are insufficiently improved in terms of flexibility in FPC. Furthermore, in the technique of Patent Document 10, the low elastic modulus and the high dimensional stability are improved to some extent. However, the technique aims at improving the bendability, and the high bendability and low stiffness ( It is not sufficient as a material for FPC requiring low power consumption.

  Therefore, development of a polyimide film for achieving excellent bending characteristics and excellent handling properties is required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a polyimide film having high flexibility and dimensional stability and good handling properties and use thereof.

  As a result of intensive studies in view of the above problems, the present inventors have obtained a flexible copper-clad laminate having high flexibility and dimensional stability at a high yield by designing the thickness, elastic modulus, and linear expansion coefficient of the film. As a result, the present invention was found. That is, the present invention includes the following industrially useful inventions (1) to (11).

  (1) A polyimide film formed by imidizing a polyamic acid obtained by polymerizing an acid dianhydride component and a diamine component, wherein the diamine component is at least 2,2-bis (4- (4-aminophenoxy) A polyimide film comprising phenyl) propane, having an elastic modulus of less than 4 GPa, and an average linear expansion coefficient at 100 to 200 ° C. of 15 to 30 ppm.

  (2) The polyimide film according to (1), wherein an average linear expansion coefficient at 100 to 200 ° C. is 18 to 25 ppm.

  (3) The polyimide film according to (1) or (2), wherein the elastic modulus is 3.5 GPa or less.

  (4) The polyimide film according to any one of (1) to (3), wherein the film thickness is 7 to 28 μm.

  (5) The polyimide film according to any one of (1) to (4), wherein the film thickness is 10 to 14 μm.

  (6) The acid dianhydride component contains at least pyromellitic dianhydride, and the diamine component contains at least 4,4′-oxydianiline and p-phenylenediamine ( The polyimide film according to any one of 1) to (5).

  (7) The diamine component contains all of 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 4,4′-oxydianiline and p-phenylenediamine, and is contained in the diamine component. 20 to 50 mol% of 2,2-bis (4- (4-aminophenoxy) phenyl) propane within a range not exceeding 100 mol%, assuming that the total number of moles of all diamines is 100 mol% And the polyimide according to any one of (1) to (6), comprising 20 to 50 mol% of 4,4′-oxydianiline and 15 to 35 mol% of p-phenylenediamine. the film.

  (8) The polyimide film as described in any one of (1) to (7), which is used as a material for a flexible metal-clad laminate.

  (9) An adhesive film comprising an adhesive layer on at least one surface of the polyimide film according to any one of (1) to (8).

  (10) A flexible metal-clad laminate comprising a polyimide film according to any one of (1) to (8) or a metal foil laminated to the adhesive film according to (9).

  (11) A flexible printed wiring board manufactured using the flexible metal-clad laminate according to (10).

  As described above, the polyimide film according to the present invention is produced using 2,2-bis (4- (4-aminophenoxy) phenyl) propane as a diamine component, and has an elastic modulus of less than 4 GPa and 100 to 200. Since the average linear expansion coefficient at 15 ° C. is 15 to 30 ppm, it has high flexibility and high dimensional stability. Therefore, by using the polyimide film according to the present invention, there is an effect that a flexible metal-clad laminate having high flexibility and dimensional stability can be obtained with high yield.

  Embodiments of the present invention will be described in detail below, but the present invention is not limited to the following description.

<I. Polyimide film>
The polyimide film according to the present invention is manufactured using 2,2-bis (4- (4-aminophenoxy) phenyl) propane as a diamine component, and preferably has the following physical properties, A specific composition, structure, manufacturing method thereof, and the like are not particularly limited.

  The polyimide film according to the present invention preferably has an elastic modulus of less than 4 GPa. If the elastic modulus of the polyimide film is too small, the handleability tends to deteriorate. On the contrary, if the elastic modulus of the polyimide film is too large, the flexibility tends to decrease. Therefore, the elastic modulus of the polyimide film according to the present invention is more preferably 1 GPa or more and less than 4 GPa, and further preferably 1.5 GPa or more and 3.5 GPa or less. If it is in the said range, it can be set as a polyimide film with favorable handleability and favorable flexibility. In this specification, “flexibility” means resistance when repeatedly bent, and “good flexibility” means high resistance when repeatedly bent. The “elastic modulus” means an elastic modulus measured according to ASTM D-882.

  Moreover, as for the linear expansion coefficient of the polyimide film concerning this invention, it is preferable that the average linear expansion coefficient of 100-200 degreeC is 15-30 ppm. If it is the above-mentioned range, although dimensional stability does not worsen or it does not become easy to produce curl, More preferably, it is 18-25 ppm. If it is in the said range, it can prevent more effectively that dimensional stability worsens or it becomes easy to produce curl.

  Moreover, when the thickness of a polyimide film is too thin, there exists a tendency for a handleability, the conveyance property of a film, and production stability to deteriorate extremely. On the other hand, if the polyimide film is too thick, the repulsive force of the FPC increases and the flexibility tends to decrease. Therefore, it is preferable that the thickness of the polyimide film concerning this invention is 7-28 micrometers, and it is more preferable that it is 10-14 micrometers. If it is in the said range, the handleability and production stability of a film will not become extremely bad, the repulsive force of FPC will not become large, and a flexibility will not fall.

  Furthermore, in the polyimide film according to the present invention, the peak temperature of tan δ by dynamic viscoelasticity measurement is preferably 300 ° C. or higher, and more preferably 320 ° C. or higher. If it is in the said range, dimensional stability will not be reduced.

  Moreover, the tensile elongation at break of the polyimide film according to the present invention is not particularly limited, but is preferably large to some extent from the viewpoint of improving flexibility. Specifically, the tensile breaking elongation is preferably 40% or more, and more preferably 50% or more. The tensile breaking elongation can be measured according to ASTM D-882.

  The physical properties of the polyimide film according to the present invention are as described above. Since the polyimide film concerning this invention has the said physical property, it can implement | achieve the polyimide film which has high flexibility and high dimensional stability.

  Here, the structure of the polyimide film according to the present invention will be specifically described below. The following description is intended to facilitate understanding of the present invention. Therefore, the present invention is not limited to the following structure.

  The polyimide film concerning this invention is a polyimide film formed by imidating the polyamic acid formed by superposing | polymerizing an acid dianhydride component and a diamine component.

  The acid dianhydride component is not particularly limited, but preferably contains an aromatic tetracarboxylic dianhydride. For example, pyromellitic dianhydride (hereinafter also referred to as “PMDA”), 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 acid Dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane Dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxy) Phenyl) meta Dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimellitic acid monoester Aromatic tetracarboxylic dianhydrides such as acid anhydride), ethylene bis (trimellitic acid monoester anhydride), and bisphenol A bis (trimellitic acid monoester anhydride), and the like It is done. These compounds may be contained singly or as a mixture mixed at an arbitrary ratio. The acid dianhydride component of the present invention preferably contains at least PMDA among the above compounds.

  The diamine component is not particularly limited, but preferably contains an aromatic diamine. For example, 4,4′-oxydianiline (hereinafter also referred to as “ODA”), 3,3′-oxydianiline, 3,4′-oxydianiline, p-phenylenediamine (hereinafter “p-PDA”) 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, benzidine, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 4) , 4′-diaminodiphenylsulfone, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4′-diaminodiphenyldiethylsilane, 4, , 4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphorus Fin oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 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, 1,3-diaminobenzene, 1,2-diamino Benzene, and 2,2-bis (4- (4-aminophenoxy) phenyl) propane (hereinafter also referred to as "BAPP"), as well as aromatic diamines, such as analogs thereof. These compounds may be contained singly or as a mixture mixed at an arbitrary ratio.

  Of the above compounds, BAPP is preferably contained in the diamine component of the present invention, and more preferably ODA and p-PDA are further contained.

  When all of BAPP, ODA and p-PDA are contained as the diamine component, when the total number of moles of all diamines contained in the diamine component is defined as 100 mol%, the amount does not exceed 100 mol%. ~ 50 mol% 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 20-50 mol% 4,4'-oxydianiline, and 15-35 mol% p-phenylenediamine. It is preferable to contain.

  According to the said structure, the polyimide film obtained by imidating the said polyamic acid has the said physical property. The polyamic acid is described in <II. The method for producing a polyimide film> is described in more detail, so please refer to that.

<II. Manufacturing method of polyimide film>
The manufacturing method of the polyimide film concerning this invention can be used suitably for manufacturing the polyimide film concerning this invention mentioned above. Specifically, it may be a production method for suitably producing the polyimide film using polyamic acid as a precursor, and the specific configuration is not particularly limited.

  In this invention, it does not specifically limit about the method of manufacturing a polyimide film from the said polyamic-acid solution, A conventionally well-known method can be used. Specifically, examples of the method for imidizing the polyamic acid include a thermal imidization method and a chemical imidization method. In the method for producing a polyimide film according to the present invention, either method may be used to produce a polyimide film, but it is preferable to use a chemical imidization method. According to the chemical imidation method, the polyimide film according to the present invention having various characteristics as described above tends to be easily obtained.

  Hereinafter, the manufacturing method of the polyimide film concerning this invention is demonstrated in detail. Here, although an embodiment in the case of imidizing polyamic acid by a chemical imidization method will be described, as described above, the present invention is not limited to the chemical imidization method. In the present invention, it is preferable to use an aromatic tetracarboxylic dianhydride as the acid dianhydride component and an aromatic diamine as the diamine component in the production of the polyamic acid. Therefore, for convenience of explanation, in the following explanation, the acid dianhydride component is an aromatic tetracarboxylic dianhydride component and the diamine component is an aromatic diamine component.

  The method for producing a polyimide film according to the present invention comprises (A) a step of reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution (hereinafter referred to as “polyamic acid production step”). And (B) a step of casting a film-forming dope containing the polyamic acid solution on a support (hereinafter also referred to as “film-forming dope casting step”), and (C) the film-forming dope After the dope is heated on the support, a step of peeling the gel film from the support (hereinafter also referred to as “gel film forming step”), (D) the gel film is further heated, and the remaining amic acid is removed. It is preferable to include a step of imidization and drying (hereinafter also referred to as “baking step”). According to the said structure, the polyimide film which has various physical properties of the polyimide film concerning this invention can be manufactured suitably.

  Hereinafter, although the four steps will be described in detail, the present invention does not have to include all the four steps. That is, an embodiment including only a part of the above four steps is also included in the present invention.

(A) Polyamic acid manufacturing process As above-mentioned, the polyimide film concerning this invention can be manufactured using a polyamic acid as a precursor. In the polyamic acid production process, the precursor polyamic acid is produced. In the polyamic acid production step, the method for producing the polyamic acid is not particularly limited, and any known method can be used. For example, first, substantially equimolar amounts of aromatic tetracarboxylic dianhydride and aromatic diamine are dissolved in an organic polar solvent. Next, the obtained polyamic acid organic polar solvent solution is polymerized with the aromatic tetracarboxylic dianhydride and aromatic diamine under controlled temperature conditions (hereinafter also referred to as “polyamic acid polymerization”). Can be produced by stirring until complete. The polyamic acid concentration of the polyamic acid solution thus produced is usually 5 to 35% by weight, preferably 10 to 30% by weight. When the concentration is within this range, a molecular weight and a solution viscosity suitable for the present invention can be obtained.

  The polyamic acid polymerization method is not particularly limited, and any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of polyamic acid is the order of addition of its monomers, that is, aromatic tetracarboxylic dianhydride and aromatic diamine. That is, various physical properties of the obtained polyimide can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any monomer addition method may be used in the polyamic acid polymerization method.

  As described above, the polyamic acid polymerization method is not particularly limited, but typical polymerization methods include the following methods.

  (1) A method in which an aromatic diamine is dissolved in an organic polar solvent, and the aromatic diamine is reacted with a substantially equimolar aromatic tetracarboxylic dianhydride for polymerization.

  (2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Subsequently, a method of polymerizing using an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar throughout all the steps.

  (3) An aromatic tetracarboxylic dianhydride is reacted with an excess molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, the aromatic tetracarboxylic dianhydride is added so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar throughout the entire process after the addition of the aromatic diamine compound. A method of polymerizing using a product.

  (4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar.

  (5) A method of polymerizing by reacting a substantially equimolar mixture of an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic polar solvent.

  In addition, these methods may be used alone or in combination.

  The organic polar solvent used for polymerizing the polyamic acid is not particularly limited, and any solvent can be used as long as it dissolves the polyamic acid. For example, amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, and N-methyl-2-pyrrolidone can be used. Among these, N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.

  Moreover, the said aromatic tetracarboxylic dianhydride which can be used as an aromatic tetracarboxylic dianhydride component is not specifically limited. For example, <I. Aromatic tetracarboxylic dianhydrides exemplified in <Polyimide film> can be used. These compounds can be preferably used alone or as a mixture mixed at an arbitrary ratio. Moreover, it is preferable to use PMDA as at least one of these exemplified aromatic tetracarboxylic dianhydrides.

  Furthermore, the said aromatic diamine which can be used as an aromatic diamine component is not specifically limited. For example, <I. The aromatic diamine exemplified in the polyimide film> can be used. These compounds can be preferably used alone or as a mixture mixed at an arbitrary ratio. Of these exemplified aromatic diamines, at least BAPP is preferably used, and ODA and p-PDA are more preferably used.

  In the polyamic acid, the polymerization ratio of the acid dianhydride component and the diamine component is not particularly limited, and may be designed so that the physical properties of the finally obtained polyimide film are as described above. . In other words, a polyimide having desired characteristics can be produced by appropriately combining these aromatic diamines and aromatic tetracarboxylic dianhydrides for molecular design. In designing the molecule, it is preferable to consider the following tendency.

  (I) When a monomer having a rigid structure such as phenylenediamines, benzidines, and PMDA is used, the elastic modulus tends to increase and the linear expansion coefficient tends to decrease.

  (Ii) When a monomer having an ether bond, a hydrocarbon group, a sulfone group, or a carbonyl group in the molecular chain is used, the elastic modulus tends to decrease and the linear expansion coefficient tends to increase.

  (Iii) When a non-linear monomer is used when viewed as a whole molecule, such as 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, the elastic modulus is lowered and the linear expansion coefficient is reduced. It tends to grow.

  The above-described molecular design will be described more specifically below by taking a polyimide film of an example described later as an example, but it goes without saying that the present invention is not limited to this.

  In the examples described later, PMDA is used as the aromatic tetracarboxylic dianhydride. Moreover, BAPP, ODA, and p-PDA are used as aromatic diamine. When manufacturing the polyimide film concerning this invention using these compounds, when there are many p-PDAs, there exists a tendency for an elasticity modulus to become high and for a linear expansion coefficient to become small. Moreover, when there are many BAPP and ODA, an elasticity modulus will become low and there exists a tendency for a linear expansion coefficient to become large. This trend is stronger with BAPP than with ODA.

  Therefore, when all of BAPP, ODA, and p-PDA are contained as the diamine component, it is preferable to mix them in the following ratio. That is, when the total number of moles of all diamines contained in the diamine component is 100 mol%, 20 to 50 mol% of 2,2-bis (4- ( 4-aminophenoxy) phenyl) propane, 20 to 50 mol% 4,4′-oxydianiline, and 15 to 35 mol% p-phenylenediamine so that these three diamines are It is preferable to make it contain.

The “monomer having a rigid structure” means “aromatic diamine having a rigid structure” and “aromatic tetracarboxylic dianhydride having a rigid structure”. Furthermore, the “aromatic diamine having a rigid structure” refers to an aromatic diamine having a rigid structure having no flexibility in the main chain between two NH ₂ groups. Examples of the aromatic diamine having a rigid structure include phenylenediamines such as paraphenylenediamine, benzidines, and substituted benzidines. Similarly, “aromatic tetracarboxylic dianhydride having a rigid structure” refers to an aromatic tetracarboxylic dianhydride having a rigid structure having no flexibility in the main chain. Examples of the aromatic tetracarboxylic dianhydride having a rigid structure include naphthalene tetracarboxylic dianhydride and PMDA.

  The “monomer having a flexible group” means “aromatic diamine having a flexible group” and “aromatic tetracarboxylic dianhydride having a flexible group”. Furthermore, the “aromatic diamine having a flexible group” refers to an aromatic diamine having a flexible structure such as an ether group, a sulfone group, a ketone group, and a sulfide group. Examples of such aromatic diamines include 4,4′-oxydianiline (hereinafter also referred to as “ODA”), 3,3′-oxydianiline, 3,4′-oxydianiline, 4,4. '-Diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyldiethylsilane 4,4′-diaminodiphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diamino Benzene (p-phenylenediamine), bis {4- (4-aminophenoxy) pheny } 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 Mention of '-diaminobenzophenone, 4,4'-diaminobenzophenone, 2,2-bis (4- (4-aminophenoxy) phenyl) propane (hereinafter also referred to as “BAPP”), and the like Can do.

  Similarly, the “aromatic tetracarboxylic dianhydride having a flexible group” refers to an aromatic tetracarboxylic dianhydride having a flexible structure such as an ether group, a sulfone group, a ketone group, and a sulfide group.

  In addition, a filler can be added to the polyamic acid solution for the purpose of improving various properties of the film such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. The filler used in the present invention is not particularly limited, and any filler can be used. For example, silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica can be suitably used.

  The particle size of the filler used in the present invention is not particularly limited because it is determined by the film characteristics to be modified and the type of filler to be added. However, if the particle size is too small, a modification effect appears. There is a tendency to become difficult. On the other hand, if the particle size is too large, the film may greatly impair the surface properties, or the mechanical properties of the film may be greatly deteriorated. Therefore, the average particle size is preferably 0.05 to 100 μm, more preferably 0.1 to 75 μm, further preferably 0.1 to 50 μm, and 0.1 to 25 μm. Is particularly preferred. If it exists in the said range, a big modification effect will be acquired, and a film will not impair surface property greatly, or the mechanical characteristic of a film will not fall large.

  Further, the number of added parts of the filler is not particularly limited because it is determined by the film characteristics to be modified, the filler particle diameter, and the like. Generally, if the number of added parts of the filler is too small, the modification by the filler There is a tendency that the effect becomes difficult to appear. Conversely, if the number of fillers added is too large, the mechanical properties of the film may be greatly impaired. Therefore, it is preferable to add in the range where the modification effect by the filler appears and the mechanical properties of the film are not impaired. Specifically, the number of added parts of the filler is preferably 0.01 to 100 parts by weight, more preferably 0.01 to 90 parts by weight, with respect to 100 parts by weight of polyimide. More preferably, it is -80 weight part. If it is in the said range, the modification effect by a filler will appear and the mechanical characteristic of a film will not be impaired.

The method for adding the filler is not particularly limited, and specific examples include the following methods.
(I) A method of adding to the polymerization reaction solution before or during the polymerization.
(Ii) A method in which the filler is kneaded using three rolls after completion of the polymerization.
(Iii) A method of preparing a dispersion containing a filler and mixing it with a polyamic acid solution.
(Iv) A method of dispersing by a bead mill or the like.

  Among these methods, (iii) a method of mixing a dispersion containing a filler with a polyamic acid solution is preferable, and a method of mixing a dispersion containing a filler with a polyamic acid solution immediately before film formation is particularly preferable. If this method is adopted, the filler can be mixed immediately before forming the film, so that the contamination of the film production line by the filler can be minimized.

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

  Moreover, when adding the said filler in order to improve the slidability of a film, when the particle diameter of the said filler is too small, there exists a tendency for the effect of slidability improvement to become difficult to express. Conversely, if the particle size is too large, it tends to be difficult to create a high-definition wiring pattern. Therefore, it is preferable to add a filler as long as such a problem does not occur. Specifically, the thickness is preferably 0.1 to 10 μm, and more preferably 0.1 to 5 μm. Within the above range, the effect of improving the slidability is exhibited, and a high-definition wiring pattern can be created.

Furthermore, when adding the said filler in order to improve the slidability of a film, the dispersion state of a filler is also important. More specifically, if a large amount of filler aggregates of 20 μm or more are contained, it may cause repellency when the adhesive is applied, or the adhesive area may be reduced when a high-definition wiring pattern is created. There is a tendency for reliability to drop. Therefore, it is preferable to lower the filler aggregate of 20 μm or more to such an extent that such a problem does not occur. Specifically, the aggregate of fillers of 20 μm or more is preferably 50 pieces / m ² or less, and more preferably 40 pieces / m ² or less. If it is in the above-mentioned range, it will not cause repellency when the adhesive is applied, and the adhesion area will not decrease when a high-definition wiring pattern is created.

(B) Film-forming dope casting step In the film-forming dope casting step, first, a film-forming dope containing a polyamic acid solution is prepared. At this time, the film-forming dope may be prepared by using the polyamic acid solution as it is as a film-forming dope. However, the polyamic acid solution may be mixed with other additives to obtain a film-forming dope. For example, in the gel film forming step described later, when a method of imidizing polyamic acid is used, a curing agent containing a dehydrating agent and an imidization catalyst may be added to the film forming dope. Although the said dehydrating agent is not specifically limited, For example, acid anhydrides, such as acetic anhydride, can be mentioned as a representative example. Further, the imidation catalyst is not particularly limited, but tertiary amines such as isoquinoline, β-picoline, and pyridine can be given as representative examples.

  The method for mixing the dehydrating agent and the imidization catalyst into the polyamic acid solution is not particularly limited. For example, a film-forming dope can be obtained by mixing a dehydrating agent and an imidization catalyst into the polyamic acid solution at a low temperature.

  The addition amount of the dehydrating agent and the imidization catalyst is not particularly limited. However, if the addition amount of the dehydrating agent and the imidization catalyst is too small, the chemical imidization occurs completely, and the firing process described later is performed. The film may break along the way or the mechanical strength may decrease. On the other hand, when there are too many addition amounts of the said dehydrating agent and an imidation catalyst, the progress of imidation will become quick too much and it may become difficult to cast into a film form in the film forming dope casting process.

  Therefore, the addition amount of the dehydrating agent is preferably in the range of 0.5 to 5 mol and in the range of 1.0 to 4 mol with respect to 1 mol of the amic acid unit in the polyamic acid. Is more preferable. Moreover, it is preferable that the addition amount of the said imidation catalyst exists in the range of 0.05-3 mol with respect to 1 mol of amic acid units in a polyamic acid, and exists in the range of 0.2-2 mol. It is more preferable. By making the addition amount of the dehydrating agent and the imidization catalyst within the above range, the film forming dope containing the polyamic acid solution can be easily cast into a film shape, and the film is broken during the baking process. And mechanical strength can be prevented from decreasing.

  The polyamic acid solution may be a polyamic acid solution produced in the polyamic acid production process, a separately prepared polyamic acid solution equivalent to the polyamic acid solution described above, or a commercially available product.

  Next, in the film forming dope casting step, the film forming dope is cast on a support in the form of a film. The said support body is not specifically limited, For example, a glass plate, aluminum foil, an endless stainless steel belt, or a stainless steel drum can be mentioned. Moreover, the method of casting the said film forming dope in a film form is not specifically limited, A conventionally well-known method can be used.

(C) Gel film formation process In the said gel film formation process, the film forming dope casted into the film form on the said support body is first heated on a support body. Although the said heating temperature is not specifically limited, It is preferable that it is a temperature range of 80 to 200 degreeC, and it is further more preferable that it is a temperature range of 100 to 180 degreeC. When heated in the above temperature range, the dehydrating agent and the imidization catalyst are activated, and the film forming dope can be partially cured and / or dried. A polyamic acid film (hereinafter also referred to as “gel film”) can be obtained by peeling the partially cured and / or dried film from the support.

  The gel film is in an intermediate stage of curing from polyamic acid to polyimide, has a self-supporting property, and the volatile content of the gel film is preferably in the range of 5 to 500% by weight, More preferably within the range of 200% by weight, even more preferably within the range of 5 to 150% by weight. By using a gel film having a volatile content within this range, problems such as film breakage during baking (the baking process described later), film color unevenness due to drying unevenness, and characteristic variations can be avoided.

The volatile content of the gel film is expressed by the following formula (1)
(X−Y) × 100 / Y (1)
(Wherein X represents the weight of the gel film and Y represents the weight after heating the gel film at 450 ° C. for 20 minutes).

  The film forming conditions and heating conditions should be appropriately changed depending on the type of polyamic acid, the thickness of the film, and the like, and are not limited to the above examples.

(D) Firing step In the firing step, the gel film is dried while fixing the end of the gel film and avoiding shrinkage of the film during curing, and water, residual solvent, residual conversion agent and imidization are performed. Remove the catalyst. Thereby, the remaining amic acid is completely imidized, and a polyimide film is obtained.

  In the baking step, the gel film is heated and dried. If the final baking temperature is too high or too low, various properties of the film may be adversely affected. Specifically, if the final baking temperature is too high, thermal degradation of the film may occur. Conversely, if the final baking temperature is too low, the desired effect may not be exhibited in the resulting film. Therefore, it is preferable to finally heat the gel film at a temperature of 400 to 650 ° C. for 5 to 400 seconds.

  Moreover, it is necessary to change various suitable baking states also with a composition, manufacturing method, etc. of a polyimide. Therefore, it is preferable to select an appropriate firing state as appropriate according to the composition and manufacturing method of the polyimide.

  Moreover, in order to relieve the internal stress remaining in the film, the gel film can be heat-treated under the necessary minimum tension when the film is conveyed. This heat treatment may be performed in the baking step, or may be provided separately.

  The heating conditions for the heat treatment are not particularly limited, and may be appropriately changed according to the characteristics of the film and the apparatus used. For example, the heating temperature is generally preferably 200 ° C. or higher and 500 ° C. or lower, more preferably 250 ° C. or higher and 500 ° C. or lower, and further preferably 300 ° C. or higher and 450 ° C. or lower. The heating time is preferably 1 to 300 seconds, more preferably 2 to 250 seconds, and further preferably 5 to 200 seconds. By performing the heat treatment at the heating temperature and the heating time, the internal stress can be relaxed. Therefore, the heat shrinkage rate at 200 ° C. can be reduced.

  Further, the film can be stretched before and after fixing the gel film to such an extent that the anisotropy of the film is not deteriorated. At this time, if the volatile content of the gel film is too small, the film tends to be difficult to stretch. On the other hand, when the volatile content of the gel film is too large, the self-supporting property of the film is poor and the stretching operation itself tends to be difficult. Therefore, the volatile content of the gel film is preferably 100 to 500% by weight, and more preferably 150 to 500% by weight. If it is in the said range, the self-support property of a gel film is favorable, it is easy to perform extending | stretching operation, and the said gel film can be extended | stretched suitably.

  The method for stretching the film is not particularly limited, and any conventionally known method may be used. For example, a method using a differential roll, a method of widening the fixing interval of the tenter, and the like can be mentioned.

<III. Adhesive film>
The adhesive film according to the present invention is an adhesive film in which an adhesive layer is provided on at least one surface (that is, one surface or both surfaces) of the polyimide film according to the present invention, and the polyimide film is used as a core film. According to the said structure, since the polyimide film concerning this invention is used as a core layer, it can be set as the adhesive film with a low elasticity modulus and excellent in dimensional stability.

  The adhesive layer in the said adhesive film is not specifically limited, A conventionally well-known adhesive layer can be used. For example, the adhesive layer can be formed by a conventionally known adhesive such as acrylic, epoxy, or polyimide.

  Moreover, it does not specifically limit about the manufacturing method of the adhesive film concerning this invention, A conventionally well-known method can be used. For example, (1) a method in which an adhesive layer is formed on a polyimide film to be a base film (core layer), or (2) a method in which the adhesive layer is formed into a sheet and bonded to the base film is suitable. Can be used.

  In the production of the adhesive film according to the present invention, the surface of the core film is subjected to various surface treatments such as corona treatment, plasma treatment, and coupling treatment before or after providing the adhesive layer, if necessary. May be applied.

<IV. Flexible metal-clad laminate>
The flexible metal-clad laminate according to the present invention is obtained by bonding the adhesive film according to the present invention and a metal foil. The flexible metal-clad laminate can also be obtained by attaching and bonding a sheet-shaped adhesive layer between a metal foil and a polyimide film. The adhesive layer in this case is not particularly limited. Specifically, the adhesive layer used for the adhesive film can be used similarly.

  In the flexible metal-clad laminate, the polyimide film is an insulating layer, and the metal foil is a conductive layer. That is, the flexible metal-clad laminate has a structure in which a metal foil as a conductive layer is laminated on a polyimide film of the present invention as an insulating layer.

  The metal foil is not particularly limited, and any metal foil can be used. For example, a copper foil, a stainless steel foil, a nickel foil, an aluminum foil, and a foil made of an alloy of these metals can be suitably used. Moreover, in general flexible metal-clad laminates, copper foil such as rolled copper foil and electrolytic copper foil is frequently used, but it can also be preferably used in the present invention.

  Moreover, the said metal foil can select what has various characteristics, such as surface treatment and surface roughness, according to the objective. Furthermore, a rust preventive layer, a heat resistant layer or an adhesive layer may be applied to the surface of the metal foil.

  The thickness of the metal foil is not particularly limited, and may be any thickness that can exhibit a sufficient function depending on the application.

  The flexible metal-clad laminate according to the present invention is as described above. However, as a more specific embodiment, when the metal foil is a copper foil, that is, a flexible copper-clad laminate (hereinafter also referred to as “FCCL”). ) Will be described below. The dimensional change rate of the flexible copper clad laminate according to the present invention is preferably ± 0.1% or less, and more preferably ± 0.05% or less. Further, the number of flexing of the flexible copper clad laminate is preferably 10,000 times or more, and more preferably 12000 times or more. In addition, also when the said metal foil is metal foils other than copper foil, it is preferable that the dimensional change rate and the frequency | count of bending of the said flexible metal-clad laminate are the same as those of the said flexible copper-clad laminate.

  Moreover, it does not specifically limit about the manufacturing method of the flexible metal clad laminated board concerning this invention, Any conventionally well-known method may be used as a manufacturing method of a flexible metal clad laminated board.

<V. Flexible printed wiring board>
A flexible printed wiring board (hereinafter also referred to as “FPC”) according to the present invention is manufactured using the above-described flexible metal-clad laminate. Specifically, the metal foil of the flexible metal-clad laminate is etched to form a desired pattern wiring. Next, in order to protect the said pattern wiring, the FPC of this invention can be obtained by laminating | stacking a coverlay film (insulation protection film) on the copper foil surface which is a conductor layer.

  As the coverlay film, it is preferable from the viewpoint of flexibility that the same film as that used for the insulating layer is used, or a film having a lower elastic modulus than the film of the insulating layer is used. Further, the thickness of the coverlay film is not particularly limited, but is preferably equal to or less than the insulating layer from the viewpoint of curling prevention and flexibility.

  Moreover, the method of laminating the coverlay film on the flexible metal-clad laminate is not particularly limited, and a conventionally known method can be used. For example, lamination can be performed using a vacuum laminator.

  The number of flexures of the FPC thus obtained is preferably 10,000 times or more, and more preferably 12000 times or more.

  Since the FPC according to the present invention has the above-described configuration, the FPC has high flexibility. Therefore, it can be suitably used as a flexible printed wiring board on which various miniaturized and densified components are mounted.

<VI. Use of the present invention>
As described above, the polyimide film according to the present invention is a polyimide film having a low elastic modulus and a small linear expansion coefficient. In other words, the film according to the present invention is a polyimide film having high flexibility and excellent dimensional stability.

  Therefore, the present invention can be used for various applications including flexible printed wiring that requires high flexibility.

  The present invention is not limited to the configurations described above, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  The present invention will be described more specifically based on 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 elastic modulus and linear expansion coefficient of the polyimide film, the dimensional change rate of FCCL, and the bending characteristics were evaluated as follows.

[Elastic modulus]
Elastic modulus was measured according to ASTM D-882.

[Linear expansion coefficient of polyimide film]
The linear expansion coefficient at 100 to 200 ° C. was measured by using a TMA120C manufactured by Seiko Electronics Co., Ltd. (sample size: 3 mm width, 10 mm length), and once heated to 10 to 400 ° C. at 10 ° C./min with a load of 3 g. Then, it was cooled to 10 ° C., further heated at 10 ° C./min, and calculated as an average value from the coefficient of thermal expansion at 100 ° C. and 200 ° C. during the second temperature increase.

[Dimensional change rate of FCCL]
The FCCL was cut into 20 × 20 cm, a reference hole having a diameter of 1 mm was drilled at four corners at intervals of 15 cm, and initial dimensions were measured. Thereafter, the copper foil was completely removed by etching and conditioned at 23 ° C. and 55% RH for 24 hours. After humidity control, the distance between the reference holes was measured and used as the dimension after etching.

  This sheet was further heat-treated at 150 ° C. for 30 minutes. Thereafter, the humidity was adjusted at 23 ° C. and 55% RH for 24 hours. After humidity control, the distance between the reference holes was measured and taken as the dimension after heating. The change rate of the distance between the holes was defined as the dimensional change rate during heating.

  In addition, the said dimensional change rate was measured about both MD direction and TD direction.

(Bending characteristics)
Using a MIT bending tester (MIT-D, manufactured by Toyo Seiki Co., Ltd.), the bending characteristics of the sample were measured at R = 0.38 mm, a tension of 750 gf, a bending angle of 135 °, and a speed of 175 times / minute. The sample was prepared according to JIS C5016.

[Synthesis Example 1: Synthesis of nylon-modified epoxy adhesive]
50 parts by weight of polyamide resin (Platabond M1276 manufactured by Nippon Rilsan Co., Ltd.), 30 parts by weight of bisphenol A type epoxy resin (Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.), 10 parts by weight of cresol novolac type epoxy resin, toluene / isopropyl alcohol 1/1 mixed An adhesive solution in which 150 parts by weight of the solution was mixed with 45 parts by weight of diaminodiphenylsulfone / dicyandiamide 4/1 20% methyl cellosolve solution was prepared.

  Next, an adhesive was applied onto a 25 μm thick PET film so as to be 11 μm after drying, and dried at 120 ° C. for 2 minutes to obtain a B-stage adhesive with a support.

[Example 1]
566 g of N, N-dimethylformamide (hereinafter also referred to as “DMF”) cooled to 10 ° C., 27.27 g of 2,2-bis (4- (4-aminophenoxyphenyl) propane (BAPP) and 4,4′- 26.60 g of oxydianiline (4,4′ODA) was dissolved, and 57.95 g of pyromellitic dianhydride (PMDA) was added and dissolved therein, followed by paraphenylenediamine (p-PDA). 20% by weight DMF solution was gradually added, and the addition was stopped when the viscosity reached about 2000 poise (200 Pa · s), and the mixture was stirred for 1 hour to rotate at a solid content concentration of about 17% by weight at 23 ° C. A polyamic acid solution having a viscosity of 2500 poise (250 Pa · s) was obtained (BAPP / ODA / p-PDA / PMDA = 25/50/25/100 (molar ratio)).
An imidizing agent prepared with isoquinoline / acetic anhydride / DMF = 6.74 / 19.03 / 44.23 (weight ratio) was added to 100 g of this polyamic acid solution at 0 ° C., and the mixture was quickly mixed. Foaming dope was obtained. This film-forming dope was cast and applied onto an aluminum foil using a comma coater. After heating this resin film at 130 ° C. × 100 seconds, the self-supporting gel film is peeled off from the aluminum foil (volatile content 47% by weight) and fixed to a metal frame, 300 ° C. × 20 seconds, 450 ° C. × It was dried and imidized at 500 ° C. for 10 seconds for 20 seconds to obtain a polyimide film having a thickness of 12.5 μm. For drying and imidization, three hot air circulation ovens preheated to each temperature were used. The properties of the polyimide film thus obtained are shown in Table 1.

After this film was treated with a corona density of 200 W · min / m ² , the B-stage adhesive-attached PET film obtained in Synthesis Example 1 was superposed and pressure-bonded at 90 ° C. with a pressure of 1 kg / cm ² .

  Thereafter, the PET film was peeled off, and bonded with a 12 μm rolled copper foil at 120 ° C. under a pressure of 2 kg / cm by a roll laminating method. The copper-clad product is heated at 60 ° C. for 3 hours, 80 ° C. for 3 hours, 120 ° C. for 3 hours, 140 ° C. for 3 hours, and 160 ° C. for 4 hours, and then gradually cooled to cure the adhesive. And a flexible copper clad laminate (FCCL) was obtained. And the dimensional change rate was evaluated about the said FCCL.

  After forming a pattern on this FCCL according to JIS C5016, a cover lay film obtained by applying an adhesive solution to a 12.5 μm polyimide film (Apical 12.5AH manufactured by Kaneka Corp.) was used with a vacuum laminator. FPC was produced by pressing at 160 ° C. and 4 MPa for 40 minutes, and bending properties were evaluated. The results are shown in Table 1.

[Examples 2 and 3]
A polyimide film, FCCL, and FPC were obtained in the same manner as in Example 1 except that the monomer addition order and the addition mole fraction were changed as shown in Table 1. These characteristics are shown in Table 1.

[Comparative Examples 1-3]
FCCL and FPC were prepared in the same manner as in Example 1 using commercially available polyimide films (Apical AH 12.5 μm (manufactured by Kaneka Corporation) and Kapton V12.5 μm (manufactured by Toray DuPont)). Flexural properties were evaluated. The results are shown in Table 1.

  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, the polyimide film of the present invention has a low elastic modulus and excellent dimensional stability. Therefore, not only can it be suitably used for FPCs and the like that require foldability, bending resistance and low stiffness (low power consumption), but also in fields related to the manufacture of electronic components using laminates made of polyimide films. Can be widely used. Furthermore, this invention can be applied also to the field | area which manufactures the various resin molded products represented by the laminated body which consists of a polyimide adhesive film.

Claims (11)

  A polyimide film formed by imidizing a polyamic acid obtained by polymerizing an acid dianhydride component and a diamine component, wherein the diamine component is at least 2,2-bis (4- (4-aminophenoxy) phenyl) A polyimide film comprising propane, having an elastic modulus of less than 4 GPa, and an average linear expansion coefficient at 100 to 200 ° C. of 15 to 30 ppm.   The polyimide film according to claim 1, wherein an average linear expansion coefficient at 100 to 200 ° C is 18 to 25 ppm.   The polyimide film according to claim 1 or 2, wherein an elastic modulus is 3.5 GPa or less.   Film thickness is 7-28 micrometers, The polyimide film of any one of Claims 1-3 characterized by the above-mentioned.   Film thickness is 10-14 micrometers, The polyimide film of any one of Claims 1-4 characterized by the above-mentioned.   The acid dianhydride component includes at least pyromellitic dianhydride, and the diamine component includes at least 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 4,4′-oxy. Dianiline and p-phenylenediamine are contained, The polyimide film of any one of Claims 1-5 characterized by the above-mentioned.   The diamine component includes all of 2,2-bis (4- (4-aminophenoxy) phenyl) propane, 4,4′-oxydianiline and p-phenylenediamine, and all contained in the diamine component. 20 to 50 mol% of 2,2-bis (4- (4-aminophenoxy) phenyl) propane and 20 mol% within a range not exceeding 100 mol%, assuming that the total number of moles of diamines is 100 mol%, The polyimide film according to any one of claims 1 to 6, comprising -50 mol% of 4,4'-oxydianiline and 15-35 mol% of p-phenylenediamine.   The polyimide film according to claim 1, wherein the polyimide film is used as a material for a flexible metal-clad laminate.   An adhesive film comprising an adhesive layer on at least one side of the polyimide film according to any one of claims 1 to 8.   A flexible metal-clad laminate comprising a metal foil laminated to the polyimide film according to any one of claims 1 to 8 or the adhesive film according to claim 9.   A flexible printed wiring board manufactured using the flexible metal-clad laminate according to claim 10.