JP2005053222A - Multilayer polyimide film, method for producing the same, and flexible circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film laminate having a high peel strength when it is pressure-bonded to a metal foil via an adhesive, a method for easily producing the same, and a circuit board using the polyimide film laminate.
A polyamic acid synthesized from an aromatic diamine containing 1 to 100 mol% of carboxy-4,4'-diaminobiphenyl and an aromatic tetracarboxylic dianhydride or a derivative thereof is converted into a polyamic acid. The polyimide film laminated body obtained by apply | coating to the one or both surfaces of the outermost layer of an acid or a polyimide film, and imidating this thermally or chemically. This polyimide film laminate has a water absorption rate of 3.0 wt% or less, has little dimensional change, and has a high peel strength of 10 N / cm or more when it is pressure-bonded via a metal foil and an adhesive.
[Selection figure] None

Description

  The present invention relates to a polyimide film laminate, a method for producing the same, and a flexible circuit board. More specifically, when bonded to a metal foil via an adhesive, a polyimide film laminate capable of obtaining extremely high peel strength without increasing the water absorption rate, a method for producing the laminate film, and the use thereof The present invention relates to a flexible circuit board.

  The polyimide film is widely used for applications such as a base film for a flexible circuit board laminated with a metal foil such as a copper foil because of its excellent insulation and heat resistance.

  However, since the polyimide film has insufficient peel strength with respect to the adhesive, it may peel off when used for a long period of time, resulting in a problem of lack of long-term reliability. In order to remedy this drawback, various electrical, physical or chemical treatments have been attempted on polyimide films. However, these treatments have a problem that a lot of reagents, time and labor are required for the treatment process. It was.

  As a method for modifying the adhesive force of the polyimide film, for example, a method of plasma-treating the film surface (see, for example, Patent Document 1) is known. In this case, the number of steps is achieved by performing plasma treatment. There was a problem that increased.

  A flexible metal foil-clad laminate using a polyimide film coated with a silane coupling agent (see, for example, Patent Document 2) is also known. In this case, a step of applying a silane coupling agent In addition to an increase in the number, the silane coupling agent is decomposed by heat treatment when the ring is closed from polyamic acid to polyimide, so that there is a problem that the adhesive force is reduced.

  Furthermore, a polyimide film containing a titanium compound and excellent in adhesiveness (see, for example, Patent Document 3) is also known, but has the disadvantage that the addition of the titanium compound causes polymer gelation and inferior film-forming properties. It was.

Furthermore, a thermoplastic polyimide excellent in adhesiveness (see, for example, Patent Document 4) is also known, but in this case, the polyimide film substrate sinks due to heat during soldering due to thermoplasticity. Had drawbacks.
JP-A-8-012779 JP 7-137196 A JP-A-11-071474 JP 2003-27014 A

  The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue.

  Therefore, a first object of the present invention is to obtain a polyimide film that can obtain extremely high peel strength without increasing the water absorption rate when bonded to a metal foil via an adhesive.

  In addition, the second object of the present invention is that the treatment for improving the peel strength of the polyimide film does not require many reagents, time and labor, and is suitable for mass production, low cost and high quality. It is to establish a method for producing peel strength polyimide.

  In order to achieve the above object, a polyimide film laminate of the present invention is a laminated polyimide film obtained by laminating two or more polyimide films, and at least one surface layer polyimide has the following general formula (I The polyamic acid synthesized from an aromatic diamine containing 1 to 100 mol% of carboxy-4,4′-diaminobiphenyl represented by formula (1) and an aromatic tetracarboxylic dianhydride or a derivative thereof is heated. It consists of the polyimide obtained by making it imidize chemically or chemically.

  Moreover, the polyimide film laminate of the present invention comprises an aromatic diamine containing the above carboxy-4,4′-diaminobiphenyl in a proportion of 1 to 100 mol%, and an aromatic tetracarboxylic dianhydride or a derivative thereof. The polyamic acid to be synthesized is obtained by applying to one or both sides of a polyimide fill or polyamic acid film and imidizing it thermally or chemically.

In the polyimide film laminate of the present invention,
The carboxy-4,4′-diaminobiphenyl is represented by the following general formula (II): 2,6′-dicarboxy-4,4′-diaminobiphenyl and / or 3,3′-dicarboxy-4, It is 4′-diaminobiphenyl.

  The laminated polyimide of at least one surface layer has a structural unit represented by the following general formulas (III) and (IV).

  (However, R1 in the formula is one of the groups represented by the following general formula,

R2 in the formula is any of the groups represented by the following general formula.

Moreover, the molar ratio of X: Y in the formula is 1:99 to 100: 0. )
When thermocompression bonding with a copper foil via an adhesive, the peel strength measured by the following method is 15 N / cm or more,
(Peel strength: using Piralux R (registered trademark of DuPont) LF-0100, which is an adhesive film, a polyimide film and a copper foil (thickness 35 μm, BAC-13-T manufactured by Japan Energy Co., Ltd.) at 180 ° C. (The peel strength is the strength obtained by thermocompression bonding at 4.4 × 10 7 Pa for 60 minutes and the resulting laminate is peeled off by the method described in JIS C5016-1994.)
The water absorption measured by the following method is 3.0 wt% or less (water absorption: after immersing the laminated polyimide film in distilled water for 48 hours, wiping the surface water, and from room temperature to 200 ° C. by heat weight loss analysis. (When heated at a rate of temperature increase of 10 ° C./min, weight loss from 50 to 200 ° C. is defined as water absorption.)
Are mentioned as preferable conditions.

  Moreover, the manufacturing method of the polyimide film laminated body of this invention is the aromatic diamine which contains the said carboxy-4,4'- diaminobiphenyl in the ratio of 1-100 mol%, aromatic tetracarboxylic dianhydride, or its A polyamic acid synthesized from a derivative is applied to one or both sides of a polyimide film or a polyamic acid film, which is thermally or chemically imidized.

  Furthermore, the flexible circuit board of the present invention is characterized in that a metal foil is pressure-bonded to the polyimide film laminate through an adhesive.

 The polyimide film laminate of the present invention has a high peel strength of 10 N / cm or more when bonded to a metal foil via an adhesive, and a water absorption of 3.0 wt% or less. When used as a flexible circuit board, it is possible to maintain the peel strength without dimensional change over a long period of time, and to provide a flexible circuit board with excellent long-term reliability.

  Hereinafter, the present invention will be described in detail.

  First, the definitions of peel strength and water absorption in the present invention will be described.

  The peel strength as used in the present invention refers to a polyimide film and a copper foil (thickness 35 μm, BAC-13-T manufactured by Japan Energy Co., Ltd.) using Pyralax R (registered trademark of DuPont) LF-0100 which is an adhesive film. Is a strength obtained by peeling the laminate obtained by thermocompression bonding at 180 ° C. and 450 kg / cm 2 for 60 minutes by the method described in JIS C5016-1994.

  The peel strength can be further improved by performing electrical treatment such as plasma treatment and corona treatment, physical treatment, and chemical treatment as necessary. However, in this invention, the value measured by the said method in the state which does not perform said process at all is defined as peeling strength. This value accurately reproduces the peel strength inherent to the polyimide film.

  The peel strength is preferably 10 N / cm or more. On the other hand, a peel strength of 10 N / cm or less is not preferable because the metal foil layer may be peeled off when used as a flexible circuit board.

  It is an essential condition that the aromatic diamine used in the polyimide layer on one or both sides of the outermost layer of the polyimide film laminate of the present invention contains carboxy-4,4'-diaminobiphenyl. This is because when the aromatic diamine is not contained, the obtained polyimide film does not exhibit the intended peel strength.

   The addition amount of carboxy-4,4′-diaminobiphenyl used for the polyimide layer on one or both sides of the outermost layer of the polyimide film laminate of the present invention is in the range of 1 to 100 mol%, preferably 5 to 100 mol%. It is important to. That is, when the addition amount is less than the above range, the intended peel strength cannot be obtained.

  In the present invention, the water absorption rate refers to a temperature increase rate of 10 ° C./min from room temperature to 200 ° C. by weight loss analysis after immersing the polyimide film laminate in distilled water for 48 hours and then wiping the surface moisture. When heated, weight loss from 50 to 200 ° C. is defined as water absorption.

  The smaller the water absorption rate, the better. On the other hand, when the water absorption rate is larger than 3.0 wt%, the polyimide film changes its dimensions due to water absorption, which may cause warpage during use as a flexible circuit board.

  Next, the components of the polyimide film of the present invention will be described.

  The polyimide layer on one or both sides of the outermost layer in the polyimide film laminate of the present invention has a polyamic acid composed of an aromatic tetracarboxylic acid and an aromatic diamine as a precursor, and is represented by the following formulas (III) and (IV): It is composed of the repeating units shown.

  (However, R1 in the formula is one of the groups represented by the following general formula,

R2 in the formula is any of the groups represented by the following general formula.

Moreover, the molar ratio of X: Y in the formula is 1:99 to 100: 0. )
Specific examples of aromatic tetracarboxylic acids that form polyamic acid as a polyimide precursor in this polyimide film laminate include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ', 3,4'-biphenyltetracarboxylic acid, 3,3', 4,4'-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-di Carboxyphenyl) ether, pyridine-2,3,5,6-tetracarboxylic acid and amide-forming derivatives thereof. In the production of polyamic acid, acid anhydrides of these aromatic tetracarboxylic acids are preferably used.

  Specific examples of aromatic diamines other than carboxy-4,4′-diaminobiphenyl which also form polyamic acid as a precursor include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4 ′. -Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene 3,3′-dimethoxybenzidine, 1,4-bis (3methyl-5aminophenyl) benzene and amide-forming derivatives thereof.

  In addition, the number of substituents of the carboxyl group of the carboxy-4,4′-diaminobiphenyl may be polysubstituted. Further, the substitution position of the carboxyl group is an arbitrary position, and specific examples thereof include 2,6′-dicarboxy-4,4′-diaminobiphenyl, 3,3′-dicarboxy-4,4′-diaminobiphenyl. And 2,3′-dicarboxy-4,4′-diaminobiphenyl and the like. However, from the viewpoint of simplicity in terms of synthesis, 2,6′-dicarboxy-4,4′-diaminobiphenyl and / or 3,3′-dicarboxy-4,4′-diaminobiphenyl are preferable. It is a condition.

  In the present invention, specific examples of the organic solvent used for forming the polyamic acid solution that is a precursor of the polyimide film include, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, Formamide solvents such as N, N-diethylformamide, acetamide solvents such as N, N-dimethylacetamide, N, N-diethylacetamide, pyrrolidone systems such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone Examples include solvents, phenolic solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, and catechol, and aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone. These alone Although it is desirable to use as a mixture, further xylene, the use of aromatic hydrocarbons such as toluene are also possible. However, from the viewpoint of solubility, it is preferable that the organic solvent for polymerizing 2,6'-dicarboxy-4,4'-diaminobiphenyl is N-methyl-2-pyrrolidone.

  The organic solvent solution (polyamic acid solution) of the polyamic acid used in the present invention preferably contains 5 to 40% by weight, more preferably 10 to 30% by weight as the solid content. In addition, the viscosity is preferably in the range of 10 to 2000 Pa · s, more preferably in the range of 100 to 1000 Pa · s as measured by a Brookfield viscometer, for stable liquid feeding. Moreover, the polyamic acid in the organic solvent solution may be partially imidized.

  In the present invention, the aromatic tetracarboxylic acids and aromatic diamines constituting the polyamic acid are polymerized at a ratio in which the respective mole numbers are approximately equal, and one of them is within a range of 10 mol% with respect to the other. It is preferably blended in excess, and more preferably blended excessively with respect to the other within the range of 5 mol%.

  The polymerization reaction is preferably allowed to proceed continuously for 10 minutes to 30 hours in the temperature range of 0 to 80 ° C. while stirring and / or mixing in an organic solvent. You can move up and down. Although there is no restriction | limiting in particular in the addition order of both reactants, It is preferable to add aromatic tetracarboxylic acid in the solution of aromatic diamines. Vacuum degassing during the polymerization reaction is an effective method for producing a high-quality organic solvent solution of polyamic acid.

  Further, the polymerization reaction may be controlled by adding a small amount of an end-capping agent to the aromatic diamine before the polymerization reaction.

  Next, the manufacturing method of the polyimide film laminated body of this invention is demonstrated.

  In the present invention, an aromatic diamine containing carboxy-4,4′-diaminobiphenyl having a viscosity at 25 ° C. of about 10 Pa · s or more and 500 Pa · s or less as measured with a rotational viscometer, and an aromatic tetracarboxylic dianhydride A polyamic acid solution synthesized from the product or a derivative thereof is prepared. As a reaction procedure for obtaining a polyamic acid solution in the present invention, an aromatic diamine is added and dissolved in an organic polar solvent, and then an aromatic tetracarboxylic dianhydride is added. Any method such as a method of adding an aromatic diamine after adding an aromatic tetracarboxylic dianhydride is possible. At this time, the addition amount of the anhydride and the aromatic diamine to the aromatic tetracarboxylic acid can be substantially equimolar.

  As a method for producing a polyimide film laminate, there is a co-extrusion method in which lamination is performed during extrusion inside a die from a lamination block, or a method in which lamination is performed after extrusion. Specifically, a polyamic acid synthesized from an aromatic diamine containing carboxy-4,4′-diaminobiphenyl and an aromatic tetracarboxylic dianhydride or a derivative thereof, a polyamic acid film containing no polyamic acid or A method of laminating on a polyimide film is preferred.

  As a method of applying a polyamic acid synthesized from an aromatic diamine containing carboxy-4,4′-diaminobiphenyl and an aromatic tetracarboxylic dianhydride or a derivative thereof to a polyamic acid film or a polyimide film. "All about coating" (edited by Processing Technology Research Group, published on December 10, 1999) or "Coating Technology Overview for Plastics" (edited by the Material Coating Research Committee Editorial Committee for Plastic Coating Technology, pp. 299-312, ( Roll Coater, Gravure Coater, Knife Coater, Blade Coater, Knife Coater, Air Doctor Coater, Screen Coating, Spray Coating, as described in Industrial Technology Service Center Co., Ltd. (August 3, 1989, first edition) , Vacuum coating, spin coater, There are impregnation coating.

  Subsequently, it is preferable to obtain a polyimide film laminated body by fixing the edge part of the obtained laminated | multilayer film, and performing heat processing at the temperature of 200 to 400 degreeC.

  When the laminated polyamic acid layer is imidized and cyclized into a polyimide film laminate, a chemical cyclization method in which dehydration is performed using a dehydrating agent and a catalyst, a thermal cyclization method in which thermal dehydration is performed, or both, Any of the ring closure methods used in combination may be used.

  Examples of the dehydrating agent used in the chemical ring closure method include aliphatic acid anhydrides such as acetic anhydride and acid anhydrides such as phthalic anhydride, and these are preferably used alone or in combination.

  Examples of the catalyst include heterocyclic tertiary amines such as pyridine, picoline and quinoline, aliphatic tertiary amines such as triethylamine, and tertiary amines such as N, N-dimethylaniline. These are preferably used alone or in combination.

  The thickness of the polyimide film laminate of the present invention is preferably 3 to 250 μm. That is, when the thickness is less than 3 μm, it is difficult to maintain the shape, and when the thickness exceeds 250 μm, the flexibility is insufficient, so that it is not suitable for a flexible circuit board.

  As the polyimide film, both stretched and unstretched films can be used. Further, it is possible to contain 10% by weight or less of an inorganic or organic additive for the purpose of improving processability.

  The polyimide film laminate thus obtained has a high peel strength of 10 N / cm or more without increasing water absorption when it is pressure-bonded to a metal foil through an adhesive, and is used as a base film for a flexible circuit board. In addition, it is possible to provide a flexible circuit board that maintains a high peel strength even in the long term and has excellent long-term reliability.

  The present invention will be described more specifically with reference to the following examples. In addition, the various specific values in an Example are the values measured with the following method.

[Peel strength]
By using Piralux R (registered trademark of DuPont) LF-0100 which is an adhesive film, a polyimide film and a copper foil (thickness 35 μm, BAC-13-T manufactured by Japan Energy Co., Ltd.) are heated at 180 ° C., 4.4. The strength at which the laminate obtained by thermocompression bonding at × 107 Pa for 60 minutes is peeled off by the method described in JIS C5016-1994 is defined as the peel strength.

[Water absorption rate]
After immersing the laminated polyimide film in distilled water for 48 hours, the moisture on the surface is wiped off, and when heated from room temperature to 200 ° C. at a heating rate of 10 ° C./min by heating weight loss analysis, the temperature is from 50 to 200 ° C. The weight loss is the water absorption rate.

[Example 1]
In a 300 ml separable flask equipped with a DC stirrer, 2.11 g (7.7 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 18.01 g (89 mmol) of 4,4′-diaminodiphenyl ether, 148.84 g of N, N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.52 g (94 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 11.19 g of an N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride was added dropwise over 30 minutes, followed by further stirring for 1 hour.

  100.00 g of the obtained polyamic acid was degassed for 5 minutes using a hybrid mixer manufactured by Keyence Corporation. A part of this polyamic acid mixture was taken on Kapton R200H (registered trademark of DuPont), and a uniform film was formed using an applicator. This was heated at 100 ° C. for 1 hour, then fixed to a metal frame, and heat-treated at 200 ° C. for 30 minutes, 300 ° C. for 30 minutes, and 400 ° C. for 5 minutes to obtain a polyimide film laminate. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Example 2]
In a 300 ml separable flask equipped with a DC stirrer, 3.91 g (14 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 16.45 g (81 mmol) of 4,4′-diaminodiphenyl ether, N, 148.96 g of N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, 20.25 g (93 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 11.06 g of a pyromellitic dianhydride N, N′-dimethylacetamide solution (6 wt%) was added dropwise over 30 minutes, followed by further stirring for 1 hour.

  The obtained polyamic acid was used in the same manner as in Example 1 to obtain a polyimide film laminate. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Example 3]
In a 300 ml separable flask equipped with a DC stirrer, 6.41 g (24 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 14.28 g (71 mmol) of 4,4′-diaminodiphenyl ether, N, 149.13 g of N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, 19.92 g (91 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 10.88 g of pyromellitic dianhydride in N, N′-dimethylacetamide (6 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

  The obtained polyamic acid was used in the same manner as in Example 1 to obtain a polyimide film laminate. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Example 4]
In a 300 ml separable flask equipped with a DC stirrer, 2.60 g (9.6 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 17.19 g (86 mmol) of 4,4′-diaminodiphenyl ether, N-methyl-2-pyrrolidone 150.78 g was added and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.19 g (93 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 9.65 g of a pyromellitic dianhydride N-methyl-2-pyrrolidone solution (5 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

  The obtained polyamic acid was used in the same manner as in Example 1 to obtain a polyimide film laminate. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Example 5]
In a 300 ml separable flask equipped with a DC stirrer, 5.11 g (19 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 15.02 g (75 mmol) of 4,4′-diaminodiphenyl ether, N— 149.78 g of methyl-2-pyrrolidone was added and stirred at room temperature under a nitrogen atmosphere. Further, 19.85 g (91 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 9.48 g of a pyromellitic dianhydride N-methyl-2-pyrrolidone solution (5 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

  The obtained polyamic acid was used in the same manner as in Example 1 to obtain a polyimide film laminate. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Comparative Example 1]
In a 500 ml separable flask equipped with a DC stirrer, 38.48 g (190 mmol) of 4,4′-diaminodiphenyl ether and 320.00 g of N, N′-dimethylacetamide were placed and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 40.27 g (185 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 22.01 g of a pyromellitic dianhydride N, N′-dimethylacetamide solution (6 wt%) was added dropwise over 30 minutes, followed by further stirring for 1 hour.

  It stirred for 5 minutes using 100.00 g of obtained polyamic acids and the hybrid mixer by Keyence Corporation. A part of this polyamic acid mixture was taken on a polyester film, and a uniform film was formed using an applicator. This was heated at 100 ° C. for 1 hour and peeled off from the polyester film to obtain a self-holding polyamic acid film. The obtained film was heat-treated at 200 ° C. for 30 minutes, 300 ° C. for 30 minutes, and 400 ° C. for 5 minutes to obtain a polyimide film. The results of measuring the peel strength of the obtained polyimide film are shown in Table 1.

[Comparative Example 2]
In a 300 ml separable flask equipped with a DC stirrer, 2.11 g (7.7 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 18.01 g (89 mmol) of 4,4′-diaminodiphenyl ether, 148.84 g of N, N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.52 g (94 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 11.19 g of an N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride was added dropwise over 30 minutes, followed by further stirring for 1 hour.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Comparative Example 1. The results of measuring the peel strength of the obtained polyimide film are shown in Table 1.

[Comparative Example 3]
In a 300 ml separable flask equipped with a DC stirrer, 3.91 g (14 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 16.45 g (81 mmol) of 4,4′-diaminodiphenyl ether, N, 148.96 g of N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, 20.25 g (93 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 11.06 g of a pyromellitic dianhydride N, N′-dimethylacetamide solution (6 wt%) was added dropwise over 30 minutes, followed by further stirring for 1 hour.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Comparative Example 1. The results of measuring the peel strength of the obtained polyimide film are shown in Table 1.

[Comparative Example 4]
In a 300 ml separable flask equipped with a DC stirrer, 6.41 g (24 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 14.28 g (71 mmol) of 4,4′-diaminodiphenyl ether, N, 149.13 g of N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, 19.92 g (91 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 10.88 g of pyromellitic dianhydride in N, N′-dimethylacetamide (6 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

   A polyimide film was obtained from the obtained polyamic acid using the same method as in Comparative Example 1. The results of measuring the peel strength of the obtained polyimide film are shown in Table 1.

[Comparative Example 5]
In a 300 ml separable flask equipped with a DC stirrer, 2.60 g (9.6 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 17.19 g (86 mmol) of 4,4′-diaminodiphenyl ether, N-methyl-2-pyrrolidone 150.78 g was added and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.19 g (93 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 9.65 g of a pyromellitic dianhydride N-methyl-2-pyrrolidone solution (5 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Comparative Example 1. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

[Comparative Example 6]
In a 300 ml separable flask equipped with a DC stirrer, 5.11 g (19 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 15.02 g (75 mmol) of 4,4′-diaminodiphenyl ether, N— 149.78 g of methyl-2-pyrrolidone was added and stirred at room temperature under a nitrogen atmosphere. Further, 19.85 g (91 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 9.48 g of a pyromellitic dianhydride N-methyl-2-pyrrolidone solution (5 wt%) was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Comparative Example 1. The results of measuring the peel strength of the obtained polyimide film laminate are shown in Table 1.

  As is clear from the results in Table 1, the polyimide film laminates (Examples 1 to 5) of the present invention have significantly improved adhesive strength without increasing the water absorption rate compared to the polyimide films of Comparative Examples 1 to 6. It is quality.

Claims (8)

It is a laminated polyimide film obtained by laminating two or more polyimide films, and at least one of the surface layers of polyimide is 1 to 100 of carboxy-4,4′-diaminobiphenyl represented by the following general formula (I). It consists of a polyimide obtained by thermally or chemically imidizing a polyamic acid synthesized from an aromatic diamine contained in a mole percentage and an aromatic tetracarboxylic dianhydride or derivative thereof. A laminated polyimide film.

(However, m and n in the formula are integers of 4 or less including 0, and (m + n) is an integer of 1 or more.) A polyamic acid synthesized from an aromatic diamine containing the carboxy-4,4′-diaminobiphenyl in a proportion of 1 to 100 mol% and an aromatic tetracarboxylic dianhydride or a derivative thereof is used on one side of a polyimide film. Alternatively, a laminated polyimide film obtained by applying to both surfaces and imidizing it thermally or chemically. A polyamic acid synthesized from an aromatic diamine containing the carboxy-4,4′-diaminobiphenyl in a proportion of 1 to 100 mol% and an aromatic tetracarboxylic dianhydride or a derivative thereof is used as a polyamic acid film. A laminated polyimide film obtained by laminating on one or both sides and thermally or chemically imidizing it. The carboxy-4,4′-diaminobiphenyl is represented by the following general formula (II): 2,6′-dicarboxy-4,4′-diaminobiphenyl and / or 3,3′-dicarboxy-4, It is 4'-diaminobiphenyl, The laminated polyimide film of any one of Claims 1-3 characterized by the above-mentioned.

The laminated polyimide film according to any one of claims 1 to 4, wherein the laminated polyimide on at least one surface layer has a structural unit represented by the following general formulas (III) and (IV): .

(However, R1 in the formula is one of the groups represented by the following general formula,

R2 in the formula is any of the groups represented by the following general formula.

Moreover, the molar ratio of X: Y in the formula is 1:99 to 100: 0. ) The laminated polyimide film according to any one of claims 1 to 5, wherein a peel strength measured by the following method is 10 N / cm or more when thermocompression bonded with a copper foil via an adhesive. .
(Peel strength: using Piralux R (registered trademark of DuPont) LF-0100, which is an adhesive film, a polyimide film and a copper foil (thickness 35 μm, BAC-13-T manufactured by Japan Energy Co., Ltd.) at 180 ° C. (The peel strength is determined by thermocompression bonding at 4.4 × 10 ⁷ Pa for 60 minutes, and the resulting laminate is peeled off by the method described in JIS C5016-1994.) The laminated polyimide film according to any one of claims 1 to 6, wherein the water absorption measured by the following method is 3.0 wt% or less.
(Water absorption: after immersing the laminated polyimide film in distilled water for 48 hours, wiping off the surface moisture, and when heated from room temperature to 200 ° C. by heating weight loss analysis at a heating rate of 10 ° C./min. (Weight loss up to 200 ° C is the water absorption rate.) A flexible circuit board obtained by pressure-bonding a metal foil to the polyimide film according to claim 1 via an adhesive.