JP2007039528A - Polyimide film, its manufacturing method and flexible circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film that is excellent in handleability and flexibility and exhibits a high peeling strength from a metal foil when glued to the metal foil via an adhesive, a method for easily manufacturing the film and a circuit board using the film. <P>SOLUTION: The polyimide film is obtained by thermal and/or chemical imidization of a polyamic acid synthesized from an aromatic diamine containing carboxy-4,4'-diaminodiphenylmethane at a ratio of 0.1-100 mol% and an aromatic tetracarboxylic dianhydride or a derivative thereof. The polyimide film has a controlled Young's modulus and has a high peeling strength when contact-bonded to the metal foil via the adhesive. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is a polyimide film that is excellent in handling property, flexibility, and dimensional stability, and that can obtain extremely high peel strength when bonded to a metal foil via an adhesive, its production method, and the same 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 and an adhesive, for example, because of its excellent insulation and heat resistance.

  The polyimide film is also required to have peel strength between a metal foil such as a copper foil and a metal foil laminated with an adhesive. However, since the peel strength is not sufficient, there has been a problem in that it may peel off when used for a long period of time and lack 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.

  That is, as a method for modifying the adhesive strength of a polyimide film, for example, a method of plasma-treating the film surface (see, for example, Patent Document 1) is known, but in this case, by performing plasma treatment There was a problem that the number of processes 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.

  The polyimide film is required to have a balance between handling properties and flexibility as well as the above-mentioned peel strength. For this reason, the Young's modulus is preferably in the range of 2.5 Gpa to 7 Gpa. However, the Young's modulus of a polyimide film composed of 4.4'-diaminodiphenyl ether and pyromellitic anhydride is less than 2.5 GPa. In order to improve the Young's modulus, a polyimide film (for example, Patent Document 3) obtained by copolymerizing a highly rigid monomer such as paraphenylenediamine is known. In this case, the Young's modulus is improved, but sufficient. The peel strength could not be obtained.

In addition to the above-mentioned peel strength, balance of handleability and flexibility, the polyimide film is required to have dimensional stability associated with higher functionality of electronic components. For this reason, the water absorption is 3.4% by weight or less, and the linear expansion coefficient is It is preferable that it is 45 ppm / degrees C or less. The polyimide film composed of 4.4′-diaminodiphenyl ether and pyromellitic anhydride has a water absorption of 3.4% by weight or less and a thermal expansion coefficient of 45 ppm / ° C. or less. In this case, sufficient peel strength is obtained. Couldn't get.
JP-A-8-41227 JP-A-6-336533 JP 61-181833 A

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

  Therefore, the first object of the present invention is to obtain a polyimide film that is excellent in handling properties, flexibility and dimensional stability, and has a high peel strength from the metal foil when bonded to the metal foil via an adhesive. It is in.

  In addition, the second object of the present invention is to control the Young's modulus, water absorption, and linear expansion coefficient of the polyimide film, and to add a lot of reagents, time, and labor to the treatment for improving the peel strength from the metal foil. It is not necessary to establish a method for producing a high-quality, high peel strength polyimide film that is suitable for mass production, low cost, and high quality.

  In order to achieve the above object, the polyimide film of the present invention contains an aromatic containing 0.1 to 100 mol% of carboxy-4,4′-diaminodiphenylmethane represented by the following general formula (I). A polyimide film obtained by thermally and / or chemically imidizing a polyamic acid synthesized from a diamine and an aromatic tetracarboxylic dianhydride or derivative thereof, and measured by the following method The rate is 2.5 Gpa or more and 7 Gpa or less, and the water absorption is 3.4 wt% or less.

(However, m and n in the formula are 0 or an integer of 4 or less, and (m + n) is an integer of 1 or more.)
(Young's modulus: according to JISK7113, obtained from the slope of the initial rising portion in a tension-strain curve obtained at a tensile speed of 300 mm / min with a Tensilon type tensile tester manufactured by ORIENREC at room temperature.
Water absorption: After immersing the polyimide film in distilled water for 48 hours, the surface moisture is wiped off, and when heated at a rate of temperature increase of 10 ° C./min from room temperature to 200 ° C. by heating weight loss analysis, 50 to 200 ° C. The weight loss up to is the water absorption rate)

Moreover, it is preferable that the linear expansion coefficient measured with the following method is 45 ppm / degrees C or less.
(Thermal expansion coefficient: The thermal expansion coefficient is measured under the conditions of a temperature range of 50 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min by Shimadzu TMA-50)

  Furthermore, the carboxy-4,4'-diaminodiphenylmethane is preferably 3,3'-dicarboxy-4,4'-diaminodiphenylmethane represented by the following general formula (II).

  Further, a polyimide film having a structural unit represented by the following general formulas (III) and (IV) is also preferable.

(However, m and n are 0 or an integer of 4 or less, (m + n) is an integer of 1 or more, R ₁ is _one of the groups represented by the following general formula,

R ₂ in the formula is any of the groups represented by the following general formula,

また、式中のＸ：Ｙのモル比は０．１：９９．９〜１００：０である）

In addition, the molar ratio of X: Y in the formula is 0.1: 99.9 to 100: 0)

  Furthermore, the polyimide film as described above having a peel strength of 15 N / cm or more measured by the following method when thermocompression bonded with a copper foil via an adhesive is also preferable.

  Furthermore, in the method for producing the polyimide of the present invention, carboxy-4,4′-diaminodiphenylmethane and aromatic tetracarboxylic dianhydride are reacted, and then an aromatic diamine other than carboxy-4,4′-diaminodiphenylmethane and The method for producing a polyimide film as described above, wherein a polyamic acid obtained by reacting an aromatic tetracarboxylic dianhydride is formed into a film, and then thermally and / or chemically imidized.

  Moreover, the flexible circuit board of the present invention is formed by pressure-bonding a metal foil to the polyimide film described above via an adhesive.

  According to the present invention, the Young's modulus is in the range of 2.5 Gpa to 7 Gpa, the handling property and flexibility are excellent, the water absorption is 3.4 wt% or less, the linear expansion coefficient is 45 ppm or less, and the dimensional stability. In addition, a polyimide film that exhibits a peel strength of 15 N / cm or more when bonded to a metal foil via an adhesive can be obtained. This polyimide film is used for flexible circuit boards with excellent long-term reliability. It can be used as a base film.

  In addition, the Young's modulus, water absorption, and linear expansion coefficient of the polyimide film are controlled, and the treatment for improving the peel strength with the metal foil does not require much reagent, time, labor, etc., and is suitable for mass production. A low-cost and high-quality high peel strength polyimide film can be produced.

  Hereinafter, the present invention will be described in detail.

  First, the definition of the physical property in this invention is demonstrated.

  That is, the Young's modulus referred to in the present invention is determined from the slope of the initial rising portion in a tension-strain curve obtained at a tensile speed of 100 mm / min with a Tensilon type tensile tester manufactured by ORIENREC at room temperature according to JISK7113 Value.

  It is an essential requirement that the Young's modulus is 2.5 Gpa or more and 7 Gpa or less. If it is less than 2.5 Gpa, handling properties are impaired, and if it is greater than 7 Gpa, flexibility is impaired.

  The water absorption rate as used in the present invention is determined by immersing the polyimide film in distilled water for 48 hours, wiping the surface moisture, and heating from room temperature to 200 ° C. at a heating rate of 10 ° C./min by heating weight loss analysis. , A value obtained from weight loss up to 50 to 200 ° C.

  It is an essential requirement that the water absorption is 3.4% by weight or less, and if it is more than 3.4% by weight, the dimensional stability is impaired by water absorption, which is not preferable.

  The linear expansion coefficient referred to in the present invention is a value measured by TMA-50 manufactured by Shimadzu Corporation under the conditions of a temperature range of 50 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min.

  The linear expansion coefficient is preferably 45 ppm or less. On the other hand, if it exceeds 45 ppm, the dimensional stability is impaired, which is not preferable.

  The linear expansion coefficient can be further reduced by stretching the polyamic acid or polyimide film as necessary. However, in this invention, the value measured by the said method in the state which does not perform an extending | stretching process is defined as a linear expansion coefficient. This value accurately reproduces the linear expansion coefficient inherently possessed by the polyimide film.

  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 subjecting the polyimide film to 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 of the polyimide film of the present invention is preferably 15 N / cm or more. On the other hand, a peel strength of less than 15 N / cm 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 polyamic acid of the present invention contains carboxy-4,4'-diaminodiphenylmethane. This is because when the aromatic diamine is not contained, the obtained polyimide film does not exhibit the desired Young's modulus and peel strength.

  It is important that the amount of carboxy-4,4'-diaminodiphenylmethane used in the polyamic acid of the present invention is 0.1 to 100 mol%, preferably 1 to 10 mol%.

  That is, if the addition amount is less than the above range, the desired Young's modulus and peel strength cannot be obtained, and if it exceeds the upper limit, the linear expansion coefficient and water absorption of the polyimide film increase, which is not preferable. It is.

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

  The polyimide in the polyimide film of the present invention comprises a polyamic acid composed of aromatic tetracarboxylic acids and aromatic diamines as a precursor, and is composed of repeating units represented by the above formulas (III) and (IV). .

  Specific examples of aromatic tetracarboxylic acids that form polyamic acid as a precursor of polyimide film include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4 '-Biphenyltetracarboxylic acid, 3,3', 4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, Examples include 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′-diaminodiphenylmethane that 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'-diaminodiphenylmethane 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′-diaminodiphenylmethane, 3,3′-dicarboxy-4,4′-diaminodiphenylmethane. And 2,3′-dicarboxy-4,4′-diaminodiphenylmethane. However, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane is a preferable condition from the viewpoint of simplicity in terms of synthesis.

  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, or 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.

  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, but one of them is within a range of 10 mol% relative 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 of this invention is demonstrated.

  In the present invention, a polyamic acid solution having a viscosity at 25 ° C. of about 10 Pa · s to 500 Pa · s measured with a rotational viscometer 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.

  Moreover, the order of adding carboxy-4,4′-diaminodiphenylmethane and other aromatic diamines is a method of mixing these and reacting tetracarboxylic dianhydride, other than carboxy-4,4′-diaminodiphenylmethane. A method of reacting aromatic diamine with tetracarboxylic dianhydride and then reacting carboxy-4,4′-diaminodiphenylmethane with aromatic tetracarboxylic dianhydride, and carboxy-4,4′-diaminodiphenylmethane with aromatic And a method of reacting an aromatic tetracarboxylic dianhydride with an aromatic diamine other than carboxy-4,4′-diaminodiphenylmethane. However, carboxy-4,4′-diaminodiphenylmethane and aromatic tetracarboxylic dianhydride are reacted in order to reduce the water absorption to 3.4 wt% or less and the linear expansion coefficient to 45 ppm or less, and then carboxy-4,4. A method of reacting an aromatic diamine other than '-diaminodiphenylmethane with an aromatic tetracarboxylic dianhydride is preferred.

  The polyamic acid solution is cast on a support to obtain a self-supporting polyamic acid film. Next, it is preferable to obtain a polyimide film by fixing the end of the obtained polyamic acid film and performing a heat treatment at a temperature of 200 ° C. or higher and 400 ° C. or lower.

  In addition, a support body here means what has a plane, such as glass, a metal, and a polymer film, and can support the cast polyamic acid, when a polyamic acid is cast on this.

  The cast means that the polyamic acid is developed on the support. As an example of the cast, there is a method of extruding a polyamic acid from a bar coat, a spin coat, or a pipe-shaped substance having an arbitrary cavity shape and spreading it on a support.

  When the resulting polyamic acid is imidized and cyclized into an aromatic polyimide film, a chemical ring closure method using a dehydrating agent and a catalyst, a thermal ring closure method using thermal dehydration, or a combination of both Any of the ring closure methods described above 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 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 of the present invention thus obtained has a Young's modulus in the range of 3.5 Gpa to 7 Gpa, excellent handling and flexibility, a water absorption of 3.4% by weight or less, and a linear expansion coefficient of 45 ppm or less. It is excellent in dimensional stability and has a peel strength as high as 15 N / cm or more when pressed onto a metal foil via an adhesive, and is extremely useful as a base film for a flexible circuit board.

  That is, the flexible circuit board of the present invention can be obtained by using the above polyimide film as a base film and crimping a metal foil to this through an adhesive, and the adhesive used here is an acrylic or polyimide Examples thereof include epoxy adhesives and epoxy adhesives, and are not particularly limited.

  The metal foil that is thermocompression bonded to the polyimide film of the present invention via an adhesive is preferably a copper foil, but other metal foils may be used.

  The flexible circuit board of the present invention thus obtained exhibits the performance of maintaining high peel strength over a long period of time and excellent long-term reliability.

  The present invention will be described more specifically with reference to the following examples. In addition, the Young's modulus, water absorption, linear expansion coefficient, and peel strength in the examples are values measured by the following methods.

[Young's modulus]
The Young's modulus was determined from the slope of the initial rising portion in a tension-strain curve obtained at a tensile speed of 100 mm / min with a Tensilon type tensile tester manufactured by ORIENREC at room temperature according to JISK7113.

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

[Linear expansion coefficient]
The linear expansion coefficient is a value measured by TMA-50 manufactured by Shimadzu Corporation under the conditions of a temperature range of 50 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min.

[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.

[Example 1]
In a 500 ml separable flask equipped with a DC stirrer, 3.28 g (11.45 mmol) of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane and 223.48 g of N, N′-dimethylacetamide were placed. 2.50 g (11.45 mmol) of pyromellitic dianhydride was added in several portions and stirred at room temperature for 5 hours in a nitrogen atmosphere. Next, 26.38 g (131.7 mmol) of 4,4′-diaminodiphenyl ether was added thereto, and 27.80 g (127.5 mmol) of pyromellitic dianhydride was divided into several portions over 30 minutes to 1 hour. I put it in. After stirring for 1 hour, 12.56 g of N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride was added dropwise over 30 minutes, and the mixture was further stirred 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 a polyester film, and a uniform film was formed using a spin coater. This was heated at 100 ° C. for 30 minutes 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. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[Example 2]
In a 500 ml separable flask equipped with a DC stirrer was placed 5.27 g (18.43 mmol) of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane and 223.64 g of N, N′-dimethylacetamide, Pyromellitic dianhydride 4.02 g (18.43 mmol) was added in several portions and stirred at room temperature for 5 hours in a nitrogen atmosphere. Next, 24.70 g (123.3 mmol) of 4,4′-diaminodiphenyl ether was added thereto, and 25.98 g (119.1 mmol) of pyromellitic dianhydride was divided into several portions over 30 minutes to 1 hour. I put it in. After stirring for 1 hour, 13.45 g of an N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride 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 Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[Example 3]
In a 500 ml separable flask equipped with a DC stirrer, 8.00 g (27.96 mmol) of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane and 223.85 g of N, N′-dimethylacetamide were placed. Pyromellitic dianhydride (6.99 g, 27.96 mmol) was added in several portions and stirred at room temperature for 5 hours in a nitrogen atmosphere. Next, 22.40 g (111.8 mmol) of 4,4′-diaminodiphenyl ether was added thereto, and another 23.48 g (107.7 mmol) of pyromellitic dianhydride was divided into several portions over 30 minutes to 1 hour. I put it in. After stirring for 1 hour, 13.82 g of an N, N′-dimethylacetamide solution of pyromellitic dianhydride (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 Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[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.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[Comparative Example 2]
In a 500 ml separable flask equipped with a DC stirrer, 10.72 g (99.1 mmol) of paraphenylenediamine, 13.23 g (66.1 mmol) of 4,4′-diaminodiphenyl ether, 223.01 g of N, N′-dimethylacetamide And stirred at room temperature under a nitrogen atmosphere. Further, 34.96 g (160.3 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 6.31 g of a pyromellitic dianhydride N, N′-dimethylacetamide solution (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 Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[Comparative Example 3]
In a 500 ml separable flask equipped with a DC stirrer, 24.70 g (123.3 mmol) of 4,4′-diaminodiphenyl ether and 223.64 g of N, N′-dimethylacetamide were placed, and pyromellitic dianhydride 25. 98 g (119.1 mmol) was added in several portions and stirred at room temperature for 1 hour under a nitrogen atmosphere. Next, 5.27 g (18.43 mmol) of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane was added thereto, and after 30 minutes to 1 hour, 4.02 g of pyromellitic dianhydride (18 .43 mmol) was charged in several times. After stirring for 5 hours, 4.67 g of N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride 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 Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

[Comparative Example 4]
In a 500 ml separable flask equipped with a DC stirrer, 8.00 g (27.96 mmol) of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane and 22.40 g (111.8 mmol) of 4,4′-diaminodiphenyl ether ), And 223.85 g of N, N′-dimethylacetamide was added. 30 minutes to 1 hour later, 30.47 g (135.66 mmol) of pyromellitic dianhydride was added in several portions and stirred at room temperature in a nitrogen atmosphere. After 2 hours, 3.37 g of an N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride 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 Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

  A polyimide film was obtained from the obtained polyamic acid using the same method as in Example 1. Table 1 shows the results of measuring the Young's modulus, water absorption, linear expansion coefficient, and peel strength of the obtained polyimide film.

  As is clear from the results in Table 1, polyimide films (Examples 1 to 3) obtained from block copolymerization in which 3,3′-dicarboxy-4,4′-diaminodiphenylmethane of the present invention is added first, Compared to the polyimide film in which 3,3′-dicarboxy-4,4′-diaminodiphenylmethane is not copolymerized in Comparative Examples 1 and 2, the Young's modulus is controlled in the range of 2.5 Gpa to 7 Gpa, and The adhesive force is remarkably modified to 15 N / cm or more.

  Moreover, as is clear from the results in Table 1, polyimide films (Examples 1 to 3) obtained from block copolymerization in which 3,3′-dicarboxy-4,4′-diaminodiphenylmethane of the present invention is added first are as follows. The polyimide film of Comparative Example 3 obtained from block copolymerization to which 3,3′-dicarboxy-4,4′-diaminodiphenylmethane is added later and 3,3′-dicarboxy-4,4′-diaminodiphenylmethane randomly Compared to the polyimide film of Comparative Example 4 obtained by copolymerization, the film was modified to have a water absorption of 3.4% by weight or less and a linear expansion coefficient of 45 ppm or less.

  As described above, according to the present invention, the Young's modulus is in the range of 2.5 Gpa to 7 Gpa, the handling property and flexibility are excellent, the water absorption is 3.4 wt% or less, and the linear expansion coefficient is When it is 45 ppm or less and excellent in dimensional stability and bonded to a metal foil through an adhesive, a polyimide film that exhibits a peel strength of 15 N / cm or more can be obtained. This polyimide film has long-term reliability. It can be used as a base film for a flexible circuit board having excellent resistance.

  In addition, according to the present invention, it is possible to control the Young's modulus, water absorption rate, and linear expansion coefficient of the polyimide film, and the treatment for improving the peel strength from the metal foil does not require much reagent, time, labor, etc. It is suitable for mass production, and can be manufactured at a low cost and with a high quality, high peel strength polyimide film.

Claims (7)

From an aromatic diamine containing carboxy-4,4′-diaminodiphenylmethane represented by the following general formula (I) in a proportion of 0.1 to 100 mol%, and an aromatic tetracarboxylic dianhydride or a derivative thereof A polyimide film obtained by thermally and / or chemically imidizing a synthesized polyamic acid, having a Young's modulus measured by the following method of 2.5 Gpa to 7 Gpa, and a water absorption of 3 Polyimide film characterized by being 4% by weight or less.

(However, m and n in the formula are 0 or an integer of 4 or less, and (m + n) is an integer of 1 or more.)
(Young's modulus: according to JISK7113, obtained from the slope of the initial rising portion in a tension-strain curve obtained at a tensile speed of 300 mm / min with a Tensilon type tensile tester manufactured by ORIENREC at room temperature.
Water absorption: After immersing the polyimide film in distilled water for 48 hours, the surface moisture is wiped off, and when heated at a rate of temperature increase of 10 ° C./min from room temperature to 200 ° C. by heating weight loss analysis, 50 to 200 ° C. The weight loss up to is the water absorption rate) 2. The polyimide film according to claim 1, wherein the linear expansion coefficient measured by the following method is 45 ppm / ° C. or less.
(Thermal expansion coefficient: The thermal expansion coefficient is measured under the conditions of a temperature range of 50 ° C. to 200 ° C. and a temperature increase rate of 10 ° C./min by Shimadzu TMA-50) 3. The carboxy-4,4′-diaminodiphenylmethane is 3,3′-dicarboxy-4,4′-diaminodiphenylmethane represented by the following general formula (II): Polyimide film.

It has a structural unit shown by the following general formula (III) and (IV), The polyimide film of any one of Claims 1-3 characterized by the above-mentioned.

(However, m and n are 0 or an integer of 4 or less, (m + n) is an integer of 1 or more, R ₁ is _one of the groups represented by the following general formula,

R ₂ in the formula is any of the groups represented by the following general formula,

In addition, the molar ratio of X: Y in the formula is 0.1: 99.9 to 100: 0)   The polyimide film according to any one of claims 1 to 4, wherein a peel strength measured by the following method is 15 N / cm or more when thermocompression-bonded with a copper foil through an adhesive.   Carboxy-4,4′-diaminodiphenylmethane and aromatic tetracarboxylic dianhydride are reacted, and then an aromatic diamine other than carboxy-4,4′-diaminodiphenylmethane and aromatic tetracarboxylic dianhydride are reacted. The method for producing a polyimide film according to any one of claims 1 to 5, wherein the polyamic acid obtained from the above is formed into a film, and then thermally and / or chemically imidized.   A flexible circuit board obtained by pressure-bonding a metal foil to the polyimide film according to claim 1 via an adhesive.