JP2005054172A - Polyamic acid, polyimide film comprising the same, method for producing the same, and flexible circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film having high peel strength when it is pressure-bonded to a metal foil through an adhesive, a method for easily producing the film, and a circuit board using the film.
SOLUTION: A polyamic acid synthesized from an aromatic diamine containing carboxy-4,4'-diaminobiphenyl in a proportion of 1 to 100 mol% and an aromatic tetracarboxylic dianhydride or a derivative thereof, and A polyimide film obtained by thermally and / or chemically imidizing a polymer.
[Selection figure] None

Description

  The present invention relates to a polyamic acid, a polyimide film comprising the same, a method for producing the same, and a flexible circuit board. More specifically, the present invention relates to a polyimide film capable of obtaining extremely high peel strength when bonded to a metal foil via an adhesive, a method for producing the film, and a flexible circuit board using them.

  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 steps. .

  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 polyimide film coated with a silane coupling agent (see, for example, Patent Document 2) is also known. In this case, the number of steps for coating the silane coupling agent is increased. Since the ring agent is decomposed by heat treatment when the ring is closed from polyamic acid to polyimide, there is a problem that the adhesive strength is reduced.

  Furthermore, a polyimide film containing a tin compound and excellent in adhesion and durability (see, for example, Patent Document 3) is also known, but the peel strength of this polyimide film is 10 N / cm or less, and sufficient adhesive strength. Did not have.

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-8-41227 JP-A-6-336533 JP-A-4-261466 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.

  Accordingly, a first object of the present invention is to obtain a polyimide film having a strong peel strength when bonded to a metal foil via an adhesive.

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

  In order to achieve the above object, the polyamic acid of the present invention comprises an aromatic diamine containing carboxy-4,4′-diaminobiphenyl represented by the following general formula (I) in a proportion of 1 to 100 mol%. , Synthesized from an aromatic tetracarboxylic dianhydride or a derivative thereof,

  (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.)

   The carboxy-4,4′-diaminobiphenyl is represented by the following general formula (II): 2,6′-dicarboxy-4,4′-diaminobiphenyl and / or 3,3′-dicarboxy-4,4 The preferred condition is' -diaminobiphenyl.

Moreover, the polyimide film of the present invention is characterized by comprising the above polyamic acid,
It has the structural unit shown by the following general formula (III) and (IV), It is characterized by the above-mentioned.

  (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. )
A preferable condition is that the 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.)

  Furthermore, the method for producing a polyimide film of the present invention is characterized in that the polyamic acid is thermally and / 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 via an adhesive.

  The polyimide film made of the polyamic acid of the present invention has a high peel strength of 10 N / cm or more when it is pressure-bonded to a metal foil via an adhesive, and peels off for a long time when used as a base film for a flexible circuit board. Strength can be maintained, and a flexible circuit board excellent in long-term reliability can be provided.

  Hereinafter, the present invention will be described in detail.

  First, the definition of peel strength in the present invention will be described.

  In other words, the peel strength as used in the present invention refers to a polyimide film and a copper foil (thickness 35 μm, BAC-13 manufactured by Japan Energy Co., Ltd.) using Piralux R (registered trademark of DuPont) LF-0100 which is an adhesive film. T) is a strength obtained by peeling off a 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 essential that the aromatic diamine used in the polyamic acid 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.

  It is important that the amount of carboxy-4,4'-diaminobiphenyl used in the polyamic acid of the present invention is in the range of 1 to 100 mol%, preferably 5 to 100 mol%. That is, when the addition amount is less than the above range, the intended peel strength cannot be obtained.

  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 following 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. )

  Specific examples of aromatic tetracarboxylic acids that form polyamic acid as a precursor of polyamide 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′-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. 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 conditions. It is.

  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 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.

  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 portion 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 high peel strength of 10 N / cm or more when it is pressure-bonded to a metal foil via an adhesive, and it is high for a long time when used as a base film for a flexible circuit board. A flexible circuit board that maintains the peel strength and is excellent in long-term reliability can be provided.

  The present invention will be described more specifically with reference to the following examples. In addition, the peeling strength in an Example is the value 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.

[Example 1]
In a 300 ml separable flask equipped with a DC stirrer, 1.85 g (6.8 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 18.23 g (90 mmol) of 4,4′-diaminodiphenyl ether, 148.82 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, 11.21 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 1 hour 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.

[Example 2]
In a 300 ml separable flask equipped with a DC stirrer, 2.63 g (9.7 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 17.56 g (87 mmol) of 4,4′-diaminodiphenyl ether, 148.88 g of N, N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.41 g (94 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 11.15 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.

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

[Example 3]
In a 300 ml separable flask equipped with a DC stirrer, 3.17 g (19 mmol) of 3,3′-dicarboxy-4,4′-diaminobiphenyl and 15.35 g (76 mmol) of 4,4′-diaminodiphenyl ether, N, 149.05 g of N′-dimethylacetamide was added and stirred at room temperature under a nitrogen atmosphere. Furthermore, pyromellitic dianhydride 20.08 g (92 mmol) was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 10.97 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.

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

[Example 4]
In a 300 ml separable flask equipped with a DC stirrer, 3.10 g (11.4 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 16.76 g (83.7 mmol) of 4,4′-diaminodiphenyl ether ) And 149.70 g of N-methyl-2-pyrrolidone were added and stirred at 50 ° C. under a nitrogen atmosphere. Further, after 30 minutes to 1 hour, 20.11 g (92.2 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 9.3 g of a pyromellitic dianhydride N-methyl-2-pyrrolidone solution (5 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. The results of measuring the peel strength of the obtained polyimide film are shown in Table 1.

[Example 5]
In a 300 ml separable flask equipped with a DC stirrer, 4.61 g (16.9 mmol) of 2,6′-dicarboxy-4,4′-diaminobiphenyl and 15.46 g (77.2 mmol) of 4,4′-diaminodiphenyl ether ) And 149.65 g of N-methyl-2-pyrrolidone were added and stirred at 50 ° C. under a nitrogen atmosphere. Further, 19.11 g (87.7 mmol) of pyromellitic dianhydride was added in several portions over 30 minutes to 1 hour. After stirring for 1 hour, 9.6 g of an N-methyl-2-pyrrolidone solution of pyromellitic dianhydride (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. The results of measuring the peel strength of the obtained polyimide film 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.

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

  As is clear from the results in Table 1, the polyimide films (Examples 1 to 5) of the present invention have significantly improved adhesive strength as compared with the polyimide film of Comparative Example 1.

Claims (7)

It is synthesized from an aromatic diamine containing carboxy-4,4′-diaminobiphenyl represented by the following general formula (I) at a ratio of 1 to 100 mol% and an aromatic tetracarboxylic dianhydride or a derivative thereof. A polyamic acid characterized by that.

(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.) The carboxy-4,4′-diaminobiphenyl is represented by the following general formula (II): 2,6′-dicarboxy-4,4′-diaminobiphenyl and / or 3,3′-dicarboxy-4,4 The polyamic acid according to claim 1, which is' -diaminobiphenyl.

A polyimide film comprising the polyamic acid according to claim 1. It has a structural unit shown by the following general formula (III) and (IV), The polyimide film of Claim 3 characterized by the above-mentioned.

(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. ) 5. The polyimide film according to claim 3, wherein the peel strength measured by the following method is 10 N / cm or more when thermocompression bonded to the 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 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.) 3. A method for producing a polyimide film, wherein the polyamic acid solution according to claim 1 or 2 is formed into a film and then imidized thermally and / or chemically. A flexible circuit board obtained by pressure-bonding a metal foil to the polyimide film according to any one of claims 3 to 5 via an adhesive.