JP2007191705A - Highly adhesive polyimide film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly adhesive polyimide film that exhibits enhanced adhesiveness to a copper foil and is excellent in dimensional stability and water wettability, and its manufacturing method. <P>SOLUTION: The highly adhesive polyimide film is formed by using a diamine component comprised of 12-30 mol% of p-phenylenediamine and 70-88 mol% of 4,4'-diaminodiphenyl ether and an acid component comprised of 50-99.5 mol% of pyromellitic dianhydride and 0.5-50 mol% of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and has surface free energy of at least 80 mN/m as measured by the contact angle method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a highly adhesive polyimide film and a method for producing the same, and more specifically, relates to a highly adhesive polyimide film having improved adhesion to copper foil and excellent in dimensional stability and water wettability, and a method for producing the same. .

  Polyimide films are known to have excellent properties such as heat resistance, cold resistance, chemical resistance, electrical insulation, and mechanical strength. Electrical insulation materials for wires, heat insulating materials, flexible printed wiring boards (FPCs) ) Base films, carrier tape films for IC tape automated bonding (TAB), and IC lead frame fixing tapes. Among these, in applications such as FPC, TAB carrier tape, lead fixing tape, etc., a polyimide film and a copper foil are usually bonded and used via various adhesives.

  However, since polyimide films often have insufficient adhesion to copper foil due to their chemical structure and high chemical resistance, a method of chemically treating the film surface with acid or alkali (for example, patents) Conventionally, attempts have been made to improve adhesiveness by applying a physical processing method such as sandblasting (see, for example, Patent Document 2).

However, since these processes require separate steps such as washing and drying after the process, they have problems in terms of not only productivity, stability and cost but also environmental conservation.
See JP 2002-294965 A See JP-A-9-48864

  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, an object of the present invention is to provide a polyimide film having improved adhesion to copper foil and excellent in dimensional stability and water wettability, and an efficient production method thereof.

  To achieve the above object, according to the present invention, paraphenylenediamine, 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride A highly adhesive polyimide film characterized in that the surface free energy measured based on the contact angle method is 80 mN / m or more.

  In the highly adhesive polyimide film of the present invention, the polyimide film uses 12-30 mol% paraphenylene diamine, 70-88 mol% 4,4′-diaminodiphenyl ether as a diamine component, and has an acidic content. It was formed using 50-99.5 mol% pyromellitic dianhydride and 0.5-50 mol% 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. Is preferred.

In addition, the method for producing the highly adhesive polyimide film of the present invention includes paraphenylenediamine, 4,4′-diaminodiphenyl ether, pyromellitic dianhydride, and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dihydrate. When performing plasma treatment on the surface of a polyimide film formed from an anhydride, the surface is coated with a dielectric and cooled to 10 ° C. to 100 ° C. in an atmosphere of 100 to 1000 Torr containing at least 20 mol% of a rare gas. At least 20 mol% of noble gas between the applied high-voltage applying electrode and the support electrode which is provided opposite to the high-voltage applying electrode and the surface on which the discharge is formed is covered with a dielectric and supports the polyimide film. The surface of the polyimide film is 5 by a high voltage applied in an atmosphere of 100 to 1000 Torr containing the above. Characterized by continuously plasma treatment 0w · min / ^{m 2} or more processing force, in this case, the copolyimide film, 12-30 mol% p-phenylenediamine, of 70 to 88 mol% Formed from 4,4′-diaminodiphenyl ether, 50-99.5 mol% pyromellitic dianhydride and 0.5-50 mol% 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride It is preferred that

  According to the present invention, as will be described below, for example, a polyimide film having high adhesion to a copper foil, excellent dimensional stability, and excellent water wettability can be obtained.

  Hereinafter, the highly adhesive polyimide film of the present invention and the production method thereof will be described in more detail.

  First, the polyimide acid that is a precursor for obtaining the polyimide film of the present invention will be described. The polyamic acid used in the present invention comprises paraphenylenediamine and 4,4′-diaminodiphenyl ether as diamine components, pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic as acid components. It is obtained by polymerizing with acid dianhydride.

  The paraphenylenediamine and 4,4′-diaminodiphenyl ether used in the present invention are preferably used after being dissolved in an organic solvent. There are various methods for obtaining polyamic acid by polymerizing pyromellitic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and paraphenylenediamine and 4,4′-diaminodiphenyl ether. For example, a predetermined amount of paraphenylenediamine and 4,4′-diaminodiphenyl ether are previously dissolved in an organic solvent, and pyromellitic dianhydride and 3,3 ′, 4,4 are added thereto. Examples thereof include a method in which polyamic acid having a predetermined viscosity is obtained by adding '-biphenyltetracarboxylic dianhydride.

  Next, a method for obtaining a polyimide film from the obtained polyamic acid solution will be described.

  First, it is preferable to obtain a polyimide gel film by cyclizing the polyamic acid by a chemical ring closure method using a ring-opening catalyst and a dehydrating agent or by a thermal ring closure method using a heat treatment. And the edge part of the obtained gel film is fixed, and a polyimide film is obtained by biaxial stretching at a magnification of 1.05-1.5 in the vertical direction and a magnification of 1.05-2.0 in the horizontal direction. Can do. By performing such biaxial stretching, the mechanical properties of the resulting polyimide film can be improved. A chemical ring closure method or a thermal ring closure method may be used. However, the chemical ring closure method has advantages such as that the elastic modulus of the obtained polyimide film can be improved and the thermal expansion coefficient can be reduced. Preferably employed.

  Dehydrating agents used in the chemical ring closure method include aliphatic acid anhydrides such as acetic anhydride, N-dialkylcarbodiimides, lower fatty acid halides, allylphosphonic acid subhalides, benzoic acid anhydrides, phthalic acid anhydrides, etc. Aromatic acid anhydrides and ketene, and the use of acetic anhydride is preferable.

  Examples of the cyclization catalyst used include pyridines such as 3,4′-N lutidine, 3,5-lutidine, 4-methylpyridine, 4-isopropylpyridine, 4-benzylpyridine, N-dimethylbenzylamine, Examples thereof include picolines such as 4-dimethylbenzylamine, 4-dimethyldodecylamine, and β-picoline, triethylamine, N-dimethylaniline, quinoline, and isoquinoline. Among them, β-picoline is preferably used. These are preferably used alone or in combination.

  In carrying out the chemical ring closure method, after mixing the cyclization catalyst and the dehydrating agent in the polyamic acid solution and imidizing, this solution is coated to obtain a polyimide film, and the polyamic acid solution is coated. For example, a method of obtaining a polyimide film by immersing it in a mixture of a cyclization catalyst and a dehydrating agent and imidizing it can be employed.

  In order to improve the mechanical properties of the resulting polyimide film, various additives and catalysts may be added to the polyamic acid, and the surface of the polyimide film is roughened to give the film slipperiness. From the viewpoint of improving process stability, an organic filler or an inorganic filler can be mixed with the polyamic acid.

The polyimide constituting the polyimide film of the present invention may be any of a block polymer, a random polymer, and a mixed polymer.
Since the polyamic acid solution is highly viscous, the polyamic acid solution is usually extruded onto a casting drum or an endless belt in a film form or cast, and at least the polyamic acid is self-supported on the casting drum or the endless belt. It is also preferably performed to make a stable polyimide film by performing heat treatment or the like as necessary after curing to the extent that it is provided.

  The highly adhesive polyimide film of the present invention comprises 20 to 40 mol% paraphenylenediamine as a diamine component, 60 to 80 mol% 4,4'-diaminodiphenyl ether, and 50 to 99.5 mol% pyromerit as an acidic component. Desirably, it is formed from an acid dianhydride, 0.5-50 mol% 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride.

  However, the addition ratio of paraphenylenediamine and 4,4′-diaminodiphenyl ether in the diamine component is such that when 4,4′-diaminodiphenyl ether increases, the polyimide film becomes soft, and conversely, when paraphenylenediamine increases, the polyimide film becomes hard. Therefore, it is preferable to set the addition ratio of both within the above range depending on the use of the polyimide film. Further, when the obtained polyimide film is used for, for example, a flexible printed board, it is preferable that the film characteristics are not too hard and not too soft. It is preferably ˜40 mol%.

  And the highly adhesive polyimide film of this invention is characterized by the surface free energy measured based on the contact angle method being 80 mN / m or more.

  Here, when the surface free energy of the polyimide film is less than 80 mN / m, the effect of improving adhesiveness becomes insufficient, which is not preferable. When the surface free energy is 80 mN / m or more, the polyimide film has high adhesiveness to the copper foil, excellent dimensional stability, and excellent water wettability.

  The highly adhesive polyimide film of the present invention satisfying the above characteristics can be produced by subjecting a polyimide film having the above composition to plasma treatment under specific conditions.

That is, in order to produce the highly adhesive polyimide film of the present invention, when the plasma treatment is performed on the surface of the polyimide film, the surface is a dielectric in an atmosphere of 100 to 1000 Torr containing at least 20 mol% of a rare gas. A high-voltage applying electrode covered with the substrate and cooled to 10 ° C. to 100 ° C., and a support electrode which is provided facing the electrode and covered with a dielectric and which supports the polyimide film The surface of the polyimide film is continuously plasma-treated at a treatment strength of 500 w · min / m ² or more by a high voltage applied in an atmosphere of 100 to 1000 Torr containing at least 20 mol% or more of a rare gas. This is very important.

  The plasma discharge in this plasma treatment is performed by flowing a coolant through the inside, so that the surface of the conductor such as a metal tube cooled to 10 to 100 ° C. is covered with a dielectric, and this electrode is opposed to this electrode. The surface on which the discharge is formed is formed between the electrode for supporting the workpiece covered with the dielectric.

  As the high voltage application electrode, one having a hollow rod structure is preferable, and as the refrigerant flowing inside, air, freon, water or the like can be mentioned, and water is particularly preferable. Examples of the dielectric covering the surface of the conductor include rubber, glass, ceramics, etc. Among them, glass is preferable, and the thickness is preferably 0.1 to 0.5 mm. The material of the dielectric is preferably selected to have a sufficient withstand voltage against the applied voltage.

  When the object to be processed is a long object such as a film, the electrode for supporting the object to be processed is preferably a drum-shaped electrode that can support the object to be processed, and the size thereof is, for example, the rod shape It is preferable to form it so as to have a diameter that is twice or more the diameter of the high voltage application electrode. Similarly, it is important that at least the surface of the drum electrode where the discharge is formed is covered with a dielectric, and the same material as that of the rod electrode such as the thickness and material of the dielectric is used.

The number of high voltage application electrodes and the number of electrodes that support the object to be processed need not be the same, and it is preferable to provide two or more high voltage application electrodes for each electrode that supports the object to be processed.
The distance between the high voltage application electrode and the counter electrode is preferably 0.5 mm or more and 10 mm or less, and more preferably 0.5 mm or more and 5 mm or less. If this distance exceeds 10 mm, the discharge becomes unstable, and if it is less than 0.5 mm, it is difficult to obtain mechanical accuracy, so that processing unevenness and processing omission are likely to occur.

The frequency of the high voltage applied to the high voltage application electrode is preferably selected in the range of 20 KHz to 100 MHz. If it is less than 20 KHz, it is difficult to start discharge, and if it is 100 MHz or more, it is difficult to achieve matching, and a preferable frequency is 50 KHz to 500 KHz.
An electrode that supports the object to be processed may be provided, or the electrode may be floated from the ground and connected to an output terminal that is paired with a connection terminal with a high voltage electrode of a high voltage power supply.

  As a matter of course, the high voltage power supply preferably has a matching circuit.

  In the plasma treatment performed in the present invention, the atmospheric gas composition is extremely important. When discharging is performed in a gas atmosphere of 100 to 1000 Torr containing at least 20 mol% of a rare gas element using the above apparatus, the discharge is normal. It is not a spark discharge (called a corona discharge by those skilled in the art), but a discharge that resembles a glow discharge that occurs under vacuum, and this glow discharge can supply more power to the discharge than a spark discharge. In addition, there is an advantage that the treatment effect on the polyimide film is remarkable and there is no drawback such as blocking.

  Examples of the rare gas element used in the present invention include He, Ne, Kr, Xe, and Rn, and Ar is most preferable. Such noble gas needs to be contained in the atmospheric gas at least 20 mol% or more.

If the rare gas in the atmospheric gas is less than 20 mol%, the discharge becomes a spark discharge, the treatment effect is low as in the case of the normal corona discharge, and the back surface and blocking are not preferable. More preferably, the atmosphere gas contains a rare gas in an amount of 50 mol% or more. Examples of the gas that can be used by mixing with a rare gas include, but are not limited to, organic gases such as CO ₂ and methane. However, the O ₂ and N ₂ concentrations should be as small as possible from the viewpoint of discharge stability and treatment effect, and are preferably less than 1 mol%, more preferably less than 0.5 mol%.

  It is important to select the atmospheric pressure in the range of 100 to 1000 Torr. When the pressure is less than 100 Torr, there is a problem that an advanced vacuum exhaust device is required. When the pressure exceeds 1000 Torr, it is difficult to start discharge. More preferably, the pressure is selected in the pressure range of 600 to 900 Torr.

Processing strength against the polyimide film may have to process at 200w · min / ^{m 2} or more processing power density, more preferably 500w · min / ^{m 2} or more, more preferably 1000w · min / ^{m 2} treatment power density in the process It is good to do. In a normal corona discharge treatment, if the treatment is performed at a power density of 500 w · min / m ² or more, the discharge becomes an arc discharge, and a pinhole is generated in the dielectric material of the film to be processed or the drum-shaped electrode. Then, such a phenomenon is not seen at all, and there is an advantage that high power can be supplied. The processing power density referred to here is a value obtained by dividing the output by the processing speed with the width of the discharge portion (the width direction of the drum electrode).

  The polyimide film is delivered to the discharge part by a delivery roll. A gas having a predetermined composition is supplied to the discharge portion from the gas introduction system and is maintained at the predetermined gas by a simple exhaust device. After the polyimide film is processed in the discharge processing section by the high-frequency high voltage applied to the high-voltage application electrode from the high-voltage power supply through the matching transformer by the discharge formed between the grounded drum electrode, It is wound on a take-up roller.

  The highly adhesive polyimide film of the present invention thus obtained has high adhesion to copper foil, excellent dimensional stability, and excellent water wettability. As a base insulating film for TAB (Tape Automated Bonding) and COF (Chip On Flex), which are base materials used for flexible printed circuit boards (FPC) such as electronic parts, or for LOC tapes as support members in semiconductor devices It can be usefully used as such.

  Hereinafter, the present invention will be described specifically by way of examples.

  In the examples, PPD is paraphenylenediamine, ODA is 4,4′-diaminodiphenyl ether, PMDA is pyromellitic dianhydride, BPDA is 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, DMAC Represents N, N-dimethylacetamide, respectively.

  Moreover, each characteristic of the polyimide film in an Example was evaluated with the following method.

(1) Surface free energy (mN / m)
The surface free energy was determined using the FACE CA-W150 of Kyoto Interface Science from the average value of contact angles obtained by measuring n = 5 times each with water, ethylene glycol, and methylene iodide on the surface of the film subjected to the surface treatment. A large value means good wettability and generally high adhesion.

(2) Adhesive strength evaluation of each film Adhesive mixed with epoxy resin adhesive (trade name Epox AH-357A / AH-357B / AH-357C = 100/5/12 weight ratio) manufactured by Mitsui Chemicals, Inc. with a coater It is applied to each film, pre-dried at 130 ° C. for 4 minutes, 18 μm rolled copper foil (BHY-22B-T, manufactured by Japan Energy Co., Ltd.) is layered, and a copper-clad laminate by press curing at 170 ° C. for 80 minutes under 2 MPa pressure. Got. A 0.8 mm circuit was cut into the obtained laminate and etched with a ferric chloride solution to prepare a sample for evaluation. The obtained metal foil part with a width of 0.8 mm was peeled off at a peeling angle of 90 ° and 50 mm / min, measured n = 5 times, and the average value was defined as the adhesive strength.

(3) Plasma treatment In the plasma treatment, a high voltage application electrode whose surface is covered with a dielectric and cooled to 25 ° C. is provided opposite to this, and a surface on which a discharge is formed is covered with a dielectric, The surface of the polyimide film is continuously applied at a treatment strength of 500 w · min / m ² by a high voltage applied in an atmosphere of 750 Torr containing at least 20 mol% of a rare gas between the support electrode supporting the polyimide film. Plasma treatment was performed.

[Example 1]
239.1 g of DMAc was placed in a 500 cc glass flask, and 1.870 g (0.0173 mol) of PPD and 3.659 g (0.0168 mol) of PMDA were added thereto and reacted at room temperature and normal pressure for 1 hour. Next, 25.398 g (0.1268 mol) of ODA was added thereto and stirred until uniform, then 8.481 g (0.0288 mol) of BPDA was added and reacted for 1 hour. Subsequently, 21.491 g (0.0985 mol) of PMDA was added thereto, and a polyamic acid solution was further reacted for 1 hour. In this polymerization, the addition molar ratio of each raw material was carried out at the ratio shown in Table 1, and the solid content weight was adjusted to 60.9 g. A 25 μm polyimide film was obtained by a known method of this polyamic acid solution, and this was subjected to the above plasma treatment. The adhesive strength and surface free energy of the obtained polyimide film were as shown in Table 1.

[Examples 2 to 9]
In the same procedure as in Example 1, after obtaining each polyamic acid solution in the ratio and order shown in Table 1 for the aromatic diamine component and aromatic tetracarboxylic acid component, 25 μm obtained by the same operation as in Example 1 The above-mentioned plasma treatment was performed on the polyimide film. The adhesive strength and surface free energy of the obtained polyimide film were as shown in Table 1.

[Examples 10 to 18]
Table 1 shows the adhesive strength and surface free energy of polyimide films obtained in the same manner as in Examples 1 to 15, except that the thickness of the film was 7.5 μm, and the ratios of the aromatic diamine component and aromatic tetracarboxylic acid component. It was as shown in.

[Comparative Examples 1 to 9]
Regarding the films of Examples 1 to 15, the adhesive strength and surface free energy of the polyimide films obtained without performing the plasma treatment were as shown in Table 3 [Comparative Examples 10 to 18].
Regarding the films of Examples 16 to 30, the adhesive strength and surface free energy of the polyimide films obtained without performing the plasma treatment were as shown in Table 4.

  As is clear from the results of Tables 1 to 4, the polyimide film according to the present invention has significantly improved adhesiveness regardless of the thickness as compared with the polyimide film not subjected to the plasma treatment.

  The highly adhesive polyimide film of the present invention has high adhesion to copper foil, excellent dimensional stability, and excellent water wettability. Useful as a base insulating film for TAB (Tape Automated Bonding), COF (Chip On Flex), which is a base material used for flexible printed circuit boards (FPC) of parts, etc., or as a LOC tape as a support member in semiconductor devices Can be used.

Claims (2)

Using 12-30 mol% paraphenylenediamine and 70-88 mol% 4,4'-diaminodiphenyl ether as the diamine component, 50-99.5 mol% pyromellitic dianhydride and 0.5 A polyimide film formed using ˜50 mol% of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, the surface free energy measured based on the contact angle method is 80 mN / m or more A highly adhesive polyimide film characterized by being. Using 12-30 mol% paraphenylenediamine and 70-88 mol% 4,4'-diaminodiphenyl ether as the diamine component, 50-99.5 mol% pyromellitic dianhydride and 0.5 When a plasma treatment is performed on the surface of a polyimide film formed using ˜50 mol% of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, it contains at least 20 mol% of noble gas. A high voltage applying electrode whose surface is covered with a dielectric and cooled to 10 ° C. to 100 ° C. in an atmosphere of ˜1000 Torr, and a surface on which a discharge is formed is covered with a dielectric. And an atmosphere of 100 to 1000 Torr containing at least 20 mol% of a rare gas between the support electrode supporting the polyimide film In the applied high voltage, the method of producing a high adhesive polyimide film of claim 1, wherein the continuous plasma treatment of the surface of the polyimide film at 500w · min / m ² or more processing force.