JP2003055487A - Method for manufacturing aromatic polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently manufacturing an aromatic polyimide film improved both in adhesion properties to a metal and in dimensional stability of a metallic article to which it is bonded. SOLUTION: An aromatic polyimide film is subjected to a heat-treatment in advance at a temperature of 200-500 deg.C and subsequently to a discharge treatment on one surface or both surfaces thereof to give an aromatic polyimide film having a heat shrinkage stress of 10 MPa or less and a surface free energy of 75-150 mN/m.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing an aromatic polyimide film having simultaneously improved adhesion to metal and dimensional stability of a metal-bonded article.

[0002]

2. Description of the Related Art In recent years, with the sophistication of electronics, there is an increasing demand for printed circuit boards used especially for high frequencies.

In the field of printed circuit boards,
In particular, it is often processed in a large area for the purpose of cost reduction, and since the applications used at high temperatures are also increasing, the adhesive used is changed from acrylic adhesive to epoxy adhesive and / or It is changing to a polyimide adhesive. At the same time, there is an increasing demand for aromatic polyimide films having improved adhesion to metals and dimensional stability of metal-bonded products.

Conventionally, a method of subjecting an aromatic polyimide film surface to an electric discharge treatment for the purpose of improving the adhesiveness to a metal is known, but in this method, an aromatic compound film which satisfies the dimensional stability of a metal-bonded product at the same time. A polyimide film could not be easily obtained.

Incidentally, Japanese Patent Publication No. 7-35106 discloses that
Aromatic polyimide film obtained by a method of preliminarily surface-treating a polyimide film by low-temperature plasma and then heat treatment is proposed, and in the publication, the aromatic polyimide film obtained by this method has a heat shrinkage rate. It is described that the size of the printed circuit board becomes smaller and the curl of the printed circuit board obtained by bonding the metal and the metal together becomes smaller. That is, the reduced curl improves the dimensional stability of the metal adhesive film to some extent. However, the special fair 7-
In the method described in Japanese Patent No. 35106, since the functional group on the film surface is subjected to heat treatment to sneak into the inside of the film due to molecular motion or undergoes a change over time, the effect of improving the adhesiveness with a metal is still insufficient. There was a problem that I could only get a film.

Therefore, an aromatic polyimide film satisfying both the adhesiveness to a metal and the dimensional stability of a metal-bonded product has not been known yet, and the actual situation is strongly demanded.

[0007]

SUMMARY OF THE INVENTION The present invention has been achieved as a result of studying the solution of the above-mentioned problems in the prior art.

Therefore, it is an object of the present invention to provide a method for efficiently producing an aromatic polyimide film having improved adhesion to metal and dimensional stability of a metal-bonded article.

[0009]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that the dimensional stability of a metal-bonded product of an aromatic polyimide film is due to stress imbalance. It was found that reducing the heat shrinkage stress of the group-polyimide film is effective in improving the flatness, and that the adhesion to metal can be improved at the same time by adjusting the surface free energy within a specific range. The present invention has been accomplished by finding a method for efficiently producing an aromatic polyimide film having conditions of shrinkage stress and surface free energy.

That is, according to the method for producing an aromatic polyimide film of the present invention, the aromatic polyimide film is preliminarily prepared in advance.
After heat treatment at a temperature of 00 to 500 ° C., discharge treatment is applied to one side or both sides thereof, and the resulting aromatic polyimide film has a heat shrinkage stress of 10 MPa or less,
In addition, the surface free energy has a characteristic of 75 to 150 mN / m.

In the method for producing an aromatic polyimide film of the present invention, the tension in the longitudinal direction of the film during the heat treatment and the discharge treatment is 10 kg / m or less, and the discharge treatment is plasma treatment. thing,
The obtained film has an electron spin density of 1 × 10 ¹⁵
More preferable conditions for achieving the purpose are to have the properties of spins / g or more, and that the obtained film further has the property of having a water contact angle of 55 ° or less.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.

The raw material polymer constituting the aromatic polyimide film of the present invention is a polymer having a structural unit represented by the following general formula (I).

[0014]

[Chemical 1] Here, R ₁ and R ₃ are tetracarboxylic dianhydride residues, and R ₂ and R ₄ are divalent diamine compound residues.

In the above general formula (I), the preferable tetracarboxylic acid dianhydride residue is any group selected from those represented by the following general formula.

[0016]

[Chemical 2] Where X is CO, SO ₂ , S, O and

[0017]

[Chemical 3] It is one selected from.

Preferred is any group selected from those represented by the following general formulas:

[0019]

[Chemical 4] Most preferably, it is a group represented by the following general formula.

[0020]

[Chemical 5] Further, in the above general formula (I), the preferred diamine compound residue is any group selected from those represented by the following general formulas.

[0021]

[Chemical 6] Here, Y is any one selected from O, SO ₂ , S, CH ₂ and CONH, and Z is C (CH ₃ ) ₂ , C
It is any one selected from (CF ₃ ) ₂ and SO ₂ .

Preferably, it is any group selected from the groups represented by the following general formulas,

[0023]

[Chemical 7] Most preferably, R ₂ in the above general formula (I) is a general formula

[0024]

[Chemical 8] And R ₄ is any group selected from the groups represented by the following general formulas.

[0025]

[Chemical 9] The aromatic polyimide film of the present invention can be produced by a generally known method, and by way of example, a polyamic acid is cast on a support in a solution state to obtain a self-supporting polyamic acid film. Then, the polyamic acid can be produced by imidizing with heat.

The above polyamic acid solution is an aromatic tetracarboxylic acid consisting of an aromatic diamine component, pyromellitic acid or pyromellitic acid and two or more kinds of aromatic tetracarboxylic acid compounds having two or more benzene rings. And the components are obtained by polymerizing in a solvent.

As a preferable method for polymerizing the polyamic acid solution, there is a production method described in Japanese Patent Application No. 11-366390.

Another preferred method for polymerizing the polyamic acid solution is to put an aromatic diamine compound in a solvent and then add pyromellitic acid or pyromellitic acid and an aromatic tetracarboxylic acid compound to the reaction components in an amount of 95 to 1
After mixing at a ratio of 05 mol% for the time required for the reaction,
Furthermore, aromatic diamine compounds are added, and subsequently, pyromellitic acids or pyromellitic acids and aromatic tetracarboxylic acid compounds are converted to wholly aromatic diamine components and pyromellitic acids or pyromellitic acids and wholly aromatic tetracarboxylic acid components. A method of adding and polymerizing so that the same amount,
And after adding pyromellitic acid or pyromellitic acid and an aromatic tetracarboxylic acid compound in a solvent, after mixing for a time necessary for the reaction at a ratio of 95 to 105 mol% of aromatic diamine compound to the reaction components , Pyromellitic acid or pyromellitic acid and an aromatic tetracarboxylic acid compound are added, and then an aromatic diamine compound is added to a wholly aromatic diamine component and pyromellitic acid or pyromellitic acid and wholly aromatic tetracarboxylic acid component. Examples thereof include a method of adding and polymerizing so as to be an equal amount.

Specific examples of the polyamic acid include paraphenylenediamine, benzidine derivative, 4,4'-
An aromatic diamine component such as diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bisaminophenoxybenzenes, diaminobenzanilides,
Pyromellitic acid or pyromellitic acid represented by pyromellitic dianhydride and 3,3′-4,4′-biphenyltetracarboxylic acid or its dianhydride or 3,3 ′
-4,4'-Benzophenonetetracarboxylic acid or an aromatic tetracarboxylic acid compound having two or more benzene rings such as a dianhydride thereof is obtained by polymerizing in a solvent to produce a non-thermoplastic polyimide. There are things to do.

As the solvent used in the above polymerization, dimethyl sulfoxide, N, N-dimethylacetamide,
Examples thereof include N, N-diethylacetamide, N, N-dimethylformamide, N, N-diethylformamide, N-methyl-2-pyrrolidone and dimethyl sulfone, and these are preferably used alone or in combination.

The polyamic acid obtained by the above polymerization is
It is adjusted to be 10 to 30% by weight in the solvent.

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

First, an extrusion die is used to cast the above polyamic acid solution on a support to obtain a self-supporting polyamic acid film. Then, the obtained polyamic acid film is fixed to a metal frame with a pin and heat-treated at a temperature of 200 to 400 ° C. to obtain a multilayer polyimide gel film.

Next, the end portion of this gel film is fixed,
1.05-1.5 in the vertical direction, 1.05-2.0 in the horizontal direction
It is preferable to stretch at a magnification of. By carrying out such biaxial stretching, it is possible to improve the mechanical properties and further improve the isotropy of the obtained multilayer polyimide film.

In the above, the support means glass,
It means a metal, a polymer film or the like having a flat surface and capable of supporting the cast polyamic acid when the polyamic acid is cast thereon.

Further, in the above, casting means spreading a polyamic acid on a support. Examples of casting include bar coating, spin coating, or a method in which a polyamic acid is extruded from a pipe-shaped substance having an arbitrary hollow shape and spread on a support.

When the obtained polyamic acid is cyclized into a polyimide film, it may be carried out by either a chemical ring-closing method of dehydrating using a dehydrating agent and a catalyst or a thermal ring-closing method of thermally dehydrating.

Examples of the dehydrating agent used in the chemical ring-closing method include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as phthalic anhydride. These are used alone or as a mixture. Is preferred. Further, as the catalyst, heterocyclic tertiary amines such as pyridine, picoline and quinoline, aliphatic tertiary amines such as triethylamine,
Examples thereof include aromatic tertiary amines such as N, N-dimethylaniline, and these are preferably used alone or in combination.

The thickness of the polyimide film thus obtained is preferably 5 μm or more. The upper limit of the film thickness is not particularly limited as long as it can be processed, but it is 3
It will be less than 00 μm.

The molecular structure of the polyimide film is
It is preferable that the acid component or the diamine component contains a flexible portion. Although the reason for this is unknown, it is presumed that it is because the flexible portion derived from the bending component is likely to be micro-roughened by being specifically treated by the discharge treatment described below. . Therefore, a polyimide film composed of three or more components having a bending component and a linear component is particularly preferable.

In producing the aromatic polyimide film of the present invention, it is an important requirement to subject the aromatic polyimide film produced as described above to a heat treatment and then a discharge treatment.

The above heat treatment and discharge treatment can be carried out continuously or individually, but it is preferable to carry out heat treatment and discharge treatment successively.

As a discharge treatment method, a molecular energy state is excited by electricity such as plasma discharge treatment, corona discharge treatment, arc discharge treatment and glow discharge treatment,
There is a method of directly or indirectly generating radicals. Most preferable are atmospheric pressure plasma discharge treatment, atmospheric pressure corona treatment and atmospheric pressure glow discharge treatment.

Further, when these discharge treatments are carried out, it is also preferable to use light, photothermal or electric energy irradiation such as ultraviolet treatment, laser treatment and electromagnetic wave treatment in combination, and by using these in combination, the molecular energy state is excited. , Radicals can be generated directly or indirectly.

The method for producing the aromatic polyimide film of the present invention will be described in more detail below.

First, a preferable processing condition for making the heat shrinkage stress of the polyimide film 10 MPa or less is to heat the film at a high temperature and a low tension. The specific maximum heat treatment temperature condition is 200 ° C. or higher and 500 ° C. or lower, preferably 250 ° C. and 500 ° C. or lower, and more preferably 300 ° C.
It is above 500 ° C.

The maximum heat treatment temperature for continuous treatment is 2
If it is less than 00 ° C, the electron spin density of the film decreases, which is not preferable. When the heat treatment is carried out at a low temperature in a batch process, the heat treatment may be carried out for 1 hour to several days, but the heat treatment time for a long product is preferably 1 second to 10 minutes.

As a preferable method for reducing the heat shrinkage stress, there is a method of performing heat treatment at multi-step temperatures. In this case, the temperature of the first heat treatment is higher than the temperature of subsequent heat treatment. For example, it is preferable that the first-stage heat treatment is performed at 400 to 500 ° C. for 1 second or longer, and then the second stage heat treatment is performed at 300 to 400 ° C. for 1 second or longer to form a multi-stage heat treatment. Specific means include a method in which a roll wound with a film is left in a heating oven, and a method in which heat treatment is performed under no tension, but heat treatment under no tension is preferable from the viewpoint of reducing heat shrinkage stress. .

However, the preferable tension condition of the heat treatment is 1 to 10 kg / m, particularly 1 to 10 kg / m in the length direction of the film.
It is advantageous to apply tension in the range of 7 kg / m, and it is preferable to perform heat treatment with hot air continuously while applying tension, and then perform cooling treatment.

If the tension in the length direction is less than 1 kg / m, wrinkles may occur in the film, causing a problem of meandering during continuous winding, and if it exceeds 10 kg / m, the heat shrinkage stress of the film becomes large. There is.

Examples of the heat source for the heat treatment include hot air, heat radiation from an infrared heater, and electromagnetic waves.

The reason why the heat treatment is performed immediately before the electric treatment is to obtain a film having a low water content.

When this discharge treatment, which will be described below, is continuously performed by long winding after this heat treatment, it is preferable to perform the heat treatment with a tension in the range of 1 to 10 kg / m in the length direction of the film.

As described above, the water content in the polyimide film can be reduced to 1/10 or less of the saturated water content of immersion by preliminarily undergoing the heat treatment step.

The moisture content of the polyimide film immediately before or during the discharge treatment is 1% by weight or less, preferably 0.5.
It is below wt%, most preferably 0.1 wt%. The reason for this is unknown, but if the water content in the film is high, the effect of discharge treatment will be significantly reduced. Since the saturated water content of the polyimide film is usually about 3% by weight, there was a problem that the discharge treatment effect fluctuated depending on the humidity in the air. By carrying out the treatment, it can be expected to obtain the surprising effect that an aromatic polyimide film having a stable treatment effect over a large area is obtained.

When the discharge treatment is not carried out immediately after the heat treatment, it is preferable to store the film in a dry state so as not to absorb moisture. Preferred means for this include storage in a drying room, storage in combination with a desiccant, and packaging storage in a moisture-proof film.

Next, electric discharge machining is performed. As the electric discharge machining means, the low pressure plasma method and the atmospheric pressure plasma method are preferable as mentioned above. Atmospheric gases in the plasma treatment include oxygen, nitrogen, argon,
A gas selected from carbon dioxide, air, hydrogen and a mixed gas thereof is included. At this time, the water content is 1000 pp
It is preferably m or less. Most preferred are air, nitrogen, carbon monoxide and argon.

The frequency of the high voltage applied to the high voltage applying electrode is preferably selected in the range of 20 kHz to 100 MHz. More preferable frequency is 50 kHz to 500
kHz. The processing strength is 50 W · min / m
Good to process in ^two or more processing power density, more preferably 80W · min / m ² or more.

In the aromatic polyimide film thus obtained by the method of the present invention, the heat shrinkage stress is 10 MPa or less, preferably 5 MPa or less, more preferably 1 MPa or less, most preferably 0.5 MPa.
It is below MPa.

When the heat shrinkage stress of the aromatic polyimide film exceeds 10 MPa, for example, COF for mobile phone liquid crystal is used.
When it is used as a flexible printed circuit board with high dimensional stability and high precision such as (chip on flex), dimensional change occurs due to partial stress concentration after etching copper. As a result, curling tends to occur, which is not preferable. If this curl is large, it is difficult to operate the flexible printed circuit board when the flexible printed circuit board is incorporated into electrical equipment, which is not preferable.

The polyimide film obtained by the method of the present invention has a heat shrinkage stress of 10 MPa or less and a free energy of the film surface of 75 mN / m or more, preferably 85 mN / m or more, and most preferably 95 mN / m or more.
It is mN / m.

The larger the value of the surface free energy, the more preferable, but the upper limit is preferably about 150 mN / m in the range studied. If the surface free energy value is less than 75 mN / m, the adhesiveness with some adhesives used for laminating the polyimide film and the metal, such as an epoxy adhesive or a polyimide adhesive, tends to be low. Occurs.

Further, in the aromatic polyimide film obtained by the method of the present invention, the electron spin density in the film is 1 × 10 ¹⁵ spins / g or more, preferably 1
× 10 ¹⁶ spins / g or more, particularly preferably 1 × 10
It is preferably ¹⁷ spins / g or more.

The electron spin density is 1 × 10 ¹⁵ spins /
If it is less than g, the adhesion with metal tends to be insufficient.

The electron spin density as used herein means the amount of radicals in the film, and the larger the amount, the better the adhesiveness. However, the upper limit is 1 × 10 ²⁵ spin because of the limit of the processing capacity.
It will be about s / g. In order to increase the amount of radicals, methods such as thermal decomposition, mixing of a radical generator or ion implantation are also effective.

The thermal decomposition conditions of polyimide can be evaluated by TGA. The standard is to heat at a temperature of 200 ° C lower than the 1% heat loss temperature. 1 of aromatic polyimide in general
Since the% heat loss temperature is 520 ° C. to 550 ° C., if it exceeds this temperature, thermal crosslinking will proceed too much, which is not preferable. The preferred heating conditions are 200 ° C or higher, more preferably 300 ° C or higher, and most preferably 400 ° C.
That is all. The atmosphere gas is nitrogen or air. When polyimide is heated to generate radicals, a part of the radicals causes thermal crosslinking. It is preferable to stabilize the generated radicals and prevent thermal crosslinking, but it is also possible to have appropriate thermal crosslinking.

The radical generator is preferably an organic substance capable of decomposing by heating at 300 ° C. or higher to generate radicals. Preferred is an organic substance having an aromatic ring having a substituent that decomposes at 1% by weight or more at 300 ° C. or higher and causes a stable radical to exist in the polyimide film. here,
The aromatic ring serves to stabilize the radical. Examples of the radical generator include benzoyl peroxide, dicumyl peroxide and cumene hydroperoxide. The addition amount is 0.01 to 1% by weight.

Further, in the aromatic polyimide film obtained by the method of the present invention, it is desirable that the water contact angle is 55 ° or less, preferably 50 ° or less, particularly preferably 45 ° or less.

The water contact angle of the aromatic polyimide film is 5
When it exceeds 5 °, the adhesiveness between the adhesive used for bonding the polyimide film and the metal or the adhesive metal tends to be deteriorated, which is not preferable. It is considered that the lower limit of the water contact angle will be about 1 °.

As described above, the surface free energy, the electron spin density in the film and the water contact angle are all requirements for obtaining preferable adhesiveness.

The aromatic polyimide film obtained by the method of the present invention is excellent in adhesiveness to metal and dimensional stability of a metal-bonded product as described above, and therefore, the metal and the polyimide film are directly bonded to each other. It is used for various purposes.

It is also preferable to carry out an adhesion treatment with a metal or a metal compound immediately or continuously after the treatment of the present invention. Further, it is also a preferable means to further form a metal plating layer on the adhesive product with the metal or metal compound thus obtained. The metal plating layer may be formed by either electroless plating or electrolytic plating. The laminated film obtained by adhering a metal to the aromatic polyimide film obtained by the method of the present invention has improved adhesiveness to a metal and dimensional stability of a metal-bonded product at the same time.

As another usage mode, it is also used for the purpose of bonding with a metal through an adhesive after the above-mentioned discharge treatment. Metals, alloys, metal compounds or metal oxides whose substrates are thin are used in the field of application of laminated constructions in which the polyimide surface is adhered via an adhesive.

Further, it is preferably used for applications requiring a high dimensional accuracy with a wiring distance of 10 to 40 μm or less. Specific applications of them include PDP
For example, a COF (Chip on Film) circuit substrate in which high-definition wiring with a pitch of 20 μm or less is formed is used for applications such as displays for LCDs and wireless suspensions for HDDs. Further, it is also suitable as a base film for FPCs similar to or used in the periphery thereof or a cover film (lining) thereof.

[0075]

EXAMPLES The constitution and effects of the present invention will be further described below with reference to examples.

In the following examples, all percentages are by weight unless otherwise stated.

The measurement and evaluation of various characteristics were carried out by the following methods. The polyimide films used below were all stored at room temperature in a vacuum desiccator except during processing or evaluation. [Heat Shrinkage Stress of Polyimide Film] TMA (manufactured by Seiko Instruments Inc., TM
A / SS120C type) was used, and the strain was measured in a constant strain mode at room temperature (25 ° C.). A test piece having a width of 2 mm and a measurement length of 10 mm was used, and the temperature rising / falling rate was 5 ° C./min.
The measurement was performed under the condition of the maximum temperature of 300 ° C. The residual stress when returning to room temperature was defined as the heat shrinkage stress. [Surface free energy] A contact angle meter (CA-X type, manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the contact angle between ethylene glycol, methylene iodide and water and the film, and the dispersion force component γd of the film surface was measured. , The dipole component γp and the hydrogen bond component γh were determined.

At this time, the values shown in Table 1 were used as the dispersion force component γd, the dipole component γp, and the hydrogen bond component γh of each liquid.

The calculation is performed on the solid surface free energy analysis software EG-11 to which the extended Fowkes theory is applied.
(Manufactured by Kyowa Interface Science Co., Ltd.) was used.

[0080]

[Table 1] [Electron Spin Density] JES-FE as an ESR measuring device
3XG (manufactured by JEOL Ltd.), microwave frequency counter (TR5212, Advantest) as an accessory device
And ESR data system (ES-PRIT23,
(Made by JEOL Ltd.).

In order to avoid saturation of the signal with respect to the microwave output, the sample with many spins had a microwave output of 4 μm.
W, a small sample was measured with a microwave output of 20 μW.
In the measurement, Mn ^{2+ in} MgO was used as an external standard sample.
Was measured at the same time.

The electron spin density is a value obtained from the ESR signal intensity obtained by numerically integrating the observed ESR signal twice, and represents the radical amount per unit weight. ESR
The signal intensity was assumed to follow the Curie law, and the radical amount was calculated using an ion-implanted polyethylene film as a secondary standard sample.

The measurement conditions used are as follows.

Measurement temperature; room temperature magnetic field sweep range; 326.2 to 346.2 mT modulation; 100 kHz, 0.32 mT microwave output; 4 μW or 20 μW, 9.43 G
Hz sweep time; 1.5 minutes x 20 times time constant; 0.1 seconds Number of data points; 2048 points cavity; TE ₀₁₁ , cylindrical [water contact angle] contact angle meter (CA-X type, manufactured by Kyowa Interface Science Co., Ltd.) ) Was used to measure the contact angle between water and the film. [Adhesive strength] Epoxy adhesive (“TI” manufactured by “TI”)
A "No. 8500" was used, and the polyimide film obtained above and the copper foil (Mitsui Mining & Smelting Co., Ltd. electrolytic copper foil "3E"
C ″ (thickness: 35 μm), and a curing reaction of the adhesive was performed under the condition of 185 ° C. for 1 hour to prepare a laminated plate composed of polyimide film / adhesive / copper foil.
A sample having a width of 10 mm and a length of 30 cm is cut out from the obtained laminated plate, and peeled by 90 degrees at a pill test speed of 50 mm / min by a tensile tester (Tensilon universal tester UTA-300KN manufactured by A & D Co., Ltd.). Was subjected to a tensile test. The value was averaged with N = 5 and evaluated in the following four stages. The x level is a level at which the adhesion strength is poor when used as a metal wiring circuit board.

Adhesion strength: 18 N / cm or more, peeling at the interface between the copper foil and the adhesive. ○ Adhesion strength, 18 N / cm or more, peeling at the interface between the copper foil and the film. Δ Adhesion strength: 14 N / cm or more and less than 18 N / cm × Adhesion strength Less than 10 N / cm [Dimensional stability (curl)] Polyimide film is coated with polyimide adhesive ("TPI" manufactured by Toray Industries, Inc.),
Copper foil was stuck on this at a temperature of 250 ° C. Then, the maximum temperature was raised to 300 ° C. to cure the adhesive. The obtained metal laminated plate was cut into a sample size of 35 mm × 120 mm, left in an atmosphere of 25 ° C. and 60 RH% for 24 hours, and then the warpage of each sample was measured. As for the warp, the sample was placed on a glass plate and the heights of the four corners were measured and averaged. The evaluation criteria are the following 3 according to the amount of warpage.
Graded. When used as a metal wiring circuit board, the X level is a level at which handling becomes difficult during transportation in a subsequent process.

Amount of warp less than 1 mm Δ Amount of warp 1 mm or more and less than 3 mm × Amount of warp 3 mm or more [Examples 1 to 5] 4,4′-diaminodiphenyl ether (hereinafter referred to as DMAc) in N, N-dimethylformamide (hereinafter referred to as DMAc) , 44 'ODA) is supplied and dissolved, and then pyromellitic dianhydride (hereinafter referred to as PMD).
(Referred to as A) were sequentially supplied, and the mixture was stirred at room temperature for about 1 hour.
Finally, the polycarboxylic acid concentration 2 in which the tetracarboxylic dianhydride component and the diamine component are approximately 100 mol% stoichiometry
A 0 wt% solution was prepared.

This polyamic acid solution was ice-cooled, acetic acid dianhydride and β-picoline were added, and the mixture was stirred to form a heat-supporting film, which was then peeled from the support to further complete the conversion reaction to an imide. Along with drying the solvent, thickness 25 μm
The film was wound into a roll as a polyimide film (Film A).

On the other hand, 30 mol% of para-phenylenediamine (hereinafter referred to as PPD) was supplied in DMAc to dissolve it, and then PMDA was supplied in an amount of 29 mol% based on the total acid anhydride to react. Polyamic acid polymer A in which 0.5 mol% of acetic anhydride was added to block the acetyl end
Was adjusted. Subsequently, 30 mol% of biphenyltetracarboxylic acid (hereinafter referred to as BPDA) and about 40 mol% of PMDA were sequentially supplied to further polymerize the polymer B.

Finally, a solution of a polyamic acid concentration of 20% by weight was prepared, which was a mixed composition of the polymer A and the polymer B in which the tetracarboxylic dianhydride component and the diamine component had a stoichiometric ratio of about 100 mol%.

This polyamic acid solution was ice-cooled, acetic acid dianhydride and β-picoline were added, and the mixture was stirred to form a heat-supporting film, which was then peeled from the support to further complete the conversion reaction to an imide. At the same time, the solvent was dried and wound into a roll as a polyimide film having a thickness of 10 μm (film B).

Each of the polyimide films (Film A or Film B) thus obtained was continuously fed into a tunnel type hot air oven, heat-treated under the conditions shown in Table 2, and then wound while cooling to room temperature. It was The film tension during heat treatment was adjusted by the difference in rotation speed between the feed roller and the take-up roller, and the heat treatment time was adjusted by the relative rotation speed of each roller.

Next, the heat-treated film A or film B was immediately sent into a nitrogen gas atmosphere of 760 Torr and plasma-treated under the conditions shown in Table 2. Other conditions for plasma treatment are: electrode width 1m, film running speed 1
4 m / min, input power was 1470 W.

The heat shrinkage stress, the water contact angle, the surface free energy, the electron spin density, the adhesive strength and the surface property of each polyimide film thus obtained by the heat treatment / discharge treatment were measured and evaluated. Are also shown.
[Comparative Examples 1 to 3] When film A was only subjected to heat treatment (Comparative Example 1), similarly when only plasma treatment was performed (Comparative Example 2), and when film B was subjected to Pragamama treatment and then heat treated. Table 2 also shows the results of measuring and evaluating the heat shrinkage stress, the water contact angle, the surface free energy, the electron spin density, the adhesive force, and the surface property of each film obtained in the case (Comparative Example 3).

[0094]

[Table 2] As is clear from the results in Table 2, the aromatic polyimide films (Examples 1 to 5) obtained by the method of the present invention, which consist of heat treatment / discharge treatment, have adhesiveness to metal and dimensions of metal-bonded articles. The stability (curl) is improved at the same time.

[0095]

As described above, according to the method of the present invention, it is possible to efficiently produce an aromatic polyimide film having improved adhesion to metal and dimensional stability of a metal-bonded product. it can. Then, the aromatic polyimide film obtained by the present invention is particularly useful for adhesion with a metal, and the application field of a structure in which a metal or a metal compound is directly laminated on the adhesion improving surface, specifically, ,
It can be suitably used for displays such as PDPs and LCDs, wireless suspensions for HDDs, etc., and especially for COF circuit substrates in which high-definition wiring with a pitch of 20 μm or less is formed.

Claims (5)

[Claims] 1. An aromatic polyimide film is prepared in advance of 200
After heat treatment at a temperature of up to 500 ° C., a heat shrinkage stress of 10 M, characterized by subjecting one or both surfaces to an electric discharge treatment
Pa or less and surface free energy of 75 to 150 mN
/ M. The method for producing an aromatic polyimide film. 2. The method for producing an aromatic polyimide film according to claim 1, wherein the tension in the longitudinal direction of the film during the heat treatment and the discharge treatment is 10 kg / m or less. 3. The method for producing an aromatic polyimide film according to claim 1, wherein the discharge treatment is plasma treatment. 4. The aromatic polyimide film according to claim 1, wherein the obtained film further has a characteristic that the electron spin density is 1 × 10 ¹⁵ spins / g or more. Production method. 5. The method for producing an aromatic polyimide film according to claim 1, wherein the film further has a water contact angle of 55 ° or less.