JP5563519B2 - Method for producing polyimide film - Google Patents

Description

The present invention relates to a method for producing a polyimide film . More specifically, the present invention relates to a method for producing a polyimide film excellent in adhesiveness to an adhesive used when a copper-clad plate is produced .

  A polyamic acid polymer solution is obtained by polymerizing an aromatic diamine typified by 4,4′-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride typified by pyromellitic dianhydride in an organic solvent. After being obtained, the polyamic acid polymerization liquid is formed into a film, and this is thermally and / or chemically dehydrated and closed, that is, imidized to obtain a polyimide film having heat resistance, insulation, and mechanical properties. In order to be superior to the above, electric insulation material for wires, heat insulation, base film for flexible building printed circuit board (hereinafter sometimes abbreviated as FPC), IC tape automated bonding (hereinafter sometimes abbreviated as TAB) It is widely used for carrier tape films and lead frame fixing tapes for ICs.

  In particular, in applications such as FPC, TAB carrier tapes and lead fixing tapes, a polyimide film and a copper foil are usually bonded via various adhesives. It is required to show good adhesion to various adhesives. However, the polyimide film surface is inherently highly water-repellent and has poor adhesion to the adhesive. If the adherence with the adhesive is poor, adhesion failure occurs when the polyimide film and another material are used together, and the reliability of the product is lowered. Therefore, it is necessary to improve the adhesion of the polyimide film with the adhesive, and to improve the adhesion. As a method for this, various methods such as corona discharge treatment, plasma treatment, chemical etching treatment, and sand blast treatment are available. Conventionally, surface modification by using a technique has been studied.

  For example, a technique for modifying an aromatic polyimide film by treating it with low-temperature plasma (see, for example, Patent Documents 1 and 2), or removing the WBL layer by the first-stage low-temperature plasma treatment, and the second-stage low-temperature plasma treatment. A method (for example, see Patent Document 3) for performing a process for increasing the adhesiveness is proposed.

  On the other hand, a sandblasting technique for the aromatic polyimide film has been developed and widely used. Conventional techniques related to this include a method of mechanically wiping the film surface (for example, see Patent Document 4) and A method using corona discharge treatment (see, for example, Patent Document 5) has been proposed. Furthermore, by rubbing the film, the film surface is made uneven to increase the adhesion of the film (for example, see Patent Document 6), and the surface modification method by plasma treatment at normal pressure (for example, Patent Document 7) has been proposed.

  However, these methods have the following problems.

  Sandblasting is widely performed because it can be processed at a relatively low cost. In this method, sand remains on the surface and surface layer of the treated film, and therefore, after treatment, cleaning treatment is necessary. There is a problem that it is not possible to clearly define whether or not the cleaning should be performed to some extent, and quality control is extremely difficult in the production process. Further, the sandblasting treatment is effective in eliminating adhesive variation and restoring the original adhesive strength of the aromatic polyimide, but there is a problem that the improvement in the adhesive strength itself is not so effective. Furthermore, since this method blasts sand with a strong force, the sand hits the film, and in the case of a thin film, the sand penetrates to form a pinhole, or the surface layer is shaved for sand blasting. There are problems such as a decrease in strength. Among them, the method described in Patent Document 4 is practical, but the reforming effect is considerably low, and it is at the same level as sandblasting. In addition, there is a concern about dust adhesion due to static electricity when wiping, that is, recontamination, and the production process. There is a disadvantage that quality control is difficult.

  In addition, since the method of rubbing the polyimide film scratches the film, it is adopted as a treatment method in recent FPCs and the like with a high fine pitch because the scratch itself causes wiring defects. Sometimes it becomes a problem. The method according to Patent Document 5 is a method in which corona discharge is performed at a discharge density of 20 to 300 W / m 2 / min, and this method has a problem that a sufficient reforming effect cannot be achieved.

  On the other hand, the method using the low temperature plasma treatment is performed by a discharge generated under a low pressure, and this method easily forms a glow discharge, which is a stable discharge. There is an advantage that modification is made. However, this low temperature plasma processing method requires the formation of a low-pressure atmosphere region, which necessitates a vacuum vessel and a large exhaust facility, which increases the cost significantly and is long for adjusting a predetermined pressure atmosphere or changing conditions. There is a problem that processing costs increase due to problems such as time. In addition, since the plasma treatment including normal pressure affects only the surface layer of the film, there is a problem that the adhesive force of the polyimide film may not be sufficiently developed.

JP 61-141532 A JP 61-229388 A JP-A-8-3338 Japanese Patent Laid-Open No. 62-184842 Japanese Patent Laid-Open No. 62-162542 JP 2008-56756 A Japanese Patent Laid-Open No. 1-138242

The present invention has been achieved as a result of studying the solution of the problems in the prior art described above as an issue. Therefore, the objective of this invention is providing the manufacturing method of the polyimide film which improved adhesiveness, especially the adhesiveness with respect to the adhesive material used at the time of copper-clad printing.

In order to achieve the above object, according to the present invention, a polyimide film is subjected to a discharge treatment under the condition that the relative permittivity of the drum electrode is 25 or less and the oxygen concentration is 500 ppm or less, and the discharge state is creeping discharge. it is, by its creeping discharge length makes the discharge treatment so that the above 3 cm, and a 50nm layer of the plane orientation index from the surface layer in the thickness direction of the film is 0.30 or more, and likewise 100nm inner layer There is provided a method for producing a polyimide film, characterized by producing a polyimide film having an in-plane orientation index of 0.25 or more .

In the polyimide film obtained by the production method of the present invention , the in-plane orientation index of the 50 nm inner layer is 0.40 or more in the thickness direction from the surface layer of the film, and the in-plane orientation index of the 100 nm inner layer is also 0.30. not less than, and, which film is surface treated by a discharge treatment, compared to before the film is subjected to a surface treatment by the discharge process, after the discharge treatment (surface treatment), the film A preferable condition is that the in-plane orientation index of the 50 nm inner layer and the in-plane orientation index of the 100 nm inner layer are each increased by 0.10 or more in the thickness direction from the surface layer.

According to the present invention, as described below, it is possible to obtain a method for producing a polyimide film having improved adhesiveness, in particular, adhesiveness to an adhesive used at the time of producing a copper-clad plate.

Schematic which shows an example of the film processing apparatus used by this invention.

  Below, the manufacturing method of the polyimide film of this invention is demonstrated concretely.

First, the characteristics of the polyimide film produced by the method for producing a polyimide film of the present invention are such that the in-plane orientation index of the 50 nm inner layer is 0.30 or more in the thickness direction from the surface layer of the film, and the in-plane orientation of the 100 nm inner layer is also the same. The index is 0.25 or more.

Here, the in-plane orientation index of the film in the present invention refers to each measurement point (in the present invention, as described later, two points of the position of the 50 nm inner layer in the thickness direction from the film surface layer, and also the position of the 100 nm inner layer) . This is a value obtained by subtracting the in-plane orientation value in the 2 μm inner layer from the surface layer of the film . Therefore, the in-plane orientation index of the film is a value indicating how much the molecular chain is oriented in a plane parallel to the surface of the film at the measurement point as compared with the 2 μm inner layer from the film surface layer. It becomes.

In the polyimide film obtained by the production method of the present invention, the in-plane orientation index of the 50 nm inner layer is 0.30 or more in the thickness direction from the surface layer of the film, and the in-plane orientation index of the 100 nm inner layer is also 0.25 or more. It is a necessary and important characteristic . Furthermore, it is plane orientation index of 50nm inner in the thickness direction from the surface layer of the film is 0.40 or more, and also in-plane orientation index of 100nm inner layer is more desirable properties to be at least 0.30.

  Adhesion between the polyimide film and the adherend layer does not depend only on the outermost surface of the polyimide film, is affected by the inner layer, and the higher the in-plane orientation, the higher the adhesive force. The reason for this is not clear, but if the in-plane orientation is aligned, the stacking of aromatic rings in layers progresses, the intermolecular force increases, and the molecules in the inner layer may affect adhesion. In addition, the degree of influence is larger as it is closer to the outermost surface and decreases as it goes to the inner layer. If the in-plane orientation index of the inner layer is low, the adhesion becomes weak because the adhesion is affected only by the functional group density of the outermost layer, and the adhesion becomes weak.

In the present invention, as a means for increasing the in-plane orientation index, it is important to treat the discharge state to be creeping discharge , particularly by treatment with atmospheric pressure plasma. Creeping discharge is known to generate a current flowing from the dielectric surface to the inside, and can efficiently affect the molecular state of the inner layer of the film. Furthermore, creeping discharge spreads so that the discharge spreads over the surface of the film and the discharge flows, so that it can be treated with less unevenness. On the other hand, it is considered that the above-mentioned characteristics can not be obtained in a discharge close to a glow discharge that is generally performed with atmospheric pressure plasma because it can affect only the surface layer of the film.

  Specifically, a polyimide film is subjected to a discharge treatment under the conditions that the relative permittivity of the drum electrode is 25 or less and the oxygen concentration is 500 ppm or less, and the discharge state is creeping discharge. It is manufactured by performing a discharge treatment so that the thickness becomes 3 cm or more.

  The discharge treatment in the present invention is a high voltage application electrode in which the surface of a conductor such as a metal tube cooled to about 10 to 100 ° C. by flowing a coolant inside is covered with a dielectric, and is provided opposite to the electrode. And a surface on which a discharge is formed is covered with an electrode for supporting an object to be processed, which is covered with a dielectric. The high voltage application electrode preferably has a hollow rod-like structure, and the refrigerant flowing inside is air, freon, water, or the like, with water being particularly preferred.

  Examples of the dielectric covering the surface of the conductor include rubber, glass, and ceramic. The relative dielectric constant (ε) is preferably 20 or less, more preferably 10 or less. The lower the relative dielectric constant, the easier the electric avalanche discharge develops into a creeping discharge that crawls on the workpiece, and the inner layer of the film being processed is more likely to be affected. Further, the thickness of the dielectric is preferably 0.1 to 5 mm. Furthermore, it is preferable to select a dielectric material having a sufficient withstand voltage with respect to the applied voltage.

  The shape of the electrode that supports the non-processed object is selected according to the form of the object to be processed, but in the case of a long object such as a film, it is preferably a drum electrode that can support the object to be processed in a freely transportable manner. The size is preferably formed to have a diameter more than twice the diameter of the rod-shaped high voltage application electrode. Similarly, it is important that at least the surface of the drum-like electrode where discharge is formed is covered with a dielectric, and the same thickness and material as that of the rod-like electrode are used.

  In the present invention, 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 two or more high voltage application electrodes may be provided for one electrode that supports the object to be processed.

  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 higher than 100 MHz, it is difficult to achieve matching. A more preferable frequency is 50 kHz to 500 kHz.

  In the present invention, the electrode that supports the object to be processed may be grounded, or the electrode may be floated from the ground and connected to an output terminal that is a pair of connection terminals with a high voltage power source.

  In the present invention, the high voltage power supply preferably has a matching circuit.

  In the present invention, the gas composition in the discharge atmosphere is preferably performed at an oxygen molecular concentration of 1000 ppm or less. In order to achieve creeping discharge, the discharge active species must cause avalanche. Since oxygen deactivates the active species, it is preferable that oxygen has a low concentration.

  In the present invention, the gas composition of the discharge atmosphere is preferably at least 50 mol% or more of a rare gas element. There is a possibility that the discharge is not stable in an atmosphere with a small amount of rare gas. Examples of the rare gas element used in the present invention include He, Ne, Ar, Kr, Xe, and Rn.

  In the present invention, it is preferable to always supply air in an atmosphere where processing is desired to the discharge processing unit. This is to prevent an increase in oxygen concentration due to an accompanying airflow generated when the treatment is performed by roll-to-roll or an active species of oxygen generated by breaking a bond in a molecule.

  In this invention, it is preferable to supply the air of the atmosphere supplied to a process part in the direction directly applied to a film. When discharge treatment is performed on polyimide, oxygen active species generated by breaking bonds in the molecule are released. Since the oxygen active species has a short lifetime, the deactivated oxygen acts on the deactivation of other active species, so the air flow is directed in the direction of the film in order to efficiently keep oxygen atoms away from the film surface with the atmospheric gas. It is preferable to head. If this is not the case, a method such as increasing the supply amount of atmospheric gas and forcibly replacing the gas can be considered. Moreover, in order to balance supply and exhaust, an exhaust device may be attached.

The treatment strength for the polyimide film is preferably selected according to the film to be treated, but is 100 W. It is preferable to perform the treatment at a treatment power density of min / m ² or more. The processing power density of the present invention is a value obtained by dividing the output by the discharge width and the film processing speed.

  In addition, according to FIG. 1, it will be as follows if an example of the film processing apparatus used by this invention is demonstrated.

  In FIG. 1, the polyimide film 1 is sent out to the discharge processing unit 9 by a feed roll 2. A gas having a predetermined composition is supplied to the discharge processing unit 9 from the gas introduction system 8, and a balance between supply and exhaust is maintained by a simple exhaust device not shown here. The film 1 is processed in the discharge processing section by a discharge formed between the high voltage application electrode 3 and the grounded drum electrode 4 by a high frequency high voltage applied from the high voltage power source 5 through the matching transformer 6. After that, the film is taken up by the take-up roller 7. At this time, the discharge can be visually observed, and the discharge that hits the film surface flows in the transport direction of the film. This state is referred to as creeping discharge, and the longer the creeping discharge, the better. However, a preferable result can be obtained if 3 cm or more can be observed.

  The polyimide film in the present invention is produced by imidizing a film using polyamic acid dissolved in an organic solvent, and the polyamic acid in the organic solvent solution may be partially imidized. A small amount of an inorganic compound may be contained.

  The polyamic acid which is a polyimide precursor in the present invention is preferably composed of an aromatic tetracarboxylic acid and an aromatic diamine and composed of a repeating unit represented by the following formula [I].

In the above formula, R ₁ is a tetravalent organic group having at least one aromatic ring, the carbon number thereof is 25 or less, and R ₂ is a divalent organic group having at least one aromatic ring. The group has 25 or fewer carbon atoms.

  In the present invention, the aromatic tetracarboxylic acids and the aromatic diamines are polymerized in such a ratio that the respective mole numbers are approximately equal, and one of them is within a range of 10 mol%, preferably 5 mol%, and the other. May be blended in excess.

  Specific examples of the aromatic tetracarboxylic acids 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-naphthalenetetracarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) propane, pyridine-2,3,5,6 -Aromatic tetracarboxylic acids derived from tetracarboxylic acids or acid anhydrides, or ester compounds or halides of the acids.

  Specific examples of the aromatic diamines include paraphenylene diamine, metaphenylene diamine, benzidine, paraxylylene diamine, 4,4′-diaminodiniphenyl 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 (3-methyl -5-aminophenyl) benzene and derivatives thereof.

  Examples of combinations of an aromatic tetracarboxylic acid component and an aromatic diamine component that are particularly suitable for the polyimide in the method of the present invention include pyromellitic dianhydride, 4,4′-diaminodiphenyl ether, and 3,3 ′, 4,4 ′. -A combination of biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether is mentioned, and further, copolymerization thereof and / or copolymerization of paraphenylenediamine is preferable. Moreover, if it is a range which does not inhibit this invention, it can also shape | mold with a multilayer body at the time of film forming.

  The intrinsic viscosity (measured in sulfuric acid at 25 ° C.) of the polyimide is preferably in the range of 0.2 to 3.0, more preferably in the range of 0.8 to 2.

  In the present invention, specific examples of the organic solvent used for forming the polyamic acid solution include organic polar amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methyl-2-pyrrolidone. A solvent is mentioned, These organic solvents are used individually or in combination of 2 or more types, but may be used in combination with non-solvents such as benzene, toluene and xylene.

  The organic solvent solution of polyamic acid used in the present invention preferably contains a solid content of 5 to 40% by weight, more preferably 10 to 30% by weight, and its viscosity is 10 as measured by a Brookfield viscometer. Those having a viscosity of ˜2000 Pa · s, preferably 100 to 1000 Pa · s are preferable because stable liquid feeding is possible.

  The polymerization reaction is continuously carried out in the temperature range of 0 to 80 ° C. for 10 minutes to 30 hours while stirring and / or mixing in an organic solvent. The polymerization reaction can be divided or the temperature can be increased or decreased as necessary. It does not matter.

  In this case, the order of addition of both reactants is not particularly limited, but it is preferable to add aromatic tetracarboxylic acids to the solution of aromatic diamines.

  Vacuum degassing during the polymerization reaction is an effective method for producing a good quality organic solvent solution of polyamic acid. Moreover, you may perform polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction.

  Specific examples of the ring-closing catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylamine, and heterocyclic tertiary amines such as isoquinoline, pyridine and betapicoline. It is preferable to use at least one amine selected from tertiary amines.

  Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, Acetic anhydride and / or benzoic anhydride are preferred.

  The content of the ring-closing catalyst with respect to the polyamic acid is preferably in a range where the content (mol) of the ring-closing catalyst / the content (mol) of the polyamic acid is 0.5 to 8.

  In addition, the content of the dehydrating agent relative to the polyamic acid is preferably in a range where the content of dehydrating agent (mole) / polyamic acid content (mole) is 0.1 to 4. In this case, a gelation retarder such as acetylacetone may be used in combination.

The polyimide film used in the production method of the present invention is obtained by peeling, stretching, drying, and heat-treating a gel film obtained by continuously extruding or coating a polyamic acid solution in a film form on a rotating support. However, as a typical method for producing a polyimide film from an organic solvent of polyamic acid, an organic solvent solution of polyimide acid that does not contain a ring closure catalyst and a dehydrating agent is placed on a support from a slit base. After casting into a film and heating and drying on a support to form a gel film having self-supporting properties, the film is peeled off from the support and then heat imidized by heat treatment at high temperature. Ring-closing method, and organic solvent of polyamic acid impregnated with ring-closing catalyst and dehydrating agent from a base with a slit The film is cast into a film and partially imidized on the support to form a film having self-supporting properties. Then, the film is peeled off from the support, heat-dried / imidized, and subjected to heat treatment. A chemical ring closure method is mentioned.

  The present invention may employ any of the above ring closure methods, but the chemical ring closure method requires a facility for containing a ring closure catalyst and a dehydrating agent in an organic solvent solution of polyamic acid, but has a self-retaining gel. It can be said that it is a more preferable method in that a film can be obtained in a short time.

The gel film referred to in the present invention is a polyimide film containing a polyimide precursor and / or a partially imidized solvent.
Next, characteristics evaluation methods and evaluation criteria used in the description of the present invention will be described.

[In-plane orientation index]
In the present invention, polarized Raman analysis was used for in-plane orientation measurement. In order to increase the aerial resolution of polarized Raman analysis, an oblique section was created to increase the aerial resolution to 50 nm. If a device with higher resolution can be obtained as a result of advances in science and technology, it is not necessary to make an oblique section as long as the same evaluation results as the section method can be obtained. In preparing the slices, in order to prevent disturbance during sample preparation, the cutting direction of all the samples was made constant, and the advancing direction of the blade was parallel to the film surface.

The in-plane orientation value at the measurement point in this evaluation is attributed to the molecular structure A that is considered to be nearly parallel to the film surface in the polarized Raman analysis when the polyimide molecules are oriented in the plane. defined by the following equation for the Raman band intensity I _B attributable relative molecular structures B considered nearly perpendicular to the Raman band intensity I _a and the film surface.
(In- plane orientation value at each measurement point) = (I _A parallel / I _B parallel) / (I _A vertical / I _B vertical )
I _A parallel : Raman band intensity I _B parallel A in parallel condition : B Raman band intensity I _A perpendicular under parallel conditions : A 1 Raman band intensity I _B vertical under vertical conditions : Raman band intensity of B under vertical conditions

Note that the parallel condition is when the excitation light polarization direction is parallel to the film surface (perpendicular to the film thickness direction), and the excitation light polarization direction is perpendicular to the film surface (parallel to the film thickness direction). Condition. The in- plane orientation value at each measurement point is measured, and a value obtained by subtracting the in- plane orientation value of 2 μm from the surface layer from the value is defined as the in- plane orientation index at the measurement point. Plane orientation index of the film samples to create 5 specimens, the average of 3 samples excluding the maximum and minimum was determined by rounding off to two decimal. Of course, the in-plane orientation index since it is ultimately determined by the difference, can be performed to reduce the difference is only the result of measurement from the same slice.

In this evaluation method, for example, when 4,4′-diaminodiphenyl ether is used as the aromatic diamine and pyromellitic dianhydride is used as the aromatic tetracarboxylic dianhydride, the molecule is considered to be almost parallel to the film surface. The structure A can use the CN stretching vibration of the imide bond attributed to 1395 cm ⁻¹ , and the molecular structure B considered to be nearly perpendicular to the film surface can use the C═O stretching vibration attributed to 1795 cm ⁻¹ .

The equipment and measurement conditions used in this evaluation are described below.
Device: PDP320 (Photon Design)
Measurement mode: Micro Raman objective lens: x100
Beam diameter: 1μm
Cross slit: 120 μm
Light source: He-Ne laser / 632.8 nm
Laser power: 35mW
Diffraction grating: Single 600gr / mm
Slit: 100 μm
Detector: CCD (Nippon Roper, Inc.)

  Hereinafter, the present invention will be further described with reference to examples. The characteristics evaluation method in the examples will be described as follows.

(1) Adhesive strength with acrylic adhesive An acrylic adhesive (DuPont Co., Ltd .: Piralux LF010) is sandwiched between a polyimide film and copper foil, a molding temperature of 160 ° C., a molding time of 30 minutes, a molding pressure of 10 .Pressing is performed under the condition of 2 MPa (400 mm square plate) to produce a laminated board. The laminate was cut into 10 mm, and 90 ° peeling was measured at 100 mm / min. In addition, the evaluation result was performed as follows, and it was considered as “good”.
A: 20.0 N / cm or more B: 18.0 N / cm or more and less than 20.0 N / cm x: less than 18.0 N / cm

(2) Adhesive strength with epoxy adhesive After applying an epoxy resin adhesive (Toa Gosei Co., Ltd .: Aronmite BX-60) to a polyimide film with a bar coater, and further placing a copper foil on the adhesive Dry at 100 ° C. for 2 minutes. Then, it hardens at 150 degreeC and 50 kgf / cm <2> for 30 minutes, and produces a laminated board. The laminate was cut into 10 mm, and 90 ° peeling was measured at 100 mm / min. In addition, the evaluation result was performed as follows, and it was considered as “good”.
A: 20.0 N / cm or more B: 18.0 N / cm or more and less than 20.0 N / cm x: less than 18.0 N / cm

(3) Evaluation of O / C, N / C ratio The atomic abundance ratio of each element on the polyimide film surface is determined by irradiating the polyimide film placed in an ultra-high vacuum with soft X-rays and analyzing the photoelectrons emitted from the surface with an analyzer. It was done by detecting. Specifically, using an X-ray photoelectron spectrometer (ESCALAB220IXL, Thermo VG Scientific) using monochromatic AlK _α1,2 line ( _1486.6 eV) as an excitation X-ray, an X-ray diameter of 1 mm and a photoelectron escape angle of 90 °. Measurements were taken. In this evaluation, the C _1s peak of neutral carbon is set to 284.6 eV.

  The O / C ratio indicates the abundance ratio of oxygen atoms per carbon atom, and the N / C ratio indicates the abundance ratio of nitrogen atoms per carbon atom.

(4) Oxygen concentration in the discharge atmosphere The oxygen concentration was sampled at a flow rate of 200 ml / min under the same conditions except that no discharge was performed while the film to be processed was transported at a processing speed. However, the measurement was performed using a zirconia oxygen analyzer (LC-850KS) manufactured by Toray Engineering Co., Ltd.

(5) Confirmation of discharge state When the discharge state is confirmed visually during the discharge process and the discharge is in a state of flowing along the transport film (creeping discharge), the equipment should be installed so that the creeping discharge length can be measured. The length was measured visually with a ruler placed beside.

[Example 1]
A normal pressure plasma treatment was performed on Kapton 50H (polyimide film [thickness: 12.5 μm]; manufactured by Toray DuPont Co., Ltd.) using an apparatus as shown in the figure. As the high voltage application electrode, a SUS304 rod electrode was used, and as the drum electrode, an alumina-coated iron electrode (relative permittivity at 100 kHz = 7) was used, and the coolant was water. As the processing atmosphere, Ar gas was jetted in a film transport direction (lateral direction) at a flow rate of 2.8 m / sec from a height of 3 cm from the film surface, the oxygen concentration was 200 ppm, and the processing strength was 150 W · min / m 2. The process was done. As a situation at the time of discharge, creeping discharge of 4 cm or more was observed. When adhesion evaluation was performed on the obtained film, the adhesive strength with the acrylic adhesive was 20.8 N / cm, and the adhesive strength with the epoxy adhesive was 20.5 N / cm. Table 1 also shows the in-plane orientation index, the O / C ratio, and the N / C ratio. The in-plane orientation index of the film before the treatment is also shown in Table 1.

[Example 2]
By performing the same operation as in Example 1 except that an iron electrode (relative dielectric constant at 100 kHz = 16) having a three-layer coating coating of polyimide resin, alumina, and barium titanate was used as the drum electrode. Then, a surface-treated polyimide film was obtained. As a situation at the time of discharge, creeping discharge of 3 cm was observed. When adhesion evaluation was performed on the obtained film, the adhesive strength with the acrylic adhesive was 19.0 N / cm, and the adhesive strength with the epoxy adhesive was 18.5 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

[Comparative Example 1]
By performing the same operation as in Example 1 except that an iron electrode (relative dielectric constant at 100 kHz = 22) with a two-layer coating of alumina and barium titanate was used as the drum electrode, surface treatment was performed. The polyimide film which performed was obtained. There was no creeping discharge as a condition during discharge. When adhesion evaluation was performed on the obtained film, the adhesive strength with the acrylic adhesive was 18.3 N / cm, and the adhesive strength with the epoxy adhesive was 17.0 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

[Example 3]
All examples except that Ar gas was jetted in the film transport direction (lateral direction) at a flow rate of 5.6 m / sec from the height of 3 cm from the film surface to change the oxygen concentration to 50 ppm. By performing the same operation as 2, a surface-treated polyimide film was obtained. As a situation at the time of discharge, creeping discharge of 4 cm or more was observed. When adhesion evaluation was performed on the obtained film, the adhesive force with the acrylic adhesive was 21.0 N / cm, and the adhesive force with the epoxy adhesive was 20.5 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

[Example 4]
Except that Ar gas was jetted from the height of 3 cm from the film surface toward the film surface at a flow rate of 2.8 m / sec (downward) to change the oxygen concentration to 180 ppm, all the same as in Example 2. By performing this operation, a polyimide film subjected to surface treatment was obtained. As a situation at the time of discharge, creeping discharge of 4 cm or more was observed. When adhesion evaluation was performed with respect to the obtained film, the adhesive force with an acrylic adhesive was 20.5 N / cm, and the adhesive force with an epoxy adhesive was 20.2 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

[Example 5]
By using the same operation as in Example 4 except that an iron electrode with a two-layer coating coating of alumina and barium titanate (relative permittivity at 100 kHz = 22) was used as the drum electrode, A treated polyimide film was obtained. As a situation at the time of discharge, creeping discharge of 3 cm was observed. When adhesion evaluation was performed with respect to the obtained film, the adhesive force with the acrylic adhesive was 18.2 N / cm, and the adhesive force with the epoxy adhesive was 18.0 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

[Comparative Example 2]
Glow discharge with Kapton 50H (polyimide film [thickness: 12.5 μm]; manufactured by Toray DuPont Co., Ltd.) under a gas composition of argon gas atmosphere, pressure of 0.1 torr, output of 150 W · min / m 2 A processed film was prepared by performing plasma treatment according to the above. Note that creeping discharge did not occur because of glow discharge. When adhesion evaluation was performed on the obtained film, the adhesive strength with the acrylic adhesive was 18.0 N / cm, and the adhesive strength with the epoxy adhesive was 16.8 N / cm. The in-plane orientation index, O / C ratio, and N / C ratio are also shown in Table 1.

  The polyimide film obtained in the present invention is a pressure-sensitive adhesive coated with a support for an electric wiring board laminated with a metal foil or a metal thin film, a coverlay film for protecting a flexible printed circuit, a wire or cable insulating film, and a film surface adhesive. It can be suitably applied to uses such as tape.

1: Polyimide film 2: Delivery roll 3: High voltage application electrode 4: Polyimide film support electrode 5 to be treated: High voltage power supply 6: Matching transformer 7: Winding roll 8: Gas introduction system 9: Discharge treatment section

Claims (2)

A polyimide film is subjected to a discharge treatment with a drum electrode having a relative dielectric constant of 25 or less and an oxygen concentration of 500 ppm or less, and the discharge state is creeping discharge, and the creeping discharge length is 3 cm or more. become so by performing the discharge treatment, in-plane orientation index of 50nm inner in the thickness direction from the surface layer of the film is at least 0.30, and it also is 0.25 or more in-plane orientation index of 100nm inner layer polyimide The manufacturing method of the polyimide film characterized by manufacturing a film . A polyimide film in which the in-plane orientation index of the 50 nm inner layer is 0.30 or more in the thickness direction from the surface layer of the film and the in-plane orientation index of the 100 nm inner layer is also 0.25 or more in the thickness direction from the surface layer of the film in the thickness direction. The method for producing a polyimide film according to claim 1, wherein the in-plane orientation index of the 50 nm inner layer is 0.40 or more, and the in-plane orientation index of the 100 nm inner layer is also 0.30 or more.

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