JP2002348388A - Polyimide film and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film improved in the surface defects caused by a polymer-modification product and an imide-modification product; and a production method for the same. SOLUTION: This polyimide film is characterized in that the density of defects caused by a polymer modification product and an imide modification product on the film surface is 6.0×10<-3> /m<2> or lower. The density of defects is obtained by a method comprising exposing the film surface to incandescence or polarized light, counting the number of projections having lengths of at least 300 μm and holes and air bubbles having lengths of at least 75 μm present on the surface of at least 170 m<2> by using a surface inspection apparatus, and calculating the density of defects by using the above-counted number as the number of defects.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a support for an electric wiring board on which a metal foil represented by a copper foil or a metal thin film is laminated, or as a coverlay film for protecting a flexible printed circuit. And a method for producing the same. More specifically, the present invention relates to a polyimide film having an improved defect attached to the film surface and a method for producing the same.

[0002]

2. Description of the Related Art Polyimide films are used in a wide range of industrial fields as electrical insulating materials requiring heat resistance because of their high heat resistance and high electrical insulation properties. In the use as a support, for example, solder can be used to connect an electric component such as an IC to a copper foil, and the electric wiring can be reduced in size and weight. Accordingly, the use of flexible printed circuit boards has been expanded, and demand for polyimide films has been growing. However, with the diversification of uses of the electric wiring board and the increase in the number of wirings, the demand for improvement in performance as an electric insulating support and improvement in workability has increased. Conventionally, a polyimide film has a tetracarboxylic acid component and a diamine component, which are substantially equimolar, and a polyamide acid solution polymerized in an organic polar solvent is cast from a die by extrusion onto a casting drum, a support of a belt, and heated. ,
After chemically or thermally ring-closing or drying and solidifying to the extent that it has self-supporting properties, the film-shaped resin is peeled off from the casting drum or endless belt, heated, stretched, and heat-treated with a tenter. Was.

However, most of the defects on the polyimide film surface are formed by protrusions, holes and bubbles caused by polymer-modified or imidized-modified substances present in the film. There was a problem.

[0004] The polymer-modified product is a high-viscosity gel-like product generated during the polymerization of polyamic acid, which is a precursor of polyimide, and the imide-modified product is a dehydrating agent and a dehydration catalyst added to a polyamic acid solution after polymerization is completed. Is a partially imidized insoluble polyamic acid generated upon mixing. When a polyimide film is used for electronic parts such as a heat-resistant flexible printed circuit (FPC), if a heat-resistant adhesive is applied to the surface of the polyimide film, application unevenness and adhesive cissing occur.
The yield was decreasing.

On the other hand, Japanese Patent Application Laid-Open No. 62-156132 discloses that
An example is shown in which a low-viscosity polymer solution having a viscosity of 100 poises or less is removed with a metal short fiber sintered metal filter. In this example, however, it is effective for removing foreign matter and minute polymer denatured substances in a solvent. However, there is no effect on removing a high-viscosity polymer denatured product generated at a viscosity of 300 poise or more, and there is no effect of improving yield such as FPC. Also, Japanese Patent Application Laid-Open No. H5-1548
In No. 92, there is an example in which a metal sintered filter having a pore diameter of 3 μm to 50 μm is used for extrusion molding of a thermoplastic polyimide resin. However, a thermoplastic polyimide film has insufficient solder heat resistance and is insufficient, and a metal powder sintered metal is used. Since no filter is used, it is not effective for removing polymer-modified substances. Polyester films with few defects are sometimes used for flexible printed circuits, but have insufficient solder heat resistance and are insufficient.

[0006]

SUMMARY OF THE INVENTION The present invention fundamentally solves the problems of such a polyimide film, and improves the disadvantages caused by polymer-modified products and imide-modified products on a film surface different from the conventional polyimide film. And a method for producing the same.

[0007]

That is, the present invention relates to a method wherein the density of defects caused by a polymer-modified product and an imide-modified product on a film surface is 6.0 × 10 ⁻³ / m ² or less. In the process of extruding a polyamic acid solution and chemically and thermally closing the polyimide film to form a polyimide film, a metal powder sintered metal filter having a mesh size of 1 to 30 μm as a filter. And filtering the polyamic acid solution using the method.

[0008] The defect caused by the polymer-modified product and the imidized-modified product on the surface of the polyimide film produced by the method of the present invention is reduced to not more than 6.0 × 10 ^-3 / m ² or less. Accordingly, the occurrence of adhesive repelling, which is a problem in flexible printed circuits, is greatly reduced, and the yield can be improved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the density of defects caused by a polymer-modified product and an imide-modified product on the film surface is the density of the number of projections and holes appearing on the film. Can be measured. <Measuring method of defect density> The incandescent light or the polarized light is applied to the film surface, and the number of the protrusions having a long diameter of 300 μm or more, the holes having the long diameter of 75 μm or more, and the number of bubbles existing on the surface of at least 170 m ² or more are measured with a surface inspection device. Count and use this number as the number of defects to calculate the density of the defects.

In the present invention, the density of this defect is 6.
It is necessary to be 0 × 10 ⁻³ / m ² or less.

The polyamic acid, which is a precursor of the polyimide in the present invention, comprises an aromatic tetracarboxylic acid and an aromatic diamine and is composed of a repeating unit represented by the following formula 1.

[0012]

Embedded image In the above formula, R1 is a tetravalent organic group having at least one aromatic ring, the number of carbon atoms of which is 25 or less, and each of the two carboxyl groups bonded to R1 is R1.
And the carbon atom to which the amide group of the aromatic ring is bonded is a carbon atom bonded to an adjacent carbon atom.
Is a divalent organic group having at least one aromatic ring,
The carbon number is 25 or less, and the amino group is R2
Is bonded to a carbon atom of an aromatic ring.

Specific examples of the above 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-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5 6-tetracarboxylic acids and their amide-forming derivatives. In the production of polyamic acid, these acid anhydrides are preferably used.

Specific examples of the above aromatic diamines include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4'-
Diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3'-dimethoxybenzidine , 1,4-bis (3methyl-5aminophenyl) benzene and amide-forming derivatives thereof. Especially, it is preferable to contain at least paraphenylenediamine.

Specific examples of the organic solvent used in the present invention include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like. May be used alone or in combination of two or more, or may be used in combination with a non-solvent such as benzene, toluene and xylene. The organic solvent solution of polyamic acid used in the present invention contains 5 to 40% by weight, preferably 10 to 30% by weight of solids, and its viscosity is 500 to 2 as measured by a Brookfield viscometer.
0000 poise, preferably 1,000 to 10,000 poise is preferable for stable liquid sending. Further, the polyamic acid in the organic solvent solution may be partially imidized, and may contain a small amount of an inorganic compound.

In the present invention, the aromatic tetracarboxylic acid and the aromatic diamine are polymerized in such a ratio that their mole numbers are substantially equal, or one of them is in the range of 10 mol%, preferably 5 mol%, and the other is in the range of 5 mol%. It may be excessively mixed. The polymerization reaction is carried out continuously for 10 minutes to 30 hours at a temperature of 0 to 80 ° C. with stirring and / or mixing in an organic solvent. However, if necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. I don't care. 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 removal during the polymerization reaction is an effective method for producing a high quality polyamic acid in an organic solvent solution. Before the polymerization reaction, a small amount of a terminal blocking agent may be added to the aromatic diamine to control the polymerization reaction.

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

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

The content of the ring-closing catalyst and dehydrating agent with respect to the polyamic acid is represented by the following formulas

[0020]

(Equation 1)

[0021]

(Equation 2) It is preferable that Further, a gel retarder such as acetylacetone may be used in combination.

As a method for producing a polyimide film from an organic solvent of polyamic acid, an organic solvent solution of polyamic acid containing no ring-closing catalyst and a dehydrating agent is cast from a die having a slit on a support and formed into a film. A thermal ring-closing method in which a gel film having self-supporting properties is formed by heating and drying on a support, then peeled from the support, and further subjected to drying and heat treatment at a high temperature for imidization; and a ring-closing catalyst and dehydration. An organic solvent of polyamic acid containing the agent was cast from a die with a slit onto a support, formed into a film, and partially imidized on the support to form a gel film having self-supporting properties. After that, a typical method is a chemical ring closure method in which the substrate is peeled off from the support, dried by heating / imidization, and heat-treated. In the present invention, either ring-closing method may be adopted, but the chemical ring-closure method requires a facility containing a ring-closing catalyst and a dehydrating agent in an organic solvent solution of polyamic acid, but a gel film having self-supporting properties is short. It is more preferable because it can be obtained in time.

The method for incorporating the ring-closing catalyst and the dehydrating agent into the polyamic acid includes a method in which the organic solvent solution of the polyamic acid and the ring-closing catalyst and the dehydrating agent are mixed by a rotary mixer, a method in which the organic solvent solution of the polyamic acid is statically mixed. A method of injecting a closing catalyst and a dehydrating agent immediately before the static mixer while feeding the mixture into a mixing machine, a method of casting an organic solvent solution of polyamic acid on a support, and then contacting the solution with a ring closing catalyst and a dehydrating agent. However, in view of the content of the ring-closing catalyst and the dehydrating agent and the uniformity thereof, a method of mixing with a mixer and feeding a mixture of the ring-closing catalyst, the dehydrating agent and the organic solvent solution of polyamic acid to the slit die is preferable. The viscosity of the mixture is 100 to 10,000
It is necessary to adjust the solid content concentration and the temperature so as to become poise. Since the polyamic acid has a property in which the viscosity becomes extremely high due to the thermal ring-closing reaction of the polyamic acid and cannot be discharged from the mouthpiece, it needs to be kept at a low temperature (for example, -10 ° C).

The mixed solution is formed into a film through a slit die, cast on a heated support, and subjected to a thermal ring closure reaction on the support to form a self-supporting gel film. Peeled from the support. The support is a metal rotating drum or an endless belt, the temperature of which is controlled by a liquid or gaseous heating medium and / or by radiant heat such as an electric heater.

The gel film receives heat from the support and / or
Alternatively, heat is received from a heat source, such as hot air or an electric heater, so that 30
Heating to 200 ° C, preferably 40-150 ° C, causes a ring-closing reaction, and by drying the volatile components such as the released organic solvent, the resin has self-supporting properties and is separated from the support.

The gel film peeled from the support is preferably stretched in the running direction while controlling the running speed by a rotating roll. Stretching is performed at a temperature of 140 ° C.
It is performed at a magnification of 5 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times.

The gel film stretched in the running direction is introduced into a tenter device, and both ends in the width direction are gripped by a tenter clip, and stretched in the width direction while running with the tenter clip. In the drying zone, the gel film is dried.

Hereinafter, the filtration method of the present invention will be described.

The filter used in the present invention is obtained by uniformly laminating and sintering a metal powder, and has an aperture of 1 to 30.
μm, and a porosity of 25 μm.
It is preferably in the range of 〜80%. 1 μm opening
Below, the pressure loss of the filter becomes too large,
Productivity decreases. On the other hand, if the opening exceeds 30 μm, removal of the polymer-modified substance becomes poor, and there is no effect in reducing defects. The metal powder may be any as long as it has corrosion resistance, but stainless steel, Hastelloy, or the like is preferable. Furthermore,
The shape of the filter can be selected according to the form of extrusion, the amount of gel, and the life of the filter, such as a screen type, a leaf type, and a pencil type. Further, other types of filters, for example, a metal short fiber metal filter may be used in combination before and after the metal powder sintered metal filter. Since metal short-sintered metal filters are made by sintering fibers, the filtration pressure of the filter increases when a high-viscosity polyamic acid solution is filtered, and the network structure formed by metal fibers is deformed, causing Although it passes through a material with a flexible structure such as a denatured material, the metal powder sintered metal filter deforms at a higher pressure than metal fibers because the fine powder is bonded in a three-dimensional stitch structure. Without this, the modified polymer is crushed and trapped, which is effective for removing the modified polymer from the polyamic acid solution. The polymer filtration method uses a metal powder sintered metal filter for filtering a polyamic acid solution having a viscosity of 100 to 10,000 poise. Preferably, the 500 to 10,000 poise amic acid solution after the completion of the polymerization is filtered through a metal powder sintered metal filter. Filtration of a low-viscosity amic acid solution having a viscosity of less than 100 poise before the completion of the polymerization is not effective because a high-polymer modified product is formed in the subsequent polymerization.

In the chemical ring closure process, a dehydrating agent, a dehydrating catalyst, and the like are mixed and cast from a die to a support. Is preferably filtered using a filter having openings of 2 to 35 μm between the bases after mixing. In this step, imidization proceeds and imide-modified substances are generated. Any filter may be used as long as it has corrosion resistance, but stainless steel, Hastelloy, or the like is preferable. When the opening is 2 μm or less, the pressure loss of the filter becomes too large, and the productivity is reduced. On the other hand, if the opening exceeds 35 μm, the removal of the imide-modified substance becomes poor, and there is no effect on the reduction of defects. The type of filter may be either a metal fiber sintered metal or a metal powder sintered metal.

[0031]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Before describing the embodiments, the evaluation method used in the embodiments will be described. <Method of measuring the density of defects> The film was exposed to incandescent light or polarized light, and the film was run using a commercially available film inspection device (PMAX manufactured by Hutec), and at least 1
The number of protrusions having a long diameter of 300 μm or more, holes having a long diameter of 75 μm or more, and bubbles existing on a surface of 70 m ² or more was counted by a surface inspection device, and the number of defects was calculated using this number as the number of defects.

Example 1 Dried N, N-dimethylacetamide 1900.6 k
4,4'-diaminodiphenyl ether 20 in g
Dissolve 0.024 kg (1 kmol) and stir at 20 ° C. while purifying powdered pyromellitic dianhydride 2
18.12 kg (1 kmol) was added little by little, and stirring was continued for 1 hour to obtain a transparent polyamic acid solution. The solution had a viscosity of 3500 poise at 20 ° C. This polyamic acid solution was used as a first filter, filtered through a metal powder sintered metal filter having a porosity of 36% with 20 μm openings, and acetic anhydride was added in an amount of 2.5 mol per polyamic acid unit.
1, 2.0 mol of pyridine per polyamic acid unit
Is mixed while cooling, and as a second filter, 20 μm
After filtering through a metal fiber sintered metal filter having a porosity of 71% with a mesh opening, a polyamide organic solvent solution was obtained. The organic solution of the polyamic acid was cooled to −10 ° C. and supplied in a fixed amount to form a film. The base slit width is 1.3mm, length 1800
extruded from a mm T die. It was cast on a metal endless belt at 90 ° C. to obtain a self-supporting gel film. The gel film was peeled off from the metal endless bell, stretched in the running direction at a temperature of 65 ° C., and then stretched in the width direction with a tenter. The gel film is dried at a temperature of 260 ° C. for 40 seconds, then heat-treated at 430 ° C. for 1 minute, cooled for 30 seconds while relaxing in a cooling zone, edge-cut the film, and the film surface is cleaned with a commercially available web cleaner. Thereafter, 500 m of a polyimide film having a width of 2000 mm and a thickness of 25 μm was obtained.

When the type and length of the surface defects of this film were measured and the number thereof was counted, the number of defects caused by the polymer-modified substance and the imide-modified substance on the film surface was 3, and the density was lower. 3.0 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Example 2 In the same manner as in Example 1, the aperture of the sintered metal fiber filter of the first filter was set to 30 μm. Cap slit width is 1.5mm, length 1500mm
Extruded from the T-die. The gel film was dried at a temperature of 260 ° C. for 5 minutes, and then heat-treated at 430 ° C. for 10 minutes, cooled in a cooling zone for 60 seconds while relaxing, and edge-cut the film to obtain a polyimide film having a width of 1400 mm and a thickness of 125 μm. 300 m was obtained.

The types and lengths of the surface defects of this film were measured and counted. As a result, the number of defects caused by the polymer-modified substance and the imide-modified substance on the film surface was two.
The density was 4.8 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Example 3 In the same manner as in Example 1, the aperture of the metal fiber sintered metal filter of the first filter was set to 5 μm.
The base slit width is 1.2mm, length 1800mm T
Extruded from the die. The gel film was dried at a temperature of 260 ° C. for 20 minutes, then heat-treated at 450 ° C. for 30 seconds, cooled for 10 seconds while relaxing in a cooling zone, edge-cut the film, 2000 mm wide and 12.5 μm thick. 1000 m of a polyimide film was obtained.
The type and length of the surface defects of this film were measured, and the number was counted. The number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 7, and the density was:
It was 3.5 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Example 4 In the same manner as in Example 1, the metal filter sintered metal filter having a pore size of 35 μm and a pore ratio of 71% was used instead of the metal fiber sintered metal filter having a pore size of 20 μm and a pore ratio of 71%.
Was used. 2000 width
A polyimide film having a thickness of 25 mm and a thickness of 25 μm was obtained in an amount of 500 m.

The types of surface defects of this film were measured and counted. As a result, the number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 5, and the density was 5. It was 0 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier.
Electrolytic copper foil is applied to the surface of the film coated with the adhesive
The laminate was pressure-laminated at 0 ° C and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Example 5 140,4'-Diaminodiphenyl ether in 1906 kg of dried N, N-dimethylacetamide.
Dissolve 02 kg (0.7 kmol) and 32.36 kg (0.3 kmol) of paraphenylenediamine and add 218.12 kg (1 kmol) of purified powdered pyromellitic dianhydride little by little while stirring at 20 ° C. And
Stirring was continued for 1 hour to obtain a clear polyamic acid solution.
The solution had a viscosity of 3500 poise at 20 ° C.
This polyamic acid solution was used as a first filter at 20 μm.
After filtering through a metal powder sintered metal filter having a porosity of 36% through the openings of the above, 2.5 mol of acetic anhydride and 2.0 mol of pyridine with respect to the polyamic acid unit were added to the polyamic acid solution. Mix while cooling,
As a second filter, porosity is 71% with 20 μm aperture
After filtration through a metal fiber sintered metal filter, a polyamide organic solvent solution was obtained. This organic solution of polyamic acid was added to -10
After cooling to ° C., a fixed amount was supplied to form a film. The die slit width was extruded from a T die of 1.3 mm and length of 1800 mm. It was cast on a metal endless belt at 90 ° C. to obtain a self-supporting gel film. The gel film was peeled off from the metal endless bell, stretched in the running direction at a temperature of 65 ° C., and then introduced into a tenter device shown in FIG. The film was stretched in the width direction with a tenter. The gel film is 26
Dried at a temperature of 0 ° C. for 40 seconds, then heat-treated at 430 ° C. for 1 minute, cooled for 30 seconds while relaxing in a cooling zone, edge-cut the film, and 2,000 m wide.
m, a polyimide film having a thickness of 25 μm was obtained in an amount of 500 m.

The type and length of the surface defects of this film were measured and the number was counted. As a result, the number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 0, and the density was lower. , 0.0 × 10 ⁻³ / m ² . Also,
A polyester / epoxy adhesive was applied to this film with a roll coater and dried at 160 ° C. with a dryer. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Example 6 4,4'-Diaminodiphenyl ether in 1942 kg of dried N, N-dimethylacetamide
While dissolving 02 kg (0.8 kmol) and 21.58 kg (0.2 kmol) of paraphenylenediamine and stirring at 20 ° C., 141.78 kg (0.65 kmol) of purified powdery pyromellitic dianhydride and 3 , 3'-
4,4'-biphenyltetracarboxylic acid dianhydride 10
2.98 (0.35 kmol) was added little by little, and stirring was continued for 1 hour to obtain a transparent polyamic acid solution. The solution had a viscosity of 3500 poise at 20 ° C. This polyamic acid solution was used as a first filter, filtered through a metal powder sintered metal filter having a porosity of 36% with 20 μm openings, and then 2.5 mol of acetic anhydride and pyridine were added to the polyamic acid solution. 2.0 mol was mixed with the polyamide acid unit while cooling, and the second
As a filter, a polyamide organic solvent solution was obtained after filtration through a metal fiber sintered metal filter having a porosity of 71% with 20 μm openings. The organic solution of the polyamic acid was cooled to −10 ° C. and supplied quantitatively to form a film. The base slit width is
Extruded from a 1.3 mm, 1800 mm long T-die. It was cast on a metal endless belt at 90 ° C. to obtain a self-supporting gel film. The gel film was peeled off from the metal endless bell, stretched in the running direction at a temperature of 65 ° C., and then introduced into a tenter device. The film was stretched in the width direction with a tenter. The gel film is 4 times at a temperature of 260 ° C.
Dry for 0 seconds, then heat treat at 430 ° C. for 1 minute, cool for 30 seconds while relaxing in the cooling zone, cut the film edge, 2000 mm wide and 25 μm thick
500 m of a polyimide film was obtained.

When the type and length of surface defects of this film were measured and the number thereof was counted, the number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 0, and the density was lower. , 0.0 × 10 ⁻³ / m ² . Also,
A polyester / epoxy adhesive was applied to this film with a roll coater and dried at 160 ° C. with a dryer. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. Repelling of the adhesive was small and a good yield was obtained.

Table 1 summarizes the results of the above examples.

[0044]

[Table 1] Comparative Example 1 In the same manner as in Example 5, acetic anhydride was mixed with 2.5 mol based on the polyamic acid unit, and pyridine was mixed with 2.0 mol based on the polyamic acid unit while cooling the mixture.
A polyamide organic solvent solution was obtained without using a metal fiber sintered metal filter having a pore size of 20% of the first filter and a porosity of 71%. 500 m of a polyimide film having a width of 2000 mm and a thickness of 25 μm was obtained.

The type and length of the surface defects of this film were measured, and the number was counted. As a result, the number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 60, and the density was lower. , 60.0 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. The adhesive was repelled frequently and the yield was poor.

Comparative Example 2 In the same manner as in Example 5, instead of the metal powder fiber sintered metal filter having a porosity of 36% with a 20 μm opening of the first filter, a porosity of 7 with a 20 μm opening was used.
Using a 1% metal fiber sintered metal filter, width 20
100 mm polyimide film 25 μm thick
0 m was obtained.

The type and length of the surface defects of this film were measured and the number was counted. The number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 65, and the density was: It was 32.5 × 10 ⁻³ pieces / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. The adhesive was repelled frequently and the yield was poor.

COMPARATIVE EXAMPLE 3 The same procedure as in Example 5 was repeated, except that the metal powder fiber sintered metal filter having a porosity of 36% with a 20 μm mesh of the first filter was replaced with a 35 μm mesh with a gap of 36 mm.
% Metal powder using a sintered metal filter
0mm, 25μm thick polyimide film 1000
m was obtained.

The type and length of the surface defects of this film were measured, and the number was counted. As a result, the number of defects caused by the polymer-modified product and the imide-modified product on the film surface was 20, and the density was lower. 10 × 10 ⁻³ / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. The adhesive was repelled frequently and the yield was poor.

Comparative Example 4 In the same manner as in Example 6, instead of the metal powder fiber sintered metal filter having the porosity of 36% with the aperture of 20 μm of the first filter, the gap of the pore 1 with the aperture of 0.9 μm was used.
A 0% metal powder sintered metal filter was used. The filtration pressure was too high, the film formation was not stable, and a polyimide film could not be obtained.

COMPARATIVE EXAMPLE 5 In the same manner as in Example 6, the metal filter sintered metal filter having a porosity of 71% with a 20 μm aperture of the second filter was replaced with a porosity of 71% with a 40 μm aperture.
Was used. 2000 width
mm, 25μm thick polyimide film 1000m
Obtained.

The type and length of the surface defects of this film were measured and the number was counted. As a result, the number of defects caused by the polymer-modified substance and the imide-modified substance on the film surface was 20, and the density was lower. 10 × 10 ⁻³ / m ² . Further, a polyester / epoxy adhesive was applied to this film with a roll coater, and dried at 160 ° C. with a drier. An electrolytic copper foil was laminated under pressure at 130 ° C. on the surface of the film coated with the adhesive surface, and cured for 24 hours to obtain a flexible copper-clad polyimide sheet. The adhesive was repelled frequently and the yield was poor.

Comparative Example 6 In the same manner as in Example 6, the metal filter sintered metal filter having a porosity of 71% with a 20 μm opening of the second filter was replaced with a 50% porosity with a 1 μm opening. A metal fiber sintered metal filter was used. The filtration pressure was too high, the film formation was not stable, and a polyimide film could not be obtained.

Table 2 summarizes the results of the above comparative example.

[0055]

[Table 2]

[0056]

According to the present invention, in the process of extruding a polyamic acid solution and chemically and thermally closing the ring to form a polyimide film, a metal powder sintered metal filter having a mesh size of 1 to 30 μm is filtered as a filter. Thus, a good polyimide film having few defects caused by the polymer denatured product on the film surface can be obtained, and the number of defects caused by the polymer modified product and the imide denatured product on the film surface is 6.0. When the content is not more than × 10 ⁻³ / m ² , the adhesive repelling defect caused by minute surface deposits is greatly reduced, and the yield as FPC is good, and excellent effects are exhibited.

Continued on the front page F term (reference) 4F071 AA60 AA88 AG02 AG28 AH13 BA02 BB02 BB06 BB08 BB12 BC13 BC14 4F205 AA40 AC05 AG01 AH36 GA07 GB02 GE02 GE16

Claims (6)

[Claims] The density of a defect caused by a polymer-modified product and an imide-modified product on the film surface is 6.0 × 10 ⁻³ / m ² or less as measured by the following measuring method. Polyimide film. <Measurement method of defect density> The incandescent light or polarized light was applied to the film surface, and the number of protrusions having a long diameter of 300 μm or more, holes having a long diameter of 75 μm or more, and bubbles existing on a surface of at least 170 m ² was counted by a surface inspection device. Then, using this number as the number of defects, the density of the defects is calculated. 2. The polyimide film according to claim 1, wherein the amine component of the polyimide contains one derived from paraphenylenediamine. 3. In the process of extruding a polyamic acid solution and chemically and thermally closing a polyimide film to form a polyimide film, a polyamic acid sintered metal filter having a mesh size of 1 to 30 μm is used as a filter. 3. The method for producing a polyimide film according to claim 1, wherein the solution is filtered. 4. The method for producing a polyimide film according to claim 3, wherein the viscosity of the polyamic acid solution is 100 poise or more. 5. A filter having an aperture of 1 to 30 μm.
4. Filtering using a metal powder sintered metal filter, mixing a dehydrating agent and a dehydrating catalyst, and extruding from a die after filtration using a filter having an aperture of 2 to 35 μm to form a film. Or the method for producing a polyimide film according to 4. 6. The polyamide acid according to claim 3, wherein the polyamic acid contains paraphenylenediamine as an amine component.
5. The method for producing a polyimide film according to any one of 5.