JP4810817B2 - Polyimide film and method for producing the same - Google Patents

Description

  The present invention relates to a polyimide film. More specifically, the present invention is produced by a so-called casting film forming method in which a polyamic acid solution, which is a precursor of polyimide, is coated on a support and dried to obtain a self-supporting film. The present invention relates to a polyimide film having excellent performance and a method for producing the same.

Polyimide films are widely used for electronic information applications. Particularly in recent years, printed wiring boards using a polyimide film as a base material have been widely used as high-density mounting boards. In such printed wiring boards, a method of forming a circuit pattern by forming a copper foil on a polyimide film without using an adhesive is becoming widespread. Since the polyimide film has an imide structure, it has some hygroscopicity. The influence of the hygroscopic property of the polyimide film becomes remarkable particularly in a state where a voltage is applied. In other words, when voltage is applied under humidification, metal resinous protrusions called electromigration are generated in or on the surface of the polyimide resin between the electrodes. Such resinous protrusions continue to grow, and eventually, the electrodes are short-circuited, resulting in electrical breakdown. Such a problem is a big problem particularly in a power supply system using a relatively high voltage and a circuit for driving a display element.
In order to prevent electromigration, it is considered effective to lower the hygroscopicity of the polyimide film itself and at the same time reduce the ionic impurities in the film. In particular, iron, alkali metals and phosphorus are managed from the raw material stage.

In the manufacturing method of a polyimide film, the location which contacts a metal directly in a solution state exists on the manufacturing method. The polyamic acid solution, which is a precursor of the polyimide film, is itself a polyvalent carboxylic acid, and the solvent is also often a highly polar solvent with high dissolving power. For the casting support that is in direct contact with the precursor solution, a stainless steel belt or drum having high corrosion resistance is generally used.
Aromatic polyamide films and aromatic polyimide films are used in the field of magnetic recording and the like, but there is a demand for smoothing the surface due to demands for higher density and smaller size. For these, three methods have been proposed. One method is to use a support made of a general-purpose metal material such as stainless steel (see Patent Document 1). In this case, the surface of the support is corroded and roughened due to the solvent used for film formation, the components contained therein, the high temperature environment, etc., and the resulting film surface gradually loses smoothness. .
Method 2 is a method using a noble metal or semi-noble metal having excellent corrosion resistance (see Patent Documents 2 and 3). However, the method is expensive and the hardness is very small, so that the surface property is improved to a good level due to scratches during use. It was difficult to maintain.
As a third method, there is a method of coating a general-purpose metal material with a fluororesin having excellent corrosion resistance (see Patent Document 4), but the surface property level is always satisfactory due to minute defects in the fluororesin layer. In addition, it was difficult to maintain the corrosion resistance of the support for a long time.
JP 09-29852 A JP-A-63-84908 JP-A 63-4914 JP-A 64-75211

Furthermore, in a film manufacturing method in which a polymer solution such as aromatic polyimide is cast on a support to form a film, a method of using an amorphous metal in at least the surface layer of the support is disclosed, and the surface smoothness of the film is disclosed. (See Patent Document 5).
In addition, a roll characterized by providing a coating made of chromium spinel oxide hydrate (hereinafter referred to as a thin film chromium layer) and a hard film layer on a surface having excellent surface durability and corrosion resistance, and a roll thereof A method for producing a solution-forming film using a film, which suppresses contamination and film surface scratches caused by apparatus corrosion when this film is run in a stretching apparatus, and stably obtains a film having a smooth surface. Can do.
After casting on a support and forming into a film (green film that is a self-supporting film of polyamic acid that is a polyimide precursor), when removing and stretching the solvent and various salts, a solution is used using the roll. A film forming method for manufacturing a film forming film is disclosed (see Patent Document 6).
JP 2001-009852 A JP 11-138626 A

  However, even though such countermeasures are taken, the migration resistance of polyimide films that are generally distributed is not necessarily high, and in particular, Fe, Ni, and Cr that have a large influence on migration resistance and insulation reliability. There was nothing that was suppressed or controlled in terms of the total content or the Fe content, and further improvements were required.

  That is, the present invention is to provide a polyimide film having excellent migration resistance, high insulation reliability, Fe, Ni, Cr, particularly a low Fe content, and a method for producing the same.

As a result of continual research, the inventors of the present invention have dramatically reduced the metal ionic impurities contained in the polyimide film by using a specific material in a specific part of the manufacturing apparatus, and a film having high migration resistance. I found out that I could get it and reached the next invention.
That is, the present invention is a polyimide film obtained by a casting film-forming method having at least a step of applying and drying a solution of a polyamic acid, which is a polyimide precursor, on a support, and containing Fe, Ni, and Cr in the film It is a polyimide film characterized in that the total amount is 20 ppm or less, and in particular, in the total content of Fe, Ni, Cr, the content of Fe is 1/2 or more of the total content of the polyimide film Furthermore, in the above polyimide film, the polyimide is polyimide benzoxazole obtained by condensation of a tetracarboxylic acid anhydride and a diamine having a benzoxazole structure.
Further, the liquid contact part of the polymerization vessel for obtaining the polyamic acid which is a polyimide precursor, the transport pipe is composed of any material selected from austenitic stainless steel and ferritic stainless steel It is a manufacturing method of a polyimide film.

  As described above, it has been intended to use a material having high corrosion resistance for a metal portion in direct contact with a conventional polyimide precursor. However, these proposals are intended to extend the life of the manufacturing apparatus and are not necessarily intended to reduce metallic impurities contained in the obtained polyimide film. In order to reduce the elution of metal ions from the manufacturing apparatus, it is sufficient to construct or cover all with precious metals, but it is unrealistic in terms of cost. In addition, the elution of metal ion impurities from the belt or roll as the support is not at a level that is problematic in terms of characteristics. Rather, elution from a portion where relatively high stress is applied, such as a polymerization apparatus or a liquid feed pump. In order to prevent elution and wear, wear is a problem, and it is not always necessary to select a material based on toughness, which is a different viewpoint, rather than a material that is generally considered to have high corrosion resistance. In particular, by suppressing the content of Fe, Ni, and Cr, particularly the content of Fe, a highly insulating and reliable polyimide film having high migration resistance can be obtained.

The polyimide film of this invention consists of a polyimide obtained by making aromatic diamines and aromatic tetracarboxylic anhydrides react.
In the reaction to obtain polyimide, first, a polyamic acid solution is obtained by subjecting aromatic diamines and aromatic tetracarboxylic anhydrides to a ring-opening polyaddition reaction in a solvent, and then a green film is obtained from the polyamic acid solution. Is formed by dehydration condensation (imidization) after molding.
In the present invention, among these aromatic diamines, aromatic diamines having a benzoxazole structure are suitable diamines. When this preferred diamine is used, the total content of Fe, Ni, and Cr in the present invention The suppression effect becomes remarkable when using a metal of a specific material.

  Specific examples of aromatic diamines having a benzoxazole structure that are particularly preferably used in the present invention include the following.

Among these, amino (aminophenyl) benzoxazole isomers are preferable from the viewpoint of ease of synthesis. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.
In the present invention, it is preferable to use 70 mol% or more of the aromatic diamine having the benzoxazole structure.

The present invention is not limited to the above matters, and the following aromatic diamines may be used. Preferably, it is a polyimide film in which less than 30 mol% of the total aromatic diamine is used together with one or more diamines having no benzoxazole structure exemplified below.
Examples of such diamines include 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl]. Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine,

  3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'- Diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1 , 1-Bi [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1 , 2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl ]propane,

  1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) Phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) Phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

  1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3 Aminophenoxy) benzoyl] benzene, 4,4′-bis [(3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-Aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoro Propane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] Ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4′-bis [3- (4-aminophenoxy) benzoyl] diphenyl Ether, 4,4′-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4 ′ -Bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- ( 4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- ( 4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-fluorophenoxy) ) -Α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4- Amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene,

  3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4 -Diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino- 4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino) -4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-Amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) pheno Si] benzonitrile and some or all of the hydrogen atoms on the aromatic ring in the aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or alkyl groups or alkoxyl group hydrogen atoms. Examples thereof include aromatic diamines substituted with a halogenated alkyl group having 1 to 3 carbon atoms partially or wholly substituted with a halogen atom or an alkoxyl group.

  The tetracarboxylic acid anhydrides used in the present invention are aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

These tetracarboxylic dianhydrides may be used alone or in combination of two or more.
In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are less than 30 mol% of the total tetracarboxylic dianhydrides. Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride,

  Bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1 , 3-Dipropylcyclohexane-1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and the like. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The solvent used when polyamic acid is obtained by polymerizing aromatic diamines and aromatic tetracarboxylic acid anhydrides is particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. Although not preferred, polar organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide Hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, halogenated phenols and the like. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the weight of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by mass, The amount is preferably 10 to 30% by mass.

Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for minutes to 30 hours. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited, but it is preferable to add aromatic tetracarboxylic acid anhydrides to the solution of aromatic diamines. The weight of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and the viscosity of the solution is measured with a Brookfield viscometer (25 ° C.). And from the stability point of liquid feeding, Preferably it is 20-2000 Pa.s, More preferably, it is 200-1000 Pa.s.
The reduced viscosity (ηsp / C) of the polyamic acid in the present invention is not particularly limited, but is preferably 3.0 or more, more preferably 4.0 or more, still more preferably 5.0 or more.

  Vacuum defoaming during the polymerization reaction is effective for producing a high-quality polyamic acid organic solvent solution. Moreover, you may perform superposition | polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.

  As a method of forming a polyimide film from a polyamic acid solution obtained by a polymerization reaction, a green film is obtained by applying a polyamic acid solution on a support and drying, and then subjecting the green film to a heat treatment to obtain an imide. The method of making it react is mentioned.

  The total content of Fe, Ni, and Cr in the polyimide film of the present invention is the mass fraction of the total content of the Fe, Ni, and / or Cr elements in the polyimide film. It is essential that the total content of Fe, Ni and Cr in the film of the present invention is 20 ppm or less. The total content of Fe, Ni, and Cr in the film is more preferably 10 ppm or less, and further preferably 5 ppm or less. The amount of the metal impurities is the total contained in the film as elements of Fe, Ni, and Cr in those contained in the metal state, those contained as the metal compound, those contained in the ionic state, and other films. When the total content of Fe, Ni and Cr in the film exceeds this range, the migration resistance is remarkably lowered. The lower limit is not particularly limited, and ideally it is preferably zero.

In the present invention, the Fe content is preferably ½ or more of the total content of Fe, Ni and Cr. When the content of Fe is less than this range, the migration resistance is deteriorated and the insulation of the film itself may be lowered. That is, since the Fe content is mainly present as an oxide, the insulation is relatively high in a normal state, and the problem becomes more prominent when a voltage is applied and a redox reaction is electrically induced. It is presumed that Ni and Cr elements are present in a metallic state at a high rate and are directly involved in a decrease in insulation in a normal state.
It is more preferable that the content of Fe, Ni, and Cr in the film does not exist as 0.1 μm or larger particles in the film.

As a method of setting the total content of Fe, Ni, and Cr in the film to 20 ppm or less, a portion in contact with the solution of the polymerization vessel used for polymerization of polyamic acid (a wetted portion), the solution transport pipe is austenitic stainless steel, This can be realized by using a specific material made of any material selected from ferritic stainless steel. The liquid contact part of the polymerization vessel is the inner wall of the vessel and the stirring blade. The transportation piping includes valves and the like.
In the present invention, the wetted part of the polymerization vessel and the metal part of the transport pipe are made of austenitic stainless steel or ferritic stainless steel. As austenitic stainless steel, SUS301, SUS301L, SUS630, SUS631, SUS302, SUS302B, SUSXM15J1, SUS303, SUS303Se, SUS304, SUS304L, SUS304J1, SUS304J2, SUS305JS3US3S3, SUS316S, SUS316S, SUS316S SUS321, SUS347, etc. can be used. As the ferritic stainless steel, SUS405, SUS406, SUH409, SUH409L, SUS430, SUS430F, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS444, SUSXM27, and SUS447J1 can be used.
In the present invention, among these, SUS301L, SUS304L, SUS316, SUS316L, SUS317, SUS317L, SUS321, and SUS347, which are more resistant to corrosion, are more preferably low carbon SUS304L, SUS316L, and SUS317L.

In the present invention, it is preferable that the wetted part of the gear pump used for liquid feeding is made of martensitic stainless steel.
As martensitic stainless steel, SUS410, SUS410S, SUS410F2, SUS416, SUS420J1, SUS420J2, SUS420F, SUS420F2, SUS431, SUS440, SUS440C, or the like can be used. Of these, SUS420J1, SUS420J2, and SUS440C having particularly high altitudes can be preferably used.
As these other stainless steels, SUS329J1, SUS39J3L, SUS329J4L, NSS431DPI, HT980, HT1770, HT1960, and the like can be used.

  In the present invention, the total amount of Fe, Ni, and Cr contained in raw material monomers (aromatic diamines, aromatic tetracarboxylic anhydrides, etc.), solvents, and other additives used is controlled within a predetermined range. It is also important to do.

  In the present invention, the support on which the polyamic acid solution is applied in order to obtain a green film includes a long film, an endless belt, a roll, and the like. As the long film, a polymer film such as a polyester film, a polypropylene film, or a polyimide film can be used. Examples of the endless belt include an endless belt made of a bendable material having a thickness of 5 mm or less, preferably 3 mm or less, and more preferably 1 mm or less. The width and length (periphery) of the endless belt are not particularly limited, but the width is 30 cm or more, preferably 50 cm or more, and the length (periphery) is 100 cm or more, preferably 300 cm or more. If the thickness exceeds this range, there may be a problem with curvature. As the roll, a roll having a surface roughness of 30 cm or more and a diameter of 30 cm or more can be used.

  The material of the support is not particularly limited as long as it does not cause significant deformation or dimensional change at the drying temperature of the material to be formed into a film, regardless of whether it is a metal or a nonmetal. Examples of the metal material include iron, stainless steel (SUS), nickel, titanium, tantalum, copper, and hastelloy. Stainless steel is preferably used as the metal material, and austenitic stainless steel is particularly preferable. These surfaces may be subjected to plating or surface treatment with chromium, gold, silver, nickel or the like in order to improve corrosion resistance, hardness, or decrease in adhesiveness. Examples of surface treatments include chromium thin film hydrated oxide film formation and silicone resin or fluorine resin film formation.

  Application of the polyamic acid solution to the support includes, but is not limited to, casting from a slit base, extrusion through an extruder, squeegee coating, reverse coating, die coating, applicator coating, wire bar coating, etc. Conventionally known solution coating means can be appropriately used.

A drying method for obtaining a green film which is a self-supporting film of polyamic acid which is a polyimide precursor in the present invention is heat drying. As the heating method, a known method such as infrared heating, hot air heating, microwave heating or the like can be used.
The film (green film) that has been dried on the support and becomes self-supporting is peeled off from the support, and a polyimide film is obtained by dehydration and ring closure of amic acid by final drying (heat treatment) at a temperature of 150 to 500 ° C. It is done.
Although the thickness of the polyimide film of the present invention is not particularly limited, it is usually 1 to 150 μm, preferably 3 to 50 μm, considering use as a base material for an electronic substrate. This thickness can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.

  In the present invention, a lubricant can be added to improve the productivity, winding property and operability of the film. As the lubricant, inorganic or organic fine particles can be used. As the inorganic fine particles, inorganic or organic fine particles having an average particle diameter of about 0.03 μm to 3 μm can be used. Specific examples include titanium oxide, alumina, Examples thereof include silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate, calcium pyrophosphate, magnesium oxide, calcium oxide, and clay mineral. The particle diameter of the lubricant that can be preferably used is in the range of 0.01 to 10 μm, and the addition amount is in the range of about 0.001 to 1% by mass of the whole film.

  The polyimide film of the present invention is usually an unstretched film, but may be stretched uniaxially or biaxially. Here, the unstretched film refers to a film obtained without intentionally applying a mechanical external force in the surface expansion direction of the film by tenter stretching, roll stretching, inflation stretching, or the like.

You may use the obtained polyimide film as a film base material as it is. When the film is not treated with a surface treatment agent or a surface activator, it is preferable to perform a surface treatment such as corona discharge treatment, low-temperature or normal-pressure plasma treatment, ultraviolet irradiation, or flame treatment.
As described above, the total content of Fe, Ni, and Cr in the film is 20 ppm or less by controlling the monomer, the solvent, the additive, the material of the reaction apparatus, the material of the film production apparatus, and the like when polymerizing the polyamic acid. A polyimide film can be obtained.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.
1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. using an Ubbelohde type viscosity tube.

2. Film thickness of polyimide film The thickness of the film was measured using a micrometer (manufactured by Fine Reef, Millitron 1245D).

3. Tensile modulus, tensile breaking strength and tensile breaking elongation of polyimide film The film after drying was cut into strips having a length of 100 mm and a width of 10 mm in the longitudinal direction (MD direction) and the width direction (TD direction), respectively, and used as test pieces. , Measured using a tensile tester (manufactured by Shimadzu Corporation, Autograph (R) model name AG-5000A) at a tensile speed of 50 mm / min and a distance between chucks of 40 mm, tensile modulus, tensile strength, and tensile elongation at break Asked.

4). Linear expansion coefficient (CTE) of polyimide film
The expansion / contraction rate was measured under the following conditions, and the range from 30 to 300 ° C. was divided at 15 ° C. intervals and obtained from the average value of the expansion / contraction rate / temperature of each divided range.
Device name: TMA4000S manufactured by MAC Science
Sample length; 20mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

5. Quantitative determination of metal impurities in polyimide film 2 g of a sample was precisely weighed and collected in a platinum crucible and incinerated with an electric furnace, and then the residue was dissolved in 20 ml of a 1.2 mol / L hydrochloric acid solution. The amount of metal in the measurement liquid was determined with a high-frequency plasma emission analyzer (CIROS-120, manufactured by Rigaku Corporation). The measured emission lines are as follows.
Iron: 259.94nm
Chromium: 205.552nm
Nickel: 231.604 nm

<Reference Example 1>
(Preliminary dispersion of inorganic particles)
0.81 parts by mass of spherical particles of amorphous silica Seahoster KE-P30 (manufactured by Nippon Shokubai Co., Ltd.), 420 parts by mass of N-methyl-2-pyrrolidone, the wetted part of the container, and the piping for infusion are austenitic stainless steel The mixture was placed in a container of SUS316L and stirred with a homogenizer T-25 basic (manufactured by IKA Labortechnik) at a rotation speed of 1000 rpm for 1 minute to obtain a preliminary dispersion. The average particle size in the preliminary dispersion was 0.38 μm, the standard deviation was 0.032 μm, the CV value was 8.4%, and the sphericity was 0.98.
(Preparation of polyamic acid solution)
A nitrogen inlet tube, a thermometer, a liquid contact part of a container equipped with a stirring rod, and a pipe for infusion were substituted with nitrogen in the reaction container made of austenitic stainless steel SUS316L, and then 223 parts by mass of 5-amino-2- ( p-Aminophenyl) benzoxazole was added. Next, 4000 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, and then the preliminary dispersion obtained above was added with 420 parts by mass and 217 parts by mass of pyromellitic dianhydride. When stirred at 50 ° C. for 50 hours, a brown viscous polyamic acid solution A was obtained. The reduced viscosity (ηsp / C) was 5.2.

<Reference Example 2>
Nitrogen introduction tube, thermometer, vessel wetted part equipped with stirring rod, and infusion pipe were replaced with nitrogen in the reaction vessel of austenitic stainless steel SUS316L, and then 5-amino-2- (p-aminophenyl) ) Snowtex DMAC-ST30 (manufactured by Nissan Chemical Industries, Ltd.), in which 223 parts by mass of benzoxazole and 4416 parts by mass of N, N-dimethylacetamide are completely dissolved and then colloidal silica is dispersed in dimethylacetamide. .05 parts by mass (0.81 parts by mass of silica) and 217 parts by mass of pyromellitic dianhydride are added and stirred at a reaction temperature of 25 ° C. for 40 hours to obtain a brown and viscous polyamic acid solution B. It was. Ηsp / C of this product was 4.6.

<Reference Example 3>
(Preliminary dispersion of inorganic particles)
Spherical particles of amorphous silica Seahoster KE-P30 (manufactured by Nippon Shokubai Co., Ltd.) 0.76 parts by mass, N-methyl-2-pyrrolidone 390 parts by mass of the liquid contact part of the container, and the infusion pipe are austenitic stainless steel SUS316L And stirred for 1 minute at a rotation speed of 1000 rpm with a homogenizer T-25 basic (manufactured by IKA Labortechnik) to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
The liquid contact part of the vessel equipped with a nitrogen introduction tube, a thermometer, a stirring rod, and the pipe for infusion were substituted with nitrogen in the reaction vessel made of austenitic stainless steel SUS316L, and then 200 parts by mass of diaminodiphenyl ether was added. Next, after 3800 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 390 parts by mass and 217 parts by mass of pyromellitic dianhydride were added to the preliminary dispersion obtained above. When the mixture was stirred at 0 ° C. for 5 hours, a brown viscous polyamic acid solution C was obtained. The reduced viscosity (ηsp / C) was 3.8.

<Reference Example 4>
(Preliminary dispersion of inorganic particles)
Spherical particles of amorphous silica Seahoster KE-P30 (manufactured by Nippon Shokubai Co., Ltd.) 0.73 parts by mass, N-methyl-2-pyrrolidone 420 parts by mass, the liquid contact part of the container, and the infusion pipe are austenitic stainless steel SUS316L And stirred for 1 minute at a rotation speed of 1000 rpm with a homogenizer T-25 basic (manufactured by IKA Labortechnik) to obtain a preliminary dispersion.
(Preparation of polyamic acid solution)
The wetted part of the vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod, and the infusion piping were substituted with nitrogen in the reaction vessel made of austenitic stainless steel SUS316L, and then 108 parts by mass of phenylenediamine was added. Next, after 3600 parts by mass of N-methyl-2-pyrrolidone was added and completely dissolved, 420 parts by mass and 292.5 parts by mass of diphenyltetracarboxylic dianhydride were added to the preliminary dispersion obtained above. When the mixture was stirred at 25 ° C. for 10 hours, a brown viscous polyamic acid solution D was obtained. The reduced viscosity (ηsp / C) was 4.3.

(Examples 1-4)
The polyamic acid solutions obtained in Reference Examples 1 to 4 are each fed using a gear pump whose gear pump is martensitic stainless steel SUS440C, which is fed onto the support, on the polyethylene terephthalate film support. (The squeegee / belt gap was 150 μm) and dried at 90 ° C. for 60 minutes. The polyamic acid film that became self-supporting after drying was peeled off from the support to obtain a green film having a thickness of 17 μm.
These green films thus obtained were passed through a continuous heat treatment furnace purged with nitrogen, the first stage was heated at 180 ° C. for 3 minutes, and the heating rate was 4 ° C./second, and the second stage was at 460 ° C. Two-stage heating was performed under the condition of 5 minutes to advance the imidization reaction. Then, each polyimide film of Examples 1-4 which exhibits brown was obtained by cooling to room temperature in 5 minutes.
Measurement results such as the performance of the obtained polyimide film are shown in Table 1.

(Comparative Examples 1-4)
Reference in place of Reference Examples 1 to 4 except that the pre-dispersion of inorganic particles and the wetted part of the container for obtaining the polyamic acid solution and the piping for infusion were changed from austenitic stainless steel SUS316L to martensitic stainless steel SUS410. The polyamic acid solutions of Examples 5 to 8 were obtained.
These polyamic acid solutions of Reference Examples 5 to 8 are fed using a gear pump in which the gear pump for feeding the solution onto the support is tungsten steel SKH51, and coated on the support of the polyethylene terephthalate film. (The gap between the squeegee and the belt was 150 μm) and dried at 90 ° C. for 60 minutes. The polyamic acid film that became self-supporting after drying was peeled off from the support to obtain a green film having a thickness of 17 μm.
These green films thus obtained were passed through a continuous heat treatment furnace purged with nitrogen, the first stage was heated at 180 ° C. for 3 minutes, and the heating rate was 4 ° C./second, and the second stage was at 460 ° C. Two-stage heating was performed under the condition of 5 minutes to advance the imidization reaction. Then, each polyimide film of Comparative Examples 1-4 which exhibits brown was obtained by cooling to room temperature in 5 minutes.
Measurement results such as the performance of the obtained polyimide film are shown in Table 1.

(Comparative Examples 5 to 8)
The polyamic acid solutions of Reference Examples 5 to 8 are each fed using a gear pump whose gear pump is austenitic stainless steel SUS304 and is coated on a polyethylene terephthalate film support. (The gap between the squeegee and the belt was 150 μm) and dried at 90 ° C. for 60 minutes. The polyamic acid film that became self-supporting after drying was peeled off from the support to obtain a green film having a thickness of 17 μm.
These green films thus obtained were passed through a continuous heat treatment furnace purged with nitrogen, the first stage was heated at 180 ° C. for 3 minutes, and the heating rate was 4 ° C./second, and the second stage was at 460 ° C. Two-stage heating was performed under the condition of 5 minutes to advance the imidization reaction. Then, each polyimide film of Comparative Examples 5-8 which exhibits brown was obtained by cooling to room temperature in 5 minutes.
Measurement results such as the performance of the obtained polyimide film are shown in Table 2.

(Manufacture of metallized polyimide film)
The polyimide films obtained in each Example and Comparative Example were cut into a 25 cm × 25 cm square and fixed by being sandwiched between stainless steel frames having an opening with a diameter of 24 cm. Next, plasma treatment of the film surface was performed. The plasma treatment conditions were a xenon gas, a frequency of 13.56 MHz, an output of 100 W, a gas pressure of 0.8 Pa, a treatment temperature of 25 ° C., and a treatment time of 5 minutes. Next, a molybdenum alloy film having a thickness of 50 mm was formed by RF sputtering under a xenon atmosphere using a molybdenum target under conditions of a frequency of 13.56 MHz, an output of 400 W, and a gas pressure of 0.8 Pa. Next, the temperature of the substrate was raised to 250 ° C., and copper was vapor-deposited at a rate of 100 Å / sec to form a copper thin film having a thickness of 0.5 μm.
Each obtained metallized film is fixed again to a plastic frame, and a thick copper plating layer having a thickness of 12 μm is formed using a copper sulfate plating bath, followed by heat treatment at 300 ° C. for 10 minutes. A metallized polyimide film was obtained.

(Formation of evaluation pattern)
Using these obtained metallized polyimide films, a photoresist (manufactured by Shipley Co., Ltd., FR-200) was applied and dried, and then contact-exposed with a glass photomask, and further developed with a 1.2% KOH aqueous solution. Next, the etching pattern of cupric chloride containing HCl and hydrogen peroxide is etched with a spray pressure of 40 ° C. and 2 kgf / cm ^2. Formed.

(Evaluation of migration resistance of metalized polyimide film)
A voltage (DC 60 V) is applied to the 40 μm pitch comb-shaped electrode from each polyimide film obtained above, and the voltage is placed in a constant temperature and humidity chamber (Etack, FX412P type) at 85 ° C. and 85% RH. The insulation resistance value was measured and recorded every 5 minutes in the loaded state, and the time for the resistance value between the lines to reach 100 Mohm or less was measured for migration evaluation.

表中、耐マイグレーション性以外はポリイミドフィルムの物性である。なお引張破断強度、引張弾性率、引張破断伸度、ＣＴＥの欄において、上段はフィルムの長手方向であるＭＤ方向の値で下段はフィルムの幅方向であるＴＤ方向の値を示す。

In the table, properties other than migration resistance are physical properties of the polyimide film. In the columns of tensile strength at break, tensile modulus, tensile elongation at break, and CTE, the upper row shows the value in the MD direction, which is the longitudinal direction of the film, and the lower row shows the value in the TD direction, which is the width direction of the film.

表中、耐マイグレーション性以外はポリイミドフィルムの物性である。なお引張破断強度、引張弾性率、引張破断伸度、ＣＴＥの欄において、上段はフィルムの長手方向であるＭＤ方向の値で下段はフィルムの幅方向であるＴＤ方向の値を示す。

In the table, properties other than migration resistance are physical properties of the polyimide film. In the columns of tensile strength at break, tensile modulus, tensile elongation at break, and CTE, the upper row shows the value in the MD direction, which is the longitudinal direction of the film, and the lower row shows the value in the TD direction, which is the width direction of the film.

  The polyimide film of the present invention is a highly insulating and reliable polyimide film having high migration resistance by suppressing the Fe, Ni, and Cr contents of the film, particularly the Fe content. Therefore, the polyimide film of the present invention is not only a base film used for the production of a carrier tape for flexible printed wiring copper-clad board (FPC) and tape automated bonding (TAB) used at an extremely high temperature. Power supply circuit used at high voltage, plasma display panel, field emission display panel, electroluminescence display panel, cold cathode ray tube display panel, base board for driving circuit such as small and flat cathode ray tube, base for wireless transmission equipment It is useful as a substrate.

Claims (4)

A step of performing a polymerization reaction in a polymerization vessel to obtain a polyamic acid which is a polyimide precursor , a step of transporting the polyamic acid solution obtained in the above step by a transport pipe, and the polyamic acid solution on a support A polyimide film obtained by a casting film-forming method having at least a step of applying and drying, wherein the liquid contact part of the polymerization vessel and the transport pipe have a metal part,
A polyimide film characterized in that the total content of Fe, Ni, and Cr in the film is 20 ppm or less and contains inorganic or organic fine particles in a range of 0.001 to 1% by mass of the whole film. 2. The polyimide film according to claim 1, wherein in the total content of Fe, Ni, and Cr in the film, the content of Fe is ½ or more of the total content of Fe, Ni, and Cr. The polyimide film according to claim 1 or 2, wherein the polyimide is a polyimide benzoxazole obtained by condensation of a tetracarboxylic acid anhydride and a diamine having a benzoxazole structure. The metal part of the liquid contact part of the polymerization vessel for obtaining the polyamic acid which is a polyimide precursor and / or the metal part of the transport pipe is composed of any material selected from austenitic stainless steel and ferritic stainless steel. The manufacturing method of the polyimide film of Claim 1 characterized by the above-mentioned.