Stock material or miscellaneous articles – Composite – Of polyimide
Reexamination Certificate
2001-03-30
2003-07-08
Hampton-Hightower, P. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyimide
C428S209000, C428S411100, C428S413000, C428S416000, C428S418000, C528S353000, C528S170000
Reexamination Certificate
active
06589662
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a composite film. More particularly, the present invention relates to a composite film whose surface is coated with polyimide membrane(s), which is excellent in heat resistance.
BACKGROUND ART
Films made of polyester resins, especially polyethylene terephthalate resins or polyethylene naphthalte resins, and films made of polyphenylene sulfide resins are widely used in various industrial fields because of the good processabilities, excellent mechanical properties, chemical properties, and the like.
However, the above-mentioned films made of polyester resins and polyphenylene sulfide resins have a drawback in that their glass transition points are low and so their heat resistances are poor for industrial uses at high temperatures, so that they cannot be used as the parts subjected to high temperatures.
In view of this, various composite films have been proposed, in which membranes made of materials which compensate the drawback of the resins are formed on the surfaces of the films made of the resins. For example, Japanese Laid-open Patent Application (Kokai) No. 57-167256 discloses a process for producing a heat resistant resin film by immersing a fluororesin film in a solution of polyamic acid in N-methyl-2-pyrrolidone to coat the film surfaces with the polyamic acid resin, and by heating the resultant to dry. However, to convert the polyamic acid into polyimide resin, dehydration and imidation reaction are necessary, so that heat treatment at a temperature as high as 300° C. is necessary.
If the polyamic acid is applied to a film made of a polyester resin or polyphenylene sulfide resin, which has a low melting point, the substrate film per se is melted, so that this method cannot be employed. On the other hand, since ordinary polyimides are insoluble in solvents, thin membranes of such polyimides cannot be formed on film surfaces.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a composite film which is excellent in heat resistance and in adhesiveness of the surface layer.
The present inventors intensively studied to discover that by applying a solution of a solvent-soluble polyimide containing a specific compound as an acid component or diamine component and by drying the solution to form a polyimide membrane, a composite film having excellent heat resistance can be obtained and the polyimide membrane has excellent adhesiveness with the substrate film, thereby completing the present invention.
That is, the present invention provides a composite film comprising a substrate film and polyimide membrane(s) formed on at least one surface of said substrate film, which polyimide membrane(s) is(are) prepared by coating said surface(s) with a solution of a solvent-soluble polyimide whose main chain is formed by polycondensation of one or more tetracarboxylic dianhydrides and one or more diamines and by drying said solution, said one or more tetracarboxylic dianhydrides including bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylic dianhydride as at least a part thereof, and/or said one or more diamines including at least one of 3,5-diaminobenzoic acid and a diaminosiloxane derivative as at least a part thereof.
Since polyimide membrane(s) which is(are) excellent in heat resistance, chemical resistance and insulation performance is(are) formed on the surface(s) of the substrate film, the composite film according to the present invention is excellent in heat resistance, chemical resistance and insulation performance. Further, the adhesiveness between the substrate film and the polyimide membrane is excellent. Therefore, the composite film according to the present invention may be applied for various uses for which heat resistance, chemical resistance and/or insulation performance are demanded. The present invention has excellent advantageous effects in that polyimide in the form of membrane can directly be formed on the substrate films with low melting points, so that the advantageous properties of both of the substrate film and the polyimide may be synergistically exerted, that the production is easy and that the production cost is low.
BET MODE FOR CARRYING OUT THE INVENTION
As mentioned above, the composite film according to the present invention comprises a substrate film and polyimide membrane(s) formed on at least one surface of the substrate film. As the substrate film, films made of thermoplastic resins on which polyimide membranes could not be formed thereon hitherto because of the low heat resistances may be advantageously employed. Examples of such a thermoplastic resin include polyesters such as polyethylene terephthalates and polyethylene naphthalates, and polyphenylene sulfides. The thickness of the substrate film is not restricted at all and is usually about 10 to 200 &mgr;m. As the substrate film, commercially available various films may be employed.
The composite film according to the present invention is obtained by applying a solution of a solvent-soluble polyimide whose main chain is formed by polycondensation of one or more tetracarboxylic dianhydrides and one or more diamines on at least one surface of the above-mentioned substrate film, and by drying the solution so as to form polyimide membrane(s) on the surface(s).
The polyimide used in the present invention is solvent-soluble. As the solvent, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), N-methylpyrrolidone (NMP), tetramethylurea, sulfolane or the like may be employed. Preferably, DMF or NMP is employed. In the present specification, the term “solvent soluble” means that the polyimide is dissolved in N-methyl-2-pyrrolidone (NMP) to a concentration of not less than 5% by weight, preferably not less than 10% by weight.
The tetracarboxylic dianhydride(s) used for forming the main chain of the molecule of the solvent-soluble polyimide is(are) not restricted. Examples of the tetracarboxylic dianhydrides include aromatic acid dianhydrides such as biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, bis(dicarboxyphenyl)propane dianhydride, bis(dicarboxyphenyl)sulfone dianhydride, bis(dicarboxyphenyl)ether dianhydride, thiophenetetracarboxylic dianhydride, pyromellitic dianhydride and naphthalenecarboxylic dianhydride; and acid dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride, bicyclo(2,2,2)-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and 4,4′-{2,2,2-trifluoro-1-(trifluoromethyl)ethylidene}bis(1,2-benzenedicarboxylic dianhydride). These may be used individually or in combination.
Examples of the diamines used for forming the main chain of the molecule of the solvent-soluble polyimide include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 2,2′-bis(4-aminophenyl)propane, benzidine, 3,3′-diaminobiphenyl, 2,6-diaminopyridine, bis{4-(4-aminophenoxy)phenyl}sulfone, bis{4-(3-aminophenoxy)phenyl}sulfone, bis{4-(4-aminophenoxy)phenyl}ether, bis{4-(3-aminophenoxy)phenyl}ether, 2,2′-bis{4-(4-aminophenoxy)phenyl}propane, 2,2′-bis{4-(3-aminophenoxy)phenyl}propane, 4,4′-bis(4-aminophenoxy)biphenyl, 2,2′-bis{4-(3-aminophenoxy)phenyl}hexafluoropropane, 1,5-diaminonaphthalene, 2,2′-bis{4-(4-aminophenoxy)phenyl}hexafluoropropane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 3,5-diaminobenzoic acid, diaminosiloxane derivatives, 1,4-benzenediamine, 1,3-benzenediamine, 6-methyl-1,3-benzenediamine, 4,4′-diamino-3,3′-dimethyl-1,1′biphenyl, 4,4′-diamino-3,3′-hydrox-1,1′biphenyl, 4,4′-diamino-3,3′-dimethox-1,1′biphenyl, 4,4′-oxybis(benzeneamine), 3,4&p
Itatani Hiroshi
Matsumoto Shunichi
Birch & Stewart Kolasch & Birch, LLP
Hampton-Hightower P.
PI R&D Co., Ltd.
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