Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1999-12-20
2003-10-07
Jackson, Monique R. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S325000, C428S330000, C428S332000, C428S409000, C428S457000, C428S461000, C428S462000, C428S500000, C428S521000, C361S301100, C361S301500, C361S311000, C361S312000, C361S313000, C361S323000
Reexamination Certificate
active
06630234
ABSTRACT:
TECHNICAL FIELD
The present invention relates to polymeric films used as electrical insulators or dielectrics. More particularly, it relates to polymeric films small in dielectric loss tangent, excellent in heat resistance and low in friction coefficient between the films, and to film capacitors comprising the polymeric films.
BACKGROUND ART
Insulators comprising thermoplastic resins are used for earth insulation, layer insulation and conductor insulation of motors and insulation of transformers, and as dielectrics of capacitors in place of conventionally used papers, cloths or impregnated products thereof, and mica. As the thermoplastic resins used as these insulators, the most popular are polypropylenes (PP). Moreover, recently, among insulators comprising thermoplastic resins, those which are high in insulation resistance, excellent in frequency characteristics and high in flexibility are used as dielectrics of film capacitors for radio communication equipment of airplanes, ships and vehicles; for household DC electrical apparatuses such as radios, televisions and audios; for driving of small motors such as those of air conditioners, washing machines and electric fans; and for improvement of electric power of fluorescent lamps and mercury vapor lamps. Polyethylene terephthalate (PET), PP and the like are used as thermoplastic resin materials used for these film capacitors and the like.
However, though PP films are good in electric characteristics such as small dielectric loss tangent, they are inferior in heat resistance. On the other hand, PET is superior in heat resistance, but has the problem of increase of temperature caused by heat generation of dielectric loss due to the great dielectric loss tangent, resulting in problems that miniaturization and increase of capacity of capacitors are difficult.
It is disclosed that films comprising thermoplastic cyclic olefin resins are useful as insulation films for communication, electronic equipment and electric equipment because they are good in electrical characteristics such as dielectric loss tangent and superior in heat resistance, and, besides, are hardly affected by environments such as water (JP-A-2-102256, JP-A-5-148413). However, these films suffer from the problem in handling that they are apt to cut or become entangled, for example, in rewinding step carried out several times in the process of production of capacitor films.
Hitherto, no films have been known which are excellent in performance as insulator films, namely, excellent in heat resistance and small in dielectric loss tangent and are free from the problems in handling, namely, tendency of cutting or becoming entangled at the rewinding step.
An object of the present invention is to provide a polymeric film which is excellent in performance as insulator film, namely, small dielectric loss tangent and free from the problems in handling that the film is apt to cut or become entangled at the rewinding step.
Another object of the present invention is to provide a polymeric film excellent in heat resistance in addition to the above characteristics.
Further object of the present invention is to provide a film capacitor comprising the above polymeric film.
DISCLOSURE OF INVENTION
As a result of intensive research conducted by the inventors in an attempt to solve the above problems, it has been found that, from the point of performance of insulator films, when a polymeric film having a dielectric loss tangent of 0.002 or less measured at a frequency in the range of 1 kHz to 1 GHz at a temperature of 25° C. is used, heat generation of dielectric loss of capacitor can be reduced and rising of the temperature can be inhibited, and, hence, further miniaturization and increase in capacity of capacitor are possible, also due to the fact that the capacitor per se can stand the rise of temperature.
Furthermore, as a result of intensive research conducted by the inventors, it has been found that the problem in handling of the films that they are apt to cut or become entangled at the rewinding step depends on the friction coefficient of the films, and this problem in handling of the films can be markedly improved by using polymeric films which are 1 or less in friction coefficient between the films of the same material. Thus, the present invention has been accomplished.
Moreover, the present invention provides a film capacitor using the above-mentioned polymeric films.
Best Mode for Carrying Out the Invention
The preferred embodiments of the present invention will be explained below on respective items.
Molding Materials as Raw Materials for Polymeric Films
Molding materials used for making the polymeric films of the present invention are not limited as far as they have a dielectric loss tangent of 0.002 or less measured at a frequency in the range of 1 kHz to 1 GHz at a temperature of 25° C., and when they are molded into films, the films comprising the same molding material have a friction coefficient of 1 or less between these films. The molding materials may be thermoplastic or thermosetting and, if necessary, may contain various additives. The molding materials comprising thermoplastic resins are preferred because of easiness in melt extrusion molding by which films can be obtained with high productivity. In order to obtain polymeric films of small dielectric loss tangent, it is preferred to select those which have a small electric dipole moment of repeating skeleton unit in the chemical formula of the resins (polymers) as raw materials.
Molding Materials Comprising Thermoplastic Cyclic Olefin Resins
Polymeric films of the present invention which have a dielectric loss tangent of 0.002 or less measured at a frequency in the range of 1 kHz to 1 GHz at a temperature of 25° C., and have a friction coefficient of 1 or less between the films of the same material when molded into films are preferably those which comprise 100 parts by weight of a thermoplastic cyclic olefin resin and 0.01-3 parts by weight of at least one kind of particles selected from the group consisting of inorganic particles and silicone particles having an average particle diameter of 0.05-5 &mgr;m.
The thermoplastic cyclic olefin resins usable in the present invention are non-crystalline and transparent resins having a hydrocarbon cyclic structure in the main chain or side chain of polymers. As examples of these resins, mention may be made of ring opening polymers of monomers having a norbornene ring and hydrogenation products of the polymers as disclosed in JP-A-63-264646, JP-A-64-1705, JP-A-1-168724 and JP-A-1-168725; addition polymers of monomers having a norbornene ring with &agr;olefins as disclosed in JP-A-60-168708; and addition polymers of cyclic olefins or cyclic dienes and hydrogenation products of the polymers as disclosed in JP-A-6-136057 and JP-A-7-258362. These resins are available in the name of registered trademark ZEONEX from Nippon Zeon Co., Ltd., and registered trademarks APEL, APO, etc. from Mitsui Petrochemical Industries, Ltd. As other examples, mention may be made of polystyrene resins having a specific structure as disclosed in JP-A-1-316246 and JP-A-6-29146.
Among them, preferred are hydrogenation products of ring opening polymers of monomers having a norbornene ring or addition polymers of monomers having a norbornene ring with &agr;-olefins, and more preferred are the hydrogenation products of ring opening polymers of monomers having a norbornene ring. This is because the resulting polymeric films are excellent in heat resistance and strength.
Examples of the monomers having a norbornene ring are norbornenes of bicyclic olefins which are adducts of ethylene with cyclopentadiene, tetracyclododecenes of tetracyclic olefins to which cyclopentadiene is added, tricyclodecadienes (also called dicyclopentadienes) which are tricyclic dienes and dimers of cyclopentadienes, tricyclodecenes which are tricyclic olefins having unsaturated bonds a part of which are saturated by hydrogenation, pentacyclopentadecadienes which are pentacyclic dienes and trimers of cyclopentadienes, pentacyclopent
Kohara Teiji
Konishi Yuichiro
Tanisho Hajime
Jackson Monique R.
Nippo Zeon Co., Ltd.
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