Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-01-24
2004-03-30
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S268000
Reexamination Certificate
active
06713581
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel, patternable polymer material of low relative permittivity, and to films, substrates and electronic units formed of it. More precisely, the invention relates to such a polymer material of low relative permittivity, which has good electric properties of low relative permittivity and low dielectric loss tangent in a high-frequency band, and which has good heat resistance even at high temperatures and good bondability and good adhesiveness to metal leaf, and has the ability to form thin-film patterns.
With the significant increase in communications intelligence in these days, greatly desired are small-sized, lightweight and high-speed communications media, for which, therefore, desired are polymer materials of low relative permittivity. In particular, portable mobile communications and satellite communications of, for example, car telephones and digital portable telephones require a radio wave of a high-frequency band of the level of megahertz to gigahertz. For supporting the significant development of communications media for means of such communications, tried is a technique of increasing the mounting density of small-sized electronic devices on substrates. For attaining the intended, small-sized and lightweight communications media applicable to such a high-frequency band of the level of megahertz to gigahertz, it is necessary to develop electric insulating materials that ensure a lot of latitude in high-frequency transmission capabilities of communication media. For further increasing the mounting density of electronic devices on substrates, employed is a build-up method of laminating a number of insulating layers on a substrate, apart from a method of fabricating multi-layered laminate boards. In addition to having good electric properties, the polymer materials to be used in such a build-up method must be patternable in order that via-holes may be formed through their layers.
For the materials having good electric properties of, for example, electric insulation and low relative permittivity, generally proposed are thermoplastic resins such as polyolefins, chlorinated polyvinyl chloride resins and fluororesins; and thermosetting resins such as unsaturated polyester resins, polyimide resins, epoxy resins, vinyltriazine resins (BT resins), crosslinkable polyphenylene oxides and curable polyphenylene ethers.
For electric-insulating materials of low relative permittivity and low dielectric loss, proposed are copolymers of cyclohexyl-having fumaric diesters and vinylic monomers, as in JP-A 208627/1997. However, the electric-insulating materials proposed are problematic in point of the patternability in use for built-up substrates, since their crosslink density is difficult to control and since they could not ensure fine patterns.
On the other hand, for other patternable materials having good electric properties, proposed are photosensitive unsaturated polyester resins, photosensitive polyimide resins and photosensitive epoxy resins. Of those, photosensitive epoxy resins are practicable for the intended purpose, and they are generally photo-cured for pattern formation.
These patternable materials are relatively resistant to heat, of which, however, epoxy resins and unsaturated polyester resins are not still unsatisfactory in point of their electric properties since their relative permittivity is at least 3 and is relatively high. On the other hand, photosensitive polyimide resins are not still on the level of practical use.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a polymer material of low relative permittivity, of which the advantages are that it bonds and adheres well to metal conductor layers, it has the ability to form patterns through crosslinking, it has good electric properties of low relative permittivity, low dielectric loss tangent and good electric insulation, and it has good heat resistance, high film strength and good workability.
Another object of the invention is to provide a substrate fabricated by coating polymer material of low relative permittivity or by laminating a film of that polymer material onto an insulating substrate base, of which the advantage is that the substrate is well workable to form patterns thereon through crosslinking of the polymer material. Further the object of the invention is to provide an electronic unit formed of the polymer material of low relative permittivity that is favorable for use in a high-frequency region.
To attain the objects above, the invention provides a polymer material of low relative permittivity obtained through copolymerization of a monomer composition that contains, as monomers, a fumaric diester and an epoxy group-having (meth)acrylate.
The terminology “(meth)acrylate” referred in the invention is meant to indicate an acrylate or a methacrylate.
In the polymer material of low relative permittivity of the invention, one monomer, fumaric diester is preferably represented by the following formula (I):
wherein R
1
represents an alkyl group or a cycloalkyl group; R
2
represents an alkyl group, a cycloalkyl group or an aryl group; and R
1
and R
2
may be the same or different.
In the polymer material of low relative permittivity of the invention, the other monomer, epoxy group-having (meth)acrylate is preferably represented by following formula (II):
wherein R
3
represents an alkylene group having from 1 to 4 carbon atoms; R
4
represents H or CH
3
; A represents an alkylene oxide having from 2 to 4 carbon atoms; n indicates an integer from 0 to 2; and X represents
The polymer material of low relative permittivity of the invention is obtained through copolymerization of such fumaric diester and such an epoxy group-having (meth)acrylate, and its advantages are that it is patternable through crosslinking, it forms films well and is resistant to heat, and it bonds and adheres well to metal conductor layers. Its other advantages are that the polymer material has good electric properties of low relative permittivity, low dielectric loss tangent and good electric insulation even in a high-frequency band level of megahertz to gigahertz.
Using the polymer material of low relative permittivity of the invention realizes easy and simple formation of electric-insulating films of good adhesion to metal conductor layers, and realizes multi-layered substrates of good workability to form patterns, and further realizes electronic units suitable for use in a high-frequency region.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention are described in detail hereinunder.
Having the ability to form patterns through crosslinking, the polymer material of low relative permittivity of the invention is obtained by copolymerizing a monomer composition that contains, as monomers, fumaric diester and an epoxy group-having (meth)acrylate, and this is a copolymer containing epoxy groups in the molecule.
The fumaric diester used to form the polymer material of the invention is not specifically limited and may be any one provided it has the ability to lower the relative permittivity of the polymer material and to make the polymer material resistant to heat. Preferably, however, the fumaric diester for use in the invention is represented by formula (I) mentioned above.
In formula (I), the alkyl group for R
1
and R
2
preferably has from 2 to 12 carbon atoms, and it may be linear or branched, and may be substituted with halogen atom(s), etc. Concretely, it includes, for example, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, nonyl and dodecyl groups.
In formula (I), the cycloalkyl group for R
1
and R
2
preferably has from 3 to 14 carbon atoms, and it may be monocyclic or crosslinked, and may be substituted with alkyl group(s), etc. Concretely, it includes, for example, cyclopentyl, cyclohexyl, adamantyl and dimethyladamantyl groups.
In formula (I), the aryl group for R
2
preferably has from 6 to 18 carbon atoms. It may be polycyclic, but is preferably monocyclic; and it may be sub
Asami Shigeru
Hotta Hiroshi
Sugahara Teruaki
Yamada Toshiaki
Aylward D.
Dawson Robert
Jordan and Hamburg LLP
TDK Corporation
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