Electric heating – Metal heating – By arc
Reexamination Certificate
2001-10-18
2002-07-09
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
C219S121660
Reexamination Certificate
active
06417486
ABSTRACT:
The present invention relates to a process for the formation of electrically conductive layers, in particular conductor tracks, on the surface of plastics by irradiation with laser energy.
Plastic moldings with integrated electrically conductive layers or tracks are well known, for example from the electrical and electronics industries.
However, in order to apply conductor tracks to plastics, metallizable plastics have hitherto been arranged in complex, multi-step processes in such a way that conductor tracks are formed by partial metallization (electroplating). Another possibility is to apply conductor tracks to the plastic surface by hot embossing.
The processes disclosed hitherto for the production of plastic moldings with integrated conductor tracks are very expensive and in some cases not very environmentally friendly, and consequently alternative possibilities are being sought. The irradiation of molding compositions containing fillers with laser energy represents such an alternative possibility.
The marking of plastics filled with conductive constituents is described in DE-A 44 15 802. In the described use of doped tin dioxide, mica plates or silicon dioxide flakes, markings can be produced by irradiation with laser energy, but conductor tracks cannot.
U.S. Pat. No. 4,841,099 describes the production of electrical conductor tracks in a plastic filled with non-conductive fibers. These fibers, preferably polyacrylonitrile fibers, are converted into conductive carbon fibers on irradiation with appropriate laser energy. However, disadvantages here are the lower conductivity of carbon compared with metals and the restrictions associated with the use of plastic fibers as fillers in another plastic.
EP-A 0 230 128 describes the production of conductor tracks on pyrolyzable substrates by irradiation with appropriate laser energy. This results in the formation of conductive carbon tracks, which can, if desired, be coated with a suitable metal layer by electrolysis. However, disadvantages here are the restriction to suitable plastics and the low conductivity of the carbon, resulting in the necessity for subsequent coating of the conductor track with metal.
The object of the present invention was to produce conductor tracks close to the surface of a substantially electrically insulating plastic.
This object is achieved by irradiation of a plastic which is filled with electrically conductive constituents, but is itself substantially electrically insulating, with appropriate laser energy.
In this process, the surface of a plastic which is filled with electrically conductive constituents is irradiated with laser energy. The irradiation causes the plastic to partially evaporate, leaving behind the electrically conductive constituents, which combine to form an electrically conductive layer or track.
The invention therefore relates to a process for the production of electrically conductive layers on the surface of plastics in which the surface of a plastic filled with electrically conductive constituents is irradiated with laser energy in such a way that the plastic is evaporated down to a predetermined depth at the point of incidence by the laser energy, leaving behind the electrically conductive constituents, which increase in concentration and thus form an electrically conductive layer.
The invention also relates to plastic moldings with integrated electrically conductive layers or tracks on their surface which can be obtained by irradiation of a plastic filled with electrically conductive constituents with laser energy, where the plastic is evaporated down to a predetermined depth at the point of incidence by the laser energy, leaving behind the electrically conductive constituents, which increase in concentration and thus form an electrically conductive layer or track.
Moldings of this type can be components used, for example, in the electrical and electronics industries, but also other large or small plastic parts of any desired shape which are provided with conductive elements in certain places. The molding according to the invention can also be a constituent of a composite article with other materials.
Since the plastic which is filled with electrically conductive constituents may differ in its chemical and in particular its mechanical properties from the same plastic without these constituents and may also be somewhat more expensive, it may be appropriate, in particular in the case of relatively large moldings, to produce the body of the molding and certain elements on which conductive layers or tracks are desired as a composite made from different molding compositions.
With respect to the plastic to be used in accordance with the invention, no particular restriction is necessary. For the process according to the invention, use can in principle be made of all organic plastics into which the electrically conductive constituents can be incorporated in sufficient amounts. These plastics can also contain. conventional auxiliaries, additives, fillers and reinforcing materials. Homogeneous and heterogeneous plastic mixtures can also be used.
The plastics to be used in the process according to the invention are plastics which are not crosslinked, in particular thermoplastics which are not crosslinked. For certain purposes such plastics may be crosslinked after they have been used to form a shaped article and have been equipped with conductor tracks on its surface by the process according to the invention. They may, for example, be photocrosslinked or by other means which will not affect the present conductor tracks.
Preferred plastics are thermoplastics.
Usually, thermoplastic elastomers are less suitable because they are more elastic than the conductor tracks produced thereon, so usage of these materials in their typical field of use may result in break of the conductor tracks, although the invention may be carried out with such materials as well. Such thermoplastic elastomers are, for example, but not restricted to brominated Butyl rubbers, chlorinated Butyl rubbers, polyurethane elastomers, fluoroelastomers, polyester elastomers, polyvinylchloride, butadiene/acrylonitrile elastomers, silicon elastomers, polybutadiene, polyisobutylene, ethylene-propylene-copolymers, ethylene-propylene-dien-terpolymers, sulfonated ethylene-propylene-dien terpolymers, polychloroprene, poly(2,3-dimethylbutadiene), poly(butadiene-pentadiene), chlorosulfonated polyethylene, polysulfide-elastomers, block copolymers, constructed from segments of amorphous or (partially)cristalline blocks such as polystyrene, polyvinyltoluene, poly(tert.-butyl styrene), polyester and similar, and elastomeric blocks such as polybutadiene, polyisoprene, ethylene-propylene-copolymers, ethylene-butylene-copolymers, ethylene-isoprene-copolymers and hydrated derivatives thereof, such as SEBS, SEPS, SEEPS, and also hydrated ethylene-isoprene-copolymers with an increased fraction of 1,2-connected isoprene, polyethers or similar, such as. for example the products sold by Kraton Polymers under the trademark KRATON®, derivatives and/or mixtures thereof.
Preferred thermoplastics are thermoplastics which are drived from, or mixtures of, the following materials:
Polylactones such as Poly(pivalolactone), Poly(caprolactone) or similar; Polyurethanes such as polymerisation products of diisocyanates such as 1,5-Naphthalin-diisocyanate; p-Phenylen-diisocyanate, m-Phenylene-diisocyanate, 2,4-Toluyl-diisocyanate, 2,6-Toluylene-diisocyanate, 4,4′-Diphenylmethane-diisocyanate, 3,3′-Dimethyl-4,4′-Biphenyl-diisocyanate, 4,4′-Diphenylisopropylidene-diisocyanate, 3,3′-Dimethyl4,4′-diphenyl-diisocyanate, 3,3′-Dimethyl-4,4′-diphenylmethane-diisocyanate, 3,3′-Dimethoxy-4,4′-biphenyl-diisocyanate, Dianisidine-diisocyanate, Toluidine-diisocyanate, Hexamethylene-diisocyanate, 4,4′-Diisocyanatodi-phenylmethane, 1,6-Hexamethylene-diisocyanate, 4,4′-Dicyclo-hexylmethane-diisocyanate or similar with long chain diols such as Poly(tetramethylene adipate), Poly(ethylene adipate), Poly(1,4-bu
Pieper Volker
Reil Frank
Tönnes Kai-Uwe
Connolly Bove & Lodge & Hutz LLP
Dunn Tom
Johnson Jonathan
Ticona GmbH
LandOfFree
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