Stock material or miscellaneous articles – Structurally defined web or sheet – Edge feature
Reexamination Certificate
2001-07-25
2004-11-02
Kelly, Cynthia H (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Edge feature
C428S213000, C428S215000, C428S297100, C428S412000, C049S490100
Reexamination Certificate
active
06811857
ABSTRACT:
The present invention relates to products of plastic material which are substantially flat and transparent at least in part, which products, by virtue of their high optical quality, are suitable for application as glazings.
As regards the composition of special glazings, especially in the field of buildings or transportation vehicles, there are both advantages and disadvantages to the replacement of glass by a plastic material.
Plastic materials are lighter than glass, giving them a major advantage for electric-powered urban vehicles, inasmuch as increased self-sufficiency is crucial. In such vehicles, it is in fact conceivable that entire doors and even complete sides of the body, including the windows could be made of one-piece plastic material, and the lower portion thereof possible could be painted. In general, the light weight of transparent surfaces is interesting relative to modem transportation vehicles, inasmuch as technical progress is being accompanied by the integration of increasingly numerous functions in the glazing (rear-window heater, radio antenna, windshield defroster, color to prevent heating of the passenger space in strong sunlight, incorporation of electrochromic compounds, display of information on the windshield, etc.), and by never-ending growth of glazed surfaces. This is leading to generally greater vehicle weights, which has negative consequences for energy consumption.
In addition, plastic materials are capable of achieving improved safety conditions compared with glass and better protection against theft, because of their greater impact strength.
No less important an advantage of plastic materials compared with glass is their better ability to be easily transformed into complex shapes.
Finally, because of the ability of sheets of plastic material to be more or less deformed in reversible manner, it is conceivable that they can be installed in body openings in much simpler manner, with snap fastening from both the interior and exterior of the vehicle.
On the other hand, this relatively slight rigidity which has just been mentioned obviously constitutes a handicap compared with glass, as do the poorer transparency and optical properties and mainly the greater susceptibility to scratching.
Several approaches have been adopted heretofore in an attempt to overcome these three handicaps.
According to a first approach, flat strips of plastic material are formed by extrusion, a piece is cut to the required dimensions and fixed on a thermoforming device, and thermoforming is performed by contact with at least one solid mold surface, possibly with the assistance of compressed air or suction. The devices used are cumbersome and, in particular, excessively long. The outputs are relatively low and material losses are inevitable. High product quality is achieved only at the cost of laborious perfection of the process and possibly of an additional resurfacing treatment.
Furthermore, the susceptibility of plastic materials to scratching, as mentioned hereinabove, is such that shaped parts must be coated with a hard varnish for optical applications or for use in transparent elements.
The need therefore exists to guarantee optical quality superior to that obtained by the aforementioned extrusion, including after formation of the hard scratch-resistant coating, which must be performed under flawless perfect industrial conditions.
This constitutes the general scope of the invention, wherein it solves its own specific problem, which is substantially to improve the functions and therefore the possibilities for application and use of plastic glazings.
This objective is now achieved by the invention, the object of which is a substantially flat product of plastic material, transparent at least in part and at least part of the exterior surface of which comprises an overmolded addition of plastic material. In other words, the new glazing made available comprises substantially a first plastic material and at least one overmolded appendage of a second plastic material. In this way the different and desired physical properties of this second plastic material are used to best advantage: adhesion to the first plastic material, ability to undergo elastic deformation, imperviousness, durable crushing reversibility, rigidity, resistance to bending, mechanical strength (especially crushing or compressive strength), etc. The overmolded addition of plastic material may be disposed on either of the two faces of the flat product: this may be an interior rear-view mirror seat overmolded on a windshield of plastic material, or some kind of positioning, centering or locating appendage, or even a fixation pin.
According to a preferred alternative version, at least part of the addition of plastic material is encapsulated at the periphery of the product. This encapsulation may comprise, as the case may be, a peripheral seal, one lip of which perfectly conforms to the body opening and has a sealing function, a fixation pin, a stiffening peripheral strip, etc.
According to a preferred embodiment, the inventive product has a core of plastic material, a skin which comprises at least one film of plastic material supporting a scratch-resistant layer and is disposed on at least one face of the core, set back from the edges thereof, on the interior of the surface bounded by the encapsulated peripheral part of the addition of plastic material.
In this configuration, the core substantially takes on the mechanical properties, especially resistance to bending, in the composite that it forms with the skin or both skins, all the more so because these skins are thin, the thickness of each being, for example, on the order of 0.25 mm. The thickness of the core can be on the order of 1 to 10 mm. Its substance is chosen from among the thermoplastics such as polycarbonate, poly(methyl methacrylate), ethylene/vinyl acetate copolymer, poly(ethylene glycol terephthalate), poly(butylene glycol terephthalate), polycarbonate/polyester copolymers, polyurethane, cycloolefin copolymer of the ethylene
orbornene or ethylene/cyclopentadiene type, the ionomeric resins such as an ethylene/(meth)acrylate acid copolymer neutralized by a polyamine, the thermosetting or thermally cross-linking plastics such as polyurethane, unsaturated polyester, ethylene/vinyl acetate copolymer. There preferably will be chosen a conventional thermoplastic, preferably one that can be injection molded, which has a relatively low softening point and is inexprensive, such as polycarbonate. The core may also comprise an association of a plurality of thicknesses of any one or more of the aforesaid plastic materials.
The thickness of the skin or of each of the two skins is advantageously chosen to be at most equal to 500 &mgr;m, preferably between 50 and 300 &mgr;m, the skin comprising one or more films of thermoformable plastic material, between which there is interposed or on which there is deposited, depending on the case, at least one functional layer, at least one of these films also being able itself to comprise such a functional layer. The thermoformable plastic material of these films is advantageously chosen from the group comprising polycarbonate, polypropylene, poly(methyl methacrylate), ethylene/vinyl acetate copolymer, poly(ethylene glycol terephthalate), poly(butylene glycol terephthalate), polyurethane, polyvinylbutyral and cycloolefin copolymer such as ethylene
orbornene or ethylene/cyclopentadiene, polycarbonate/polyester copolymer, ionomeric resin.
The scratch-resistant layer has a thickness on the order of 1 to 10 &mgr;m; it generally forms the exterior surface of the inventive product.
It may be substantially inorganic and in particular comprise polysiloxanes and/or derivatives of silica and/or alumina, or it may be mixed, such as comprising networks of inorganic and organic molecular chains intermingled and cross-linked to one another by means of silicon-carbon bonds. Such a mixed layer exhibits excellent properties of transparency, adherence and scratch resistance. It seems that the inorganic network imparts to the coating its
Benyahia Rym
Bravet Jean-Louis
Bureau Bernard
Ducreuzot Fabrice
Ferguson L.
Kelly Cynthia H
Saint-Gobain Glass France
LandOfFree
Plastic glazing sheet with added overmoulded plastic material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Plastic glazing sheet with added overmoulded plastic material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Plastic glazing sheet with added overmoulded plastic material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3338913