Vehicle sunroof and method of making the same

The present invention relates to a vehicle sunroof having variable optical transmission and a method for making the same. Specifically, a vehicle sunroof is provided that, in accordance with the present invention, comprises a relatively thin film having variable optical transmission and a relatively thick substrate layer of clear plastic material adhered to a surface of the relatively thin film. The relatively thin film is positioned in a first molding die of a pair of injection molding dies such that it is adjacent a surface of the first die. The relatively thick substrate layer is adhered to one surface of the relatively thin film while in contact therewith in a molten state under heat and pressure within a cavity defined by the injection molding dies.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a vehicle sunroof, and in particular, to a 
vehicle sunroof having variable optical transmission. 
2. Description of the Related Art 
Motor vehicle designs, particularly passenger vehicles, are driven 
increasingly by concerns of fuel efficiency, weight reduction, and 
esthetics. Greater latitude in the curvature of vehicle panels, including 
sunroofs, is required to meet those concerns. Indeed, recent vehicle roof 
designs are incorporating sloping and rounded surfaces. Yet, the cost of 
producing a curved sunroof having additional functional layers like 
electrochromatic films is expensive. Electrochromatic materials are 
provided or formed typically as a planar film and are, consequently, 
difficult to attach to the surface of a curved sunroof. While such films 
can be applied to glass sunroofs, it is difficult generally to remove air 
bubbles between the film and the glass sunroof once the film is attached. 
Yet, it is well-known that glass has been the preferred material for 
vehicle windows for many years. It is also well-known that plastic 
materials, such as polycarbonates, if employed in lieu of glass, could 
reduce the weight of the sunroof. Nevertheless, glass continues to be 
selected most often for use in vehicle windows. Apparently, therefore, the 
shift from glass to plastic sunroofs will follow only when plastic 
sunroofs offer additional advantages. 
Thus, it would be advantageous to provide a cost-effective method of 
attaching electrochromatic films to curved, plastic sunroofs. With such an 
arrangement, plastic sunroofs would offer not only weight reduction, but 
also the ability to variably block ambient light. 
SUMMARY OF THE INVENTION 
Thus, an object of the present invention is to provide a vehicle sunroof 
having variable optical transmission and a method for making the same 
which provides a cost effective way of attaching electrochromatic films to 
sunroofs without the aforementioned problems. In accordance with the 
principles of the present invention, this objective is achieved by 
providing a vehicle sunroof comprising the combination of a relatively 
thin film having variable optical transmission and a relatively thick 
clear substrate layer. Initially, the relatively thin film is prepared or 
purchased and generally includes at least two layers. The first layer of 
the relatively thin film is a relatively thin sheet of plastic material 
compatible with the substrate material. For example, the relatively thin 
sheet of plastic material and the relatively thick substrate layer could 
be made of polycarbonate material. Adhered to the relatively thin sheet of 
plastic material, the second layer of the relatively thin film is a layer 
of electrochromatic material including for example, liquid crystals. 
Optionally, the relatively thin film can include a layer of abrasive 
resistant material disposed on an exposed surface of either the thin sheet 
of plastic material or the electrochromatic layer. 
The relatively thick clear substrate layer is of a plastic material having 
opposed surfaces curved into a vehicle sunroof configuration. The 
relatively thick substrate layer is adhered to one surface of the 
relatively thin film while in contact therewith in a molten state under 
heat and pressure within a cavity defined by two generally parallel curved 
die surfaces of cooperating injection molding dies so that, upon 
solidification, the surfaces of said relatively thin film are retained in 
a curved configuration in generally parallel coextensive relation to 
corresponding curved surfaces of said relatively thick substrate layer. 
The provision of injection molding the sunroof enables the use of planar 
films, including electrochromatic films, in making the sunroof because the 
relatively thin film can be attached to the substrate layer without the 
aforementioned problem of air bubbles forming under the film. Accordingly, 
another object of the present invention is to provide a method of making a 
sunroof having curvatures in two planes sufficient to accommodate a wide 
variety of designs and having an electrochromatic film incorporated 
therein. In the accordance with the principles of the present invention, 
this objective is achieved by providing a relatively thin film having 
electrochromatic properties and having opposed surfaces. Thereafter, the 
relatively thin film is mounted adjacent a curved die surface of a molding 
die arranged to be disposed in cooperating relation with a second molding 
die having a similarly shaped curved die surface. The first and second 
molding dies are disposed in cooperating relation so as to bring the two 
curved die surfaces into generally parallel relation to form a die cavity 
with a spacing between the two curved die surfaces substantially greater 
than the thickness of the relatively thin film. Finally, a clear plastic 
material is injection molded under heat and pressure into the die cavity 
formed between the two generally parallel curved die surfaces so as to 
form a sunroof having curved exterior surfaces including a curved 
relatively thin film having the electrochromatic layer adhered to a 
relatively thicker substrate layer of clear plastic material. 
Other objects, features, and characteristics of the present invention as 
well as the methods of manufacture will become more apparent upon 
consideration of the following description and the appended claims with 
reference to the accompanying drawings, wherein like reference numbers 
designate corresponding parts in the various figures.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
As shown in FIGS. 1-3, a vehicle sunroof in accordance with the present 
invention is generally indicated by the reference number 10. In the 
broadest concept of the invention, the sunroof consists of two layers: a 
relatively thin film 12 including electrochromatic material and a 
relatively thick substrate layer 14 of clear plastic material. The various 
embodiments of the present invention include additional layers and/or 
different configurations. 
As shown in FIG. 1, in the first embodiment of the present invention, the 
relatively thin film 12 includes three layers. The relatively thin film 
may be purchased as an assembly of three layers or the relatively thin 
film may be assembled prior to further processing. Notwithstanding, the 
three layers include a relatively thin sheet of plastic material 16, a 
relatively thin material 18 having variable optical transmission, and a 
layer of abrasive resistant material 20. The relatively thin sheet 16 is 
formed from any suitable thermoplastic material. Preferred materials are 
taken from the group consisting of polycarbonate or polyester resin, with 
polycarbonate being a preferred embodiment. The relatively thin material 
18 having variable optical transmission is adhered to one surface of the 
relatively thin sheet 16. The relatively thin material 18 having variable 
optical transmission is formed from any suitable electrochromatic film. 
Preferred films would have liquid crystals. Finally, the relatively thin 
film 12 includes preferably a layer of abrasive resistant material 20 
adhered to the other surface of the relatively thin sheet 16 such that it 
constitutes an exterior surface of the sunroof 10. The abrasive resistant 
material 20 preferably comprises a thermoset material taken from the group 
consisting of polysiloxane, acrylic resin, or aliphatic polyurethane. As 
constructed and arranged in the first embodiment, the relatively thin film 
12 has a thickness, including any abrasion resistant material if applied, 
within an operative range of 0.2 to 2.0 millimeters and a preferred range 
of 0.2 to 1.0 millimeter. A preferred thickness for the relatively thin 
film 12 is approximately 0.5 millimeters. 
As described above, the abrasive resistant material 20 is adhered 
preferably to the surface of the relatively thin sheet 16 opposing the 
surface which adjoins the relatively thin material 18 having variable 
optical transmission. The abrasive resistant material 20 is applied before 
the relatively thin film 12 is adhered to a relatively thick substrate 
layer 14 and preferably by a spraying procedure. In the alternative, the 
abrasion resistant material 20 as well as an abrasion resistant material 
22 disposed on an inwardly facing surface of the sunroof 10 can be applied 
to the sunroof 10 by a dipping procedure following attachment of the 
relatively thin film 12 to the substrate layer 14. These procedures have 
the effect of coating an exterior surface of the sunroof with the abrasive 
resistant material 20. Additionally, both abrasion resistant materials 20, 
22 can be applied by spraying following attachment of the relatively thin 
film 12 to the substrate layer 14. If only one abrasive resistant coating 
is incorporated in the sun roof, however, it preferably should be disposed 
on the surface of the sunroof 10 that forms part of the exterior roof of a 
vehicle. As configured, the abrasive resistant material 20 provides wear 
resistance as well as resistance to ultraviolet radiation. 
The electrochromatic film forming the relatively thin material 18 having 
variable optical transmission changes opacity as voltage is applied across 
the film. As shown in FIG. 6, buss bars 19 are disposed along the 
perimeter of the electrochromatic film. Voltage from a vehicle power 
supply is applied across the buss bars 19 to change the opacity of the 
film. 
A relatively thick substrate layer 14 is disposed in adjoining relationship 
to the relatively thin film 12. The relatively thick substrate layer 14 is 
preferably formed from thermoplastic material taken from the group 
consisting of polycarbonate, cyclic polyolefin, and polymethyl 
methacrylate. A preferred material is polycarbonate. The relatively thick 
substrate layer 14 has a thickness within an operative range of 3 to 13 
millimeters, and a preferred range of 3 to 7 millimeters. A preferred 
thickness of the relatively thick substrate layer is approximately 5 
millimeters. 
As shown in FIG. 1, in the first embodiment, the sunroof 10 may include 
optionally the additional abrasion resistant coating 22 on the inwardly 
facing surface of the sunroof 10--i.e. the surface of the sunroof 10 that 
upon installation in a vehicle faces an interior of the vehicle. In this 
case, the abrasion resistant materials 20, 22 are applied by a dipping 
procedure. 
FIGS. 4-5 illustrate the method of making a sunroof in accordance with the 
present invention. The relatively thin film 12 is prepared by printing, 
laminating or bonding the relatively thin material 18 having variable 
optical transmission to the relatively thin sheet 16 with an adhesive 
appropriate for the materials. As discussed above, the abrasion resistant 
coating 20 may be sprayed onto the thin film 12 prior to attachment of the 
thin film to the substrate 14, the coating 20 may applied by a dipping 
procedure after the substrate 14 is attached to the thin film 12. 
Following attachment of the relatively thin material 18 having variable 
optical transmission to the relatively thin sheet 16 (thereby forming the 
relatively thin film 12), the relatively thin film 12 is then mounted 
within a molding die 24, such as shown in FIG. 4. The molding die 24 
includes a curved die surface 26, and the relatively thin film 12 is 
mounted with respect to the molding die 24 so that it is adjacent to the 
curved surface 26. In this embodiment, the relatively thin sheet of 
plastic material 16, or the abrasive resistant material 20 if one is used, 
of the relatively thin film 12 is mounted adjacent the curved surface 26 
of the die 24 such that the relatively thin material 18 having variable 
optical transmission is disposed interior of the relatively thin sheet 16. 
As indicated by FIG. 6, the curved surface 26 may have curvature in two 
planes--a prevalent practice with respect to vehicle sunroofs. 
It is contemplated that the relatively thin film 12 has a thickness which 
when mounted in the molding die 24 would conform simply and generally to 
the curved die surface 26. Preferably, the relatively thin film 12 is 
mounted within the molding die 24 adjacent the die surface 26 so that a 
marginal edge extends past the die surface 26. The outwardly extending 
marginal edge portion of the relatively thin film 12 is engaged by a 
cooperating marginal edge of a second molding die 28 which cooperates with 
the molding die 24 when moved into cooperating relation with the die 24. 
As best shown in FIG. 5, the cooperating molding die 28 includes a curved 
die surface 30 which is generally parallel with the curved die surface 26 
of the molding die 24. The curved die surfaces 26 and 30 form a die cavity 
32 when the molding dies 24 and 28 are moved into cooperating relation. 
The die cavity 32 has a thickness between the curved die surfaces 26 and 
30 which is substantially greater than the thickness of the relatively 
thin film 12. 
After the die members have been moved into cooperating relation, the 
plastic material which is to form the substrate layer 14 is injected into 
the die cavity 32 above the relatively thin sheet 16 and molded under heat 
and pressure in accordance with conventional practice. During the 
injection molding, the surface of the relatively thin film 12 adjacent the 
die surface 26 is forced against the die surface 26 thereby assuring a 
proper surface configuration. Optionally, the relatively thin film 12 can 
be preformed prior to engagement of the molding dies 24 and 28. 
The resulting sunroof 10, as shown in FIG. 6, includes exterior surfaces 
which are curved to conform with the die surfaces 26 and 30. The 
relatively thin material 18 having variable optical transmission is 
captured between the relatively thin sheet 16 and the relatively thick 
substrate layer 14 which now has a curvature corresponding to that of the 
molding dies 24 and 28, and such layers are retained in the curved 
configuration by their adherence to each other. 
As shown in FIG. 2, a second embodiment of the present invention is 
designated generally by the reference number 110. In this configuration, a 
relatively thick substrate layer 114 is disposed between an abrasive 
resistant material 122 and a relatively thin film 112 having variable 
optical transmission. In this embodiment, the relatively thin film 112 
including the material 118 having variable optical transmission does not 
include a relatively thin sheet, but it does include an abrasive resistant 
material 120. The abrasion resistant materials 122, 120 are applied as 
described above by spraying or dipping. The second embodiment of the 
present invention is assembled as described above except that the 
relatively thin film 112 is mounted on the cooperating molding die 28 
rather than the molding die 24. 
Finally, as shown in FIG. 3, a third embodiment of the present invention 
designated generally by the reference number 210. This embodiment is 
identical to the previous embodiment except for the deletion of an 
abrasive resistant material on the exterior surface of the relatively thin 
film 212. 
While the invention has been described in connection with the preferred 
embodiments, it should be understood readily that the present invention is 
not limited to the disclosed embodiments. Rather, the present invention is 
intended to cover various equivalent arrangements including, for example, 
a sunroof comprised of a relatively thin film having variable optical 
transmission and a relatively thick substrate layer adhered thereto and 
other arrangements included within the scope of the appended claims.